Lt-1 Question

[David Crenshaw]

I have a 1971 LT-1 And someone said that the, the M22 rock crusher LT-1 cars in 1971 had a motor pad code of CGY , the CGZ was for the M20 or M21 cars is my understanding. My car says CGZ, and has the org M22 in it now... Can you help adress that?

[John H.]

Re: Lt-1 Question

David -

I believe the CGY suffix was exclusive to the ZR-1 package, which included the M22; ZR-1 also used the 403 bellhousing and 10.5" clutch, which made the LT-1 engine assembly different from the non-ZR-1 LT-1, which used the 621 bellhousing and 11" clutch, thus the unique CGY suffix. M22 was available with the regular LT-1, but didn't change the CGZ engine suffix.

[Warren F.]

Re: Lt-1 Question

David,

Do you have an original Corvette Order Copy document that shows your LT-1 ordered with a M22 transmission option? I would be very interested in seeing any factory documentation you have that supports this trans option.

I conduct the survey/registry of '71 LS6 optioned Corvettes and only know of the 8 LT-1 ZR1 Corvettes having an M22 trans.

I believe all the remaining M22 installations went into the LS6 ordered cars.

[Drew P.]

Re: Lt-1 Question

Hello David,
Can you look at the transmission to get some information stamped?
Their are 2 sets of numbers one will be the date of the build of the transmission. Stamped verticaly on the passenger side of the main housing next to the tail extention and other stamping is the VIN.
Can you post the information this will help to answer your question.
Regards,
Drew Papsun

[David Crenshaw]

[Warren F.]

Re: Lt-1 Question

David,

The VIN sequence on your transmission doesn't start with the correct sequencing for a 1971 model year Corvette. The assembly stamping would be for a 1972 model year.

[Joe L.]

Re: Lt-1 Question

Warren and David------

The transmission assembly code "P1M13C" denotes a 1971 model year Muncie M-22 transmission assembled on August 13. However, the VIN derivative stamping (if that's what it is) is not a correct stamping sequence for any model year.

[Warren F.]

Re: Lt-1 Question

Joe,

That late date still puts its application for a '72 model year.

[Patrick H.]

Re: Lt-1 Question

Not August of 1971?

[Terry M.]

Transmission dates

I shouldn't do this without looking it up, but -- Transmissions are dated by the model year (NOT calendar year). So it is for a 1971. Only the VIN definitive will tell us what model the case was originally installed in.

[Patrick H.]

Re: Transmission dates

My thought too.
The odds of a 1971 MY transmission being built in August of 1971 are really quite low.

Patrick

[Joe L.]

Re: Lt-1 Question

Warren-----

Yes, it would seem like if it was manufactured in August 1971, it would be for a 1972 model year vehicle. However, the "1" after the "P" indicates that it's for a 1971 model year. Transmissions are stamped by model year. The "M" could represent August of 1970. I don't think that transmission month codes are assigned "sequentially".

Also, it's possible that the assembly code indicates a SERVICE transmission manufactured for the 1971 model year. The "VIN derivative" reported might not be a VIN derivative, at all, or it might be something that was stamped "later".

[Joe L.]

Re: Transmission dates

Terry-----

That's my understanding, too. The second character in the assembly code series (in this case a "1"), represents the model year the transmission was built for and not the calendar year.

[Chuck S.]

Re: Lt-1 Question

"The "M" could represent August of 1970. I don't think that transmission month codes are assigned "sequentially".

August IS the correct date, Joe, M=August on a Muncie...as you and Terry said, August 1970. According to the book, the letters F,G,I,J,L,N,O, and Q were not used as month codes on Muncies.

[David Crenshaw]

Re: Lt-1 Question

I will post some pic's of the Engine pad, Rear end stampings (I had a hard time finding the 4:11 code for the rear, I thought the rear had been changed. But that was not the case) and trans stampings soon. I will have to put it on a likt. THANKS FOR ALL YOUR HELP!!!!!!!!!!!!!!!!!!!!!!!!!!!!!