ZF6 fluid alternative to ATF

[greenskeeper]

Apparently my 3rd gear synchro is failing when cold. Crunches going into 3rd when upshifting, downshifting is fine. Clears up after driving a short distance.

Who here is using something besides ATF in the ZF6?

I KNOW THAT ATF IS SPECIFIED, just looking for alternatives to keep it going a little longer.

 

[trackspeeder]

Stick with ATF.

 

[greenskeeper]

I am going to try some 75w-90 gear oil (undecided on brand as of now) and see how that goes.

I am prepared to purchase a rebuilt transmission, it certainly doesn't owe me anything at 237k miles.

 

[trackspeeder]

Using any gear oil in a ZF6 will waist the tranny quickly. The pump isn't designed to pump heavy lube.

 

[79jasper]

The newer trucks called for it. (With no major design changes in the trans)

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[F-SERI-ouS]

ok, so I am getting ready to put my rebuilt engine back into my truck, a 94 350 idi with the zf-5. I am also wondering what fluids you gents have been using and getting good luck with. for the record my trans was also hanging up on 3rd gear just prior to me pulling the engine. I also know that ATF is the spec'd oil, but I am wondering if anyone has used synthetic stuff with better results? maybe amsoil or something? or should I just stick the conventional fomoco atf?

sorry to piggy back off this thread, I cannot figure out how to start my own.

 

[79jasper]

I posted a link in his other trans thread. Go check it out.

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[94f450sd]

As far as i know synthetic atf only.youll burn it up with gear oil plus you may not even be able to shift it.

If youre dead set on using a heavier oil id go with either a motor oil like honda and toyota use in thier manual trannies or 30wt synthetic heavy truck transmission oil.

 

[greenskeeper]

removed 1 qt of the ATF and added 1 quart of Lucas Oil 75w-90.

no more crunch into 3rd gear during a test drive this evening.

 

[trackspeeder]

You may have eliminated the crunch into third. But you wont stop it from melting down when the pump fails.

 

[greenskeeper]

You may have eliminated the crunch into third. But you wont stop it from melting down when the pump fails.

The transmission pump is similar to the LPOP in our trucks. I can't see 1/6 of the fluid being a "light" gear oil at 75w-90 doing any harm. Time will tell and I'll be the guinea pig. Transmission has 237k on it and doesn't owe me a thing.

 

[greenskeeper]

So I ended up switching completely to pennzoil syncromesh which is slightly thicker than ATF. The ZF6 absolutely loves it. No 3rd gear crunch anymore and just buttery smooth shifts and engagement. 10k miles so far and I am going to service the transmission again at 30k intervals.

245k miles and s-t-i-l-l going!