Hi all,
I have a 1990 ford e350 ambulance with 7.3 diesel and with automatic tranny with overdrive.
it is shifting fine, but on the highway it seems this has a lockup converter or something which is unlocking and locking at weird times on the highway cruising in overdrive. how is this controlled so i can fix it. thanks.
mark

 

It is controlled by the computer that controls the entire transmission.

 

Tapping the brakes enough to turn on the brake lights will unlock the converter, you might check the brake light switch to see if is set so sensitive that a rough road will activate the brake lights.

I'm not saying this is your problem, but it is one thing to eliminate... Good luck.

 

Ok I will check my brake light switch, and when the other person says "the computer controls it", . what does the computer control it with? if vacuum, my vacuum pump is out and been using a electric brake vacuum booster, only to power my brakes, the rest of the vacuum system isnt working, and there seems to be a shift cable of some type that isnt hooked to anything near the injection pump. . thanks. i dont know what trans it is, but its the one with the overdrive off button on the dash if that helps.
mark

 

It's an E4OD. It is completely electronically controlled. Vacuum has no part in it.

 

Ok , so the brake light switch is the only thing beside the computer that controlls it? I explained I have cable lying near the injection pump that isnt hooked up, look like a throttle cable.. I had a 1986 buick grand national with a GM 200r4, that had a brake light switch, then relied on a throttle position sensor too , both would have effect on when the converter locks and unlocks. does this have anything connected to the gas peddle? thanks..

,mark

 

The computer controls the torque converter clutch, along with the rest of the transmission. The brake light switch is one of many inputs to the computer. So is the throttle position sensor, the trans range sensor, the vehicle speed sensor, etc.

You would be well advised to see if there are any codes stored in the computer.

 

ok so this does have a throttle position sensor. i didnt know that, and where is this located. thanks

 

It's located on the injection pump.

 

Ok thank you, iam 100 percent positive something is misadjusted that controls it. its a reman tranny 30k ago . Iam just wondering, does the throttle position sensor need to be calibrated every so often?, also do you know where I can find out where things like where the speed sensor is grounded, and the ground for the computer. I want to check to make sure they are all nice and clean as Iam chasing down a small electrical problem already (if I hit a bump, a buzzer comes on and stays on under the dash,used by the rear paramedic to signal the driver, also i lose battery 1 and 2 indicators) but those are ambulance related. thanks for the help.
mark

 

The throttle position sensor doesn't need to be adjusted every so often, but it does need to be replaced every so often. They wear out.

I don't have diagrams to tell where the grounds are located.

 

Without seeing it about the only thing I can imagine this would be is speed control (or to use a generic name, Cruise control)
The cable sometimes gets left off when doing other repairs.
It wouldn't have any effect on your transmission problem, so don't worry about it now, that's another "project"

 

the cruise control in this appears to be ran off vacumm lines. the vacumm pump has been out so Ive been using a electric vacuum pump to supply brake pressure and arent putting vacuum to other things.

 

I was referring to the "SHIFT CABLE OF SOME TYPE" that you mentioned, I was not talking about any vacuum lines...

The cruise control uses a CABLE to activate the throttle... this is what I thought you might be speaking of..

Sorry I tried to help!!!!!!!!!!!!

 

ok, ty... youve been a great help xD Ill be probally posting what i find within the next few days