Torque Converter Clutch Slipping?
 

I have 2000 F150 4x4 5.4L 4r70W with an ATI Procharger. It seems when I'm in third gear, the TCC slips. It doesn't seem like it fully locks up. This is under WOT with boost at 9psi. This problem doesn't seem to be there in 1 2 or 4.

Also, when just trotting around town in part throttle it seems that 3rd gear doesn't have any lock-up. If i just barely tap the gas at 60 mph while in 3rd gear (O/D off) then the rpms will rise about 300 rpms and then go back down. It's almost like the TCC slips the engine a little bit and then re-engages.

I'm not too sure I'm describing this prob accurately. Does this sound familiar? Thoughts?

If you are off the throttle the torque converter will be unlocked. That's the way it is supposed to work. When you press the throttle again it has a 1 or 2 second delay before it will lock, so that is also working as designed.

As for slipping while in third, I don't know. I do not know if this model is supposed to lock then or not. If it slips enough and it should be locked the OD OFF light will flash and a code will be set.

Mark

That's the same problem I have. But mine does it when I let off on the pedal and while it's in OD. Especially around 1500 rpm's and it'll jump for a second and go back to normal. I've Been trying to diagnose it from a while now. Ford says there's nothing wrong. I replaced the two VSS (speed sensors) on top of the tranny but nothing. I used the Auto-XRay scanner and no codes were found. Is it possible the TPS (throttle position sensor) cold be causing this?:confused: Any ideas?

You can replace every part on the truck and it's still going to do it. As the dealr told you, there's nothing wrong.

If you let off the throttle and get back on it there is a delay programmed into the lock. You need the change the computer's program to get rid of this delay.

Mark

Exactly what Mark said! It's annoying but true.

INteresting...
 

I suspect that it is a computer controlled "feature" built in to the profile. It seems Ford has made these trannies to be sweet and gentle. I wonder if a copmuter chip could help.

Interestingly, I've rec'd in the mail a Baumann Engineering shift kit. I hope to install it when 3 things happen: warms up, my buddy mooches his boss's inch-pound torque wrench, and I get the courage to do it. Ha ha! Actually the directions are pretty good. I think it will be ok.

NOW - regarding the TCC, Baumann also sold me a suplimentary part with my kit called a "Bypass Clutch Control Sleeve and plunger valve." It's made by Sonnax and looks like one of your grandma's thimbles. Along with the new part, is a diagram and directions to drill out 2 holes on the valvebody separater plate. Just like a traditional shift kit install. This is what the doc says it will do regarding improved performance:

"For firmer, quicker TCC apply, install sleeve as is and follow separator plate alterations." (and then there's a littl pic of the sep plate and arrows pointing to 2 holes with directions to drill them out to .062")

As FYI, the next line of the directions states that "to restore OEM feel of TCC apply" and gives some more directions to drill a hole somewhere else.

HOWEVER, i'm wondering if the phenominae of the TCC unlocking when you let off gas and then reapply (not the lock-up firmness which this part and drill scheme pertains to) can be remedied with a computer chip???

Thoughts?

Yes, the relock delay that you don't like could be changed with a chip. I don't know if any of the commercial chips do this or not. The delay is in the PCM programming, and the chip modifies the programming, so it can change it.

I think if you get it changed you won't like it.

Mark

Let me go into some details. A few months back, I had some tranny problems where it would stall in reverse and shift erractically. It was coincendence it happened right after installing the FT valve body. Greg was very helpful and we tried several things and finally found out it was one of the speed sensors.

The RPM jumping started doing this about a month after getting the tranny problem resolved. I even removed the chip and/or FT valve body and it still does this. When I took the truck in for the "cylinder head oil leak" fix a few weeks back and the tech said this was normal. So like I said, the tranny never did this prior to the speed sensor problems. So I'm thinking maybe the trucks computer may need to be reflashed?

Ignore that last post. I can't delete or edit it, and I really did type words of my own. I don't know what happened to them, and why all it posted was the post before it.

Anyway, I think your problem is the Transmission Range Sensor. It is on the driver's side of the transmission where the shift cable attaches. It tells the computer what position the gear shift is in.

As it begins to fail it tells the computer that you have shifted to neutral. The computer then shifts the transmission to neutral. The failure only lasts part of a second, so the transmisison quickly goes back into gear.

Get a new sensor and install it, or have a shop do it for you. They will probably argue that you don't need it because there will not be a code set for this. It won't set a code until the sensor is totally failed. That will take a long time, and probably destroy your transmission first.

Mark

Thanks for the info Mark. I'll definitely look into that. I've been trying to get rid of those little gremlins for some time now.