zf5 trouble

[burt]

I have a 94 f350 zf5 s47 4x4 with a cummins in it. sounded fine till one day coming down a steep grade with about 10k in tow i heard a snap bang then a **** sound. i pulled over immediatly clutch in. so for diagnostic reasons i pulled the tcase to get that out of the equation. All gears except 4th are locked. i can shift in and out of all of them fine but if I start to let out the clutch motor starts to bog and no rotational movement happens. 4th is fine. So I think countershaft must have grenaded or something must have. I dropped the fluid and it looked ok. Not burnt looking no metal chunks. kinda shimery like metal dust in it maybe. Then I opened it up and to my surprise nothing appears to be broken. tranny doesnt have a bunch of miles on it since rebuild may be 30k. Ive rebuilt a few transfer cases but never opened a tranny before so im not real sure how everything is supposed to work in there but was expecting obvious carnage. Any ideas or experiences would be appreciated. Thanks

 

[dunk]

That's odd... I would be looking closely at shift forks and sliders. Maybe a bent fork hanging up so it can be in two gears at once? Maybe something going on with reverse? Was reverse idler shaft tight and gear/bearing in good condition? Input/output/pocket bearing condition? When you pulled it was there slop in either input or output shaft before splitting the case? If it made a loud bang something broke or otherwise moved. Did you check the cases for cracks? When I've ripped the tailhousing mounts off the case it's always a loud snap bang sound. That wouldn't explain it being jammed up though.

 

[burt]

Thanks for the reply. I found it. the pocket bearing I think its called between the input and main shaft is all destroyed. either melted or worn catastrophically. had to pry the two apart. why would this happen? Probably welded itself then snapped loose? everything else looks good. Didnt have any slop before I opened it up.

 

[dunk]

What fluid was in the trans? Too heavy of a fluid and the pocket bearing will not get sufficient lubrication. ATF is required, synthetic recommended. Gear oil will cause accelerated wear. As per ZF manual: Diesel units must use ZF recommended Dexron III/MERCON® XT-2 QDX or DDX equivalent.

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[burt]

The "race" part of the input has some black to it but doesnt look beat up. it doesnt look like a replacable race to me so does it need a new shaft to go with the new bearing or is it not that critical for some reason? Im really trying to not take it too far apart if I dont have to since it should have pretty fresh bearings and seals otherwise. Also is there other parts that need to be replaced regardless like throw out bearing when r &r a tranny. clutch and flywheel are pretty new. Thanks in advance

 

[riotwarrior]

In tech qrticles is an exceptional zf rebuild thread..read it.

 

[burt]

It was atf. Ive been reading that tech article plenty. Im not really wanting to rebuild the whole thing if its not needed. Im concerned that if I just throw a new pocket bearing on it and do nothing to the cup it goes into it will eat itself.I will pay close attention to pre load which could have been not setup right last time I guess. May be it was flat towed with the d shaft attached?

 

[dunk]

The race is part of the input shaft, so if it's damaged you need a new input shaft. I wouldn't cut corners if it's boogered, PITA to pull and service the trans. I would be more curious to find the root cause of the failure so as to avoid having this problem again. Have a close look at the input and output shaft bearings and races. Maybe preload was set wrong?

 

[79jasper]

Input shafts aren't that "expensive."

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[burt]

Ya I got an input shaft and bearing coming. Seems like it must have starved for lube or had wrong preload. Idk what else I can do besides replace those two parts and get the preload to spec. I cant think of anyone lately getting a good rebuilt tranny this one included. Thanks for the replies

 

[ifrythings]

What did the seal look like on the pocket bearing? If that seal is missing or gets shredded off it can take out the bearing.

Pick of what I'm talking about.

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[burt]

That seal looks pretty new. Does that seal just keep the oil level higher on the pocket bearing? That is the oil scoop that the manual above is referring to, right? I should probably put a new one in anyway.

 

[burt]

Anybody remember if they used a paper gasket between the main and tail housings?

 

[Kheg]

You need a tube of anaerobic sealer. Lay a nice bead and torque to spec.

 

[ifrythings]

Yes that seal is new in that picture, and the seal does keep a certain amount of oil in there to lubricate the bearing, if the oil baffle in the front of the case is missing it will starve the pocket bearing too.

No seal between the case haves just sealant