T/C not staying locked

[Big A]

Fellas,

I have a question, I'm hoping you can help me with. Is it normal for the T/C to unlock when you give it a fair amount of throttle?

I took it to the dealer, and they replaced the TPS, but if I'm going down the road at let's say 65, and I give it a fair amount throttle, the T/C unlocks momentarily. I never had that problem before, any ideas?

Thanx

Big A

 

[Joe G.]

Have you tired adjusting the kick down cable? I know that your rig is electronic and mine is mechanical, but that adjustment affects the kick down pressure regardless of transmission type. I think yours has some sort of fragile clamp on the adjustment that you have to remove with your fingers instead of a tool.

 

[Shooter]

Is it unlocking or slipping ?????

 

[Valkyrie99]

Mine was doing the same thing. There is a TSB out on the problem. I took it mine to the dealer and he reflashed it. Works great now. (TSB 18-02-99) You may want to check it out.

 

[Terry]

Hey Al, mine started acting up last week also. It just can't seem to decide if it wants to stay locked up. I'm taking it in next week for that, and a problem with the seat belt chime coming on whenever it wants to. I hope the reflash will take care of the transmission but I don't understand what caused it to need this flash after 23000 miles trouble free!

 

[Big A]

Thanx for the replys fellas. I agree with you Terry, my truck went 35,000 trouble free miles too, before the transmission started doing this. The dealer replaced the TPS, I guess the PCM reflash is next.

Thanx again

Big A

 

[Bill Kondolay]

Big A



Having your tc unlock under hard excelleration is a good thing not a bad thing. Most transmission & tc failures i come across are caused by the tc not unlocking under hard accelleration.



On my own personal truck i have the tc unlocking anytime i am over 3/4 throttle. When Stefan is driving our truck, i have it set to unlock the moment he sneezes.

 

[Extreme1]

Originally posted by Bill Kondolay

When Stefan is driving our truck, i have it set to unlock the moment he sneezes.

ROFLMAO!!

 

[Stefan Kondolay]

Who needs lock-up.

 

[Duraque]

Locking????

This is a question for Bill K. Maybe a stupid one but here it goes. How do I know when my transmission is "locked" and when it's not???

 

[Terry]

Hey Al, I had my truck in the dealer today. They replaced the accelerator pedal postion sensor and checked the software in the computers. The tech. said it had already had the 18-02-99 flash. The other dealer I took it to last year to get the 18-11-99 flash done must have done it also. The tech. said that the APP voltage was very erratic at a steady speed, after reading the entire 18-02-99 TSB it makes me think this flash helps cover for a crappy sensor that should be replaced anyway. Any way it sure does shift better and the converter clutch is working the way it used to.

 

[Big A]

Well I'm taking it to the dealer again to see what they can find. This time I'm taking the diesel tech for a ride and he's bringing along his diagnostic laptop.

We'll see

Big A

 

[Tom W]

My TC lockup was behaving erratically and Bill K suggested I clean the battery terminals. It fixed my problem and the truck has never run smoother. It might be worth a try.



Tom

 

[Fred Swanson]

Duraque, on a stock truck when you hit lockup, the RPM's drop and you feel like you actually have power. This is where people get into trouble. They try to force lockup with switches and then add more power. Poor converter clutch.





When you're not in lockup, anytime you give it more pedal, the RPMs' go up, and the truck doesn't feel like it goes any faster.



When you drive it now you'll see the RPM's go to 2000 RPM's and stay there through the gears, then it hits lockup and the RPM's drop like 500 RPM's or more. That's probably the easiest way to tell someone the difference.

 

[Duraque]

Originally posted by Stefan Kondolay

Who needs lock-up.

Anyone with a E-Brake!!!

 

[Steve M]

When you give it throttle and the TC unlocks, it feels like it loses power but it's not. It's giving you the go ahead to put your foot in it and feel the torque multiplication of the unlocked TC.

After having a '95 auto/3. 54 with it's absolute ornary personality, and then a '98 5spd/4. 10 with it's awesome power and chattering, grabbing clutch giving me pats on the back with spring wrap-up every time I have to back my trailer into my yard, I welcome the auto in my new 2001 with it's greatly improved program, firm shifts, deep trans pan and no need for a vibration damper on the drive shaft. And it responds to the throttle. When the day comes that it needs a TPS, I'll go get it one. This one is great!

Also, don't discount the possibility of a bad transmission temp sensor causing unlocking TC problems. It's easy to check with an ohm meter and easy to replace if it's suspect.

These trannies are based on the ol' bulletproof 727 of years past. They're strong and reliable in a stock truck. The TPS and temp sensor can cause trouble but are easy to diagnose and replace. Bombing is rough on any transmission. Even the Allison will suffer if abused.