One Ton Dodge 6 spd Tranny Question

[71-LS6]

I changed my transmission oil about 10K miles ago, it was the first oil change, so the factory oil was replaced with off the shelf lube from the local auto parts place. I accidentally put a qt. of 90W in it when refilling the case (the specs call for 75-85 synthetic API grade GL4). I replaced the rest of the oil with 75-85 synthetic as called for, and put it back on the road. First and second gear were impossible to engage, unless it was not rolling or until it was fully warmed up. I drove it about 5,000 miles (or about one week) until I had time to drain and replace the oil with some off-the-shelf 75-85 synthetic. The thing is a little easier to shift, but 1st & 2nd are still stiff. Both times that I drained the oil there was no evidence of shavings or any type of gear wear whatsoever.

Here's my question, did I damage the synchro rings in this transmission by using that 1 quart of 90W? If not, is there some sort of anti-friction additive in the factory gear oil that the aftermarket stuff does not have? I usually get 200-300K miles out of my trucks, this has me a little concerned.
Thanks, Steve

[Big Block Bill]

Steve

You can try draining all the fluid again, re-filling with the proper synthetic gear oil, and adding a bottle of GM Limited Slip Differntial additive or Ford Friction modifier. It was a must when servicing or overhauling the ZF 5-speeds found in Ford Trucks from the 1990's. We also have had to use this process in the Mustang 5-speeds and GM 14 bolt rear differentials with posi "Chatter" on the 3/4 ton Suburbans, Pickups, and 1 tons. It is a cheap fix to a potenially expensive problem. I hope this helps.

Bill

[71-LS6]

I'll give it a try, I think that tranny is used in Fords also.