66 390hp transmission question

[Randy T.]

Hello everyone,
I'm a new member and recently purchased a 66 390 coupe. Someone put a super T-10 and I am not sure which Muncie wide ratio being the car has a build date of 12/20/65. Do I use a 325 box with a date like P1115 or a 010 box with a date like P1115? Is there a link with a chart of build time frames and boxes used? Thanks all...

[Joe L.]

Re: 66 390hp transmission question

Hello everyone,
I'm a new member and recently purchased a 66 390 coupe. Someone put a super T-10 and I am not sure which Muncie wide ratio being the car has a build date of 12/20/65. Do I use a 325 box with a date like P1115 or a 010 box with a date like P1115? Is there a link with a chart of build time frames and boxes used? Thanks all...

Randy-----


Main case should be casting #3885010. I doubt that any '010' main cases were used for the 1966 model year.

By the way, not all 1966 L-36 were wide ratio.

[John H.]

Re: 66 390hp transmission question

Randy-----


Main case should be casting #3885010. I doubt that any '010' main cases were used for the 1966 model year.

By the way, not all 1966 L-36 were wide ratio.

Joe -

Could you expand on this?

[Michael H.]

Re: 66 390hp transmission question

Joe -

Could you expand on this?

I was curious too... but wasn't gonna ask.

[Wayne M.]

Re: 66 390hp transmission question

Randy-----


Main case should be casting #3885010. I doubt that any '010' main cases were used for the 1966 model year.

By the way, not all 1966 L-36 were wide ratio.

I'm sure Joe L. made a typo with the '010' (meant to say '325') .

To add for Randy, the 1966 dealer order form and the powertrain chart for the 390hp shows wide ratio with 3.08 or 3.36, and close ratio with 3.08, 3.36, or 3.70.

Probably someone has kept lists of '66 VIN vs. assy date code, but all I can contribute is the one that's in my basement: 6S114095 with P0211, so using birthday calculator, you can get at least the spread on this one.

If you find a '325' with a P1115 stamped on the driver side rear flange (not on the side cover corner), this one will have the round upper rear boss on the top of the maincase.

Actually, there was quite a few improvements on a '010' vs. '325: ""coarser pitch input and counter gear; larger diameter countershaft; damper plate (M20 only); new synchro rings; maincase modified for damper plate and inserts for larger countershaft; increased press fit of countershaft"" this from 1966 New Product Training Manual; published August 1965. This applies to all passenger and Corvette. This had to start with beginning of model year run, or else it would be heck for service.

[Joe L.]

Re: 66 390hp transmission question

Joe -

Could you expand on this?

John-----


I just blew it. I should have typed '325'.

[Joe L.]

Re: 66 390hp transmission question

This had to start with beginning of model year run, or else it would be heck for service.

Wayne------


Absolutely correct.

[Hector G.]

Re: 66 390hp transmission question

I have the original 66 BB close ratio muncie trans with the original 3.55 ratio rear end. According to Adams, page 343, when the L36 came with a 3.55 ratio rear differential it was combined with the M21 close ratio trans. I'm at work and don't have access to the main trans casting #s but would gladly post them later if you'd like.