Kens94

I'm close to pulling the trigger on changing out my 2.59 gears for 3.07 I've never done a gear change and was wondering for those of you that have paid to have it done, what can I expect cost wise? Since I want to keep some highway MPG is the 3.07 ideal or does someone have a better idea? Thanks in advance for your thoughts! Car is a 1994 auto stock except muffler eliminators.

1994BlackRose6spd

I have never had an A4 Corvette. I have had a 94 Z28 with an A4. I have 3.45's in my 94 6 spd car and will go to 4.10's if I change my gears.

I have had 2 cars that I changed the ring and pinion on.

1. 1995 Mustang GT. I went with 3.73's and was happy. My roommate in college also had a 1995 Gt and had 3.55's and they were about the same. I would not have put 4.10's in that car or have gone more than 3.73.

2. 1999 Cobra. I put 4.10's in the the car and loved them.

I didn't experience massive drops in MPG's. The car accelerated more easily and I didn't have to push the gas down as hard to keep up with traffic. I had all the same fears. What if I get to much gear or to little? What will happen to my MPG's?

The easy answer is go for it!! Also, I would absolutely put in more gear. 3.40 - 3.70's would have been ideal for my old Z28. I would not go past 3.70's for your car. All of the old 5.0 mustang's with A4's went to 3.55 - 3.73 for the perfect ratio.

bob arrowsmith

i had it done when the engine was stock, made a good difference , you will loose some top end shift point at a lower speed then i went with a 383, cam and rr s, gained a bunch of torque , had a tune to shift at 6200, i am a very conservative driver but now and then its a hoot to let the horse out, as far as cost have someone who knows there business with replacing rearends,, should run somewhere around 1500 bucks. give or take.

bjankuski

Honestly you could save money by just buying a used dana 36 3.07 center section and swapping that in place of your 2.59 center section. Get it done in 4 hours and probably cost $300.00.

Dt86

That's what I did. Paid $200 for the used diff and whatever the gasket, oil and lsd fluid cost.

1994BlackRose6spd

I paid less than $500 total for the GT (Motive Brand 3.73 Ring and Pinion, labor, fluid, and speedo gear change to 13 tooth) and about $580 for the Cobra (I asked for the Ford Racing Performance gear but I couldn't tell you if they used that or Motive Gears at the speed shop I went to. I used a Hypertech programmer to adjust the MPH with the Cobra). You definitely want a quality job done so the backlash is spot on and the gears are quiet. I would ask around locally. Join a Corvette club around Columbia and see who has had this done and how they feel about who they used etc.
Best of luck to you. I have no experience with having this done on a GM vehicle.

drcook

3.07 will work pretty good, that is what I have. there was a recent thread about "performance rear end/ration" here on the forum. With a 3.07 you will be right around 2000 rpm at 70 mph, which is what most of the responders said.

with the dang low gear in the A4's too much stiffer for street driving will hurt your mpg's and also on the other end, push the rpm's up.

you can kinda figure out a ration by putting your rpm's over 70 -vs- 2000/70 for the 3.07's or vice versa. if I had your rpm's at 70 we could figure out pretty closely what the difference in rpms is for the next gear up, which is 3.54's IIRC.
(for the Dana 36).

make some phone calls to the Corvette recyclers. As the other posters above said, you can probably find a 3.07 differential and just swap it in.

C409

..... Go big or go home ! Put some 3.73's in it and just try to wipe the smile off your face ! .....

pologreen1

Someone selling d36 with 3.73 in it here. Just put it in.

Mike Kamholz

I did the whole bat wing and did swap took 3 hours but nor very hard. Cost me a total 300$. Love the pick up it has now. Went from 2.59 to 3.07.

sprink94

Did you have to re program the PCM for the speedometer and transmission?

FASTAZU

I went from 3.45 to 3.73 and love it not a big change but just right for my driving style. I also boosted HP by 100+ at the same time

A Peter C4

How did you correct speedometer?

Corvette40

I used Abbott’s Electronic Ratio Adapter. Mounted it behind the bread loaf.

STL94LT1

10 years ago I paid $350 for gears and $350 for a complete turn-key install.

Tunercat makes it easy to correct the speedo and shift points.

BlackRocket

Whatever you do...DO NOT re-use the stock rear end differential to bat wing cover bolts. They are slightly triangular from the factory and will strip the aluminum in the differential when torqued down. GM made them this way intentionally so they cut the threads at the same time they were installed. Just go to a good hardware store and get the same exact size/length metric flange bolts.

aDigitalPhantom

Last year I paid about $700 for 4.10 gears (D44), and for a shop to setup the gears. I removed the differential, and that's all I took to the shop. When the gears were changed I put it back together. I had the speedometer corrected in the PCM.

Cool Runnings

I have 3:07 in the 92 auto, 2,000 rpm's is about 60 mph. 70 is about 2,200 rpm's

drcook

Back in your thread about "performance axle", another board member's car does about 2K rpm at 70, but he didn't say auto or stick

https://www.corvetteforum.com/forums...ance-axle.html

It would be interesting to have a poll of folks who have the 3.07's in an auto car, separated by the type of trans (mine is a 4l60E due to being a '96) to see who does what. Mine has a stock converter also.

Kens94

Good info everyone! I've got a good idea what it will run me so I can save up for it. Someone mentioned that the speedo will need to be adjusted. Is this done mechanically or by the cars computer? Last one I did was a speedo gear. Thanks!