late shifts

[wdkingery]

My 1989 GMC sierra 6.2 shifts late and hard.

I had a bad TPS sensor, but it is fixed. I have since gone thru an made sure the sensor is reading correctly, is adjusted correctly.. In fact, the torque converter does lock up (can hit the brake while holding 60 mph and hear it unlock.)

Still, it wants to delay the 1-2 upshift and then BANG into second gear. Other shifts are late.

someone one suggested there is something sticking in the transmission that will unstick when warm. some ball or something. EDIT: have read that it's likely a th700r4/4l60e, and that the TV valve is sticking. duraguard to unstick it? i disconnected it and pulled it like a million times, and left it unhooked, and it seems to shift earlier and less drastically, but it might be just cause it's warm.

any input out there?

[DmaxMaverick]

Start with changing the fuel filter.

[wdkingery]

I've got one, so I'll try that, but why you reckon that's it? Fuel filter light ain't on.

[DmaxMaverick]

Actually, it's a dead-ringer for the symptoms. A plugged filter will reduce power for a given throttle position. This skews the throttle position to TV cable (pressure/timing of transmission) correlation. More throttle input and less (anticipated) power equals late/hard shifts, every time. A damaged or improperly adjusted TV cable can cause similar symptoms, for the same reasons.

[DmaxMaverick]

Also....
The WIF (Water In Fuel) lamp may or may not light up, depending on the specific conditions. On my 85, it was like clockwork. When it began to "flicker" on hard acceleration, it was time for a filter. Putting it off meant seeing the same symptoms you have in a short time. Others I've had didn't all act the same, some too early and others not at all. While it could be caused by other fuel system restrictions or a failed fuel lift pump, these conditions won't normally trigger the WIF lamp. It requires differential fuel pressure, before and after the filter, or the presence of significant water.

[wdkingery]

If I unhook the tv cable it shifts the same. Used to be I could cut it off and back on and it would go away. A bottle of Lucas transmission goo didn't help

[wdkingery]

should the TV plunger contact the throttle cable cam? cause mine is way below that