99 PSD ZF6 Grinds going into 3rd? Only 95k on it - Diesel Forum

schmegly7 · 06-01-2011, 09:45 AM

My 99 PSD w/ ZF6 is grinding going into 3rd. No problems going into any other gear, so I have been skipping from 2-4 whenever I can. Could this be fluid level related or is it something else? Thanks

RT · 06-01-2011, 03:44 PM

Mechanically, it would be a stuck synchronizer. Whether you could free it up with a oil change is a crap shoot. Not likely, but weirder things have happened.

schmegly7 · 06-01-2011, 04:17 PM

Thanks for the reply. So I am guessing that I will need to have the tranny torn down and replace that synchro along with anything else that looks bad?

schmegly7 · 06-01-2011, 04:21 PM

I thought that the ZF6's had synchros for two gears tied together. 1-2, 3-4, and 5-6. Are they individual for every gear?

**klhansen** · 06-01-2011, 05:32 PM

The synchros are paired L-R (yes, reverse is synchronized), 1-2, 3-4, and OD. The parts list, just lists the synchronizer assemlies. You could probably repair one side of the pair if you could find the individual parts, but most just replace all the synchros once the tranny is opened up. I was quoted a price of $2000 locally, just to tear down my ZF6 when I had problems with coolant in the oil. I wound up getting a rebuilt tranny installed, with Ford kicking in some money since it was JUST out of the 36,000 mi warranty.

In it's last throes, I was running a ZF3

I'd try a fluid change first and see what happens. A synthetic ATF might be the ticket, if you want to spend the $40 or so it would cost for 6 qts.

Or you might try one of Redline's products that might be a little thicker than ATF. (This suggestion is untried by me, so take it with a grain of salt, however, the newer ZF6's behind the 6.0L & 6.4L's specify gear oil instead of ATF.)

TransBrain · 06-02-2011, 11:38 AM

Synchro rings have worn out.

mcintoshjr · 03-14-2012, 12:10 PM

So what was the damage did you do it yourself? If so how big of a job was it?

firefighter9208 · 03-14-2012, 01:07 PM

You need Synchronizers. Pretty big job. Have to also replace some other parts. Mine was done at 55,000. I bought the truck with 52,000 (in 2002) and it was grinding occasionallly. Actually did it on the test drive. The saleman told me there was no problem. Within 3000 miles it started jumping out of 3rd and grinding on every shift.

I live in a small town and took it back. The owner ate the cost of a rebuild, because he didn't want "bad press" and I had pointed out on the test drive that there was a problem.

There were more than one ZF6 offered. In 2000 they came out with a higher HP and torque rated ZF6. I would go to a local "big truck" dealer and try to buy a later higher rated ZF reman.

Ford ZF S650 6 speed Rebuild Kit Manual Transmissions - Drivetrain.com

It looks like a reman from the same company is about $2500.00 plus core.

Chris

schmegly7 · 03-15-2012, 10:03 AM

My damage was caused by a hole in the radiator which allowed coolant into the tranny fluid. Entire tranny was rusted inside, so I had it all rebuilt locally. New clutch while we were in there and a new radiator of course. I know that this fixed the problem. Looking back the only way I would have known is if I had checked the tranny fluid more often. It never leaked on the driveway or in the garage. I could have tried draining in and puting a synthetic fluid in or even pouring in 6 quarts of marvel to see if it would loosen up, but I bit the bullet and just had it rebuilt.

**klhansen** · 03-15-2012, 08:51 PM

Quote:

Originally Posted by schmegly7

My damage was caused by a hole in the radiator which allowed coolant into the tranny fluid. Entire tranny was rusted inside, so I had it all rebuilt locally. New clutch while we were in there and a new radiator of course. I know that this fixed the problem. Looking back the only way I would have known is if I had checked the tranny fluid more often. It never leaked on the driveway or in the garage. I could have tried draining in and puting a synthetic fluid in or even pouring in 6 quarts of marvel to see if it would loosen up, but I bit the bullet and just had it rebuilt.

Really?!!
That's exactly what happened to my original tranny.

The OTW cooler broke, allowing coolant into the tranny and ATF in the coolant. It took out the synchros in short order, and finally puked pink stuff out the radiator cap. Ford dealer replaced it with a rebuilt (and a new radiator). It was at 40k miles (just out of warranty) but Ford chipped in half the cost as they'd never seen that happen before, and I had good maintenance records.