TCC Slip when showing fully locked.

[mhburton]

I am trying to verify a fresh rebuild on my 4L60E for my truck. This is the first Electronic Trans I've done (I have built a few TH350's & 400's in the past) and also the first time I have tried to use FlashScanV2, so the learning curve is a bit steep at the moment.
My truck is a 1999 5.3L LM7 Chev Silverado 4WD 4L60E Trans. Stock tuning.

Judging from the data I have so far, the TCC is failing to lock up. (Solenoid bad?) Also 3-4 felt mushy at higher TP%, but I want to make sure I am recording the right PIDs before I try to log that.

I recorded a log file and was wondering if one of ya'll could take a look at it a let me know what I might need to add or delete from my PID file. I don't want to burn up a new tranny trying to figure this out if there is something wrong with it.
Thanks guys.

[jfpilla]

You have the right pids and the TC is not locking, as you said. The trans is not slipping.
The WOT shift speeds are lower for upshifts than the downshift speeds. Doubt that is the problem since the lock should occur at part throttle. But it should be corrected. Maybe you could get lucky and it does have some effect.
Have you tried setting all the misfire tables to 32000. Misfire will unlock the converter, but you should feel it lock and unlock, so I don't think that's it either.
I don't see anything in the tune that would be an issue, either.
You might try setting D2801 to yes. Not as a recommended way to run the truck, but to see if it will lock at all.
Sorry not to have any good news help.

[joecar]

Also try setting:
- D2903 to 90%,
- D2904 to 100%.

Also try setting D2901 to 80 psi (or something).

[mhburton]

Thanks guys for the help. I am going to replace the all the solenoids/internal wiring harness etc. (I should have done it when I rebuilt the tranny with so many miles on it, the harness was pretty brittle, but thought I could get by without changing it and save 160.00) They will be here Tuesday, so I'll know if they are the culprits soon.

I currently only have scan capabilities with my FlashScan so I can't change any parameters yet, but will be upgrading it to tune soon.

[jfpilla]

You mentioned that you don't have the tune software, so it made me curious about the WOT shiftpoints. It seems that yours are correct. So, it doesn't downshift until you exceed the upshift speed for that gear?

[mhburton]

You know,
I need to do some checking to see exactly what it is doing regarding WOT shift points. My solenoids just showed up a few minutes ago, so I am off to replace them and give it a whirl.

[acomp917]

bump. What happened???

[mhburton]

Sorry about the time lapse. I work a weird schedule and sometimes drop off line for a while.

The solenoid kit didn't work, but the wiring harness needed replacing anyway so it wasn't a total waste of money. I kept the original solenoids for spares.

After looking at it further, I have decided that the TCC is working fine, I was looking at the data wrong. Although it is trying to shift, the trans isn't going fully into 4th gear, and the PCM is showing it as TCC Slip instead of a failed shift, I suppose, since it sees an initial RPM drop at the shift. The fluid temp starts increasing if I drive it in D4. If I pull the shifter back to D3, it seems to work fine. The Temp stabilizes, and TCC slip drops to 0 RPM.

I have been puzzling over how the PCM could tell the difference between TCC and transmission clutch slip anyway, since the only speed inputs from this trans are the output shaft speed at the transfer case and the engine speed. I have decided the PCM assumes all is well since it sees an initial RPM drop and is reporting any RPM difference as TCC slip instead of 4th gear slip.

1-2-3 work fine with good solid shifts so I am looking at the the band as the problem now. I must have gotten something screwed up internally. Hopefully I just screwed up the 2-4 servo piston, since that can be corrected without pulling the everything back out. I did replace the stock piston with the larger one that came with the TCI kit I put into the trans. If that isn't it, then I will pull it back out and check the valve body bore for the 4th gear shift valve and the check ball in the servo bore. (I didn't know until after I already had everything back together how notorious 700R4/4L60's are for wear in these two areas.)
I just bought a Kent-Moore servo rod length checking tool off of eBay to check rod length with.
Any thoughts?

[acomp917]

mhburton,

I won't be able to help much. I have never had an E trans apart, although I read somewhere that there is a sensor on one of the main power input parts(you would have probably seen it). If that is true the PCM can offset engine/input/output RPM's and figure out what is actually slipping(or at least the ratio there of). I have done some trans logging and suspect that one of the "slip" pids is actually a ratio. I'm still too new to KNOW for sure.

If you have changed any of your TC/TM settings, you could have this trouble. I posted a couple of files here. In the first I went nuts on removing torque management and the trans would slip in 4th. I then put the old tune back in the truck.

Files, never bothered finding the problem.

S

[joecar]

Yes, the 4L60E has only the VSS(OSS) sensor and the CKP (engine RPM) sensor...

If the PCM thinks it can lock the TCC, it then uses the internal gear ratios to obtain a calculated ISS... if ISS doesn't match RPM, then the PCM may decide the TCC is slipping... but you're right, it really can't decide between slipping TCC or slipping gear.

If it still happens after checking/fixing the 4th apply piston/seal in the servo, then maybe check for leaky 3-4 accumulator (since you'll be pulling the VB).

Edit: I rephrased what I was trying to say...