I just bought an IC off a craigslist guy and got to talking about trucks - of course. He parts a lot of accident damaged trucks and has an SD 7.3 he's going to start breaking up. It's 4x4 and is a ZF6. There's 215k on the truck and he says he'll sell me the tranny, t-case and both driveshafts for $1500. It seems like a decent deal, I'm just not familiar enough with the ZF6 to have much of an idea of how much more more life is left before a rebuild. I do realize the work needed to make a ZF6 work, but I'll be doing a lot of body work and cab mounts soon, so it'll be a good time to do the work (and a body lift) if I'm ever going to do it. I'm looking at a new tranny soon anyway as the used zf5 I just put in has nearly dead synchros - especially in reverse. So i need to decide if I want to just rebuild that one or make the jump to the 6er and plan on rebuilding that in - what, 50k, 100k? I know it depends on the driving habits of the previous owner, but the guy did say the truck was a utility bed service truck that didn't even have a tow setup on it, for whatever that's worth... Any opinions are much appreciated.

 

the zf6 will be good with your 3.55 axle, overdrive is the same as the zf5, the zf6 has closer ratio gearing so less stress when getting a load moving. I had to change the zf6 in my service truck at 230,000 but only because the previous owner hit a rock with the cooler line and dumped all the fluid while towing and it gernaded the trans.
I paid $1,000.00 for mine (2wd) and it shifts like crap. (only had 60,000 miles on it?)

 

Um...hard to get into reverse? Non syncronized in reverse. my money is your clutch is NOT releasing properly. otherwise...that price may not be terrible but i would want it for less since you can't drive it. it have fluid in it still? Maybe drain and inspect.

 

Tranny, t case, and both driveshafts for $1500. Then you'll need to figure $ for a clutch, the cooler and lines if you want it on there, the driveshaft resizing/balancing, whatever bearings/bushings it may need, fluids, and maybe a flywheel and master/slave cylinders. Not to mention the rebuild in xxx miles(which could be as little as zero).

I'd rebuild the ZF5 and be good to go for a LONG time to come. All of that said, I think it would be cool to have the 6 but that's what I'd do.

 

It sounds to me like you want the zf6 . I paid a lot more than $1500 for my zf5 swap. If I'd found a zf6 with all that for the same price I would have bought it. I'm in the same boat that thinks it would be really cool to see.

 

Thanks guys. Good to know that it may well need a rebuild immediately-to-very soon. I guess I figured that, but was just hoping everyone would say : 'it's guaranteed to be good till 500k'. ... An unrealistic hope obviously.

And yeah, I kind of do just want to do it, though I'd really rather not deal with immediate issues after install like I did with the zf5. Though that was my fault for just buying the cheapest one I could find - which is what I'd be doing again here I guess.

I guess I'll just sit on it and think about it for a while. I really shouldn't spend that kind of money now what with the engine rebuild I'm working on currently, but I don't want to let a good deal pass by either.

...decisions decisions.

 

What are you going to use the truck for? If it is going to be used for towing heavy, the ZF6 will help to get the load going. If the truck is going to be a daily driver, the ZF5 will do the same job for less hassle. It would be cool to see the ZF6 in an OBS, but I would stay with the ZF5. You can get the full rebuild kit for less than 500 bucks for it, if you can do the work yourself. I'm kind of old school, I don't like changing to much on these old gals, unless it is add ons to change the performance.

 

I had to rebuild the ZF6 in my 99 F550

truck had 160k on it

needed
- Input shaft (bad pilot bearing and chipped tooth)
- Output shaft (splines worn almost completely off)
- bearings(popped out of 4th)
- Syncros and seals(because the trans was apart)

tease needed
- input shaft (spines worn almost completely off)
- range fork(pads worn down)

It costed me $2300 to have it rebuilt(that was giving it to the trans guy out of the truck)

My 160k zf5 I handed to the same guy and it costed me $450(bearings, syncs and seals. NO hard parts needed)

You do the math

Pics of worn spline on zf6

 

I dont know that that is indicative of the zf6 though. It has a pretty good reputation.

 

Double post.

 

I had the same thoughts till I owned one and bought parts for one. They are quite common parts to go bad. The places I got my parts from sell them all the time and my trans guy had 2 other zf6s apart at the same time mine was there

 

That math alone is enough reason to stick with a ZF5 for me. You could almost buy two rebuilt ZF5s for $2300!

 

Exactly. There is a Reason Good Used ZF6s sell at junk yards here for $2200!!!!!

And ZF5s sell for 5-800

 

The only thing I can see to gain with the ZF6 swap is the low 1rst gear. I took the wide ratio guts out of a 460 gas ZF5 and put it all in a diesel case, and what little bit I have got to drive it since it's been finished, I think I'm really gonna like it a lot for towing. 1rst gear and reverse are really low for towing heavy, and I don't think it's really gonna lose any highway drivability because 4th is exactly the same and 5th (OD), there isn't enough difference to tell. I'd say the 460 gas ZF5s should be a little easier to find than the diesel ones too. I'll have to actually do some towing with it before I can say for sure it was a good idea, but so far I like it.

 

I have a spare diesel case here and looking for a "cheap" gasser trans to do the same thing