Odd problem

I was cruisin around one day last week, and sitting at stoplights, car was warm, cause it was in stop and go traffic. Car was running perfectly fine. I stopped at a gas station to buy something, a pop or something (unrelated), came out got it, started her up, backed out of my parking spot, pulled out into traffic, accelerated lightly, driving fine, and WHAM, slammed into 2nd gear, was thinking, oh, first time that has happened, must have been a glitch, SLAM into 3rd gear. I mean very very hard shifts under very very light throttle. I thought, wtf is going on here, pulled over, turned the car off thinking maybe its computer related, started her back up, accellerated even slower, same issue, in all gears. didnt get fast enough for overdrive though. Was near a target parking lot, pulled in, and turned her off. I was checking everything i could think of. Vacuum leaks (even though its a 4l60e thats shifted electronically) checked tranny fluid (red as usuall and not burnt). Went inside the target to get piece of mind thinking what my next step should be. came out about 10 minutes later thinking ill baby her home (7mi) and figure it out there. Jumped in took her doen the road, and she shifted smooth as ever. I couldnt figure it out. Its been a week now and no issues. I thought maybe the tcc was siezed half in because of heat and when allowed to cool was fine again, but it makes no since, the car has been hotter and has worked fine on hotter summer days. Could it be a tps on the way out? (i have noticed sometimes when i go to accellerate at highway speeds when i slowly push the gas, the rpms and the speed is unresponsive untill i get to about a certain point. maybe i'll ohm check that tomorow) Any ideas about what caused the hard shifts? Richtazz? Maxwedge? Jeffcoslacker? Cadgear? (where has he been?) Thanks guys

That's how it started when my tps went bad....

I was cruisin around one day last week, and sitting at stoplights, car was warm, cause it was in stop and go traffic. Car was running perfectly fine. I stopped at a gas station to buy something, a pop or something (unrelated), came out got it, started her up, backed out of my parking spot, pulled out into traffic, accelerated lightly, driving fine, and WHAM, slammed into 2nd gear, was thinking, oh, first time that has happened, must have been a glitch, SLAM into 3rd gear. I mean very very hard shifts under very very light throttle. I thought, wtf is going on here, pulled over, turned the car off thinking maybe its computer related, started her back up, accellerated even slower, same issue, in all gears. didnt get fast enough for overdrive though. Was near a target parking lot, pulled in, and turned her off. I was checking everything i could think of. Vacuum leaks (even though its a 4l60e thats shifted electronically) checked tranny fluid (red as usuall and not burnt). Went inside the target to get piece of mind thinking what my next step should be. came out about 10 minutes later thinking ill baby her home (7mi) and figure it out there. Jumped in took her doen the road, and she shifted smooth as ever. I couldnt figure it out. Its been a week now and no issues. I thought maybe the tcc was siezed half in because of heat and when allowed to cool was fine again, but it makes no since, the car has been hotter and has worked fine on hotter summer days. Could it be a tps on the way out? (i have noticed sometimes when i go to accellerate at highway speeds when i slowly push the gas, the rpms and the speed is unresponsive untill i get to about a certain point. maybe i'll ohm check that tomorow) Any ideas about what caused the hard shifts? Richtazz? Maxwedge? Jeffcoslacker? Cadgear? (where has he been?) Thanks guys
You do have a modulator on the trans, up till 98 as far as I know. anyway if this was bad the shifts would be hard and delayed. Yes the tps can cause this also but usually that also includes a delayed shift. It could be the issue with the worn tcc valve bore in the valve body causing a line pressure boost, or a sticking pcs solenoid in the trans both of these will cause that exact symptom and may require scanning for pending code 1811 or 1870.

ok, great thanks guys. Im going to ohm check that tps and see whats happeneing there, and if it checks out, im just going to wait for it to happen again and go from there.

And for reference, you don't have a 4L60-E in a Lumina.

He meant 4T60E...

Hey blake, I found another reference...check out the 2001...

1997 Chevrolet Lumina/Monte Carlo: All models gained daytime running lights, and a sporty new Lumina LTZ sedan arrived during 1997. The LTZ included unique front and rear fascias, a rear spoiler, and alloy wheels, with the 3.4-liter dual-cam engine as an option. The V6 was no longer available in the Lumina LS. A new automatic transmission, used with the 3.4-liter engine, promised smoother, more prompt shifts.

1998 Chevrolet Lumina/Monte Carlo: A 200-horsepower 3.8-liter overhead-valve V6 replaces the dual-cam 3.4-liter V6 on Monte Carlo Z34s and Lumina LTZs. Otherwise, changes are minimal.

1999 Chevrolet Lumina/Monte Carlo: Lumina and Monte Carlo carried on into 1999 with little change. Both got more standard equipment, and the Lumina LTZ lost its rear disc brakes in favor of drums.

2000 Chevrolet Lumina/Monte Carlo: Only one Lumina model was available, equipped between the 1999 base and LS editions. Only the 3.1-liter V6 engine was offered, retuned for 15 extra horsepower. Front bucket seats were no longer available, leaving only a standard 60/40 bench. GM's OnStar communications system disappeared from the options list. A new optional Appearance Package included a CD player and 16-inch aluminum wheels with higher-performance touring tires. Chevrolet redesigned its Monte Carlo coupe for 2000, switching from the Lumina platform to that of the new Impala.

2001 Chevrolet Lumina/Monte Carlo: No changes were made to the Lumina as it was sold exclusively to fleet buyers.

so mine is basically a 2000 lumina? thats still strange that the ac delco part number for plugs for a 2001 is 41-979 and for 2000 is 41-940. I am also considering a set of taylor high performance ignition wires from summit racing. They will actually cost the same shipped here as the ac-delco ones would from the dealer. any takes? Sorry to change the topic of this thread. Lumina tps will be tested tomorrow for sure as now i have batteries in my multimeter. thanks for the info jeff, and everyone.