I think I am going to try rebuiling one of my spare 904 trans, what special tools do you really need to do these? what tools can you make? any sketches would help too.
Thanks

You will need a couple snap ring pliers and a compressor for the big spring in the front drum. Other than that just sockets and wrenches should do it.

Oh yeah and lots of brake cleaner

need to replace bushing in tail shaft...pump and front drum...

can take thoses to a trans shop if bushing drivers are not available.

A list of some tools that will make it easier, but not absolutely needed

A 3/8x16 slide hammer to screw into the front pump to remove. Most pumps you can pop out from inside, but 904s set the pump in real deep, so sometimes it can be hard to pop it from inside.
Something to compress the spring assy on the front drum.
Snap ring(flat) pliars
Retaining ring(round) pliars
Bushing drivers or a bushing cutting chisel to remove any worn bushings. You can press new bushings in with a socket or similiar
A 904 is very basic to build. Leave the low spring and roller assy in the case. Do not remove it unless it is bad
Unless you are using a Shift Kit, build it back to the same specs as OE. Do not listen to some who say tighten this, or loosen that. This trans has been around for almost 50 years and has worked well,even stock!

I would add inch-pound,and foot-pound torque wrenches to the must-have list.You should also check the 7 digit PN to find out what year of trans you are working on before you order parts.The correct year of service manual would also be a big help for a first-timer.

I used this and a C-clamp to compress the spring assy on the front drum in a 727 I rebuilt. I threw it together in about 10 minutes with some scraps I had laying about. Never thought I'd need it again so its a real cobble job, but it worked so well I kept it. Now I will be using it on my 904 soon