3.11 Axle?

[mack mhe9]

i was just wondering if someone was bulshting around about mack making a 3.11 and if it would be for a cr 92 93 rear. thanks

[Rob]

i was just wondering if someone was bulshting around about mack making a 3.11 and if it would be for a cr 92 93 rear. thanks

We don't allow any "bullshitting" on this site. Never have, never will.

I've never seen anything higher than a 3.65:1 ratio myself in a CR92, and 93 series.

Rob

[rhasler]

The spec sheets show a 3.11 ratio, it's for the new CRD150/151 series differential. As far as I know the CRD92/93 differentials are no longer being put in new trucks.

S40 TAN068 2010.7.26.pdf

[RowdyRebel]

http://macktrucks.com/default.aspx?pageid=2269

The C150/151 Axle Carriers deliver improved efficiency, higher ratings, improved durability and quieter operation. They are engineered with lower numeric ratios, allowing engines to run at reduced RPMs at cruise speeds, which boosts fuel economy and allows the engine to run much closer to the lower peak torques. This makes the C150/151 Axle Carriers ideal for highway applications. They are designed to handle the relentless punishment of demanding vocational operations and are rated for severe-duty applications.

I figgered that meant you weren't being bullshitted...but I couldn't find anything to back that up.

On a side note, what happened to the spec sheets like rhasler posted that USED to be on the Mack website?

[rhasler]

http://macktrucks.com/default.aspx?pageid=2269

I figgered that meant you weren't being bullshitted...but I couldn't find anything to back that up.

On a side note, what happened to the spec sheets like rhasler posted that USED to be on the Mack website?

I'm not sure what happened to them. They also used to have the chassis sheets showing all of the basic dimensions of the truck up there too, but they mysteriously disappeared from the website sometime around 2003 or 2004.

[mack mhe9]

thanks, solved that problem, just trying to get into direct at 60 and realy dont want to swap out rears, thanks

[Underdog]

thanks, solved that problem, just trying to get into direct at 60 and realy dont want to swap out rears, thanks

Ther has been a trend recently to spec "faster" axles with a direct transmission to take advantage of low RPM engines and maximize fuel economy. Some "experts" advocate ratios in the 2.65-2.88 range. Seems odd, but just not what we are used to seeing. For many years the trend was for overdrive transmissions. A direct drive will net better fuel economy, but beware of startability in the low gears.

Gregg

[RowdyRebel]

Ther has been a trend recently to spec "faster" axles with a direct transmission to take advantage of low RPM engines and maximize fuel economy. Some "experts" advocate ratios in the 2.65-2.88 range. Seems odd, but just not what we are used to seeing. For many years the trend was for overdrive transmissions. A direct drive will net better fuel economy, but beware of startability in the low gears.

Gregg

Yup...those "faster" ratios always seemed like it'd be a LOT of stress on that drive shaft & u-joints trying to spin those large tires under heavy loads. I don't care what they say about "gear fast run slow"...I've driven trucks with 475 cats, 10 speeds, and 3.36 rears that got 5.75 mpg running down the highway...and I've driven trucks with 435 mercedes, 10 speeds, and 3.55 rears and they'd get 5.75 mpg running down the highway. Neither one of those could pull a load up a friggin hill. I've driven trucks with 435 mercedes, 10 speeds, and 3.90 rears and they'd get 5.75 mpg running local/regional that would hold it's own on a hill...but STILL no comparison to the 460 Mack, 13 speed, 4.35 rears that I used to play around in the friggin woods, run WAY over gross, and would pull a hill like it was nothing and STILL got 5.75 mpg.

Which is why I bought a Mack with the 460, 18 speed transmission, and 4.17 rears. If I could afford to change the gearing, the only way I'd go would be to a 4.35 or MAYBE a 4.42 since I run 11R24.5's. Then again, I spend more time on the 2-lane roads than I do on the big road...if I had a sleeper truck and ran across several states per day without getting off the paved road too often, I'd leave it alone or maybe go to a 3.94. Gotta spec the truck for what you want to do with it.

[cgallamore]

Yup...those "faster" ratios always seemed like it'd be a LOT of stress on that drive shaft & u-joints trying to spin those large tires under heavy loads. I don't care what they say about "gear fast run slow"...I've driven trucks with 475 cats, 10 speeds, and 3.36 rears that got 5.75 mpg running down the highway...and I've driven trucks with 435 mercedes, 10 speeds, and 3.55 rears and they'd get 5.75 mpg running down the highway. Neither one of those could pull a load up a friggin hill. I've driven trucks with 435 mercedes, 10 speeds, and 3.90 rears and they'd get 5.75 mpg running local/regional that would hold it's own on a hill...but STILL no comparison to the 460 Mack, 13 speed, 4.35 rears that I used to play around in the friggin woods, run WAY over gross, and would pull a hill like it was nothing and STILL got 5.75 mpg.

Which is why I bought a Mack with the 460, 18 speed transmission, and 4.17 rears. If I could afford to change the gearing, the only way I'd go would be to a 4.35 or MAYBE a 4.42 since I run 11R24.5's. Then again, I spend more time on the 2-lane roads than I do on the big road...if I had a sleeper truck and ran across several states per day without getting off the paved road too often, I'd leave it alone or maybe go to a 3.94. Gotta spec the truck for what you want to do with it.

i got 393 gears 460 13spd 5.75 mpg running coast to coast, pulls like its pissed off and it will run faster than i want to ride it.

i have allways had colant push issues with high gears and low rpm's. maybe i dont know how to drive them???

[cgallamore]

i think the next time im at the shop, instead of agrevating mackpro im gona turn mine into a 18 spd. better do it there so he can bail me out if needed.....

[RowdyRebel]

i think the next time im at the shop, instead of agrevating mackpro im gona turn mine into a 18 spd. better do it there so he can bail me out if needed.....

99.9% of the time, I drive mine like an 13. The ability to split the low range is nice when climbing up out of a quarry or getting started on a hill...can work your way up through the gears a little easier...but I'm not sure it would be worth the time/effort/money to convert....unless it was a cheap, fast, & easy thing to do.

[rhasler]

99.9% of the time, I drive mine like an 13. The ability to split the low range is nice when climbing up out of a quarry or getting started on a hill...can work your way up through the gears a little easier...but I'm not sure it would be worth the time/effort/money to convert....unless it was a cheap, fast, & easy thing to do.

It is.

[Mike]

We don't allow any "bullshitting" on this site. Never have, never will.

I've never seen anything higher than a 3.65:1 ratio myself in a CR92, and 93 series.

Rob

Funny ya say........onetime ago, I thought I found some BS on here, also.............found out I was mistaken once............... only once. Please let us know if ya happen to find any BS sometime, cause we have this special kind of BS Hound....we like to call him OtherDog. He's out there lookin out for us keeping things clean on here.

Right Men.......Right,.... carry on Men.

mike

[mack mhe9]

if im not mistaken running in direct your not spining the counter shafts, right now i run in 17th 60mph at 1500. would like to get into direct at 60 and go to full lockers, we hall electronics from wi to east coast and have to have airide we deliver in to job sites and all ways stuck. when fuel was 1.10 a gal i'd run 70 all the time, just trying to save fuel and keep my v8. thanks

[RowdyRebel]

if im not mistaken running in direct your not spining the counter shafts, right now i run in 17th 60mph at 1500. would like to get into direct at 60 and go to full lockers, we hall electronics from wi to east coast and have to have airide we deliver in to job sites and all ways stuck. when fuel was 1.10 a gal i'd run 70 all the time, just trying to save fuel and keep my v8. thanks

Problem is, when you gear your rear ends to be faster...to cruise highway speeds in lower transmission gears....you are also making your low gears faster, which isn't a good thing when you get into soft/slick/uneven ground. I'm not convinced that running 3.11 rear gears and driving in 16th is going to gain enough fuel mileage to make up for the deficiencies created by losing your low gears...not to mention the cost of doing the swap in the first place. I just don't see the point in gearing your truck to have 2 top-end gears you can never use without getting a high dollar driving award.

Not to mention, when you gear your rears that fast, you are going to have to downshift more often on smaller grades than you currently do because you've geared out a bunch of your torque and power.

[Rob]

I was always partial to the two speed rears myself for the best of both worlds.

Rob

[slpwlker]

I was always partial to the two speed rears myself for the best of both worlds.

Rob

I got 2 speeds in mine and I really dispiese them. Alot more to fix and not everybody knows how anymore. and tempermental ass all hell. Looking to put a set of 4.56's in mine get alittle more bottom end out of this then what the 4.11's do now. 5.60's I top out at 60 flat out 2100

[Rob]

I've certainly had a lot of them, (mostly Eaton) and have never torn up a set. The electric motors however are a weak point. Never have had an ounce of trouble with an air shifted rear axle though. You are correct in that a lot of shops don't know how to work on, or set them up properly, but when set up and maintained, they work really well.

Rob

[slpwlker]

I've certainly had a lot of them, (mostly Eaton) and have never torn up a set. The electric motors however are a weak point. Never have had an ounce of trouble with an air shifted rear axle though. You are correct in that a lot of shops don't know how to work on, or set them up properly, but when set up and maintained, they work really well.

Rob

Bought the truck in Pa and Live in Fl. Had the front drive rebuilt had teeth missing on the ring gear always had metal on the plug. Made racket go figure. Got it back was still alittle noisy and took it out 11 months later. had a bolt that had fell out and was on the bottom of the rear. Trying to figure out how it never got pulled into the gears while moving and greanading the case. Got it back and was grossing 160k was getting of in Byron ga and shifted into lo to make it alittle easier as the ramp is alittle steep and the driveway of the truckstop is at a decent angle. and hell thats what I got 2 speeds for. Shifted while rolling and 1 went in the other didn't. Needless to say i moved but it made all kinds of racket,fought and pushed the clutch in and came to a stop. Limped it in the truckstop got fuel and rocked back and forth. everything went back into hi range and that is where it has been ever since. I really want to put a 4 speed aux behind the 18 and gear the truck down to 4.88. I'll have some great crawl speed and run out good on the highway with a lower rpm or in the power band.idk hell truck is 29k bobtail whats alittle more weight

[Rob]

Bought the truck in Pa and Live in Fl. Had the front drive rebuilt had teeth missing on the ring gear always had metal on the plug. Made racket go figure. Got it back was still alittle noisy and took it out 11 months later. had a bolt that had fell out and was on the bottom of the rear. Trying to figure out how it never got pulled into the gears while moving and greanading the case. Got it back and was grossing 160k was getting of in Byron ga and shifted into lo to make it alittle easier as the ramp is alittle steep and the driveway of the truckstop is at a decent angle. and hell thats what I got 2 speeds for. Shifted while rolling and 1 went in the other didn't. Needless to say i moved but it made all kinds of racket,fought and pushed the clutch in and came to a stop. Limped it in the truckstop got fuel and rocked back and forth. everything went back into hi range and that is where it has been ever since. I really want to put a 4 speed aux behind the 18 and gear the truck down to 4.88. I'll have some great crawl speed and run out good on the highway with a lower rpm or in the power band.idk hell truck is 29k bobtail whats alittle more weight

I have several friends that haul new Caterpillar equipment out of Morton, IL at both Daily Express, and Keen Transport. That heavy stuff is hard on equipment without a doubt. I've seen a lot of guys run older equipment that is way overbuilt for average trucking and not have problems constantly. Then again, there are guys that run new trucks and seem to have more breakdowns from wear and abuse than properly rebuilt and maintained older stuff.

One of the guys actually runs a 1977, or 1978 4300 series IH tractor and always is permitted when hauling usually with parts of a new D-10, or D-11. The engine is a Cummins built by Pittsburg Power and dynos a little over 800hp for short periods. I know the radiator is near eight inches thick in the core to cool it too. I don't know what trans is in the truck, but the rears are two speed in the mid 6.XX on the low, and high 4.XX on the high side and it gets used. It is interesting to listen to him take off from a stop with a D-10 minus the "U" frame, blade, and ripper teeth in the upshift. You can hear the rear(s) on the upshift with the distinctive teeth mesh.

I think he spends all his money on Talbert brand trailer as he has three of them and seems to have a new one each year.

Rob

[GearheadGrrrl]

I suspect the new 3.11 rear gears are intended to mate with Volvo's mDrive tranny, which IIRC is available with a direct top gear. It'll probably work OK and get good mileage behind the Mack/Volvo 11 and 13 liter engines for highway use at 80k pounds GCW. But for higher torque engines and heavy hauling you need an overdrive tranny and deep gears to keep from destroying the driveshaft U-joints.