What to do before installing an M46? (Transmission Maintenance)

I recently got an M46 and various other parts for a manual swap of my 91' 245.

The m46 is a bit of a mystery. It has a J type overdrive and came from an older 200 series but I don't know exactly what year. It has fine input shaft, but the bell housing does not have a 'thin spot" to knockout for the sensor.

My questions is what to do to maintain the m46 while its on a bench. All I know about it is that I can put it into all 4 gears + reverse and it turns easily and without any noises. Obviously it would be great to rebuild it, but I don't have the knowledge and skills for that sort of thing.

My general plan is this. (Previous owner installed new shift linkage bushing and a new rubber mount.)

1. Degrease it
2. Remove the overdrive pan and clean the overdrive unit and filter screen.
3. Replace front and rear seal.
4. Fill with Redline
5. Check Operation of Reverse and 4th gear switch.
5. Hook the input shaft up to my lathe or large drill and bench test the overdrive by applying 12V to the solenoid.


Anything else I can do while it is on the bench.

Looks like you've got just about everything covered.

The 1 thing I will suggest is that you get an OE or OEM input shaft seal.

We have the input shaft seal and an OE front gasket in stock.

We don't stock the OE rear output seal, but the aftermarket seal we sell works just fine and is cheaper.

dandeluca said:

2. Remove the overdrive pan and clean the overdrive unit and filter screen.

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There is an additional filter behind one of the round port covers you might as well inspect and clean if needed.

This is also the time to repair or replace the wiring harness for the m46. I'd also suggest the oring on the shift coupler and the plastic bushings for the ball socket on the shifter and the clevis bushings. I like to use the bronze aftermarket clevis bushings but the plastic on the ball socket of the shifter. There are also bushings under the shifter bracket to check and replace if needed.

As far as parts not to forget. Be sure to get the snap ring that holds the pilot bearing in place in the end of the crankshaft.

Yes, there is that filter that is under the large plug that can be removed and cleaned.

Be aware that there should a large diameter aluminum washer inside the filter pocket that sometimes falls out after you've removed the plug and filter. The washer is thin and can be overlooked.

Thanks for all the advice. I'm just going to update the thread with some pictures and questions if thats okay.

I was weak and cracked open the M46 today. Luckily everything looked pretty good in there.



Do the experts think this crusty clutch fork could be reused?



I would wire brush it and hit it with a coat of primer. However it seems to have lost one of the rivets that hold the little ball socket. I could give it a little spot weld to secure it.


Finally looks like the drive shaft that I got with the transmission does not match. The flanges are different sizes. Seems like this simplest thing to do would be to find a larger flange to attach to the transmission, or would it be better to find a drive shaft that matched.

I've got a larger flange for you. The throwout bearing arm is bad. The pivot ball on that design is supposed to be captive in the little bracket. If it comes out it's bad. It is only supposed to have one rivet in it from the factory. I've put one in there but it doesn't seem to need it.

I've re-posted my brothers link to the TSB covering the missing rivet.

If you can't see the picture just right click on the image and open it in another window.

Dave I?ll be in touch about the flange, thank you.

So if I understand correctly there is only supposed to be one rivet but the ball should not separate from the socket.

I could pop the the one pictured in and out quite easily.

Yes, you are correct in your understanding. Give me a shout and we'll go get a flange.

dandeluca said:

Anything else I can do while it is on the bench.

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