TH400 Valve Body Differences

[mathman]

I picked up a TH400 (complete with Quadra-Trac and low-range unit) out of a V8 Cherokee a few months ago with the idea of rebuilding it for my J-20. In looking through the parts book the only part of any consequence that has a different part number is the valve body. Anybody have an idea of what the differences in the valve bodies are between a TH400 in a V8-powered (think it was a 401) Cherokee and a TH400 in a J-20 with a 360? The Cherokee was either a '77 or '78; the J-20 is a '78.

Thanks,

[fulsizjeep]

I am not aware of any significant differences in valve bodys used in T400 for FSJs.

[babywag]

If you're talking about a Jeep parts book, just because it's a different number doesn't mean it's a different part.

OEM's change part numbers all the time, even when no physical changes to the part occurred.

A TH400 valvebody will work in any TH400 AFAIK.

[mathman]

If you're talking about a Jeep parts book, just because it's a different number doesn't mean it's a different part.

It's the '74-'80 Jeep parts book. The thing about the part numbers is that every other part in the transmission is the same part number on the V8 Cherokee and the J20, it's only the valve body that differs. The six-cylinder Cherokees have a few things that are different (mostly to do with the governor) but not the V8. Since the cases are the same I'm sure the valve bodies will bolt in place - but it makes me wonder what little (or not so little) was changed to warrant the separate part number on the valve body.

[Stangrcr1]

It's the '74-'80 Jeep parts book. The thing about the part numbers is that every other part in the transmission is the same part number on the V8 Cherokee and the J20, it's only the valve body that differs. The six-cylinder Cherokees have a few things that are different (mostly to do with the governor) but not the V8. Since the cases are the same I'm sure the valve bodies will bolt in place - but it makes me wonder what little (or not so little) was changed to warrant the separate part number on the valve body.

Usually the only changes that would happen in a valve body would be different springs to raise or lower pressures and maybe a different separator plate with smaller or larger ports. These ports and springs would determine the firmness of the shifts. The Cherokee would probably get smaller ports for softer shifts, increasing passenger comfort. Only way to know for sure on the separator plates is to put them one ontop of the other and look at the ports.

[Subic Jeep]

TransGo

Have a look at Transgo web page

http://www.transgo.com/index.html

Download video gives a good idea how the valve body works.

Videos are for TransGo's Heavy Duty Reprogramming or Performance kits.

http://www.transgo.com/video.php

Operation Transgo kit installation video loaded on Laptop



TH400 open heart surgery



The transgo kits are designed to be done with transmission in car so on the table everything is inverted............



Kit installed:
400-1&2
Automatic shift; Street or full-race; Holds 1st and 2nd to any rpm; Backshifts to 2nd and 1st at any rpm;
Tow & Go and Competition combination

[mdill]

My best guess is the J-20 got a little high line presure and harder shifts, than the Cherokee. (i.e. Jeep put a shift kit in it to shift harder and hold tighter) I would expect it to be pretty much the same idea as the after market shift kits, if you don't plan on working the J-20 hard, I would use the Cherokee valve body, if you plan on hard work then use the J-20 version or buy a after market shift kit.

Mike D.

[mathman]

...if you don't plan on working the J-20 hard, I would use the Cherokee valve body, if you plan on hard work then use the J-20 version or buy a after market shift kit.

Plans for the J-20 include towing and occasional heavy hauling. Sticking with the J-20 valve body or checking into a shift kit is likely what I'll be doing...

Thanks all,