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TH400 direct swap.

Gyoas759

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Reading, PA
I'm thinking about swapping the trans myself to save a little money on my project. It's a TH400 on a 89 3/4 ton 4x4 burb. I've done quite a bit of automotive work and am not shy with it, but this would be my first transmission replacement so I'm in uncharted ground. Anything special to the swap beyond a bunch of nuts and bolts? Any tips or write ups available? Just looking for a little know how so i can have th confidence to go ahead with the swap. Is it a reasonable one man job for someone like me who hasn't done one before?
 
oh yeah its super easy.
drain the trans and tcase, they are seperate fluids.
unplug the vac hose on the pass side and then do the linkage on the driver.
remove the convertor dust cover and unbolt the torque convertor on the six bolts from the motor.
remove the driveshafts, speedometer cable, plugs, and the tcase, leave the adapter and crossmember on.
then set the trans jack under it and support the trans.
then remove the adapter and crossmember.

now you can lower down the trans just a bit and have a little better time getting to the bellhousing bolts.
undo those and back the jack out slowly watching for interferance with the exhaust or anything.
the convertor will come with the trans, thats heavy and full of ATF. dont drop it!
NOW is the time to do a rear main seal on the motor. two weeks from now it will leak and laugh at you.

as for going back in, the convertor goes in the trans first then you install the trans in the truck.

try to use a paper gasket between the trans and adapter. rtv bits can get caught in the trans and who knows where it will go.

and it really helps of your truck is lifted, the bellhousing is kinda tall so i hope you can get it out!

thats what i can think of now, but ask questions. overall its really really easy and i can do it now in a couple hours. ive done four remove and installs and its gets easier every time. they never get lighter though.
 
exhaust interference

Ill second that removal set of directions, seems to be very well covered. Though if your exhaust is unmodified from the factory Y.pipe location, you will likely have to "break" the transmission loose completely from the engine, slide the transmission off of the jack and onto the exhaust, where it crosses over, rest it on the exhaust gently. Have a helper if possible to balance the assembly while you reposition the jack behind the exhaust. Slide the transmission onto the newly repositioned jack and Voila .If you want to save the balancing act of the whole situation , harbor freight makes a scissor style trans jack that goes up plenty high and has a strap to secure it. I have one and have had a friends lunky 6sp ZF trans, a bulky E4OD and a few 700-r4's on it even in a hugely lifted truck it does the job well for sure. If i recall correctly it was only 60 bucks and has come in handy in numerous other situations.
 
Make sure that the torque converter is fully seated before you bolt the transmission to the engine, if you don't you risk breaking the tangs on the pump. There are 3 seperate things that align: the turbine shaft, ground sleeve and the pump.

Gus
 

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