R686St Banging Noise And Jerking

[RyanL]

that story i was talkin about if you are interested in readin it go to google and search for mack r-model odd story, its the one on heavyequipmentforums.com

[HK Trucking]

Well, you've found the problem!

.

[RyanL]

i'll get a different pinion gear and change it out and hope that fixes it. ive basically got a new truck now and lots of experience and lessons learned,lol Thanks for all the help guys. I'll will post a update towards end of week, on whether it fixes it or not.

Edited March 24, 2010 by RyanL

[fjh]

i'll get a different pinion gear and change it out and hope that fixes it. ive basically got a new truck now and lots of experience and lessons learned,lol Thanks for all the help guys. I'll will post a update towards end of week, on whether it fixes it or not.

You need to count the bull and spur too, there CAN be a difrence there as well!Pull the fill plug on the rear diff and count the teeth thru the hole!

Jack it up and have somone turn the wheel and count!other wise you'll be in the same pickle jar!Make sure the rear matches the front!

[RyanL]

k thats what i was wandering if they would be different too. ill count to nite

[RyanL]

well i counted bull gears thru plug and they are the same. so i will get me another ring and pinion sometime this wk, and another inner cam and stuff for power divider, cuz i chewed the one i just put in up. does anyone know what the backlash is suppose to be for these or any other things i should know when putting back together.

[fjh]

well i counted bull gears thru plug and they are the same. so i will get me another ring and pinion sometime this wk, and another inner cam and stuff for power divider, cuz i chewed the one i just put in up. does anyone know what the backlash is suppose to be for these or any other things i should know when putting back together.

Backlash 10 to 15 thou! middle is best 12.Tri to create the same pattern you see on the new gear set your installing!

Low to center in the middle of the tooth! and endup with 12 thou and your laughin!The pinion nut needs to be 1200 to 1600 foot pounds!you need a 4 to one multiplier set the wrench to 350 and it will get you 1400 !Good enuff

Put RED locktight on the pinion nut!Be sure to put the power divider inner cam with the grooves on the flat facing to the rear of the diff apon assembly so the oil can travel the tube! bull wheel cap torque 350 set the bull bearings to zero end play + one notch extra to engage the lock dowel!

[RyanL]

thanks for the specs, but i dn't have the tools i need yet to do all that, so i bit the bullet and took it to a local truck shop, after i done had it all tore apart. they charge a flat rate of 6hrs @ $65.00 hr ouch. but they goin complete thru and check all and put together, with used parts when possible at my request. They jus called me today and said it was dne and cost $1200.00. WOW! i wish i had tools to done it myself,lol So i will get it picked up and back in truck first of the week. Man, i kinda wish i would have listened to everybody tellin me that it ain't worth ownin your own truck,lol everythng i do to this truck cost me a fortune, and now i got a pretty much new truck with more money in it than i'll ever get out of it. And me being young, insurance and plates kill me, and i dn't even use truck for anything other than farm stuff pretty much. Sorry bout long post bout nothing,lol

[Rob]

thanks for the specs, but i dn't have the tools i need yet to do all that, so i bit the bullet and took it to a local truck shop, after i done had it all tore apart. they charge a flat rate of 6hrs @ $65.00 hr ouch. but they goin complete thru and check all and put together, with used parts when possible at my request. They jus called me today and said it was dne and cost $1200.00. WOW! i wish i had tools to done it myself,lol So i will get it picked up and back in truck first of the week. Man, i kinda wish i would have listened to everybody tellin me that it ain't worth ownin your own truck,lol everythng i do to this truck cost me a fortune, and now i got a pretty much new truck with more money in it than i'll ever get out of it. And me being young, insurance and plates kill me, and i dn't even use truck for anything other than farm stuff pretty much. Sorry bout long post bout nothing,lol

I don't think there is a single one of us here that hasn't been "upside down" into a project at least once. Will pass along a little bit that there is a lot of satisfaction to be had in knowing that when that truck is full of dirt, it will get you to the dump spot rather than shitting the bed in the middle somewhere along the line. That $1200.00 expense will be looked at as "chump change" when the rebuild holds up, as opposed to the truck letting you down. $65.00 an hour to do heavy truck repairs is damned cheap cause most of that type work can bust $100.00 an hour around here.

Rob

[MACKS]

LOL,65 an hour,last time I had my truck at Mack they charged me 125 an hour for labor and the two hour job turned into a six hour job Ryan just get that truck working and you'll make that money back in a heart beat.Once you get to work you'll see your truck is worth every penny you put into it.

[fjh]

thanks for the specs, but i dn't have the tools i need yet to do all that, so i bit the bullet and took it to a local truck shop, after i done had it all tore apart. they charge a flat rate of 6hrs @ $65.00 hr ouch. but they goin complete thru and check all and put together, with used parts when possible at my request. They jus called me today and said it was dne and cost $1200.00. WOW! i wish i had tools to done it myself,lol So i will get it picked up and back in truck first of the week. Man, i kinda wish i would have listened to everybody tellin me that it ain't worth ownin your own truck,lol everythng i do to this truck cost me a fortune, and now i got a pretty much new truck with more money in it than i'll ever get out of it. And me being young, insurance and plates kill me, and i dn't even use truck for anything other than farm stuff pretty much. Sorry bout long post bout nothing,lol

Thats 8 hrs labor and parts not bad as long as it holds together.

dont feel ripped off cause, you got off cheap.an exchange would have been a sight more than that.

[RyanL]

well guys that fixed the problem, i hauled some topsoil today and it done good, it runs like a new truck almost,lol Thanks for the help from everybody.

[cgallamore]

well guys that fixed the problem, i hauled some topsoil today and it done good, it runs like a new truck almost,lol Thanks for the help from everybody.

glad to here it worked out okay for ya. good luck!!!!!

[mikejudge]

Hi, well i have a 78' R686st mechanic's special truck that i bought and put a 14' dump bed on and done alot of fixin up. anyway it makes this banging noise and jerks. it don't do it all the time, i can make it start doing it with heavy acceleration, etc. it has tandem 38k axles wit 4.50 gears it says. i have put all new caps on trk. I have replaced and checked almost everything i can think of, have changed trans, replaced wedges and cams, spider gears,axle gears, bull gears,axles,etc I have counted all teeth on one gear carrier, but forgot to count on frnt carrier before i stuck in back down in housing. What are the odds of having different ratio's? What is acceptable size/wear difference between rear tires?

first thing that i would check is the tire height between #2 and 3 axles. mack diffs have very little tolerance for any difference in height. the difference is taken up in the front diff power divider which binds up and then releases causing a banging and and jerking condition. have seen this dozens of times and is almost always cured by having matching tires installed.

mike

[HK Trucking]

Looks like someone didn't bother to read all the replies.

[Rob]

Sooooo, do you all think if I was to install my 11.00X20 tires on the road side of the drives, and my 9.00X20 tires on the curb side, I could stike me a deal with either M&M Mars, or Hershey's for making peanut butter with my Mack power divider? I do have a few 7.50X20 tires which could be used for a "finer grind" if need be but don't have the correct spacers for them.

I could market the idea such as: Rare Earth Mineral Candy.

So, good proposition or what?????

Rob

[randyp]

Sooooo, do you all think if I was to install my 11.00X20 tires on the road side of the drives, and my 9.00X20 tires on the curb side, I could stike me a deal with either M&M Mars, or Hershey's for making peanut butter with my Mack power divider? I do have a few 7.50X20 tires which could be used for a "finer grind" if need be but don't have the correct spacers for them.

I could market the idea such as: Rare Earth Mineral Candy.

So, good proposition or what?????

Rob

sure would have to charge a lot for the peanut butter, you may have a lot of overhead expense in it, however dont know what the ratio of peanut butter made to power dividers consumed would be,,,may need to do some testing,,,randy

[Rob]

sure would have to charge a lot for the peanut butter, you may have a lot of overhead expense in it, however dont know what the ratio of peanut butter made to power dividers consumed would be,,,may need to do some testing,,,randy

I know the experts here at BMT wouldn't steer me wrong so I ask as to avoid making mistakes.

Rob

[HK Trucking]

I know the experts here at BMT wouldn't steer me wrong so I ask as to avoid making mistakes.

Rob

Rob, you could market that stuff as "Iron Enriched" Peanut Butter.

.

[hillconst1]

That was the Eaton 3 speed tandem axle setup you're referring to.

1 was both axles in low, 2 was 1 axle in low and 1 axle in hi, and 3 was both axles in high.

Those used a conventional spider gear type inter axle power divider though, and not the cam & wedge type power divider like the Mack tandems.

A spider gear type power divider will not clunk or bang if there is a difference in axle ratios or tire sizes the way a cam & wedge type power divider will.

That's why with "brand X" tandem setups you can match the tires the same across each drive axle without concern for any discrepancy in diameter from front drive axle to rear drive axle, whereas on a Mack tandem, you must match tires the same front and back on one side and then do the same on the other side so there is not a great difference in average tire diameter from front drive axle to rear drive axle(keeping the larger 4 on the curb side to compensate for road crown).

Eaton 3 speed worked as follows

LO-both rears in low range

Intermediate-one rear in high the other locked out

High-one rear in high the other locked out

Basically two two-speed rears with the same low ratio and different high ratio

[HK Trucking]

Eaton 3 speed worked as follows

LO-both rears in low range

Intermediate-one rear in high the other locked out

High-one rear in high the other locked out

Basically two two-speed rears with the same low ratio and different high ratio

I don't believe so.

"Locked out"?

Please explain.

Also, your "intermediate" and "High" both say the same thing: "one rear in high the other locked out". How would you get 2 different "speeds" with the same combination?

.

[theakerstwo]

I don't believe so.

"Locked out"?

Please explain.

Also, your "intermediate" and "High" both say the same thing: "one rear in high the other locked out". How would you get 2 different "speeds" with the same combination?

.

Basily they are a two pair of two speed rears. But unlike todays eaton power divider the older power divider did have a rubber wiper pad to wipe the oil from the ring gear as it turned and would collect the oil up high and run oil into the top of the spider assembley to keep cool and lubed.Todays two speed can not be used as a three speed set up because the power divider will not lub the spider like the three speed did.This set up was at one time very common. Loike been said low range both it low and intermedit range one is in low and one in hi and it dont matter which one is were and in hi range both are in hi range.There will be a switch on the power divider to lock out the shifter to were if the power divider is lock for in the mud then it can not be shifted into nothen but high range on both rears.This is called lock out. That way if one was in low and the other in hi and the inter lock was engaged then you would have two different ratio rears pulling against each other.

[theakerstwo]

Not too many years ago it was common for some guys to install a two speed rear in the rear housingand use it when not wanting to drop too many RPM and shift it to low.This was ok if used sparingly. If used to much it would eat the power divider because the newer power divider is not made to divide that much difference in ratios of the two rears.I think they ended up with something like a 200 RPM split.I do not think it would be a good ideal but was common to do so.That was a was of haveing a cheap 13 speed.

[HK Trucking]

Basily they are a two pair of two speed rears. But unlike todays eaton power divider the older power divider did have a rubber wiper pad to wipe the oil from the ring gear as it turned and would collect the oil up high and run oil into the top of the spider assembley to keep cool and lubed.Todays two speed can not be used as a three speed set up because the power divider will not lub the spider like the three speed did.This set up was at one time very common. Loike been said low range both it low and intermedit range one is in low and one in hi and it dont matter which one is were and in hi range both are in hi range.There will be a switch on the power divider to lock out the shifter to were if the power divider is lock for in the mud then it can not be shifted into nothen but high range on both rears.This is called lock out. That way if one was in low and the other in hi and the inter lock was engaged then you would have two different ratio rears pulling against each other.

Yes Glenn, I agree with you. I understand how the 3 speed rear setup worked.

What I was questioning was the post made by b6133994, as that post did not make sense to me based on what I know about the 3 speed rears.

.

[theakerstwo]

Yes Glenn, I agree with you. I understand how the 3 speed rear setup worked.

What I was questioning was the post made by b6133994, as that post did not make sense to me based on what I know about the 3 speed rears.

.

Yes he may have been reading in the eaton lit about them and i think they do mention lock out but as i was speaking of.Lock ot switch is for keeping them i9n same range when inter locked together.I like the set up but then the road ranger trans put them in the past.We had a carrier out of Dallas that ran all 3 speed rears. Even when the 13 speed was on the scene. Dont know why but they like them.