'69 Turbo 400 code?

[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.

[Rowdy Rat]

Rick,

I figured it was a "big" Chevy from your previous posts... I gather that this is a 1969 L-72 car? Very cool if it is! I've been hunting for a 1969 L-72 Biscayne, Bel Air, or Impala for a while now... Not many out there as I'm sure you're aware. I'd love to hear more about your car when you get the opportunity.

I don't disagree with what you and others have located in print about the "CY" transmission usage with the 427/335. I would guess that it might be a mistake (unless the "CY" transmission used in this application is VERY different than the other applications listed). You mentioned that that this is a low horsepower engine; it is also a low rpm engine. I'm sure that someone will post the redline, but I'd be willing to bet that it is 5,500 rpm or less. With a redline (and powerband) that low, why do you need a transmission that shifts at 6200+ rpm? Logically it doesn't make much sense. I'd like to hear some feedback on this point as well...

Regards,

Stan Falenski

[Mr70]

My information shows the 1969 427/335HP Chevrolet as getting the CQ Suffix.Not the CY.
It states this code for only that L-36 engine.
1968 list shows CE as the trans.for Chevelle-Camaro with an L-78 engine.CL for the 427 Corvette.No CY or CX in 1968.
The CY trans. was avaiable before the CX was in 1969.
The CX was the trans.in the letter dated 7/12/68 in Colvins book.It was used,as the letter states,in 1969 Special Hi-perf Engine Novas,Chevelles,Camaros,Chevrolet,and Corvette.It looks COPO specific and L-72 Impala or Corvette L-71 and up also got it.
I have seen the CX in a 69 COPO chevelle with a 4:10 Posi.I believe it was specific to these rear ratio cars in 1969.

In 1970 the CY was the trans.of choice for the Hi-perf LS-6 engine.All the LS-6 M40 buildsheets have the CY code available with ANY rear ratio.Not just 4:10.Although I think the 1970 Corvette could get the CX still.Any Corvette documentation out there to prove this?


[Edited by mr70 (08-16-2001 at 01:58 PM).]

[SS427]

mr70,
The car was built in December '69 which might correlate with your statement about CY preceding CX in '69. The rear is an 3:55 large ring posi and I am positive it is the original rearend.

I need to get more numbers off the car, see if it had a tach (I don't think I would have missed that ugly thing) and check the speedo for the max speed. Many of the L-72's I have seen had 140 speedos in them. I still need to find a build sheet somewhere!

[Rowdy Rat]

<BLOCKQUOTE><font size="1" face="">quote:</font><HR>My information shows the 1969 427/335HP Chevrolet as getting the CQ Suffix.Not the CY.It states this code for only that L-36 engine.<HR></BLOCKQUOTE>

That certainly makes a lot more sense...

<BLOCKQUOTE><font size="1" face="">quote:</font><HR>The CX was the trans.in the letter dated 7/12/68 in Colvins book.It was used,as the letter states,in 1969 Special Hi-perf Engine Novas,Chevelles,Camaros,Chevrolet,and Corvette.It looks COPO specific and L-72 Impala or Corvette L-71 and up also got it.
I have seen the CX in a 69 COPO chevelle with a 4:10 Posi.I believe it was specific to these rear ratio cars in 1969.
In 1970 the CY was the trans.of choice for the Hi-perf LS-6 engine.All the LS-6 M40 buildsheets have the CY code available with ANY rear ratio.Not just 4:10.Although I think the 1970 Corvette could get the CX still.Any Corvette documentation out there to prove this?<HR></BLOCKQUOTE>

I've had the opportunity to look at quite a few 1969 Corvettes equipped with the high performance engines (L71, L89, and L88) and automatic transmission. Without exception, they have all had a "CY" code. If "CX" was somehow linked to a 4.10 rear axle ratio, that would certainly explain why the Corvettes didn't receive it. As I mentioned previously, the highest numerical ratio that could be ordered with the big block and automatic transmission was 3.36; the high performance 427s received a "special" differential with its own code of "AX" (or "CAX" depending upon how late in 1969 the car was built). As far as 1970, my understanding is that had the LS7 Corvette gone into production, it would have used the "CY" transmission along with the same "CAX" rear axle (at least the power team chart for 1970 Corvettes show a 3.36 ratio as the "performance" axle with the the LS7/M40 combination).

You and Joe both touched on a possible transmission - rear axle relationship... Could this have determined which was used for a given application?

Regards,

Stan