Transmission issues

[Kristov]

So my 91 F350 with the E4OD has started shifting stupidly hard from 1-2 and not until 3k. I'm hoping that it's just a kinked line or something simple and inexpensive but a more mechanically inclined friend of mine at work said the transmission is probably going out. He's also offered to do the work to seal my truck to straight drive. Any thoughts on this particular issue?

 

[no mufflers]

might probably be the TPS on the IP. thats what controls the shifts and you can check the voltage or just replace it. its pretty cheap and easy.

 

[DrCharles]

Even if it's the valve body causing the shifting problems, can't those be replaced instead of the whole transmission? If it shifts super hard that's usually better than soft and slipping... the clutches are still doing their thing.
Or if it has to come out, might as well rebuild the whole trans.

He's also offered to do the work to seal my truck to straight drive.

Sorry, I don't understand what this means?

 

[Kristov]

@DrCharles That should read "switch my truck to straight drive." I posted from my phone and it was being stupid apparently.

@no mufflers I'm sure I've looked at it in the shop manual half a dozen times at this point but I'm not sure where to check the voltage on it.

 

[gandalf]

Your truck seems to have gone into "Limp Mode". That's a safety feature designed to save the transmission from destroying itself.

The transmission is controlled by the TECA, the transmission Electronic Control A... There are 3 primary things feeding the TECA: the TPS (or FIPL), the little speed thing on the differential, and one other item which slips my mind. If any one of those things feeds bad information to the TECA, then the TECA puts the E4OD into Limp Mode. It sounds vary much as though that is what has happened.

 

[trackspeeder]

It's much easier to scan for codes first. See what it says and go from there.

 

[Kristov]

Well I let the rig sit overnight with the batteries unhooked. It still shifts hard but not nearly as bad and at 2k. If I let off the throttle right before it shifts it's a nice smooth shift. One of the big rig truckers that makes daily deliveries to my work said it sounds like the torque converter is staying locked. Does that sound like a reasonable guess and how hard of a fix is that? Codes will be checked Saturday. Thank you all for bearing with the diesel newb.

 

[no mufflers]

thats a hard no from me. like mentioned its more then likely electrical related. personally i think its the tps. that and the speed sensor are basically what controls the e4s entire operation.

 

[trackspeeder]

Well I let the rig sit overnight with the batteries unhooked. It still shifts hard but not nearly as bad and at 2k. If I let off the throttle right before it shifts it's a nice smooth shift. One of the big rig truckers that makes daily deliveries to my work said it sounds like the torque converter is staying locked. Does that sound like a reasonable guess and how hard of a fix is that? Codes will be checked Saturday. Thank you all for bearing with the diesel newb.

TC lock up doesn't have anything to do with your issue. Because the batteries were disconnected any trouble codes (if any) are lost.

You could fiddle with or replace TPS.