tranny ? for average250

catman

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What kind of power / torque do you think a healthy zf 5spd could take. I have a 93 f350 c/c 4x4 and would like to put a cummins in. The 5 spd is a low click reman.
 

averagef250

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If the ZF is tight you'll blow through an organic single disc 12" clutch before anything will break. If you really pound on trannies then step up to a 6 speed.

In comparison to other things the diesel ZF's are extremely common and cheap. NV4500's are outrageous and have ratios that just plain suck. If you break the ZF toss another in and don't do what you did to break it or step up to a S6-650 or NV5600/G56.

I hear talk about how weak ZF's are or how some guy's brother in laws buddy blew up 5 ZF's in a week, but I just don't see that myself. I've had a bunch of trucks with them and fixed/rebuilt a bunch of them with 95% having very minor issues. For as many ZF's as are running around out there I don't see as many in comparison to other 5 speeds of the same era.

The worst ZF I ever got in was a very early IDI one with nearly a million miles on it and still shifting until one day it somehow got itself in reverse and first at the same time. For the life of me I couldn't figure out how it could do that, I went to the site where the truck was at, popped the shift rods around through the shift tower hole and got it to drive to my shop. I drain 1/2 a quart of black goo out of it, pulled it and tore it down. I found the needle bearings under the mainshaft gears had all entirely come apart and the gears were flopping around enough inside to let the shift rods/forks **** and cause what locked it up. Even with replacing the input, mainshaft and several gears the repair bill still wasn't that bad.
 

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