Transmission Issues - Diesel Forum

George_7.3IDI · 03-21-2008, 02:13 AM

Hi there TDS members,

I was hoping that someone could help me out with some input on several transmission questions that I have.

1. In general how many miles should a manual ZF 5 speed transmission last? Currently the one I have in my '90 F250 has about 121,264 miles on it. I am wondering only because it seems as though it's shifting hard lately but at the moment I'm not sure whether it's a clutch problem or a transmission problem.

I recently drained the transmission fluid that was in it, which I think was ATF, and refilled it with AMSoil 80W90 Gear Oil.
The symptoms:
(A)When leaving for work in the morning after truck has been plugged in for 4 hours and temperature outside is around 5 to 10 degrees farenheit I push clutch in to shift gears and when I push my shifter into the next gear it is very stiff but doesn't grind usually. (There isn't any sort of heater pad on my transmission either.)
(B)Often times, when warm, shifting fast between gears with the clutch in I feel the synchronizers grind. But if I then pull my vehicle out of that gear and then shift back in it doesn't grind the second time. Also with vehicle warmed up if I shift into gear slowly it goes in just fine without any grinding at all.
(C)Also I think that the person who I bought this vehicle from replaced the clutch himself. Not sure though and I've only been driving this truck for about 6 months so I'm not sure how hard this transmissions life has been.
Any available input in how I might go about figuring out what's wrong would be helpful

Thanks
George

cdnsarguy · 03-21-2008, 09:11 AM

ATF is the only lubricant for the ZF5-42.....
Check the firewall for cracks and flexing at the booster area.......clutch pedal assy/arms for worn out bushings.

http://www.zf-group.com/pdf/S5-42.pdf

Mark Kovalsky · 03-21-2008, 10:52 AM

Gear oil will cause both problems A&B. It will also not lubricate your trans very well, so either change it and use ATF, or you'll be buying a new trans in the not too distant future.

George_7.3IDI · 03-21-2008, 05:17 PM

Oh well the damn Ford dealer that I asked about it said that gear oil would be fine for it as long as it had the non cast aluminum case. Then again I don't trust the damn dealers much these days and my truck is old enough so that they've probably not dealt with any like it in a while. But anyways thanks guys for the information.