2002 F250 5.4 Auto CC LWB 4X4; 109,000 miles

-IIRC, trans fluid changed twice by dealer, last time at approx 60,000
miles; IIRC, $69 ... so I guess just pan-filter/fluid changes, not flush-??

-I have a 4r100 trans - ????

-The transmission shifts gears fine ... smooth and crisp.
-The truck starts off from a stop fine.

-The problem is ..... when at high speed, or at least at high rpm, when you remove your foot from the accelerator pedal, and then press down on the gas again, there is a hesitation before the transmission grabs. The truck makes a "winding up" sound, and then transmission kicks in, and you start accelerating, etc.

-My son had borrowed the truck, and he was telling me this over the phone this morning. He will bring it to me this evening. I will check for any codes, examine the atf fluid, etc

-I asked him if the truck was trying to downshift and was having problems, he said no ... the truck is going too fast to want to downshift.

-It does not bang or clank when the transmission catches, or stops slipping ... whatever is going on here.

-Again, the transmission runs perfectly ... except when you remove your foot from the gas at high speed or high rpm, and then replace your foot while still at high speed or rpm.

Any thoughts?

Thanks.

 

Bumping it for the evening crew.

 

AFAIK, this is normal behavior. When you let off the gas, the converter unlocks. When you get back on the gas it locks again. This will cause a flare and make it seem like it's slipping.

 

This is exactly what's going on.
JL

 

I thought it was the torque converter, too .... since the transmission shifts fine. Over days, it became harder and harder for it to lock back in.

Update ... I still don't have my hands on the truck ... but I told my son over the phone to override the overdrive, by using the button in the end of the trans shifter stem (like we do sometimes when towing). And, that pausing/straining/slipping is gone.

I still have not had the chance to look for any codes

So, I have a torque converter clutch problem?

Driving, for the time being, with the overdrive shut off ... I am not doing any damage?

Any chance a transmission flush would solve the problem? The fluid is a little old.

Is it the torque converter itself that is failing? Or is it an external component, part of the electronic control system, that is failing and may need to be replaced?

Thanks for any info.
(Suddenly find myself unemployed, and have no money for a major repair)

 

I am surprised you never noticed that before...

 

It has just started to do this. It is not normal operation.

Thanks

 

You can drive the entire life of the truck with the OD off and not hurt anything.

Is the fluid low?

 

I think you need to drive the truck personally and confirm this. Selecting 3rd gear (again IIRC) changes the lockup characteristics of the torque converter. I don't think it does the lock unlock thing in 3rd.

 

Yea ... tomorrow I'll have the truck ... actually look at the fluid level and condition, etc ....
The TC clutch locks up in 3rd, too? So, this is the 4r100 shift sequence:

1st; into 2nd; into 3rd; TC locks; TC unlocks/into 4th; TC locks

Thanks

 

Right, but I think it holds in 3rd, it doesn't unlock when you let off the gas.

 

The torque converter unlocks as soon as you let of the gas. They do this to prevent a noise from the slop in the drivetrain which you would get if the TQ stays locked. Its a lot easier to notice the TQ lockup in 3rd and 4th but the TQ will lock up in 2nd if you hold the gear long enough. You just don't notice TQ lockup in 1st and 2nd because it rarely happens. The stock shift and TQ lock strategy on the 4r100 blows and thats putting it lightly. This was all done to make a nice smooth quiet truck which most people want or they will complain.

Might want to take the truck to a qualified local trans shop. Dealers are no good at working on transmissions in my experience.

 

I think the lockup in 2nd varies on year and PCM program revision too.

 

That is correct.
JL