Technical Tailhousing for a th425 trans ?

Anyone know if theres tailhousing for fwd 425 trans that will take propshaft or flange for one? please delete if deemed unsuitable, thanks Moon

 

No there is not one. The output shaft is different too, you can replace those parts but it will probably be cheaper to get another transmission

 

Your request has been done before. A guy from Baltimore built this cab over a few years ago. He used a TH425. Since the TH425 runs backwards, he had to put the engine in backwards ( note the bellhousing up against the back of the cab ). He made an adaptor where the normal differential bolts on that included a TH400 tail shaft. It seemed to work well. He also used a quick change rear so he could flip the ring gear o everything works correctly.
I have a TH425 in my sbc powered 65 Corvair. I do have the name and phone number of a place in California that does a lot of different gear sets along with posi and spool carriers

 

I hate to start anything but all engines run the same direction, and so do the transmissions

 

No they don't.... Aircraft, marine and even Smokey Yunicks Hudson ran "backwards". A lot of old side by side dual engine dragsters used one CW and one CCW engine.

So you can't say ALL.....

 

Yes they did but these were special built engines, anyway back to the original question the TH425 is a heavy duty unit that doesn't use a slip yoke, the output yoke bolts to the shaft, so it needs to be replaced with a different output shaft and housing

 

And that is what was said about the unit on the truck above. An adaptor was made to allow a TH400 output shaft to be used into a 2 piece driveshaft
The output of the TH425 is a short splined shaft ( maybe 3 inches ) that fits into a splined female pocket in the differential. It would not take much to turn the output to a standard splined shaft...….some simple machine work would do the trick.
Even a Corvair engine runs backwards along with at least half of the marine engines in boats regardless of displacement

 

All modern FWD transmissions turn "backward" , after the converter , drive gear and chain.

 

Thanks for all the in/output keep it coming.............

 

My boat had 327 SBC's, one ran CCW and then other CW

 

That's not true. The output shaft just faces in a different direction.

If you are viewing the rotation of the output shaft on a rear wheel drive from the rear it turns counterclockwise, the front wheel drive turns clockwise. You are just viewing it from a different perspective. The transmission internals turn the same direction as the engine.

If the converter, drive sprocket gear and chain turn clockwise, then so does the driven sprocket gear and output shaft.

If the output shaft turned in a different direction as you say, then the transmission would not be capable of direct drive, usually 3rd gear. It would have to have a planetary changing the direction, then there would be really no direct drive.

The only way the direction could be changed is the transmission would have to have two sprockets and no chain.

Have you ever seen a chain driven camshaft with two sprockets turn opposite of the crankshaft?

Maybe there are some funky ultra late model, many forward speed, front wheel drive transmissions that way, but I have never seen one.

Bill

 

To clarify a little more. The direction does get changed in the differential. Modern FWD trans have the differential internal where the TH425 is external.
In a modern FWD, you cant see the output shaft like you can see a TH425 without the differential mounted.
If it a sprocket driven trans without a chain then the trans internals turn opposite of the engine and the differential then does not change the final rotation.
Bill

 

I did it.

 

I have no doubt that you did^^^^

 

I can give more details tonight, after work.

I am working on a 6-71 blown Chrylser 354 Hemi mid-engine Model A.

I rendered the tail housing in CAD, to use modified off-the-shelf parts.

A TH425 is 98% a TH400.

Mine will have TWO chains

 

The output shaft turns clockwise when moving forward on a FWD trans /differential . A RWD output turns CCW when viewed from the rear. One is "backward" from the other. We are dealing with semantics now, my friend.You use yours. I'll use mine.

 

A few things about the TH425:
It is almost all a TH400.
You can swap the female output from the TH425, for a male one from a TH400. It is a direct interchange.
Almost all of the hard parts inside are the same as a TH400 parts, including the one-way parts. Those are just installed backwards.
The torque converter is the same as a TH400.

The adapter that I designed is set up to be the shortest that can be made with GM parts. It used a 4x4 TH400 yoke, that has been drilled and tapped to take a fixed yoke. I then shortened a TH400 bolt on yoke, back cutting the splines, so they slip over the TH400 speedometer gear area. You don't use the TH400 speedometer gear, in this setup, as the speedometer in the TH425 is driven off of the governor shaft.



My adapter takes a stock gasket, stock wide bushing, and stock seal.


I will be using a Winters magnesium non-quickchange, which can be flipped over, to correct the rotation issue:

 

And I was not kidding about dual chains.

 

You didn't start anything. Aside from being off-topic, pre-2000 Hondas turned counterclockwise, when viewed from the crank front, the transmissions turned the opposite way.

To make matters more complicated, if you feel like machining gears, a TH425 will run reversed, just as well as forward. You just need to flip the sprag over.

Since the front pump is attached to the engine, it always pumps the same. The valve body does not care. It has been done.

 

As far as I know, it is not just any old quickchange center section, but a Dick Spadaro reproduction.

What makes these unique is that they do not have the third pinion bearing, past the pinion head, and no webbing to support it. With neither of those there, the differential carrier and ring gear can be put in on the other side, reversing the operation. Some other quickchange center sections out there don't have the third bearing, too.

Spadaro:


Most others:


My non-quickchange has the bearing, and the support webbing, but is otherwise symmetrical, so the entire center section can be flipped over.

 

Here's a Frankland SL:

No third bearing.

 

This whole thread is really OT

 

To you.

 

If you want to use a Reverse Rotation Ring & Pinion, Winters makes them and a Quickchange Center with the pinion opening on the other side of the case. This is the 3/4 ton based unit not the wimpy V8 stuff.

I have also built a couple of QC's that had the pinion nose bearing and housing support removed.

Contact me if you need more information and/or Winters parts.

 

How big is the ring gear in the 3/4-ton unit?

 

10"

 

Since the shop at work is shutdown for the long weekend, I ran off a 3D test print in plastic.

It's a good thing I did. I somehow got the 3-o'clock bolt hold 1/4" too low.

Easy fix. This takes the output shaft, and yoke I have previously shown.

As soon as I fix the bolt hole, and verify the bushing and seal press fit tolerances, versus an OEM piece, I will let chips fly.


**Edit** I made this from a scan of a gasket, and a few measurements. That gasket was made wrong. I will correct the model, and laser cut a few gaskets.

 

I revised the last design, for a more smooth appearance.

Wish me luck, chips are flying.

 

I bet that feels really good!

Good luck!!!

 

Sure does!

It's done! I will post a picture after I leave our secure facility. No photos are allowed in here.