Picked up a mid-length TH400 today, it has an 87 LRA date code and HD on the bellhousing. Is there anything special about it? I can't find any information about the "HD" markings anywhere!

Thanks!
Bill

sure its not a 475?
Some of those have strait cut gears that were strong/noisy http://www.nastyz28.com/ubb/wink.gif

Wow, I don't know. Would a 475 be any good for drag racing?

Oh yea http://www.nastyz28.com/ubb/smile.gif
Good stuff http://www.nastyz28.com/ubb/smile.gif
You can also get the strait cut gears out of a 4L80E and put them into a older TH400.

I havent seen any of the heli gears fail but I have seen some with a lot of loading marks that the strait cut version dosent get.

Man, that is exactly what I wanted to hear! I was told this trans came out of a very large truck, too. If only I could find some info on how to make sure. Any ideas?

Some of the heavy duty stuff like motor homes etc had that kinda trans and made a very noisy gear wine on take off kinda like school bus.

Its really hard to tell it apart from a normal 400 without going in and seing the gears.

it may be a "K" case.
Slightly stronger case.
It will have a bolt on dust pan, not screwed on with tapping screws.

straight cut gears are not so much stronger themselves, the fact that they cause less fore and aft loading of the planteries on gear change, accel/decel, etc..
Kinda like a M22.

TH400's have a weakness here under severe use, that can cause damage to the case.
I have a fix for this using the regular planetaries.
Really isn't an issue unless dealing with heavy towing, lots of power, or manually shifting, especially downshifting.

I also keep the rear endplay tighter than stock on a Th400, to help prevent this.


87 transmisison will have an intermediate roller clutch.
Nothing really fancy about them.


If it is the 475 (If I remember right it is actually a 425) it will have a thick wall yoke and different tailhousing.

<font face="Arial,Verdana" size="2">Originally posted by jakeshoe:
it may be a "K" case.
Slightly stronger case.
It will have a bolt on dust pan, not screwed on with tapping screws.

straight cut gears are not so much stronger themselves, the fact that they cause less fore and aft loading of the planteries on gear change, accel/decel, etc..
Kinda like a M22.

TH400's have a weakness here under severe use, that can cause damage to the case.
I have a fix for this using the regular planetaries.
Really isn't an issue unless dealing with heavy towing, lots of power, or manually shifting, especially downshifting.

I also keep the rear endplay tighter than stock on a Th400, to help prevent this.


87 transmisison will have an intermediate roller clutch.
Nothing really fancy about them.


If it is the 475 (If I remember right it is actually a 425) it will have a thick wall yoke and different tailhousing.</font>

Thanks a lot for the info. So I will have to get a different driveshaft yoke then?

You may or may not have to get a different yoke (assuming you already have a 400).

If it requires the bigger yoke I would swap the tailhousing from another TH400. Just bolt on a regular TH400 tailhousing and use a new seal and bushing, all set.
The output shafts are the same.

What about torque converter/flexplate bolts? I was told that TH475's have 6, and TH400s have 3? Any truth to that?

Some truth to it.
Very HD applications use the 6 bolt pattern.
You would probably not use a stock 6 bolt converter anyway so it's really a non issue.
These converters were for towing.

Military Hummers used them with a regular TH400, as well as most diesel applications, etc..

If you did use the 6 bolt converter and your flywheel would only bolt to 3, you would just use 3, not a problem.

Ok, one final question. Do you know of any online sites where I could decode the trans information stamped on the plate?