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rear end trouble


bubbamobilin
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Been having a growl noise coming through the trans almost like the noise one makes when you accidentally run with the airbags deflated. We jacked it up today and ran it with the wheels off the ground. The rear/rear makes more noise than the front. Pulled the side cover off but no smoking gun. No gears messed up, not a lot of excess metal. Ran it again. Took it up to 70 mph on the jack stands. Checked the temps with a heat gun. Front/rear 103-105, rear/rear 123-125. Only ran it about 5-10 minutes. Is this temp differnce normal, or is that my smoking gun?

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Make sure the air bag hright is set as it should be.You cant be off very much or damage will happen..

We did check the height. It was out about 3/8 of an inch. Is that enough to cause damage? Now that the height is correct the growl is worse. Should I be looking at the tranny?

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is that mack rears or vendor? if the growl change with height I would suspect a bad u-joint. maybe the angle of the driveline is incorrect.

Mack rears. 3:87 ratio. I've been told that 3:87's and 3:65's are weak gear sets and that I need to replace with 3:86's because they have more meat on the gears. I also just put a new set of drive tires on a few months ago, noise started shortly there after. Seems like the last time I changed drive tires I had a rear/rear go bad.

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Power divider is a good suspect.

When you got new tires, did you put them on the same axle, or move them around?

Front drive is turning different speed from rear drive=power divider.

BUT, check U-joints, carrier bearings, pinion.

Hell, pull the axles too

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Power divider is a good suspect.

When you got new tires, did you put them on the same axle, or move them around?

Front drive is turning different speed from rear drive=power divider.

BUT, check U-joints, carrier bearings, pinion.

Hell, pull the axles too

Thanks hatcity. When I put the new tires on I put all 8, same brand name and everthing. I'm going to drop the drive shaft today and run it just to eliminate the transmission as a suspect. We rebuilt the tranny back in April so I don't think that is the problem. It shifts really good and does not bind up in any gears. We replaced the two carrier bearings on the drive shaft a few weeks ago and that made no difference. I wish something would just explode so I would know what to fix, but NO I gotta chase ghosts!!!

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  • 4 weeks later...

if you put lug tires on it is seemed to get worse more than likely one of your tandems is running out of whack. and what you hear or feel is the friction between rubber and road. If one tandem is trying to go one direction and the other is going straight you will get this.. can you feel it in your seat or in your hands more??

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  • 2 weeks later...

Mack rears. 3:87 ratio. I've been told that 3:87's and 3:65's are weak gear sets and that I need to replace with 3:86's because they have more meat on the gears. I also just put a new set of drive tires on a few months ago, noise started shortly there after. Seems like the last time I changed drive tires I had a rear/rear go bad.

I got the same info on my 3.65's, they have the smallest gears in Mack rears, I think Im going to swap to 3.86 rears too, they have the same ring and pinion as a 4.17,4.42,4.64 supposedly, the top gears are the only difference. I know that unless the power divider is locked your putting all your power to the rear axle and it will run hotter on the road than the front, at least mine always have, seems like my old RW ran about 130-140 degrees hauling gross on the interstate in the summer, the front was always around 100. Its interesting you got the same info on the rear gear sets, Bill @ Winrock truck parts told me about it, hes supposedly going to find me a set of 3.86 or 4.17 carriers to swap for my 3.65's.

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Just our of curiosity you haven't been running with a big difference in drive tire wear from front to rear and side to side have you? I have seen some issues with Mack rears that were supposedly caused by running tires that were almost gone on one axle and new on the other, cant be too far off with Mack rears the way the power divider and carriers are set up, definitely not from side to side.

"Any Society that would give up a little LIBERTY to gain a little SECURITY will Deserve Neither and LOSE BOTH" -Benjamin Franklin

"If your gonna be STUPID, you gotta be TOUGH"

"You cant always get what you want, but if you try sometimes you get what you need"

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if you put lug tires on it is seemed to get worse more than likely one of your tandems is running out of whack. and what you hear or feel is the friction between rubber and road. If one tandem is trying to go one direction and the other is going straight you will get this.. can you feel it in your seat or in your hands more??

With the tandem out of whack thing being said, would it be possible for a u-bolt to be stretched and letting the rear walk a little bit? In theory, that would also make the tires drag a little and give the rubber on road friction noise. I'm not sure, just spitballing. Good luck

Being in the process of getting your CDL's is like sitting on death row...

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  • 2 weeks later...

If you can get it loaded, pull forwards and backwards 25-30 yards and then measure from center of steer to center of each drive axle, with unit on the ground do not jack up... the pulling forwards and backwards should get it in the normal running position with the exception of the movement it will have while gassing on it with rubber on the road. see what your measurements are and let me know. what you dont want is one side being spot on and the other side being off 1/4 or so off. this will cause irregular tire wear, and also the driver will have to fight the wheel all day. i do adjust my parameter for the alignment on my trucks according to the average MPH the truck runs, because it takes different dynamics for lower MPH trucks. Hope this helps

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