ZF input shaft play: new bearings or full rebuild?

[Ford F834]

Question for those of you who have rebuilt their ZF's... if there is noticeable input shaft play, does it follow that the rest of the transmission needs rebuilt (bearings, synchro's etc.,) or if the rest of it seems tight should I just replace the front cone and roller bearing and the related seals?

To clear up some questions, I actually have 3 ZF's, 2 diesel, 1 gas, I don't know the mileage or history. One of the diesel ZF's has a tight input shaft but ruined quill tube, the other diesel ZF and the gas ZF have input shaft play. My goal is to case swap or type 4 mod the wide ratio gasser ZF to replace my T-19, and get a narrow range "spare" out of the deal.

Naturally my choices will be different depending on how much work is likely to be required of each. If I'm looking at a full rebuild I might just change the quill tube on the tight ZF and run it " for now", while I build the wide range one, otherwise I might case swap the two "loose" ZF's, put new input shaft bearings, and leave the quill tube project for later... thoughts? Suggestions?

 

[hesutton]

I've swapped a "typ4" modded 460 ZF5 into my 6.9 crew cab. The low 1st gear and reverse are very nice when hauling a load. But, the low 1st is really not much use when empty.

ZF parts are $$$$ and I'd personally have a good look at the other parts of the trans and just replace what's needed. I had mine at the trans rebuilder for a new reverse gear, slider, synchro, and seals. That was $800.


Heath

 

[Ford F834]

But, the low 1st is really not much use when empty.
Heath

That's my whole point... To be able to skip 1st gear for daily driving! I really don't care for that 17:1 final drive ratio I get in 1st gear with my T-19 and 4.10's. Much prefer the 12:1 as a start out gear unless heavily laden.

Thanks for the advice. I seem to be reading a lot of " just rebuild it since you're in there..." comments, but a complete ZF rebuild is a far cry from a case bearing replacement and pre-load procedure, both in price and amount of work. I've read through the tech article on how to do this, and while it's a bit out of my comfort zone, I'm sure I could do it. I just didn't want to go there (full rebuild) if it wasn't really necessary. I'm just not sure if I would recognize light vs. normal vs. excessive wear on parts, but I do have 3 to look at and compare ha ha. They all need to be opened for one reason or another before being put into service.

Thanks again for the tip, and I'm glad to know you like the wide ZF in a crew cab 6.9, which is what I have. What is the US Gear under drive ratio? I have Gear Vendor under/overdrive that will go behind mine, 0.78 ratio when engaged. Should make for a sweet highway gear, 2,000 rpm at 75 mph in 5th+OD.

 

[hesutton]

Double overdrive would be nice. The US Gear underdrive gives a 20% reduction. The crew cab is used to haul the fifth wheel camper, and I keep it in underdrive until I'm cruising on the highway. I makes getting that heavy load up and moving much easier.


Heath