Please Recommend A Transmission

[mackattack2]

hi,

This is a 4-part complex question with I hope simple answers. First, I admit that I don't have much experience with heavy trucks. Growing up in Los Angeles all my friends have sports cars and I'm the only one who ever seemed to like trucks. I know for many people their truck is their main tool for making a living. This post is to people who actually drive these trucks and work on these trucks that I direct my questions.

First, some background. I'm an accomplished shade-tree mechanic restoring old GM light and medium trucks (but never diesel) as a life-time hobby. Recently I've acquired a sedan model L pumper firetruck. On the advice of those here I've decided to change the engine from the old 707 gaser that's froze-up to a 237 diesel. And I've decided to go from the 5 speed direct-drive to a 6 speed over-drive trans. Now this is where my questions come in. In my research into these types of transmissions I bought a Feb 1983 6-speed trans Mack service manual. But I was very surprised by what I found in it. It's publication 10-TRXL1070-100.5 and covers 6-speed transmissions TRXL1070, TRXL10710, TRXL1070A, and TRXL10710A transmissions. The first thing I noticed is that these transmissions have no syncroes. GM has been putting gear syncroes in their truck transmissions ever since the mid 1940's.

-A- Does that mean even these newer 1980's transmissions (and all 6-speed Mack trans) must be double-clutched every time they are shifted?

-B- Or do all heavy truck transmissions not use syncroes? Must they all be double-clutched? This is where I depend on your heavy truck experience. And please explain proper heavy-truck shifting technique to me.

Also, according to this publication, these are triple counter-shaft transmissions but I noticed, according to the pictures in the service manual, that all the gears are spur-cut (straight) cut gears, not the angle-cut (I think they are called helical) gears used by GM and Spicer since the mid 1940's. Angle-cut gears are much more quiet and stronger (because several teeth are in constant contact at the same time). With angle-cut gears the trans would only need two counter-shafts, not three, would still be stronger, and much lighter and cheaper to manufacture. This is not exactly cutting-edge technology.

-C- Why is Mack so far behind in their engineering, or is there something I don't understand?

-D- Finally, and most importantly, what transmission would you recommend I get for my truck? I'll be using a 237 diesel engine, with a 6.14 rear axle and 900x20 tires. I'd like a very low 1st gear, a very high over-drive gear, a trans with syncromesh gears, and a trans that I can shift with one hand. I don't mind having a two-stick trans, (in fact, it might be fun) but in watching this video,

I feel both hands off the steering wheel so much of the time is just plain unsafe and should be unnecessary with today's technologies. I want really low low first gearing, but also to travel at 70mph on the freeway. What do you recommend, perhaps an auxiliary trans in addition to the main transmission?

Thank you for your recommendations, and your help in explaining Mack transmissions and proper truck-driving techniques to me.

Steve

[Maxville Truck]

Not to many transmission manufacturers in the heavy truck world offer syncro transmissions!!! Personally I think it is because syncros are prone to failure and heavy truck manufacturers want strong products, not failure prone products. Volvo I know has or had a syncro heavy transmission. Double clutching is the book method for shifting all heavy non syncro transmisions. I personally use the clutch for starting out and changing direction. and occasionally to get out of gear on a tough conditon, otherwise listening to the engine and feeling the light "scratch" you can shift like butter without the clutch.I can't speak to the "superior" helical design vs. spur gear design, but i'm pretty sure that mack by far has the strongest transmission of any other manufacturer. But I would recommend only 2 transmisions for your needs either a t2060 or t2070 transmissions. Both have a .6 to 1 over drive. so your should see close to 70 mph in high gear. the t 2060 has a 9.02 to 1 low gear while the t2070 has a 14.16 to 1 low gear. I'm sure that many people could argue these points with me....... :SMOKIE-LFT:

[mackattack2]

Not to many transmission manufacturers in the heavy truck world offer syncro transmissions!!! Personally I think it is because syncros are prone to failure and heavy truck manufacturers want strong products, not failure prone products. .... But I would recommend only 2 transmisions for your needs either a t2060 or t2070 transmissions. Both have a .6 to 1 over drive. so your should see close to 70 mph in high gear. the t 2060 has a 9.02 to 1 low gear while the t2070 has a 14.16 to 1 low gear. I'm sure that many people could argue these points with me...

hi,

Thank you for your reply and your insight. Are both transmissions double-stick and do either use syncroes? I used to sometimes shift the old GMC trucks without the clutch, but I thought it was possible for me to do so only because the transmissions had gear syncroes, not because I was matching the engine, road speed and gear speeds. Any idea what bellhousing I would use between a 237 diesel engine and the t2070?

Thank you again.

Steve

[ThaddeusW]

I hate to break it to ya but no heavy truck transmissions here in the USA is synchronized. The Eaton 5 and 6 speed medium duty transmissions are synchronized but the most torque is 860 foot pounds. In Europe they are all Synchronized and they use single heavy counter shafts with helical gears. We may sound behind here in the USA but there isn't a big technology push. The reason is what we have works fine and gets the job done. Sure the European trucks might sound technology superior but guess what they are expensive, heavy and do the same amount of work.

[HK Trucking]

I hate to break it to ya but no heavy truck transmissions here in the USA is synchronized. The Eaton 5 and 6 speed medium duty transmissions are synchronized but the most torque is 860 foot pounds. In Europe they are all Synchronized and they use single heavy counter shafts with helical gears. We may sound behind here in the USA but there isn't a big technology push. The reason is what we have works fine and gets the job done. Sure the European trucks might sound technology superior but guess what they are expensive, heavy and do the same amount of work.

An unsynchronized transmission is actually a safety feature. The transmission cannot accidentally be put in the wrong gear while going down the road.

Think of it this way: You could drive a manual transmission car down the road at 60 MPH in hi gear, and due to the fact that the transmission is synchronized, you could depress the clutch pedal and the synchronizers would make it possible to shift into first gear with no problem (keep in mind the car is going 60 MPH) So what do you think happens when you re engage the clutch?

Yup, massive overspeed of the engine, shock to the driveline and more than likely catastrophic damage.

Now picture that scenario in a 80,000 lb truck with a synchronized transmission.

I think that's one good reason why class 8 truck transmissions are not synchronized.

[Freightrain]

Welcome to the world of REAL trucks. Like previously mentioned, you'll not find a HD class tranny with synchros. No real need for them, as I think the only reason they were put in ANY transmisson was for the fact that ANY person could then drive. Back in those early days it took a real person to "man handle" a car. Then with the technology, synchros were added and now anyone could drive a car/truck easily. Well, in the world of large trucks, not "anybody" drives them, it does take some talent. Beside the fact it would be just more parts to wear out and it's not really needed. Most late model tranny's do have synchros but they are in the back box(splitter) and they do wear out. Never have to pull a two stick apart to replace brass because it would shift.

Anyway, as you found in the video(it's me by the way), that two stick trucks do take some education to drive. You can drive them ONE handed(or two if you please). The late model 5-6 spd transmission do not shift like the old triplex's anyway. You can float the gears very easily, just with a 6 spd, they will be farther apart and take longer as the motor has to drop rpm alot more then the older motors.

You should also know that straigh cut gears are FAR superior in strength to helical gears and since it's a truck, noise is not a real issue(can't hear over the motor anyway). With the torque that these motors are putting out, 3 countershafts make it bulletproof.

[mackattack2]

Hi,

Thank you for your replies everyone. I'm learning... but I don't understand how a straight cut gear can be stronger than an angle cut gear. As an extreme example, the pinion and ring gear in a differential are not straight-cut gears, or else they would break easily.

How does one first learn the shift points on an unfamiliar truck drivetrain - just double clutch every shift until familiar with the truck? Also, I was once told that if the gears even once in a manual trans scratch, that tiny bits of metal are now in the oil and the bearings will begin to fail in a few hundred miles. How much of a scratch or clash or how many times can this happen before its imperative to flush the oil in a manual trans? What's been your real-life experience with this?

Thank you everyone, its been educational.

Steve

[theakerstwo]

Hi,

Thank you for your replies everyone. I'm learning... but I don't understand how a straight cut gear can be stronger than an angle cut gear. As an extreme example, the pinion and ring gear in a differential are not straight-cut gears, or else they would break easily.

How does one first learn the shift points on an unfamiliar truck drivetrain - just double clutch every shift until familiar with the truck? Also, I was once told that if the gears even once in a manual trans scratch, that tiny bits of metal are now in the oil and the bearings will begin to fail in a few hundred miles. How much of a scratch or clash or how many times can this happen before its imperative to flush the oil in a manual trans? What's been your real-life experience with this?

Thank you everyone, its been educational.

Steve

It is ok to scratch a gear one time but not two times but if in doult about it i can tell you that all trans have magnets in them just for new driver to scratch gears. If it is a play truck you will never need to change the grease. glenn

[Maxville Truck]

Oh if only a scratch was all I heard....!!!!! :wacko: My guys "GRIND" the living sh&% out of my T2060 transmissions. (i get the fingernail down the chalk board feeling every time I hear it, but I can't drive em all myself!!)and they work day in and day out. as far as getting used to the shift point any small bit of common sense you should get it with about 1 days worth of driving, if not please stick with synchros. As far as "scratch" goes, I don't mean press the shifter with a lot of pressure to get into the next gear.... just enough pressure to barely feel the gears "scratching" and by the way unless your drain your transmission.... there should be a film of 80 w90 between the "scratching" slider clutch and intermeshing gear.. so not much metal should be flaking of the meshing gears!!

[Freightrain]

Thank you for your replies everyone. I'm learning... but I don't understand how a straight cut gear can be stronger than an angle cut gear. As an extreme example, the pinion and ring gear in a differential are not straight-cut gears, or else they would break easily.

Like I mentioned, straight cut gears are very noisy. If a ring and pinion were straight gears, you'd hear it howling over everything in sight. Cars are refined, and made to be quiet. There are limitations to car rearends, but for the most part are strong enough to survive. John Force goes 300 mph on one. The old Mack double reduction rearends have straight cut gears in the final ratio, but the speed they turn keeps the noise from being audible.

I'm sure you've heard of the Muncie "rock crusher" 4 spd. Yup, straight cut gears and it whines big time. Cool for a hot rod, but most don't care for noises like that(like old solid lifter motors).

Learning to drive a truck tranny just takes time/patience/smoothness. Can't jam it along like a car. It has to be worked like a walking on eggs. I learned on my truck on the way home from buying it. Still "grind" a gear on occasion(nobody is perfect). Just have to live/learn.

[vanscottbuilders]

Learning to drive a truck tranny just takes time/patience/smoothness. Can't jam it along like a car. It has to be worked like a walking on eggs. I learned on my truck on the way home from buying it. Still "grind" a gear on occasion(nobody is perfect). Just have to live/learn.

You have gotten some excellent information in this discussion.

I would like to add that some of your confusion about shift points is the difference from a gasoline engine to a diesel.

The heavy truck diesels operate in a relatively small power band. Say from 1,200 rpm to 2,000 rpm. By contrast your gas motor might make adequate power from 850 rpm to 3,000 or more, depending on what it is.

Don't forget - the diesel is making huge torque in that narrow power band. And each shift is made at essentially the same point on the tach, unlike the gas trucks.

Learning a diesel truck, as Freightrain said, is pretty easy. Simply a matter of running the tach up to about 2,000, lift your foot gently and ease the shifter to the next appropriate position. It is easily accomplished with your left foot planted firmly on the floor. In fact it is easier than trying to clutch for each shift. Done properly you shouldn't be scratching or worse, grinding any gears. You can feel the next gear, and the transmission will let you know when to drop the lever in place. Maybe a little blip of throttle to help smooth the process once in a while. With no synchronization, the clutch probably won't help a lot, if you miss, anyway.

If Freightrain was clutching each shift in those videos, he would be walking in very small circles because his left leg would four times as big as his right.

As everyone here has said - straight cut gears with no synchros are a different animal than your light truck synchronized transmissions, and for good reasons. We are dealing with torque numbers unlike any gas motor produces.

Trying to get a super low 1st gear and a super high final gear is really asking a lot from these old trucks, too.

The TRD 2070 transmission does go a long way toward this goal.

So the moral of the story is - get in the truck and have fun!

Paul Van Scott

[Noid93]

I worked on a truck in Maxvilles shop that had a fully syncro'd tranny. Big sticker that said "always engage the clutch when shifting gears to prevent transmission damage". Early 90 s volvo (conventional set back axle heavy speced milk truck) with volvo engine and butterfly valve engine brake. Neat truck for those who desire that setup. THE ONLY FULLY SYNCRO'S TRANNY I HAVE EVER SAW, BUT THEY MAKE THEM!!!!!!

[Maxville Truck]

hi,

Thank you for your reply and your insight. Are both transmissions double-stick and do either use syncroes? I used to sometimes shift the old GMC trucks without the clutch, but I thought it was possible for me to do so only because the transmissions had gear syncroes, not because I was matching the engine, road speed and gear speeds. Any idea what bellhousing I would use between a 237 diesel engine and the t2070?

Thank you again.

Steve

The 2070 and 2060 have an integral bell housing, and should bolt right up, and they are both an air shifted trans mission....

Here is the "book" method for shifting right out of the manual!!

The T2060/T2070 are non-synchronized transmissions. There is a Lo and Hi auxiliary section controlled by an air-shift range selector on the shift lever. Lo-range provides one low ratio in the T2060 and two low ratios in the T2070. In Hi-range there are five forward gears which can be shifted in the standard manner. Remember, however, to double-clutch whether moving up or down through the gears. For normal highway use, start in Hi-range first gear and shift through second, third, fourth and fifth. The Lo-range in these transmissions is designed for use in off-highway and slow-moving operations (curb pouring, material spreading, heavy load/steep grade). Reverse can be used in Lo-range or Hi-range.

UPSHIFTING

To upshift the T2060, begin in first gear, Lo-range. Depress the clutch pedal and release the accelerator pedal. Flip the air-shift range selector to Hi-range (the vehicle is still in first gear). Release the clutch pedal and apply the accelerator to reach the top of the operating range. Shift through second, third, fourth and fifth, while double-clutching.

To upshift the T2070, begin in first gear Lo-range (referred to as Lo-Lo, shown on the shift pattern diagram). Upshift to second gear Lo-range (referred to as Lo) in the normal manner (double-clutching). When ready to upshift again, depress the clutch pedal and release the accelerator pedal. Move the gear shift lever to neutral, flip the air-shift range selector to Hi-range, double-clutch and move the gearshift lever back to first gear position. This is first gear Hi-range (next higher ratio). Release the clutch pedal and apply the accelerator pedal. Continue to upshift through the normal second, third, fourth and fifth gear ranges, while double-clutching.

DOWNSHIFTING

Downshift the T2060 as normal from fifth to fourth, third, second and first (remember to double-clutch). When at the low end of first gear Hi-range, depress the clutch pedal, release the accelerator pedal and flip the air-shift range selector to Lo-range. Release the clutch pedal.

To downshift the T2070, downshift as normal from fifth to fourth, third, second and first in Hi-range (double-clutch between them all). The next lower shift will be to second gear Lo-range (referred to as "Lo"). When ready for this gear, depress the clutch pedal and release the accelerator pedal. Move the gearshift lever to neutral and flip the air-shift range selector to Lo. Double-clutch and move the shift lever to second gear (Lo). The vehicle is now in second gear Lo-range. The next lower gear (and lowest ratio) is first gear Lo-range (Lo-Lo). Double-clutch and downshift to first Lo-range at the appropriate time.

[other dog]

I might as well put my 2 cents worth in-I'm not a mechanic,or rebuilder,but I've been driving for almost 29 years,and i've scraped as many gears as anyone ( still do sometimes,and that's just laziness ). I'd go with the old 5 speed maxitorque with that 237. In 1980 I got out of a '74 IH with a 903 Cummins and 13 speed into an F-model with a "300" (actually 285 hp) and a five speed. The 903 was a 2600 rpm engine,you downshifted at about 1900 or 2000 rpms,and the Mack you just let pull down to about 11-1200 rpms before you had to downshift. You never got in a hurry shifting it.You could downshift easily without the clutch after you got used to it,but that's about the only truck i've ever driven that I double-clutched up shifting,but like I say you couldn't really shift them very fast anyway. It took way more skill to shift that 5 speed Mack than the Eaton-Fuller 18 spd. I drive now. Oh,I bought an m22 Muncie once and put it in my '72 Nova.It came with a 3 spd. in the floor. Put a competition plus shifter on it,then bought a vertigate because it looked "tuff".I liked the look of all them levers in the floor even then.The vertigate was an in-line shifter,and did look tuff,but I found it really wasn't as quick as the hurst. Sometimes simplest is the best. Like a 5 speed Mack.

[HK Trucking]

It took way more skill to shift that 5 speed Mack than the Eaton-Fuller 18 spd. I drive now.

You're right. You actually have to have a sense of timing with the 5, 6, and 7 speed transmissions.

With the 18 speed Fuller (and it's sisters, the 8LL, 9 speed, 10 speed, and 13 speed, if you just move the stick as quickly as possible to the next gear, you can upshift successfully.

[b61mack]

You're right. You actually have to have a sense of timing with the 5, 6, and 7 speed transmissions.

With the 18 speed Fuller (and it's sisters, the 8LL, 9 speed, 10 speed, and 13 speed, if you just move the stick as quickly as possible to the next gear, you can upshift successfully.

on the 5 speed Mack there are 2 magnetic plugs you can takeout on each side of the transmission catches the metal shavings, dont know about the others. Ron

[bulldog man]

i could drive a duplex , quadbox & triplex before i could a airshift (@15yrs old) 1st airshift tranny i drove was a 7spd mack @ age 26

it took me a couple of days when we got a DM W/ the 2070 (7spd) to learn 3rd gear (1st high gear) was back over where 1st gear postion was ...lol

but once i got the hang of it it was riding a bike

ive seen guys (& a few women too ) try speed shift a 6,7, & 8 spd Maxitorque tranny like a Roadranger & grind gears so hard I HAD TO SHOW THEM TO BASICALLY GLIDE THE STICK TO THE NEXT GEAR ........ A bunch of the guys that got out of say a KW Dump into a dump moan & complain that they cant "speed shift" the Mack like a roadranger

I Myself get out of a Mack & into a truck w/ a Roadranger i have to remember to shift a ittle quicker than the Maxitorque

I My self perfer the OLE 2Stick trd & td series &trl trx series &2000 series over the Roadrangers but will drive a roadranger

but ya know what they say bout opinons

just my 2 cents yall

Later

[HK Trucking]

on the 5 speed Mack there are 2 magnetic plugs you can takeout on each side of the transmission catches the metal shavings, dont know about the others. Ron

....And this is relevant to the quote you used from my post how?????

[waslucky]

lol well while ever one else is at it i,ll add my copper coins worth .........all i can add is its a patiencegame Steve ....i,ve found that Mack boxes have Big gears w TEETH !!! an true with a Roady u can sorta race up an down box once mastered with eng revs an road speed but with a mack box all is acomlished with a little patience ...i have a MIR with a 237 coupled to a 9spd O/D Roadranger and a R688 with a 350 2 valve coupled to a 12spd twin stick Mack box an hafta catch myself jumpin from one to the other as both require different attitudes to driving style. only advice i can offer is dont stress we all Clean teeth an at end of day after all they ARE in a BOX unless your trying to jam a gear with poor ol girl bouncin on governor an your shoulder behind stick u cant really kill a mack Box......theyr,e straight cut gears for a Reason.. as like the golden sayin BUILT LIKE A MACK TRUCK . sound like you have a steep learning curve ahead of you Steve ...anyway enough of my rambling ...keep it shiney side up ..

[other dog]

i could drive a duplex , quadbox & triplex before i could a airshift (@15yrs old) 1st airshift tranny i drove was a 7spd mack @ age 26

it took me a couple of days when we got a DM W/ the 2070 (7spd) to learn 3rd gear (1st high gear) was back over where 1st gear postion was ...lol

but once i got the hang of it it was riding a bike

ive seen guys (& a few women too ) try speed shift a 6,7, & 8 spd Maxitorque tranny like a Roadranger & grind gears so hard I HAD TO SHOW THEM TO BASICALLY GLIDE THE STICK TO THE NEXT GEAR ........ A bunch of the guys that got out of say a KW Dump into a dump moan & complain that they cant "speed shift" the Mack like a roadranger

I Myself get out of a Mack & into a truck w/ a Roadranger i have to remember to shift a ittle quicker than the Maxitorque

I My self perfer the OLE 2Stick trd & td series &trl trx series &2000 series over the Roadrangers but will drive a roadranger

but ya know what they say bout opinons

just my 2 cents yall

Later

:mack1:That would probably be me too-i've driven about every roadranger there is , drove a couple of Freightliners with Meritor transmissions,they used to be Rockwells I think, but I have no experience with any of the later model Mack transmissions and probably wouldn't know what to do with one either.

[mackattack2]

I might as well put my 2 cents worth in-I'm not a mechanic,or rebuilder,but I've been driving for almost 29 years,and i've scraped as many gears as anyone ( still do sometimes,and that's just laziness ). I'd go with the old 5 speed maxitorque with that 237. In 1980 I got out of a '74 IH with a 903 Cummins and 13 speed into an F-model with a "300" (actually 285 hp) and a five speed. The 903 was a 2600 rpm engine,you downshifted at about 1900 or 2000 rpms,and the Mack you just let pull down to about 11-1200 rpms before you had to downshift. You never got in a hurry shifting it.You could downshift easily without the clutch after you got used to it,but that's about the only truck i've ever driven that I double-clutched up shifting,but like I say you couldn't really shift them very fast anyway. It took way more skill to shift that 5 speed Mack than the Eaton-Fuller 18 spd. I drive now. Oh,I bought an m22 Muncie once and put it in my '72 Nova.It came with a 3 spd. in the floor. Put a competition plus shifter on it,then bought a vertigate because it looked "tuff".I liked the look of all them levers in the floor even then.The vertigate was an in-line shifter,and did look tuff,but I found it really wasn't as quick as the hurst. Sometimes simplest is the best. Like a 5 speed Mack.

I would like to thank everyone for all this great information - nothing beats actual experience. Believe it or not I was once actually told to always use the clutch or else I'd wear out the trans. Therefore the only time I shifted without the clutch is when I knew I intended to put the truck up for sale and it no longer mattered to me if I wore it out. I must admit that after driving a year or two without the clutch, by the time I actually sold the truck, the trans still worked just as good.

OK, here's three more related questions - hope you don't mind..

-A- My 707 gasser has a 5 speed direct trans with only 56k miles of use, would it bolt up to a 237 diesel? And do different Mack 5 speeds have different gear ratios?

-B- I have a Spicer 5831 auxiliary overdrive trans I've used in 1 ton trucks. Would this trans handle the torque of a 237 diesel?

-C- What is the proper way to shift an auxiliary? In the past because I was so worried about scratching the gears, I would only shift it if I was stopped. In other words, I would anticipate my driving, for example if I knew I was going to take the freeway I would shift it into overdrive before I started. This trans has no magnetic plugs to collect any metal chips from scraped gears and it has one bearing no longer available new.

Thank you everyone for sharing your experience.

Steve

[ThaddeusW]

-A- My 707 gasser has a 5 speed direct trans with only 56k miles of use, would it bolt up to a 237 diesel? And do different Mack 5 speeds have different gear ratios?

No. The torque of the 707 is much much lower then the 237. The 237 will twist that old 5 speed apart. It might last for a while but someone here will know better.

-B- I have a Spicer 5831 auxiliary overdrive trans I've used in 1 ton trucks. Would this trans handle the torque of a 237 diesel?

We are talking about 820 foot pounds of torque from that 237. Whereas the 5831 is rated at only 275 ft/lbs. So its a no go. There are heavier aux transmissions availible for that kind of torque.

-C- What is the proper way to shift an auxiliary? In the past because I was so worried about scratching the gears, I would only shift it if I was stopped. In other words, I would anticipate my driving, for example if I knew I was going to take the freeway I would shift it into overdrive before I started. This trans has no magnetic plugs to collect any metal chips from scraped gears and it has one bearing no longer available new.

Well depends on the setup but it follows the same basic shift technique of the two stick Mack transmissions. You split each gear so its 1st-direct-hi, 2nd-lo-direct-hi etc...

[Freightrain]

Using the aux, is a "need to" type arrangement. Only split when you need the power, and skip along when you don't. That is how I drive mine for the most part, and you'll find that most guys on here with old two stick trucks do the same. No sense wearing your arm out LOL!

Just remember upshifting is the simple part, just let the rpm's drop enough to get it into gear. Down shifting you have to raise the rpm to match. As you watch my little video, you'll see that when I downshift the compound(after upshifting the main box), I blip the throttle to raise the rpm enough to drop it into gear. Depending on how wide the ratio is makes the difference in how many rpm you have to raise to get back into gear. It's all in just learning your set up.

[fuzzy buzzard]

Just read thru all the replys - I can might near taste gear teeth now! Deeper into this man's question. A 6.14 rear on them tiny tires at 70 mph!!!!!!!!! Its going to take about a 0.50 overdrive to make all this happen. A trans with a 0.60 OD and a 3 or 4 way aux box with 0.84 OD = 0.504 OD in highest gear - now we can go down the road!! And with the spur gears in both trans howling, we won't be able to hear that 6.14 rear screaming cause its nearing terminal velocity.

Just saw one of your other questions, don't even think about using that 5831 aux cause thats a 500 ft lb box. At least get a 8XXX box, they are 800 ft lb.

Over & out from Ignorant Ridge

Tom

PS Wish I could have gotten pic of the old wide body last Sat - Had my B67 on the hook making 75 mph down I 77 in WV in the 3 stick 2 stack Mack with a shack on the back. Life don't get no better!!!!!!!!!

[Greg Rider]

Remember the TH475 automushbox that GM put in bigger trucks and some motorhome chassis.It was the same as a TH400 but had straight cut gears for strength.If you were in one or next to it,you could hear it whine while it went through the gears.The strength of straight cut comes from the depth of cut and the pitch.Angle cut gears do have a weakness,if you put too much load on them they will "climb"and either push or pull apart.Engineers have them cut so when they are loaded the pattern makes the gears pull together to keep them engaged.This is where the strength comes from.But like I said,they can pull together hard enough to break things.