What trans
 

Here is what I have now..a 84 chevy3500 2 wheel drive with a industrial cummins 5.9 12 valve eng.have the standard 4 speed truck trans with a us gear over/under aux trans behind it..the overdrive stop working.the electric motor that engages it went out and company no longer exist..the 4 speed trans has bad bearings in it so I have bad trans and bad overdrive...I only use truck to tow race car trailer that weighs 12000 lbs loaded..is there a auto trans that I can go to that would have final gear ratio that I have now with my 4 speed trans and overdrive,

I figured if go auto trans I'd need to beef it up..if so then what do I need to do to make it strong enough..I have a 700r4 but not sure if it has same finel gear ratio as what have now plust don't know if can be made strong enough..

Why not get a 47RH and build it. It shouldn't require any electronics to run it.

Never heard of the 47RH..what's it out of?is it a overdrive trans?do you know if it is lower or higher final gear ratio of my combo I have now?has to elctrontic part of the 700R4 trans isn't a issue..there is a kit you install in the 700R4 that lets it work on older non putter cars/trucks..only $90 for it

The 47rh came in the older dodges. And can be built to hold a good bit of power. Not really sure on the setup you have but it can run without a computer. You should be able to pick them up cheap. Seeing as in stock form they will last a little while but built they last longer.

My engine isn't a dodge cummins..it is a industrial diesel cummins that was used in bluebird busses

IMO, a Getrag 5spd (89-93) or NV4500 (94-02) from a dodge/cummins truck makes the most sense. Ensure you get it with the flywheel housing, flywheel, starter, bellhousing, clutch fork, and shifter. The clutch and driveshaft are nice to have.

If you buy the trans a la cart, then you'll probably spend the same again on all the other stuff.

Right it will be easier in the long run to drop a manual in vs an auto. Most autos do not like diesel torque. I think you would be happier with it in that setup. I know I am with my trans swap.

My truck already has the eng adapter /Chevy flywheel/clutch/Chevy trans bell housing..would like to stay with a Chevy standard trans..what would be a good Chevy standard trans that will hold up to the 5.9 industrial cummins eng?going after fuel milage so thing 5 speed or 6 speed or more as long as I can keep my bell housing..ok with building new trans cross member and shorten of drive shaft if needed

An NV4500 won't fit the SM465 bellhousing.... it has a different (wider) bolt pattern.

However, a NV4500 w/bell should still fit the cummins/gm flywheel housing. You just can't run as big a clutch as the Dodge guys can.