lewingjr

I just traded for a 1999 Yukon that has an issue sometimes when I come to a stop and then take off it starts jerking and acts like it is still in second or third gear trying to take off. The previous owner said it started doing it after he had the TCC valve changed with one with o-rings to fix his P1870 code.

Anyone have any ideas what can be causing this?

mrvedit

Sorry that isn't much to go on.
The Fitzall TCC valve generally works very well, but it is important to install the correct one as there are two different ones. IIRC one for < 2000 and one for year 2000+.
Since the valve body (VB) had to be removed, it is easy for something to go wrong when it is reinstalled. Perhaps a checkball is in the wrong position or the gasket tore.

You might start with a rebuilt valve body which are often on ebay for about $150. Get a new separator plate and gaskets and try swapping the valve body.

Unlikely as it doesn't quite agree with your symptoms, but the P1870 code indicates the converter lockup is slipping and perhaps the converter's lockup clutch is now worn or defective.

lewingjr

I did remove the valve body and found the o-ring on the valve torn. I did not want to just replace that part so I ordered a reamman valve body and replaced it. The trans works fine driving around in town but when I take it to the highway then come to a stop sign it takes off ok then after a few feet it kind of hesitates then it seems to shift early (at around 1200 rpm). It does not matter if I am in OD or 3 it will do this.

lewingjr

I did some more test driving with a scanner connected. What I noticed is after I drive enough to get to overdrive and torque converter lock up, then stop it takes about 8 seconds sitting in one place before it will not do the jerk when I start moving. I also noticed on the scanner that the tcc slip goes to about 0 when the jerk happens like it is locked. Is this a possible bad torque converter?

mrvedit

Does the scanner show you when lockup is commanded?
Often transmission "problems" are caused by bad sensors (MAF, TPS, VSS) or even PCM, and you want to eliminate those before tearing further into the trans.
So far, a bad torque converter is a possibility; it would help to know what changes in those 8 seconds.

lewingjr

Tcc mode is a 4 that is supposed to mean locked mode. On my Scanner I see tcc slip, tcc mode, engine torque, trans output speed, tft sensor, vehicle speed, coolant temp, trans fluid temp, tcc duty cycle, tp angle, current gear, transmission hot mode, tcc brake switch, tcc enable short circuit, tcc enable open circuit, tcc enable feedback.

I just drove it with the brake pedal depressed so it did not go into locked mode and it did not have any issues when I stopped and then restarted.

I did change the Tp sensor and the brake pedal switch.