'69 Turbo 400 code?

[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

[Chevy454]

Ray:

Long time no type! It's been a while, but it's glad to have you back. Sorry I missed you the other day, but dad and I did have a nice visit with Mike. Seemed like an awfully long lunch break...you must have been HUNGRY!

Anyway, I seem to remember Jim Mattison saying there were more than the 50 Gibb cars built with the 400th in '68. I want to say the number was right around 60(?), including the Gibb cars.

[JoeC]

Hello Ray, thanks for the reply. The 1005 serial no. is interesting. Did the later (07+) 1968 L72 Impala or the 1968 L71 L88 Corvette use the CY TH400?
"elcamino" posted on "chevy talk" that his Chevy books listed the 1969 CY application as;
Y - 427 335 HP Chevrolet
Y - 427 425 HP Chevrolet
Y - 427 430 HP Corvette
Y - 427 435 HP Corvette
Y - 396 375 HP Chevelle, Nova, Camaro
Anyone have the list for 1968?
Was the CX trans only used in 1969 427 COPOs? If so, the CX trans serial no. may give a clue as to how many 427 TH400 COPO cars were built.

[Rowdy Rat]

Joe,

As far as Corvettes, I can tell you that the "CY" code THM 400 was only used behind the solid lifter big blocks in 1969; it was not offered as an option in 1968 for use with the L71/L89/L88. I'm also curious as to the 335hp 427 application you listed. Why would a low rpm utility engine need a high rpm shift point automatic?

Your description of the "CY" code automatic for the 1968 COPO Novas sounds quite a bit like the Corvette unit in 1969... 6200-6400 rpm full throttle upshifts.

William,

Your comments regarding different part numbers for the case and valve body were enlightening... I had always been told that the Corvette "CY" and Camaro/Chevelle "CX" automatics were nearly identical. If it isn't too much trouble for you to look them up, I would be very interested to learn what the part numbers for "CX"/"CY" transmissions were for the torque convertor, valve body, and case. I would appreciate any information that you can provide.

Regards,

Stan Falenski

[SS427]

Stan, I too found the information last night (had it all the time and didn't know it!) My information also listed the "Y" code for 335 hp. I am clueless as well and have owned numerous 335 hp motors, none of which had the "Y" code. If true, I suspect it was so that the car could get out of it's own way. The transmission likely comensated for the low horsepower of the engine.

I hope to get all the numbers off this transmission in the near future. I am also curious to see if it has 6 torque convertor bolts. Incedently, this is in an Impala.