I'm having problems with my early 99' F-350 diesel automatic transmission. When I'm cruising in traffic at 38-45 mph, it starts to shake and surge like a stickshift does when the rpms are too low. I depress the overdrive button which kicks the rpms up, the problem goes away. After 45 mph in OD it drives fine. Is this a symptom of a bad torque converter? Has anyone had any experience with Trans X fluid?

 

I wonder if something screwy is going on with your torque converter. Right in that range is where it shifts from 3rd to 4th. When in 4th gear, running at 40 mph my rpm's are at 1,000 and if I drop below that it'll down shift to 3rd. I wonder if your T/C is staying locked up and the tranny is not downshifting, resulting in your surging. I've got a T/C lock-up switch where I can lock my T/C manually, and if the rpms get too low, it'll do as you say. I know there have been TSB's out on these T/C's saying they should get replaced, but talking with the Ford tranny guy he says they're just fine. ??? So can't help you much there.

 

honestly sounds like a u joint

 

I have never heard of a u-joint doing that to a truck at those speeds. The shaft is spinning too fast at those road speeds, it would just sound like a hum. I agree on the torque converter issue. Check your fluid level, and odor. Make sure none of the wires going to the trans are damaged. Converter clutch control valve might be stuck, or sticking.

 

I had the fluid changed, it was slightly dark in color without any sort of pungent odor. I read about guys having the tranny reprogrammed to shift at different points. I wonder if I have some sort of computer glitch that is jerking me around. Is the Ford Dealer the only place I can go to have this checked, or can any reputable tranny shop do it? If it is the TC, will it blow up on me or can I drive it until I have the dinero to fix it?

 

I just posted about this in another thread, but I had my truck at the dealer and they reprogrammed the PCM and it improved my shifts a lot! They said there was an update for the old program, they plugged their computer into the truck, and it listed a bunch of stuff it would change, most everything I was having problems with, and it did fix all of them. I got it done for free(my old man works at the dealership-connections ). But I think it would cost around $30-$50 for them to reprogram it.

 

thanks FarmBoy, I'm gonna check into that. I can't stand the way it drives now considering how much time I spend at that mph range. I wonder if a quality chip would remedy it?

 

A chip won't be able to fix this problem. All the chip does is make the shifts firmer and quicker, nothing with when the T/C locks up. I think it's worth your $50 to go to the dealer and have them reprogram it.... then get a chip.

 

I've been told by a couple of tranny guys to turn od off whenever you are on the surface streets. They say it will definately extend the life of an e40D