i have a weird problem that FASTCHIP cannot answer and so far noone on this site has answered this so i thought i would propose an experiment and then ask for feedback...this problem may only be unique to the 86 cars..........
i like to downshift alot, so when approaching a stop i may downshift from d2 to d1 and then when my speed drops enough i may drop in to 2nd gear at around 40-35mph and stay there till i come to a stop. my problem is that when the tach needle drops to 1000rpm the engine will surge and the tach needle will jump back up to 1500rpm. so, in essence you now have to apply more brake pedal pressure to compensate for the increase pull to still be able to stop at the correct spot/time. the surge only happens once each time you downshift, but, if you were to leave the trans in 2nd gear and drive to the nexst stop the surge would occur again. it did it on the old original chip and it does it on the FASTCHIP also. i have called Ed Wright and he cannot find a paremmeter on this....thats hard to believe on someone that makes chips, so, i would like to know if everyone else's car does this

thanks

 

When my car was all stock it did the same thing. I asked around and was told that it has to do with the solenoid in the tranny. When you down shift to second the car stays in that gear till about 1000 rpm, then it shifts itself into 1st causing the engine to speed up to make up the difference in engine speed and vehicle speed (sometimes my tires would even chirp when this happend) Something about when you slow down in drive normaly the solenoid doesnt keep as much pressure so its like your coasting to a stop in neutral. I think thats how it was explained to me ?? made sense at the time. Hope that helps at least a little.

Kevin

 

My '86 (T.A., not IROC) does downshift, but not that hard. It didn't do it with the original EPROM nor with the Hypertech, nor the upgraded GM replacement PROM (that it has now).

Is your TV cable adjusted correctly? I also have the later '86 TH700-R4 with the newer pump and secondary valve body, if that makes a difference.

 

Man, I hate paying someone to rebuild 700r4s! I'd be afraid to do it in my 86 IROC for fear of leaving a pile of parts on the road behind me. I dont' know anyone with a 700r4 that hasn't had to have it rebuilt at least once. I've even seen Chevy dealer rebuilt/installed 700r4s fail again. I save the downshifting for the 81Z with the Muncie. Your car, your choice, maybe you'll be luckier than I've been.

 

Every 700r4 I've ever driven has done this - even my new one. It's not computer related, it's trans related. Just stop downshifting like your not supposed to do. When you want to stop, put it in OD, and that jolt is gone.

 

Maybe I didn't understand the original statement, but if you put the trans in '2' it is a forced downshift. When in that position, the car should start out in 2nd instead of 1st, as well.