Should I change gears ?

[Ron H.]

I have a 65 vert, with an L76 motor. Our club does a lot of long range trips, which require hours of high speed interstate cruising. I am considering swapping my stock 3.36 gears for stock 3.08 gears. I can cruise at 70-75 mph turning about 3400 rpm's. If I can reasonably expect that to drop to 2500-2600 rpm's, does anyone think this will have some long term relief on the motor ?

If so, any reliable sources for replacement gears ?

[William C.]

Re: Should I change gears ?

3.36 to 3.08 is about a 10% change, so expect about 3000 with the change. Per the '67 Sales Brochure, 3.36-23.1MPH/1000, 3.08=25.6MPH/1000 so you can work it out from there, about 10% change for a lot of $ and effort, plus don't forget the change needed in the trans to keep the speedo accurate. L-76 will hum @ 3500 all day long.

[Kenneth B.]

Re: Should I change gears ?

I agree. Not enough difference to change. Engine will run fine at 3600 RPM. You would get a little better gas milage with a 3.08 but les of the line speed.

[Michael H.]

Re: Should I change gears ?

I have a 65 vert, with an L76 motor. Our club does a lot of long range trips, which require hours of high speed interstate cruising. I am considering swapping my stock 3.36 gears for stock 3.08 gears. I can cruise at 70-75 mph turning about 3400 rpm's. If I can reasonably expect that to drop to 2500-2600 rpm's, does anyone think this will have some long term relief on the motor ?

If so, any reliable sources for replacement gears ?

Ron,

Something doesn't sound right here. 70-75 MPH at 3400 RPM sounds more like you have a 3.70 rear. Not a 3.36. Have you checked your actual speed with a GPS? 70 MPH at 3500 RPM would be typical of a 4.11.

[William D.]

Re: Should I change gears ?

I agree with Mike. I have a 65 with L76 but with 3.70 rear. 3500 at 70mph. Car loves it!

Bill

[Michael H.]

Re: Should I change gears ?

Here's a link to a differential/MPH calculator that should show speeds at RPM. I think 26" for tire diameter would be about right.

http://www.angelfire.com/fl/procrastination/rear.html

[Gary R.]

Re: Should I change gears ?

It would not be worth it if you change from 336-308,s if that is what you have. I agree that you have to determine what you really have, unless you have the history of the car you may not have the original diff in the car. Sounds like you could benefit from an OD transmission more then a gear change for your application but those are $$$.

The only R&P set I use now are Tom's (US Gear) they are still made here in the US. The other vette gears out there are now imported. What do you have for a trans? That engine might not be the best if you have a CR and go to 336 or 308. A lot of those came with the CR & 370's.

[Ron H.]

Re: Should I change gears ?

It would not be worth it if you change from 336-308,s if that is what you have. I agree that you have to determine what you really have, unless you have the history of the car you may not have the original diff in the car. Sounds like you could benefit from an OD transmission more then a gear change for your application but those are $$$.

The only R&P set I use now are Tom's (US Gear) they are still made here in the US. The other vette gears out there are now imported. What do you have for a trans? That engine might not be the best if you have a CR and go to 336 or 308. A lot of those came with the CR & 370's.

Unless someone swapped out the gears, they are 3.36 gears. I dont want to spend the $$ for a tremec OD, plus want to keep originality of the car.

[Don H.]

Re: Should I change gears ?

I have 3.36 and powerglide in my '65. I have had to cry "uncle" on NCRS Road Tours when cruising high speed (well in excess of the speed limit) in hot weather with the AC on. My temp kept slowly climbing - most of the other Corvettes were C-many and had no problem. They slowed down and I had no problem. Since we get where we are going in plenty of time, I feel it is not too much to ask. Don H.