I have developed a horrible whine in the rear end of the corvette. Has been getting worse for a while now. When under moderate acceleration it is the worst. Coasting it is silent. Under heavy acceleration it is silent. Tried a differential fluid change and that improved it about 50% but its still bad, and I can feel the vibration in the shifter. So weighing my options. The Corvette recycling place near me in Kaysville currently has 2 good C5 rear ends.

The first is from a 97-99 car and has a 3.42 ratio. It is a very low mileage rear with only about 35K on it and the fluid in it looks pristine. Problem for me is the earlier case appears to be a weaker design. The bracing molded into the case on the newer rear ends seems more robust and definitely has more bracing in it. I figure if Chevy changed that in the later cars there is a reason.

The second is from a 2002 but has a 3.15 ratio which I believe means it came from an automatic car. Good in one sense as I tend to believe an auto was probably driven differently, bad in that I think my stock ratio is 3.42 so a 3.15 would slow me down. And its not like I need a taller rear end. As it is my car is turning around 1700RPM at 80MPH. So this rear has the same case as the current rear end with the improved case design, but with a taller gear ratio. It has about 55K on it but also looks very clean.

My third option is to have my current rear end rebuilt. I have no idea what I should expect to pay for that but I am betting its quite a bit more than the $500-$600 I will pay for a used rear end to swap in. At least I would know for sure what I had and know it is all new and good parts. I would also have the option of putting in a 3.73 setup, but honestly don't know if it is enough different from the 3.42 to make it worth the difference.

Anyone here had experience with this? Any advice to offer?

Frankly I am surprised that the stock rear is getting noisy at 93000 miles. I don't beat on the car. I have had it on a track 3X, but not constant abuse. Once was the 1 1/2 mile run at Mojave, and twice at a private 2.5 mile course in southern Arizona. But again, not ragging the thing out. Most of the time it is a weekend cruiser.

 

Yeah it is nice to have the beefier case I guess but have you read or seen anywhere that the earlier cases were problematic or cracking or anything? You said you mostly adult drive the car anyway. Just my thoughts to maybe help you sort out your process.

 

I usually use it as a weekend cruiser. It has been to the track 3X in 3 years. So maybe you're right. I have not seen anything about them being problematic. I just tend to think if GM (or gettrag) changed it up maybe there was a reason...

decisions decisions...

 

not sure what year your car is but do you have a 3 rib case?... get in touch with Rick at rkt56, he has a lot of experience with swapping c6z differential guts into the c5 case and that would be stronger than what you have now for not a ton of money... rpm would be another place to ask, they assembled the diff in my car (I supplied the parts) and their labor was very reasonable... you can't go wrong with either of those companies in my opinion

 

Thank you. Yes. I have a 3 rib case. The one from the 97-99 is a one rib. I think the C6 internals may be a great idea. Where can I source what I need?

 

02 Z51 6 speed

 

I pinged Rick and will wait to hear from him. Thanks for the direction.

 

Good conversation with Rick. Think I'm going to send my rear end to him, and have C6 Z06 guts installed. Probably 3.90 ratio.

 

My personal taste is that the 3.42 is too much gear, I'd opt for the 3:15s if given a choice. But, that said, if the 3.42s are working fine for you now, why change?

Imo, 1st gear in a Vette is basically worthless, especially if you've added some HP/Torque. Take an LS3 in a M6 C6, 1st gear is a waste. The ONLY thing it could be good for is if you launch your car all the time. I don't do that, I don't care if it's a drag race machine, so I'd opt for gears that would make the car more drivable. Your 3.90 option does not sound like something I would care to drive. Even 3.73's, WAY too much gear for my taste. But to each his own.

As cheap as a replacement rear is, I'd get the working rear and bolt it in. No messing around with gear lash setup in the diff. Given that yours is whining bad, I wonder if that's not the cause of the problem to begin with. They are not notorious for just 'wearing' out.

(edit to add),

C6 ZR1s came with 2.73s. Just sayin...

My car has 3.15s in it now.

 

I'm pretty sure all manual c5's and c6's regardless of trim level come with 3.42 rear gears and to my knowledge there is no aftermarket gear set for the c6 z06/zr1/manual grand sport

 

With the 3.42 now it is turning 1700 rpm at 80. Going between Phoenix and SLC, which I do a lot, 80 is a pretty common speed for me. So on the open road it is great right now. Issue is around town, which I also do a lot, 6th gear is useless. I figure the 3.90 is a good compromise. Should still not be much north of 2100rpm at 80, not bad. Probably more in the power band anyway...

I don't launch it all the time thought, so maybe you have a point. I am sure I dont want to put anything lower than stock thought. That is for sure. If I did 6th might as well not be there.

I do wonder about the cause because as you mention above, I have not heard about the rear end being a real weak point for these cars, and mine doesn't have super high mileage or anything, and it has been mostly driven in an adult manner.

 

Rick from rkt56 tells me it is an option with the C6 Z06 innards, and as he will likely be doing the rebuild for me I figure he probably knows what he has available. Everything I have found about him on the board has been pretty positive.

 

in a c5 case it is possible, I was referring to the c6z/zr1/grand sport cases

 

Gotcha. I didn't think changing cases was an option, that I had to be satisfied with just chaiging the bits inside...

 

if you want to use a newer style case you will need to swap in the tr6060 trans as well because those mount up differently, 8 bolts instead of the 5 that hold the c5 trans/diff together... you would also need a c6 rear cradle, conversion mounts, c6 rear lcas or coilovers, and a few other small modifications... Rick can also tell you about those swaps, he specializes in them... I swapped mine over to c6z stuff but for the power level you are at and what you use the car for it most likely wouldn't be worth the money, it isn't a cheap swap