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GM Tech (Cam)
GM Tech (Cam), Chevy Technician
Category: Chevy
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Experience:  GM Grand Master Technician 2007. 11 years experience.
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1998 chevy tahoe: 4wd..seal..rear end..on gas peddle or just coasting

Customer Question

1998 chev tahoe, 4wd, replaced rear yoke and pinion seal, could not use old nut as reference to retighten at exact thread count, did not replace crush collar, hoping to get by without it, test drive revealed chatter, assumed pinion nut needs further tightening, tightened nut further, drag with yoke seemed tighter, upon 2nd test drive, no chatter, BUT rear end wining when I let up on gas peddle or just coasting, upon acceleration..sounds fine, suggestions requested before I readjust pinion nut
Submitted: 6 years ago.
Category: Chevy
Customer: replied 6 years ago.

1998 Tahoe 4WD 5.7


Already Tried:
all in original question
Expert:  frank replied 6 years ago.
You have a problem with the bearings.The torque spec on that pinion nut is 10"lbs of ROTATING torque -preload on the bearings for used- and another 15 lnch lbs for the case bearings and with out the tires on ots about 30 for used bearings.On new bearings its 30 inch lbs of totaion torque on just the pinion.If the ponion seal was leaking that bad the pinion bearings are shot.
Customer: replied 6 years ago.
No, perhaps I was unclear,

I have replaced the yoke with a new yoke and am adjusting the tightness of the yoke,

(I ran into a problem replacing u-joints and decided to replace the yoke due to tight working quarters),

I replaced the pinion seal not because of leaks, but only because I had immediate access to it, I reinstalled the yoke, and on day 1 I tightened it based on approximate thread count and took it for a test drive, originally it sounded fine and about a mile into the trip I heard some chatter and returned to readjust pinion nut,

I tightened pinion nut in small increments and upon test drive it sounds normal when accelerating, but as I ease off the gas or coast, I hear a whining noise,

The question is: have I over tightened the pinion nut, or am I still too loose?

I would prefer not adjusting the nut a third time until I have a better idea about the noise,
Again, when I ease off the gas or just coast I can hear a whining noise, please keep in mind I have not driven extensively during this process, only test drive, and nothing was wrong with the rear end prior to replacing u-joints, I don't expect that the bearings are toast,

PS wasn't looking for specs, just a diagnostic opinion, thanks









Expert:  frank replied 6 years ago.
YOU donot under stand-the nut is set to A ROTATION TORQUE of the yoke-NOT A TORQUE ON THE NUT.USually seating the crush sleeve works.YOU HAVE BEARING PROBLEMS.
Customer: replied 6 years ago.
Thanks for your quick response,

I completely understand about rotational torque and inch lbs, and the fact that a new seal might add additional drag, there was nothing wrong with this rear end when I started the u-joint job and I have no reason to believe anything was damaged during the installation of the new yoke and seal, I drive this truck and have a good ear for sound and there wasn't any previously,

I'm just hearing a new sound now during deceleration and questioning whether I should have tightened the nut further, but without changing the proper rotational torque drag,

I did not tighten this pinion nut to hit bottom/crush colloar, and it could definitely be tightened further without much resistance, just looking for some confirmation whether I should have tightened it further until I felt a solid bottom,

this is a problem resulting from assembly, not mechanical failure, yet.....
Expert:  GM Tech (Cam) replied 6 years ago.
I agree with everything Frank has said. Also, based on your description, I don't think you have tightened the nut enough. By the sounds of it, you left it too loose and the rear end started to chatter, which may have done some damage to the bearings. I would remove the drive shaft and lift your rear end .Grasp the yoke and see if it will move in and out or up and down. Also turn it. See if it is smooth. If there is play and it is smooth, tighten it till you get the proper rotating torque. If it is not smooth, you have rear end bearing damage as Frank has suggested. Let me know what you find.
GM Tech (Cam), Chevy Technician
Category: Chevy
Satisfied Customers: 27667
Experience: GM Grand Master Technician 2007. 11 years experience.
GM Tech (Cam) and 7 other Chevy Specialists are ready to help you
Customer: replied 6 years ago.
well, good call journeyman,

after Franks last message I felt the need to check and feel the pinion bearings, so
earlier this AM I checked the yoke and it had some play, I suspect the new yoke may not have seated completely when I had previously tightened the nut,

it was clear that the pinion nut needed further tightening,...it turned smooth, the previous test drive was quite short, apparently no immediate or obvious damage

seems and works like it did previously, nice and quiet,

you guys have a great day....

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GM Tech (Cam)
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