I am finishing up the rebuild of my engine and decided to have a friend look at and potentially "refresh" or rebuild my transmission while it is out of the car.  Unfortunately I found a really bad "patch job" done by the PO next to the dipstick housing as it enters the trans. Don't know how bad it is until I clean it up. 

Anyway I wanted to know if anyone could give me any input on my trans based on the attached pictures, Pilates, numbers, etc.  See the attached pics.

Can anyone recommend where I could buy a refresh / rebuild kit?

Anything special or unique that we should know about refreshing / rebuilding these?  My friend has been doing thransmissions for about 10 years but I want to make sure we don't miss anything.

Finally, is there any difference between a 63 or 64 turbo trans?  How about the non-turbo 63 and non-turbo 64 trans?  Are the coupe and couple de vile trans interchangeable?

Any advice and input  would be greatly appreciated.


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I have a 63 convertible I am doing a TH 400 swap.  You mentioned the different tail shaft lengths. Any idea what would be the right length to use? Also what stall fo the torque converter. I know the idle is very low on theses cars 450-500 RPM. 


Don't order transmission parts for a 1964 Cadillac, from Rockauto, if you have the Hydra-Matic. Even if you order for a Series 62 you will get parts for a Turbo Hydra-Matic.

When ordering parts for a 1964 Cadillac with a Hydra-Matic transmission order for a 1963 and you will get correct parts.

A very big part of the --joy of driving my 64 convertible --is the way the Turbo 400 trans ( th-400) interacts with the 429 engine
There is always instant power available at almost any speed you are driving when called on
The torque converter of the Turbo 400 is the reason for power availability at any speed and is unique to it
I owned a 62 -390 with the hydramatic trans for many years and it was a great combo and very enjoyable driving experience
The Turbo 400 trans is legendary in its --bullet proof design --being used in many high power race cars with modification for many years and that is always a plus
I believe the trans was a major brake thru in trans design that has proven itself into the future
Sure would be interesting to consider this trans when thinking about what to do with you present worn trans-- anchor
The fact that there is a company that makes this possible to do with the correct adapter is inspiring
The different crank shafts sizes ( 2 ) of the 390 and some 429 engines in front of the there respective transmissions has made this swap difficult to consider before the correct adapters were available

I would love to know the results of putting the turbo 400 in place of a hydramatic to see if that would result in the feeling of an improvement and upgrade of some kind to a given cars driving experience


I used the Wilcap adapter to put a  crate TH-400 behind a '61 390. While the '63 390 and '64 429 have more HP and torque, I would venture to say the results and performance would be about the same. 

While I went from 4 forward gears to just 3, they seemed to be spaced better for acceleration when jumping onto the interstate or pulling out on a busy road. I think the Jetaway was by far a more gentle shifting car but loved the durability and parts availability of the TH-400 not to mention that it literally was a bulletproof, trouble free transmission and being vacuum shifted I could jettison the throttle valve rod and adjustment that went with it.

I was in the same boat as JAS is currently and had to make the decision on whether to rebuild or retrofit. Seeing as my car is a daily drivers and not really geared for resale value, I went with the newer transmission.  

I bought the car for $9500 in 2001 with ok original paint, carpet and interior, drove thousands of miles, replacing only the transmission ($1200 including adapter), one headlight and tires in 14 years and sold it for $9500 with faded original paint, carpet and interior.  I figure I did not lose a penny when you factor in what I would have spent buying a new or good used car, driving it for 14 years and trying to sell or trade it in.

Where did you get the adapter kit from? also where did you get the work done? I think this might be a possible modification for my caddy. 

Hi Kris.  There is an adapter available manufactured by Wilcap through Speedway Motors part # 91628920 for $579.99. These come up on Ebay from time to time as well. This will let you place any late model GM transmission behind a 331, 365, 390 or 429 mill. Parts included are the adapter, flexplate, necessary bolts and adapter ring.  You will need to choose your transmission (TH-400, 700R4, etc), torque converter (LOTS of choices here, "high stall", "fuel mizer", etc.) and linkage.

I used one of these behind a '61 Cadillac 390 with high stall torque converter and small block Chevy linkage adapted to fit the Cad.  If you are lucky enough to own a '64 Cadillac, there are holes drilled and tapped in the X frame to use Cadillac shift linkage BUT it must be from a '64!  If you own a '63, you will have to do what I did on my '61. Also, you will need a new transmission mount and will have to drill holes on your current transmission crossmember to mate everything up.

I had to shorten my drive train approximately 2 inches but you may be able to find a transmission tail shaft to suit your needs?  

Note to anyone wanting to do this- I chose the TH-400 due to durability, availability and overall cost. It will handle to tremendous torque that a 390/429 puts out. The TH-350 or 700R4 would need significant internal mods in order to "beef them up" as Chevy motors often surpass Caddys in the HP department but WE HAVE THE TORQUE!!  This is the force that will literally twist a driveshaft and transmission guts to dust.

Michael the gear spacing that felt more appropriate at different speeds was actually the torque converter. It allows the engine to speed up without changing gears or road speed. The converter allows the motor to spool up into a rpm that has more appropriate torque for the job of getting going. It's also called a torque multiplier as it allows the engine to run closer to it's peak power curve at any gear or road speed. The torus is more of a one to one connection and the torque converter is variable and did not lock up one to one until later years. So they are actually more of a variable speed than a three speed. The same goes for two speed power glide, its not really a two speed transmission either. 

Hi Clovis.  Awesome insight, thanks as usual!! Always good to know the science behind the modifications we are making!

I am enjoying your posts on the trans info once again
Your experience with the replacement info is great to share
There is nothing better than --been there --done thst !
Real nice upgrade for a 61
My 62 convertible with AC started my love of the early 60's Cadillacs that is as strong as ever in 2017 ( thats a long time )


Thank you --for the detail explination of how the Th400 torque converter and the power glide transmissions perform

I always have had a great affection for the th400 always supplying power when called on to do so But did not understand exactly how that happened
I know the power glide trans is used in drag racing a lot but never really understood why as i always drove a stick when racing



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