I bought a used 3.70 rear a few years ago when I had my 4.11s in the car. I blew the 4.11s up so I had to put in the 3.70s which I like even better. I rebuilt the rear, all new bearings and clutches and so on. Set up the pattern to which I thought was perfect. This is not my first set of gears I have set up. The rear is OK but when coasting or not on the gas I get a gear whine. When accelerating even slightly the gear whine goes away. I suspect either the pattern was slightly off or the used gears were just bad gears. When the top is down it is hardly noticable but I have been driving some with the top up and it is quite annoying and I just don't like things not right with the car.
Now do I yank it out and fix it (probably with a new set of gears) or just let it be. I have about 2500 miles on them and I don't fear them breaking it is just annoying.
Next question is do I go with a 3.55 gears since I reduced my tire diameter slightly with the 17 inchers. By reducing the tire dia. I increased the ratio by 2%. If I go with the 3.55s and the 17 inchers I reduce the ratio by 2% over the old 3.70 and and larger tires. With the Tremec in the car either one would be OK for highway. Just kicking this around for the last month or so. Just looking for some opinions.

 

I have the 3.36 in mine and it really makes it long legged. Probably not too good for autocrossing but they are fine for cruising.

 

Gordon, I just went thru this and we have about the same setup just different model cars. I have 3:70's with the TKO500 and contimplated the 3:55 when I just did the diff rebuild. As you posted in the other thread in my vette anything below 55 mph or so I'm lugging in 5th gear. I thought about going to 3:55 too for a better 1st gear launch however I thought it might be a little silly not being able to use 5th until 65-70 mph in my situation. I too have 17" rims with 225/50/17 with a rolling diameter of about 26.5". In the end I just replaced my old used up 3:70's with a set of Yukon gears and spiders from Randy's... Dave..

 

Gordon , try refilling your differential with Redline synthetic gear lube . This has removed gear whine for me a number of times on road race applications in both tranny and differential .

geo

 

Thanks Dave. I have been following your car and our setups are similar. I will probably stay with the 3.70s as most of my driving is around town and I don't take any real long cruises. Even with the new tires I am at 2400 rpm and keep up with highway traffic. A few years ago with the 4.11s I was at 4000 rpm to keep up with traffic . I'll probably just replace the gears. Do you have any noise with the new gears?

 

I still haven't gotten the diff back in, I just finished cleaning up the rear frame area yesterday along with all the bumper brackets and tank bracket. I plan on getting it back together hopefully by next weekend. I made a trip up to VA for thanksgiving 200 miles each way on I-95 with a posted 70 mph traffic moving at 80+ mph and I was only turning about 2300-2400 at 80mph the sound of the pipes was tolerable and the gas mileage was about 18 or so mpg... I'm positive I won't have any gear whine b/c the person that set it up for me is more of a perfectionist than me and it was setup perfect. Here is a shot of the wear pattern..

I think the only issue I'm going to have is a little bit of chatter b/c it was decided to go with 600 lb clutch springs for the posi. Strange gears are still not available but the Yukon's have been deemed to be just as good. The series three Eaton posi carriers are not available right now my friend Bill called a lot of places in the US and there are none to be had. Dave..

 

Dave, that pattern looks very good. I had that pattern on the Acceleration side but I did not check the coast side and that is where the noise is coming from. Where did you get the 600 Lb springs from. I might look into that while it is apart.

 

I installed a used 3.54 gear last spring and I had a medium whine noise at cruise. Most of the noise went away after the summer, around 6000 miles. Used gears have to wear their last pattern before they get right.

Stephan