304 to 360 Engine Swap Tranny Trouble

304 to 360 Engine Swap Tranny Trouble

Wildcat385

Jeeper
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Location
central kansas
Vehicle(s)
83 CJ8, 304 vs, automatic, stock besides motor.
Having a hard time finding anyone who can give me a definite answer on what flexplate I need to go from a 72 amc 360 out of a wagoneer to my 904 tranny in my CJ8 with the 304 in it. Finally found someone who seemed to be very knowledgeable on the swap. He said that on an amc 360 that old, that I would have to grind the crank about a 1/4 of an inch to make it fit the 904, or it would eat flexplates. Would I be better off to grind the crank, or find a different automatic transmission, such as a turbo 400? Is the 904 or the turbo 400 a better transmission?
 
I've heard good thing about the turbo 400.

As for the flexplate you should use... These AMC V-8's are externally balanced, meaning in case you didn't know, you must use the 304 flex plate on a 304 or vice-versa for the 360.

Not sure if that was part of your question, or if you already knew that...

Have you looked on Novak's web site yet for some details? They'll usually have a lot of conversion / swap info on there.

On their site, this is read towards the bottom:

AMC V8 to TH400 torque converter sizing ring

A part often overlooked by installers is the factory Jeep sizing ring or shim bushing between the TH400 torque converter pilot and the AMC crankshaft bore. This ring is critical for the precise centering of the torque converter to the crank. Failure to install this part can cause front pump failure and other issues.

Novak manufactures and carries this part under Jeep #J5352374 or #5352374, as seen here..

I think that is what you may be reffering to...

Here's a full kit also what you may be reffering to: Adapting AMC I6 & V8 Engines to GM Automatic Transmissions

Check this out: The GM HydraMatic TH400 Transmission - Novak Conversions

Hope helps?
:chug:
~ JR
 
Well the turbo 400 is a lot stronger trans than the torqflite 904, as for grinding a 1/4 inch off the crank I would say no go, you wouldnt want to weaken your crank. The best way I can think of to dispell this is to get a flexplate for a 360 and measure how far it sticks out past the block and do the same for the 304. If there is a diffrence than make a spacer to go between the block and tranny. I just made a spacer for my 360 to mate to an NV3550 and used the old dust sheild as a guide. If you keep the 904 make sure you keep the kick down rod adjusted correctly. If you take it off you will be rebuilding the trans shortly.(the 904 thinks its in park without the kick down rod attached and will burn it self up) hope this helps :chug:
 

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