How can I tell "which" transmission I have?

[Jim F.]

Got a 1970 Corvette 454/4spd. People ask me "which" trasmission and rear end do I have. How can I tell?

[Tom H.]

Re: How can I tell "which" transmission I have?

Hi Jim !

For me, I use the book and cheat. I had to look at the codes. In 70 the date code has a suffix added to it to identify the first gear ratio.

A is 2:52 1 Wide ratio. B is 2:20 1 Close ratio, and C would be the M22 close ratio with 2:20 1 first gear ratio.

As far as the rear end goes, you will find the three letter code on the bottom of the differential carrier. It is a stamped code that you might be able to see with the car on the ground if you can wiggle your way under there !

[William C.]

Re: How can I tell "which" transmission I have?

With respect to the trans, run it up to 2200 rpm in low and shift to fourth gear. If you are running in 4th at 1000 rpm it is a close ratio trans. If running at about 850 it is a wide ratio. If the car has air conditioning, it has a 3.08 rear axle. Otherwise, the standard package was 3.36 rear with a close ratio (2.20 low) trans and 3.08 with a wide ratio.

[Chris H.]

Re: How can I tell "which" transmission I have?

Jim, in the attached 2 photos you can see:

1) Trans stamp from a '69. Notice the "C" on the end. That means it's an M22. "A" would mean wide ratio (most likely for your LS5), and "B" would mean close ratio.

2) This is a photo of my '70 LS5 diff stamp. "CAU" is the optional 3.36 ratio. The standard is a 3.08 which is "CAV".

My LS5 has the wide ratio "A" trans.

As a fellow '70 LS5, 4 speed owner, I'd be curious to know what you have.

[Jim F.]

Re: How can I tell "which" transmission I have?

Thanks guys for all the help. A picture IS worth a thousand words. I can't wait to check mine out tomorrow. I will post what I find!
Jim