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97 Suburban differential disaster

razur65

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From the "Don't worry about that noise, it's nothing" department... this has been a busy, busy summer. Between work making money, house renovation, new heat pump install, replacing windows, replacing carpet with flooring, and putting some work into the 'Burban, taking it off the plow truck roster, replaced both front CV shafts, front wheel bearings, new front brakes, removed the plow pump, new AC compressor back in it's place. It started to whine from the rear end, checked fluid, it was full but dark. Told Mrs. Razur I would get fluid changed, should be fine to drive for now, famous last words! Broke down 5 miles from the house when she was on her way to her sisters house, and boy was she mad! So dragged it back to the barn on the trailer, opened it up and found the pinion bearing was destroyed. Some damage on pinion teeth, didn't look terrible. So I tried to cut the budget and just did a bearing kit, wrong answer. I put it back together and used a 4" grinder with a cut-off wheel and flap disc to try and clean up the gear damage... yeah, no, had the worst noise ever.
So break out the Master Card, $800 in more new parts later got me some good stuff, spent all of a Friday night half way to Saturday morning putting this back together the right way. Patience is truly a virtue in setting these correctly!
Lessons learned: 1. Don't ignore the noise and, 2. Do it right the first time because it's gonna take more time and money to do it a second time!

Sub Diff_1.0x.JPGT

"Don't worry about the noise, we drove the dually for two years with the same noise and it was fine..."
Notice the broken cover bolt upper right, ahh good times, good times!


Sub Diff_1.01.JPG

Some intense online shopping looking for best options for the money. Bumped up ratio to 3.73 from 3.42 to help compensate for 18's on Moto rims.

Sub Diff_2.0x.JPG

Heated new ring gear with shop heater, slid right onto carrier nicely!

Sub Diff_2.IX.JPG

New Auburn assembly fit nice and snug, added Yukon Gear bearings after, used the main shim assembly set included with bearings and had .007 backlash right from the start!

Sub Diff_2.01.JPG

Without that $500 set up tool it sure takes a lot of trial and error to get the depth set correctly!

Sub Diff_2.XI.JPG

I can't remember if this was final set or if I did one more, I know the last pattern I had looked exactly like the pic in the Motive Gear instructions and boy was I happy to see that!
 

THEFERMANATOR

FRANKENBURBAN
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Make sure and check your critical speed rating on your driveshaft. GM was known for using the smallest diameter shaft possible. If you re-gear and go lower, you could put yourself into a situation where your driveshaft will pretzel from the extra rpm's. I know I started to regear my tahoe from a 3.42 to 3.73 until I looked at the shaft, checked the length, and found I had zero room to increase shaft rpm's without hitting a critical speed failure in the shaft at the vehicles 98mph speed cutoff. Not saying this is an issue for you, but you should always check whenever you re-gear.
 

razur65

Member
Messages
49
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96
Location
Central NY
Make sure and check your critical speed rating on your driveshaft. GM was known for using the smallest diameter shaft possible. If you re-gear and go lower, you could put yourself into a situation where your driveshaft will pretzel from the extra rpm's. I know I started to regear my tahoe from a 3.42 to 3.73 until I looked at the shaft, checked the length, and found I had zero room to increase shaft rpm's without hitting a critical speed failure in the shaft at the vehicles 98mph speed cutoff. Not saying this is an issue for you, but you should always check whenever you re-gear.
Thanks Ferm, I was thinking about having the driveshaft checked over by a shop because there is a driveline vibe from somewhere. With all the work I've done this summer, front shafts, wheel bearings, and now rebuilding the rear, new axle bearings too, I still get a steady low vibration at highway speeds, not terrible, just annoying. When I got the truck a few years ago it had the same vibe, I started looking for cause and replaced U-joints and took a drive shaft and transfer case from a low-mileage (75k) parts donor I had. Vibration was unchanged so I thought maybe it was from the front. Needless to say I've been replacing worn parts (with new, donor is long gone) as I go along. The truck is stronger now but still has that irritating rumble at highway speeds.
 
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