Need Driveline Diagnostic Help

[MMLX89]

Long story short (ish), I bought a 72 C-10 Short bed recently. Drivetrain is late model 5.3l backed by 4L65E. I drove it for about 150 miles with no issues, until one day the drivetrain locked up on me (grinding,whining, then failure). I dropped the trans pan to see no metal, then looked in rear and saw it was almost dry, and metal in the case.

Took it to a shop where rear end was rebuilt with 373's, and then determined that as part of the failure it took out the sunshell in the trans. I then replaced the transmission with a re-manufactured unit from Geared Up Transmissions out of Florida.

Got the truck back and there is a noticeable whining/grinding on deceleration and even more so when turning right. Shop says the driveshaft is too long, so I had it shortened. Problem is still there....

They are now saying it needs a 1 piece DS, but I don't believe a deceleration and right turn problem is the driveshaft. I don't want to throw any more money at the issue without concrete details. My gut feeling says axle bearings could be responsible for the noise. Does that make sense as the next logical place to look?

[LockDoc]

Originally Posted by MMLX89

Long story short (ish), I bought a 72 C-10 Short bed recently. Drivetrain is late model 5.3l backed by 4L65E. I drove it for about 150 miles with no issues, until one day the drivetrain locked up on me (grinding,whining, then failure). I dropped the trans pan to see no metal, then looked in rear and saw it was almost dry, and metal in the case.

Took it to a shop where rear end was rebuilt with 373's, and then determined that as part of the failure it took out the sunshell in the trans. I then replaced the transmission with a re-manufactured unit from Geared Up Transmissions out of Florida.

Got the truck back and there is a noticeable whining/grinding on deceleration and even more so when turning right. Shop says the driveshaft is too long, so I had it shortened. Problem is still there....

They are now saying it needs a 1 piece DS, but I don't believe a deceleration and right turn problem is the driveshaft. I don't want to throw any more money at the issue without concrete details. My gut feeling says axle bearings could be responsible for the noise. Does that make sense as the next logical place to look?

I would think axle bearings would make noise all the time not just on deceleration. Sounds like something is still screwed up in the carrier to me....

LockDoc

[MMLX89]

I think it's just more pronounced on decel because of the exhaust maybe. I don't disagree with you though, but they took it apart twice and swear everything internally is good to go.

[Redline novdog]

IMO. sounds like rear end . i would guess ring and pinion are not set right (or not so good gears). should be able to see the pattern wear on the ring and pinion after a few hundred miles(if it makes it that far). If you have warrantees on all that you replaced and not sure whats wrong drive it awhile. The problem will come to the surface!
Is this this truck have a posi trac diff?? Might need posi clutch lube in the gear lube.

[ss454conv]

I agree. Sounds like ring and pinion. Had a similar situation on a Chevelle. It was not properly setup.

[Alignman88]

Ask around about who is the best high end repair shop, that have real technicians, and ask if they have an EVA Meter (Electronic Vibration Analyzer) and a sharp guy to operate it. You can drive the truck while they gather data with a magnetic accelerometer placed in different locations as you drive around exposing the issue.

A drive shaft vibration will typically throw a P2 Propshaft second order harmonic, can't remember what frequency range maybe 150-200 hertz? A differential will typicall throw a harmonic in the 250-350 hertz range? The right guy can eliminate throwing hours and dollars at something and just diagnose it correctly.

Good luck finding the right people, good technicians still exist.

[MMLX89]

The main reason I don't believe it's DS related is that the issue wasn't present before the rear end locked up. The fact that the rear end was dry when it failed, it leads me to believe that the bearings were burned up since the are lubricated by the diff oil.