90 Ls400 Transmission Stuck In Gear

[dingster]

I just purchased a 90 LS400 with out traction control with 146k miles.

On the highway it won't down shift when I floor the gas. If I slow down for a EZ-pass toll and accelerate, it will be stuck in 3rd or 4th gear and the engine rpm will stick to about 2300rpm and the car will accelerate slowly. I guess until the converter locks up. Once I get off the highway it seems to be normal again.

The car will down shift if I force it by using the shift lever so I guess mechancially there's nothing wrong? Could this be a ECU issue? Do cars with and without the traction control use the same ECU?

TIA.

[VMF]

i'm not sure about your model year but there is separate unit to control the transmission.

[Dr. Henry]

Good Day,

I have the exact same problem with my 91 wanting to be in fourth gear all the time, but it sometimes downshifts when I floor it and sometimes it will just stay in fourth and accelerate slowly. I am breaking my head over this one problem, It seems to be some kind of pedal adjustment problem or maybe something related to the throtle position sensor or maybe something worst with 2nd and 3rd gear clutches worn out.... I dont know, but I do know that if I take it to the dealership they will tell me that it is the worst and most expensive.

[jzz30]

i have similar problems with my previa van (toy. of course) and well it used to shift too much between 2nd and 3rd. so i was looking at the tps sensor and stuff around there and found a vacume hose that had become old and hard and looked like it leaked so i changed the hose and now the shiftyness stoped but now it will only shift up during driving and it will only shift down manualy or when i come to a stop.....so maybe its something to do with a vacume leak(s). but i dont really drive that car so i didnt bother with it further.

[SKperformance]

make sure the tranny kick down cable is attached beside the throttle pedal cable on the throttle body assmbly