TR69

MY 69 4spd seems to have a noticable "clunk" or maybe scraping when at low speed, turning and shifting...it also seems to be there at higher speeds when turning> Is is possible that he half shafts are making that noise or could it be in the tranny..?? thanks for any help at all....

ACECO

Could be the rear diff. This is a very common issue with C3 posi units if the fluid hasn't been changed in years. You get a clunking, grinding, chattering, scraping, etc noise when turning.

Assuming it's not completely worn out (usually not), a simple removal and replacement of the diff fluid along with a couple bottles of GM posi additive will usually quite a noisy rear down. Just get a suction pump and extract the fluid thru the overflow/check plug hole and replace the new fluid thru same. Add two bottles of GM posi additive and then top it off with whatever diff oil you choose until it just starts to run out of the hole.

After you change the fluid, go to a empty parking lot and do a bunch of tight figure 8's to work the new fluid into the posi unit.

Hope this helps. Good Luck!

TR69

Thanks, I did just have all the fluids changed and come to think of it I believe that it is worse now, maybe that narrows down the possibilities...

ddecart

Yup. Try putting in some of the GM Positraction additive. be careful though, the stuff smells absolutely nasty!

When I had my diff out, it was noisy until I put that stuff in. Quieted it right down.