C2 noise rear axle

[Joep F.]

Dear all,

I have wile driving forward, now and then a stump coming from the rear axle.It makes a noise and it can be felt as well. Its not permanent and neither always under the same circumstances like while turning or braking or something. It just happens a few times per day. It is like a sticky brake, coming loose after some driving. However brakepads are moving freely, so what can it be?

Thanks for your help,
Joep

[Wayne W.]

Re: C2 noise rear axle

Probably posi clutches. Change fluid and additive.

[Kent K.]

After following Wayne's advice

find an empty parking lot and drive at least ten figure eights of a fairly tight radius to work the additive in.
Regards, Kent #6201

[Joep F.]

Re: After following Wayne's advice

Thanks. However I did check the lubricant level in the axle. Its up to the level it should be. Shop manual advises not to change it. Does the lube deteriorate thoughout the times, that changing is needed? I am just afraid perhaps the axle yoke's or some bearings need changing.

[Kent K.]

If it is the differential positraction noise

you may not be driving enough. My '67 had similar clicking comming from the rear as you wrote about. Had the fluid changed and it went away. I have only driven about 750 miles since restoration in 1994.
Regards, Kent #6201

[John H.]

Re: After following Wayne's advice

Joep -

The blurb in the shop manual that says not to change the "lifetime" lube didn't contemplate a vehicle "life" of 40 years; if you don't have maintenance records for the car, assume the diff lube has been in it forever, and change it, using 80W90 GL-5 diff lube and the GM Posi additive, then do the figure-8 routine.

[Joep F.]

Re: After following Wayne's advice

Ok I see. I will change the lubricant asap. I do have the service history of the car, which states only a recommendation of "Speedy lube" in Manchester NH to change the differential oil in 1990. There is no record that it actually was done.
The car since 1985 has been driven 6.000 miles, out of which around 1000 during the last 10 years. Hopefully change the lube will help.
Thanks.
Joep