Rear axle ratio in 1978 corvette?

[muddbros]

Hello,

I've got a 1978 L48 that has been "converted" into an L82 by the previous owner (dual snorkel, updated headers and cam, and dual exhaust) I drove it up North about a week ago and started noticing a whining sound from the rear end. I decided I better take it to someone who knows what they are doing (my Parents mechanic who I know I can trust and who builds his own race cars). He's going to drop the rear axle and check out the rear end to see what is up there (as well as go over the entire car to give me a list of stuff to work on over the Winter). I'm wondering while he has it apart if I should consider (or if it even possible) to change the ratios of the rear end. The car doesn't have the M21 (close ratio) and I'm wondering since it has much more power than it did originally if I should consider modifying the ratio in the rear since I want to keep the tranny matching numbers (Standard 4-speed manual). Sorry in advance if this is an ignorant question.

Thanks!

 

[6880 Mike]

You can change ratios. Pick the one you want and have your machanic make the swap when he R&Rs the differential.

 

[Vettehead Mikey]

What ratio do you have now and how do you intended to drive the car? M20, M21 and M22 all have the same ratio 1:1 in top gear BTW.

 

[GTR1999]

Probably has 336 or maybe 355's. For years the 336 was the std ratio with the base eng WR 4 speeds. Some use 308s other were 355 or 370.
You may want to look up my threads on rebuilding diff's before you commit to a job, it may save you some $$.

 

[muddbros]

Probably has 336 or maybe 355's. For years the 336 was the std ratio with the base eng WR 4 speeds. Some use 308s other were 355 or 370.
You may want to look up my threads on rebuilding diff's before you commit to a job, it may save you some $$.

Sorry, should have provided more info. It has an M20 and the rear end ratio is currently 336. It took a little while for him to get to it since he isn't charging me much, but he opened it up today and said things were a bit "chewed up in there"... he said he thinks the guy who rebuilt it recently didn't set it right. He already ordered the parts was advised by the GM guy he ordered them from to keep it at 336. I'm not so sure how a 308 work out anyway in the top gear (good point Vettehead Mikey). Fortunately, it looks like there is nothing wrong with the transmission... really nice to keep all the numbers matching.

The best thing out of this, I'll have had a guy I know I can trust go over the whole car and give me a good list of things to work on through this coming winter.

Thanks for the feedback everyone!

 

[GTR1999]

I would find out just what chewed up means. I've rebuilt a lot of these and have had many odd ball finds once the cover was off. Most of them were caused by previous rebuilders.