1974 rear end noise

**cams74** · 05-03-09, 08:15 PM

I have a 74 with 3.36 rear and it works fine until it warms up and then when I start out from a stop the rear end really chatters almost grinds it does not matter if I am turning, straight or in reverse. I have changed the oil and did add the posi trac lube, did not help. No highway noise, only does this up to about 10 mph. Any ideas?

**Patrick** · 05-03-09, 10:17 PM

Cams74,
As your question is about a 1974 Corvette, I'm moving this thread to the C3 Technical/Performance forum.

-Patrick

**GTR1999** · 05-04-09, 11:44 AM

You have clutch hammer. Since this is a 74, if still original, it has the snowflake clutches in it. If you sucked out the old oil and used 1 bottle of GM additive with new 90 wt or 85-140 wt gear oil and still have the problem, try another bottle. Use only the GM additive as it works the best.
If that doesn't solve it then you may have to drop the diff for a closer look. This is a lot of work so check the oil first.

**cams74** · 05-04-09, 11:50 AM

Thanks Gary, i will drop the oil and try it again. it has amazed me how it does not seem to get any worse.

**GTR1999** · 05-04-09, 05:55 PM

you don't have to remove all the new oil,the additive is only 4 oz per bottle. remove enough to add the oil and top off with gear oil. Drive it in figure 8's to work it in and see. Hope that works for you.