So I've got a 2001 SCAB with the 4r70w. At 150K the transmission took a dump. It put me in a bind and I hastily had a used transmission installed which I've regretted ever since. It's held up, but it's never shifted right. It holds gears too long and shifts hard and I wouldn't be surprised if it died on me any day.

The truck now has 176K on it. 90% of that has been pulling a trailer. I normally do tranny fluid at every 30K miles so I'm planning on doing it at 180K. I know some guys don't do it at all. I've come to find that the mechanic who did the trans swap for me uses cheap quality parts and fluids. He used some kind of generic (cheap) Dexron fluid with a Mercon "conditioner". I've also heard that these Ford transmission are picky on what type of trans fluid is in them so I'm hoping that a fluid change with quality fluid might do it some good and smooth it out. However, I'm kind of afraid to mess with it at all.

I would really, really like this truck to last until about 200-210K without another major repair at which point I should be in a better position to get rid of it. It's not a good time for me to buy a new truck right now.

So for those of you who know more about transmissions than I do, any advice on this situation? Flush it? Leave it alone? Something else? I did try some Lucas Transmission Fix which had no effect whatsoever. Also, after adding the Lucas TF, it ironically developed a small leak.

Sorry if this is a bit long, I appreciate any constructive advice!

 

Change the transmission fluid. Use MERCON V fluid.

 

Mark,
I do intend to, but the fluid alone probably wouldn't cause that hard shifting would it?

 

No, it would not.