'69 Turbo 400 code?

[SS427]

AHHH! I am getting closer, thank you Stan. It was my understanding that the Corvettes also used the CX transmission so that is a new one to me. Do you or anyone else have anything documentation pertaining to this Y code behind a Corvette or any other Chevrolet for that matter? Thanks again!!

[Rowdy Rat]

1969 Corvettes that were available with the THM 400 automatic transmission used one of three codes: CK for base engine applications (ZQ3), CL for hydraulic lifter 427 applications (L36 and L68), and the CY for solid lifter 427 applications (L71, L89, L88, and ZL1). To the best of my knowledge, the CY and CX coded THM 400s were practically identical... Revised valve body with higher shift points, fully welded torque convertor, six attaching bolts for the torque convertor, etc. In addition, Corvettes equipped with the CY automatic also received a special AX or CAX (depending upon when the car was built) code 3.36 to 1 ratio rear axle as the "performance ratio". I know of one L88/M40 that is said to have a 2.73 rear, but every other car that I have seen or know about has a 3.36. Nothing numerically higher was listed which is odd considering the fact that MANY Camaros and Chevelles with the CX transmission had 4.10s. For whatever reason, the automatic was never received well in the high horsepower Corvettes and as a result, very few were built. Resale on these 1969 cars is still substantially less than a comparable four speed car with the same engine and can be real bargains if you are able to find a nice one.

This CY transmission was also used behind 1971 LS6 Corvettes and was planned for use with the 1970 LS7 Corvette if it had been released for sale. As with the 1969 version, a 3.36 rear axle ratio was the highest numerical ratio listed.

I am not aware of any other application for the CY transmission... I guess that it would be possible, but I have not heard of any such usage outside of Corvettes.

What additional information were you looking for?

Regards,

Stan Falenski

[Mr70]

BINGO!!!
It took me a while,but I knew I had this.It is a 1969 Technicians Engineering Catalog.In house only.
It lists all the Engine,Trans.and rearend codes for the 1969 Chevrolet Carline.
It tells how to break down the Date codes as well.Even the transmission and rearends.In it it states:
CY-Coded TH400.
396/375HP Chevelle-Nova-Camaro
427/435HP Corvette
427/430HP Corvette
427/425HP CHEVROLET
All with High-shift point.
If you list all the numbers off of the tag,I can tell you the dates and other meanings as well.
By the way,I am curious as to the rearend suffix ratio.Do you know that as well?
Yes Yellow does mean Hi-Perf.

[Edited by mr70 (08-14-2001 at 05:56 PM).]

[William]

I have the engineering parts listing for all 1969 T400s. It shows a CY using a different case & valve body than the CX.

[SS427]

I knew I should have come here first!!!!!

I about wore my fingers out at the other sites and you guys come thru. As always Rick P. You Da Man!!! I really do need to get out to your place and "play" in your library.

The rear code is DK for 3.55:1 Posi with large ring gear. Also a plus.

Thank you everyone on the Supercar site. This will definately help me.
Rick

[JoeC]

I have not heard of any 427 COPO cars with the CY trans. I wonder if the CY was only used with a 3 series rear gear and not the 4:10? There is a copy of a Chevy Bulletin dated 7-12-68 in the Colvin book page 291 on this new HD "high speed" THM400. It states that the trans will "accommodate engine speeds up to 7800 RPM" and Max upshift point is 6300 RPM.
What was the code on the 1968 COPO L78 Novas? Also there is a question in the TECH section on what is the stall speed of the hi po torque converter. Anyone know? I could not find it listed anywhere.

[Ray Morrison]

Joe,
I have the same information on the tech bulletin dated July 12, 1968. Although the transmissions were called 69's since they were built just as the 68 models were winding down, this 400 transmission they have reference too I'm pretty sure is that of the CY code. The code on the Gibb Nova's are CY, however they do not have the yellow tag mentioned in an earlier post. They are green & silver. An interesting thing on these transmissions that I have noticed is the serial numbers on all that have been located with original documentation start at 100 and go upward with all these being below 50. Example, the serial number on mine is 1005 and the highest one that I have is 1041, presuming this to be number 5 and number 41? The protect-o-plate merely calls this transmission 68C100, but there is a big yellow CY painted in yellow on the upper right of the bell housing. The metal tag on the side of my transmission reads CY 68 1005. As far as the stall speed on the original Cy transmissions, I think it was somewhere around 2,000 rpm. These things were pretty tight. It is also my understanding that the CX transmission introduced on October 25, 1968 had a higher stall converter, and just a couple of small modifications to that of the CY. The transmissions built for the Gibb cars were built in June, which was just prior to the first 2 weeks of July that the Gibb Novas were all built. I would be interested to know what application that the CY transmission being discussed in this thread and the build date of that application to see if there may have been some cars built between the Gibb cars and the introduction of the CX transmission? Ray