on my way back to WI from Dearborn yesterday, I got caught in 2 hours of stop-and-go traffic. After I finally got out of it, my car decided it no longer wanted to downshift on moderate tip-in. For the rest of the ride, it took a LOT more throttle input to actually trigger a downshift than it did before. It also usually used to downshift when I was accelerating with cruise control, but after I got through Chicago it didn't do that anymore. This transmission just got rebuilt last summer. Any idea what the heck is going on?

 

Sounds like slip slip slip -- DOH! Might want to look into not just a rebuild, but having the trans built to handle more "use".

 

Don't drive your car in Chicago, cars hate going through that city just as much as people.

 

may have overheated. see how the trany fluid looks and smells. could try resetting the computer

 

I did, just last summer (not even a year ago). It's not a heat issue, I drove the car yesterday after sitting for a couple of days and it had the same problem. I'll check the ATF today

 

check fluid level and color/smell

then, since you are OBD2, get it scanned to see if you have an over temp code for the tranny

 

there are a few sensors used to decide when to shift or down shift. tps, maf/map, speed sensor, crank/cam sesor. have you gotten under the car to make sure there are no lose or damaged wires to the trany?

 

tps, maf/map, speed sensor, crank/cam sesor.
Clean the connection then slightly bend the male connection spray with wd40 and make sure the water seals are there. A bad tps will cause trany problems.

 

so I took the car to the shop that did the rebuild. No fluid issues, no codes. The guy said he "couldn't replicate the problem," which is BS because if he had driven the car before and after it started acting up, it would be a night and day difference. Also, idk if I mentioned this before, but sometimes in stop-and-go traffic when I actually start building some speed, the car sort of "hiccups," like it decides to downshift and suddenly says "just kidding." Something the trans guy said is it may be the throttle position sensor. That will have to be the next thing I check out.

 

Doubt it's the TPS unless an intermittant issue before failure. I had the TPS code on my SS when my TPS failed -- was one of the first problems I had with that car... Anyhow, the TPS is cheap, and a couple screws -- easy to swap.