I just got a 1991 f250 diesel 2wd. It has the e40d transmission in it. It has only 91000 original miles on it.
Well when I went and got it, it drove good for about 80 miles then I was cruising at like 70 on the interstate and all of the sudden the Rpms went up and the speed went down. The gear didn't catch again until about 50mph.

Now SOMETIMES when we get in I get hard shifts and it acts like it doesn't want to shift or wants to go back and forth. But then sometimes it's really smooth shifting. It had started doing that so we changed the trans fluid and there was no big metal flakes in the pan or anything like that. Added the oil back and added Lucas anti slip stuff.
But it still does it only sometimes.
Off of those details can anyone tell if the trans is bad or if it may be the solenoid pack inside the trans that is going bad. Or am I way off?
I also went and talked to a transmission shop and they actually said it sounded more like the TPS than anything else.
Any help would be appreciated

 

It could be a lot of things...


You might get a better response from the pre power stroke idi forum...


I don't know these trucks that well...

 

TPS, harness, or speed sensors.

 

• Quote:

  Originally Posted by Ford_Six

  TPS, harness, or speed sensors.

that's what I was thinking....causing TC to unlock maybe?

 

The computer (any computer) can only make it's decisions based on the input it gets. If the input doesn't make sense, then it won't know what to do and will generally go into a fail-safe mode.
In the case of the transmission controller in your truck, the shift strategy is controlled by a map. If the TPS is at X, the fluid temp is at Y, speed is Z, then it needs to be in a certain gear or shift a certain way. If any of that input is outside of the map, it has no idea what to do.