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Loud Hum Noise when coasting

andyh1956

Member
40
22
8
Location
kosciusko ms
Try removing the rear driveshaft. Tape a zip loc bag over the transfer case rear output shaft housing where you just removed the driveshaft yoke. Put the transfer case in 2WD High & drive the truck. If the noise is gone then the rear diff is suspect. If it is the same then the problem prolly is with the transfer case or transmission.
Oh yeah be SURE that 208 is FULL of ATF!
 

simp5782

Feo, Fuerte y Formal
Supporting Vendor
12,125
9,385
113
Location
Mason, TN
Do you have an infared temp gun? Go for a drive for about 10min of road use then Use it to check temps on the transfer case output, the u joints, pinion nut/gear and the diffs. Just shoot it around. You will see a higher temp if you come across a part that is wearing more than normal
 

Matt5

Banned
214
3
0
Location
NY
FLIR camera if you got some $$$ thing can be VERY VERY useful to do diag... can get the phone version... can also pick up a snap on camera cheap on ebay...
 

cucvmule

collector of stuff
1,155
591
113
Location
Crystal City Mo
Great Idea simp. I have a voltmeter that has a lead on it to check for temperatures by touch, works good, I use for temp check on header tubes.
 

erasedhammer

Active member
843
60
28
Location
Maryland
Try removing the rear driveshaft. Tape a zip loc bag over the transfer case rear output shaft housing where you just removed the driveshaft yoke. Put the transfer case in 2WD High & drive the truck. If the noise is gone then the rear diff is suspect. If it is the same then the problem prolly is with the transfer case or transmission.
Oh yeah be SURE that 208 is FULL of ATF!
The rear output seal of the transfer case has been damaged by the rust on the slip yoke. Judging by the ground it didnt loose much fluid, which could mean the leak wasnt that bad or it was already very low on fluid.
 

andyh1956

Member
40
22
8
Location
kosciusko ms
Yes. There is a spacer between the rear pinion brgs called a "Crush Sleeve" & as the pinion nut is tightened the sleeve "Crushes" down until no play is left between the brgs & you stop at a certain preload measured with a beam type torque wrench.
Caution! Over tightening the pinion nut can "Lock" the brgs by "Over Crushing" the sleeve & when you try to loosen the nut the brgs will go floppy because the sleeve won't "Rebound" back to it's previous length & the only repair is to install a new sleeve & start over.
 

erasedhammer

Active member
843
60
28
Location
Maryland
Yes. There is a spacer between the rear pinion brgs called a "Crush Sleeve" & as the pinion nut is tightened the sleeve "Crushes" down until no play is left between the brgs & you stop at a certain preload measured with a beam type torque wrench.
Caution! Over tightening the pinion nut can "Lock" the brgs by "Over Crushing" the sleeve & when you try to loosen the nut the brgs will go floppy because the sleeve won't "Rebound" back to it's previous length & the only repair is to install a new sleeve & start over.
Recently installed a new nut and crush sleeve. Torqued it down pretty good, but there is still some play left in the pinion.
Small leak, now out of the input seal. Maybe lost 2 ml of fluid.
 

Chaski

Active member
684
56
28
Location
Burney/CA
Recently installed a new nut and crush sleeve. Torqued it down pretty good, but there is still some play left in the pinion.
Small leak, now out of the input seal. Maybe lost 2 ml of fluid.


I think you found your problem.

Stop driving it now- you are currently damaging your ring and pinion along with the pinion bearings.

What led you down the path to replace the crush sleeve in the first place?

FYI- when your replace a crush sleeve the amount of torque that must be applied to the pinion nut to start crushing the crush sleeve can be quite high. Like a few hundred foot pounds. Once it starts deforming it gets a little easier, and you slowly tighten it up until nearly all the play is removed. Once you get to that point work in even smaller increments (maybe turn it 30min at a time if it was a clock). Checking between every small pinion nut tightening operation with a dial or beam type inch pound torque wrench. Continue until the drag (preload) is within specification. Be careful not to overshoot, you cannot go backwards.

Download and read the rear axle section of the TM.

I find that it is easier to remove the pinion carrier from the 14 bolt axle and do the work on the bench, with a very sturdy vice or use a hydraulic press to hold everything while torquing the daylights out of the pinion nut.
 

erasedhammer

Active member
843
60
28
Location
Maryland
I think you found your problem.

Stop driving it now- you are currently damaging your ring and pinion along with the pinion bearings.

What led you down the path to replace the crush sleeve in the first place?

FYI- when your replace a crush sleeve the amount of torque that must be applied to the pinion nut to start crushing the crush sleeve can be quite high. Like a few hundred foot pounds. Once it starts deforming it gets a little easier, and you slowly tighten it up until nearly all the play is removed. Once you get to that point work in even smaller increments (maybe turn it 30min at a time if it was a clock). Checking between every small pinion nut tightening operation with a dial or beam type inch pound torque wrench. Continue until the drag (preload) is within specification. Be careful not to overshoot, you cannot go backwards.

Download and read the rear axle section of the TM.

I find that it is easier to remove the pinion carrier from the 14 bolt axle and do the work on the bench, with a very sturdy vice or use a hydraulic press to hold everything while torquing the daylights out of the pinion nut.
Previous pinion flange had the u joint bolts snap off in the threads. Replaced the whole u joint, flange, nut and crush sleeve.

This is on a m1028, with the Dana 70hd axle, not the GM axle.
 

Chaski

Active member
684
56
28
Location
Burney/CA
Previous pinion flange had the u joint bolts snap off in the threads. Replaced the whole u joint, flange, nut and crush sleeve.

This is on a m1028, with the Dana 70hd axle, not the GM axle.

That makes it a little less fun since you have to do it under the vehicle instead of on the workbench.
 
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