standswithabeer

hello all,
bought my 79 c3 in october of 2013 with 52,100 miles on her, now has 53,300 miles. am pretty sure it's not 153K based on the condition of the interior. she needed carpet due to minimum driver's side wear at the throttle with little wear seen on the pass side, has just a bit of driver's side "butt rub", and other clues (ie rivets were drilled out for recent parking brake work). i have complete maint records going back to 1989. PO had some diff work done just before my purchase, and i have a question.

the records show that in 2004 at 51,870 miles the car was brought in to fully refurb the parking brake system, when the shop noted worn out rear wheel bearings and a diff leak. while the diff was out they noted worn splines.

so they rebuilt the parking brake system, replaced the rear wheel bearings and spindles, replaced all the diff seals, axle clips and axle shafts.

i have a slight whine in the diff at part throttle around 35mph. could this be caused by incorrect set-up when the seals were replaced? or is it likely the pinion set-up is incorrect, or there's a worn-out gearset?

after i have a second (or third) opinion on the noise i'm hearing, the diff will have to be pulled this spring. am wondering if i'm looking at just labor to reset the pinion or a new gearset?

many thx!
bob p

wombvette

The 79s were absolutely terrible for rear axle shaft wear. With that much metal ground up in there is is most likely caused by wear in the gear set. It might be possible to get it out with adjustment, but it is a long shot, and if it is no worse than you say, I wouldnt bother with it.

Solid LT1

If the shop changed the pinion shaft seal without disassembling the differential, they could only guess on proper torque of the pinion nut on reassembly. The bearing pre-load is a critical part of proper differential reliability. How talented are the guys working on your Vette?

standswithabeer

many thx for your replies! i lurked here for three years during my search for the perfect c3.

all the work done on the parking brake, spindles, diff seals and axle shafts was done about 350 miles prior to my ownership. i did call the shop that did the work, but is now under new ownership and i can't make arrangements to talk with the mechanic that worked on the car. he's gone.

i seem to have just enough previous history to trigger some questions. my plan is to get a couple of opinions locally on the noise, and the cost to make it go away if that's worthwhile. the nearby large chev dealer has a corvette expert of some repute. fwiw, i did change out the diff fluid, using the GM additive per the shop manual.

it's my understanding (after much reading on diff service/repairs in the chev c3 shop manual came with the car) that off/part throttle whine is caused by incorrect lash, while other noises are caused by incorrect bearing preload or bearing condition. there is no speed related rumbling.

so if during seal replacement only bearing preload is affected, the noise i'm hearing might have been there for some time? it's slight, only noticable on off/part throttle at 35mph or so. it's repeatable.