Buddy of mine just called with truck troubles... He's owned this for half a year or so and it drives nice until a few days ago.

1997 F250 Ext Cab automatic with around 170k miles. A previous owner got rid of the stock turbo and put in a Banks setup. At some point there was a problem with the compression brake 'feature' and someone pulled a wire and disabled it. That was a few years ago so I don't think it's directly related to this problem but it definitely muddies things up.

The problem? For some reason his torque converter appears to not be disengaging automatically.

He was driving and everything was fine - went to stop and he killed the engine. When he started it the transmission shifted hard into drive and away he went. If he puts it in neutral it'll go out of gear and idle normally. When he takes off if he shifts down to second it goes into gear smoothly and then he shifts up to drive, transmission shifts smoothly so it pretty much acts like a manual transmission or a very stupid automatic.

He said when he drove it a little later in the day it acted normal but then when he left work or wherever he was the problem was back. He's driven it a couple of more times after checking fuses, looking for bad vacuum lines etc. and the problem remains.

Any ideas would be great.

 

Oops, forgot. He borrowed my code reader but it wouldn't pull codes off the 97's data port.
Since it's 1 in the morning he had to get some sleep but i sent him the procedure for reading codes from the flashing cel.
I'm curious if that will work. He says that before this problem his cel would light up momentarily when starting the vehicle and go out.
He thinks that the cel came on initially when he tried to stop and killed the motor but it hasn't come on nor does it light up when he starts the vehicle now. As if the bulb has burned out.
I believe that his recollection of the light working before is probably right. This fella's attention to little details like that are pretty good and have surprised me more than once.

 

Check your fluid, third brake light bulb, and the VSS sensor on the diff. You can the VSS and see if it changes anything, but be careful with it. Low fluid will cause the stalling and hard shifting. The brake bulb will keep the TC from locking. Other than that,might need a rebuild, but check the simple stuff first.

 

Do the brake lights work?

 

I don't know much, but stalling when coming to a stop happened to me in an old Dodge Dakota. It was caused by a bad torque converter. I guess it was kind of like having a manual transmission and braking to a stop in gear without pressing the clutch pedal.

 

Do like Byron says. Low fluid can defiantly cause this problem.

 

You never know, so Ill check those wires first, if they are well connected acording to the original diagram. Seems that the problem is the torque converter is lock up, and maybe there are other switch that manually locks up it, like in my truck, that can be on, right now. IDK.

 

Sounds to me like the TC is staying locked. Inspect the wiring to the TC for a short to ground. If my memory serves me correctly its pin #9 on the harness going down to the trans.

 

First of all thanks for the ideas. He's still at work but I sent him a list of things to check.
He hasn't had a chance to jumper the scan port and see if he can dump any codes yet.
What's the 'third brake light'? The one over the rear window?

I don't know if he can check the speed sensor or the trans connector electrically but he can certainly visually inspect them.

Seems to me if we can check the signal wire to the torque converter we could isolate the problem to the transmission or not.

Keep you posted.

 

Yes, that one