$0D and 1998 4L60e

[Marcus]

what do you mean "hangs at 2"? meaning it doesn't shift to 3rd or 4th gear? Or it revs up but doesn't go anywhere?

The transmittion stuck in 2nd and no change for 1st, 3rd or 4th. Truck moves with obvious limitations.

[brian617]

"Limp mode" on a 4l60e is 3rd gear. The way you can tell is both shift solenoids will be OFF.

[tayto]

is it possible it's putting itself into limp mode because of the codes being set? either way i would get that in order especially if it's fine on initial drive and then goes into limp mode.

[Marcus]

Friends,
Today I did a new 'test drive' which lasted about 30 minutes.
First I warmed up the engine.
I used the TunerPro log recorder.

Initial Conditions:
Engine Temperature: 176 degrees
Transmission temperature: 86 degrees
Oil pressure: 65 lbs (idle).

During the first 12.5 minutes, I did a mixed course and everything went perfectly. All gears shifted correctly including TCC. Oil pressure varying by load.
Engine temperature: 190 degrees
Transmission temperature: 155 degrees
Oil pressure: 65 lbs (idle).

Then, from the 13th minute onwards, the gear 'locked' in 2nd and the oil pressure practically fixed at 110 pounds. I drove home for a few more minutes.

Final conditions: Engine temperature: 183 degrees
Transmission temperature: 220 degrees
Oil pressure: 110 lbs.

I turned off the engine. After every 5 minutes I turned it on and wrote down the pressure. After approximately an hour the pressure returned to normal (idle, 65 lbs).

My impression is that the ECM is forcing this situation, I just can't figure out the cause. Clearly it's turning on solenoid B and putting a current of 0.7 amp into the Force Motor.

Any idea?

[brian617]

Trans over temp? Hot mode?

[Marcus]

Trans over temp? Hot mode?

no...

[Marcus]

Trans over temp? Hot mode?

Does not seem to me. At the time of failure the temperature is normal. Even at the end of the route it is on the limit, but without codes. I'm also suspicious of the temperature, that's why I kept an eye on it.

[brian617]

220* is not normal, might be worth looking at the parameters for trans temp to see how close you are getting.