TC Slip Desired - blip when shifting into 5th OD?? (pics)

[usapadyra]

Since I got my truck 50k miles ago, it has always had a slight RPM flare when shifting into 5th (OD) gear.

It has always been a small flare. Maybe 100 or 200rpm. And it hasn't gotten any better or worse over the time I've had the truck.

Under certain heavier throttle / higher speed shifts it won't flare at all. It's almost 'worse' when accelerating very gently.

Today I recorded a few PIDs on ForScan, and was very surprised to see that there is a 'blip' on TC_SLIPDSD when the shift into overdrive happens.

The pics show first a regular shift into overdrive from joining a 55 zone, and the second two are me disabling overdrive and re-enabling it while cruising.

You can see the small RPM increase I'm talking about.

Is this normal?? If the blip is appearing on the desired PID that must mean it is actually being commanded by the PCM or some other module? Right?

I guess I'm wondering if this is causing extra wear on the TCC or overdrive band?

 

[usapadyra]

Link to the full video of the screen record here if it's any use:

 

[wollimann]

I don't know if this small RPM increase is normal, to my feel there should be no slip.
Normaly the RPM's fall down 200-300 RPM while the transmission shifts into 5th gear.

May be there's a internal pressure leak, -> valvebody seal, overdrive servo piston, valvebody valve braket broken,
loosen valvebody bolts or band tension.
Did you use MerconV oil? Oil change how long ago? Color?

if this is causing extra wear on the TCC or overdrive band?

Slippage always causes extra wear and a little higher oil temperature.
You have no DTC's?

 

[usapadyra]

I don't think it's normal either. I've tried watching various 'test drive' videos of the same truck / transmission on YouTube etc and I can't hear anything other than a straight drop in RPM when hitting 5th.

Possible internal pressure leak. I have no way of verifying. Only thing is, every other gear change up down and in between is flawless - always.

Oil is good. I had it serviced (pan drop fluid / filter change) 10000 miles ago. Since then over those miles I've probably extracted and replaced close to 30 quarts. Fluid is very close in shade to fresh Mercon V.

I use O'Reilly's Full Synthetic Mercon V. I have 5Q of Motorcraft arriving tomorrow so I'll drain and refill with that out of interest. I don't think it will make any difference, however.

Up until yesterday I thought it was overdrive slipping, but now with the data from ForScan (TC_SLIPDSD) I'm thinking it's actually the torque converter being commanded to open up for a sec when shifting. Since you can see the data in the pictures.

I also get a solid 2nd gear that shifts good and holds under load so I don't think it's the overdrive servo or band.

 

[usapadyra]

Slippage always causes extra wear and a little higher oil temperature.
You have no DTC's?

So even in summer I have a hard time getting the transmission up to temp if I want to check fluid level. I don't find that shifting in and out of overdrive on the highway is that effective at generating heat, I have to crawl around town or my local area starting and stopping to reach operating temp.

No DTCs, never had a flashing OD light and no check engine light. I've heard that some transmission codes won't necessarily trigger any warning lights, but if I scan DTC's with ForScan I get nothing, so I'm asumming I'm good there.

 

[Turdle]

You might log the throttle position sensor also.

Just a tad high output from it will delay upshift. Just to rule it out if anything.

 

[usapadyra]

You might log the throttle position sensor also.

Just a tad high output from it will delay upshift. Just to rule it out if anything.

TPS should be good. I've gone through 3 (or 4?) since getting the truck and the overdrive shift character has never changed.

I think my TPS now is 0.94v when closed, and when I replaced it recently only a few months ago, it read a smooth voltage curve increasing in line with throttle input.

But next time I go for a drive I will add the TPS PID and record that as well to see if it does anything funny when shifting.

 

[usapadyra]

I posted this on another forum and an ex Ford transmission engineer said that the torque converter is commanded to have a small amount of slip during the shift so it's smoother.

This makes sense, and explains why it hasn't changed in 50k miles, and also why under heavy throttle it doesn't really do it. Presumably because of the harder shift commanded at load.