: Switch Pitch Conversion for TH425 Trans



imanustsunami
03-25-11, 05:31 PM
I've heard that there are Switch Pitch Conversion kits out there that work with any TH400 Transmission. This has a replacement body that provides hydraulic pressure to be shunted to a mechanism inside a special torque converter. This converter would have a stall of 2000 RPM for fuel efficiency, and can switch to a stall of 3000 RPM for racing.

Does anyone know if a TH400 kit like this can be used on a TH425 from a 1973 Cadillac Eldorado? With the torque of a modified Cadillac 500 would a 3000 RPM converter ever get it's power to the ground? If the car weighed less than 3500 lbs. and had fat tires, would a high stall converter on a street/strip motor be advantagous?

Thanks,

Don

drmenard
03-26-11, 12:30 AM
Until Bruce Roe sees this post and will give you the best advice, let me say this... Not all th400 can be converted to switch pitch... At one point they took out metal in the case and the conversion can not be done....But I think I have read that all the th425 can be converted, Bruce will know.. I am not sure what parts are the same for both the th400 and th425, and what ones are different.... If I were doing that swap , in a car like yours , I would start with a stock 13" convertor..

BRUCE ROE
03-26-11, 12:53 AM
The TH400 & TH425 use the same torque converter. But all the other parts for a 425 are different, so a 400 kit won't work. Really a conversion means finding a 66-67 SWitch Pitch TH425 to supply all the needed parts, which include the chain plate + pump assembly and the valve body. There are some TH425 cases missing the stator oil passages needed for SWP. You can see this and some other stuff on transmission sub albums under my PHOTOBUCKET site. You can get a ready to go heavy duty SWP TH425 from the GMC motorhome people, Manny specializes in SWP. Bruce Roe

http://s93.photobucket.com/albums/l71/bcroe/

(that is a lower case "L"71, not an upper case "i"71)

click on a Sub-Album
click on a picture to enlarge + description

imanustsunami
03-28-11, 11:24 AM
Thanks for the answer. I was hoping that this would be easy, I guess not. I saw this on Ebay ending tomorrow night - "Torque Converter switch Pitch Conversion Kit Turbo 400".

Don

PeterMeyer
08-24-12, 03:52 PM
Hello Bruce,

Im quite new in the US-Car business, because Im livin in Germany and did old Mercedes.
For one year or so I got a 472cui 1968 Caddy Sedan Deville.
Next winter I want to do the engine stuff.
Is it possible to put a switch pitch converter into my TH 400?
Where can I get such a kit?
I really want to do that.
For cruising the stock stall speed is o.k.
But if I got such a great engine, I want to let it run sometimes, and for that I would need a stall speed of 3Trpm and a shift kit.
I hope, you can help me, because here in the forums they say, you are the man.

Thanks,
pm

BRUCE ROE
08-24-12, 05:55 PM
Hello Bruce, Im quite new in the US-Car
business, because Im livin in Germany and did old Mercedes.
For one year or so I got a 472cui 1968 Caddy Sedan Deville. Next winter
I want to do the engine stuff. Is it possible to put a switch pitch converter
into my TH400? Where can I get such a kit? For cruising the stock stall
speed is o.k. But if I got such a great engine, I want to let it run
sometimes, and for that I would need a stall speed of 3Trpm and a shift kit.
I hope, you can help me, because here in the forums they say, you are the
man. Thanks, pm

PM, your 68 TH400 is a good candidate for conversion to SWitch Pitch. The
most economical way is find a 65/67 big block Buick, Olds, or Cad TH400 &
take the SWP out for your 68 conversion. Unfortunately none of those years
bolt directly into a 68. If the 68 is original, its due for reconditioning with
rubber seals anyway, and the conversion then would be easy. The parts can
be shipped from the USA, but this is a very expensive way to get them. I
just had a batch of extended high stall range torque converters rebuilt.

Look at my PHOTOBUCKET sub albums mentioned in posts above,
SWITCH PITCH TRANSMISSIONS &
BUILD A SWITCH PITCH TRANSMISSION to get some ideas. If you get the
trans conversion working well, we could talk about ways to control the hi
stall function. good luck, Bruce Roe CLC # 14630