Well, the ZF5 got pissed on the way to work and I had to pull over and decided to have a friend drag me home to avoid more damage. I was bummed. I bought the trans freshly rebuilt from a shop that the owner was retiring. Everything appeared in good working order and I got 12,000 miles without issue until 2 weeks ago.
Lately, driving to work on really cold mornings, I would hear a quick "zing" noise from what I thought was the trans, but it would only happen once, real quick and only on mornings when the truck was cold, the air temp was sub-30F and only on the interstate in OD @ 75mph. This would only happen every 5th time under only those conditions, making it real hard to diagnose the problem. Well 2 weeks ago, with an air temp of 24F, it happened 10 miles into my commute, then again and again every 1/8 mile. It didn't take long before everytime I heard the noise, you could feel the truck bog down.
I popped the t-case in neutral and coasted off the interstate. By the time I got onto the frontage road, the trans was pissed and could stall the engine when letting the clutch out with both trans and t-case in neutral. I was guessing either input bearing or secondary shaft bearings.
By the time my friend showed up, things had cooled off and were operating normal again. Not to risk it, we strapped it and tow it home. I dropped the trans and last week with a friend in town, we cracked the case open. I was relieved to find nothing major like giant metal flakes. The fluid was a little dark and the magnet seem to have an excess of sludge on it.
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We pulled the gear cluster and at a glance, things looked to be in good condition. Main shaft bearing were good, but counter-shaft bearings looked a little dull with signs of high axial loading.
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This was my suspicion all along. Reading the S5-42 service manual, proper preload is important to the bearings due to case expansion. I bought a 3-jaw internal puller and yanked both bearing cups. The only shim was the original single spacer the factory would have used after performing statistical analysis of the mfg tolerance stacks. Best I can tell, when the thing was rebuilt, it was just
ped back together and no one checked preload. With a cold case, the aluminum would have contracted tighter on the bearings until the ATF could no longer penetrate the space between the rollers and the bearings went dry.SO, now bearings are on order and I get to run through the pre-load procedure.
when I priced out the recommended bearing puller from Ford. $1700!!!