[pa69bird]

Looking for input on best gear ratio for my 69 rebuild, please.

Car came with 3:23 non-posi but plan to upgrade during resto. The factory manual I have indicates 3:55 is highest (lowest) available for M20, with 3:90 available for M21 only. Any experience on how a 3:90 might work with my factory transmission or should I search for a 3:55?

Thanks in advance.

[3tas4me]

Originally Posted by pa69bird

Looking for input on best gear ratio for my 69 rebuild, please.

Car came with 3:23 non-posi but plan to upgrade during resto. The factory manual I have indicates 3:55 is highest (lowest) available for M20, with 3:90 available for M21 only. Any experience on how a 3:90 might work with my factory transmission or should I search for a 3:55?

Thanks in advance.

What do you plan on doing with the car? The wide ratio trans and deep rear gears will give you a lower first gear. This combo will have no effect on the final drive as all Muncies are 1:1 in 4th gear. Your 3.90 rear gears will mean you are turning a lot of RPM on the highway. My '71 T/A with 3.42 rear end and 15" tires turns over 3000 RPM at 65 mph. I am tempted to put a 5-speed in it and put the original M22 on the shelf.

[pa69bird]

Thx. Car will be a weekend around town driver with minimal if any long highway trips. Keeping the car mostly stock including the 14" wheels.

[Scarebird]

I would stick with a 3.23 and a wide ratio for best overall use, especially with 14's.

[trmjr1]

I agree. Wouldn't go any higher than 3.36:1 if you plan on driving on the highway much..