MauriSSio

my brother has a 1990 TBI and someone sold and installed the wrong tranny into the car. They Put a 4L60e in it instead of a 700r4. It seems to run ok still but doesnt downshift and speedometer dont work and seems to run better when he manually shifts it. ANyways what problems can this cause?? Also, the car seems to be running poorly, a big lack of power and getting bad mileage. Could this be at all unrelated like possibly bad MAP sensor or TPS sensor?? Or is this all because of the 4L60e?

funina91ss

I guess he is lucky it even shifts at all. His only option is to run it the way it is or pull it out and put a 700R4 back in it.

redneckgames

a 4l60e is a computer controlled transmission. You have to have the correct computer (or a stand alone unit) for the transmission to work properly. I wouldnt run it like it is. Fix it.

MauriSSio

yeah, hes making plans on looking for somebody to trade trannys. But i was surprised that it even shifts as well. But you think thats why it feels like really down on power?? It starts from 1st gear and all but power FEELS as if its doing a third gear start (obviously its not because you can feel it shift or manually shift it). Would not being able to connect it to a pcm make the tc bog down the engine like that? or would the low power be engine related??

cars3

As far as your bad gas mileage question my 89 formula with the 305 TBI gets 12-13 mpg in the city, and 25mpg on the highway. Most people I knew that had the TBI got worse gas mileage than people with TPI. Both of my TPI cars listed below get 16 mpg city and 23 mpg highway. My car is in excellent running condition with 129,000 miles.

kd5icr

I agree on the get a 700r4. He also needs to make sure that the VSS is hooked up and working. After all the 4L60e is nothing more than a computer controled 700r4 but it has to have a computer to make it work. A 700r4 built will be great for his car.

Marc 85Z28

Uh, if it's got a 4L60E that isn't connected... I've got news for you... 1st gear isn't happening. The trans is in limp mode, which means a forced 2nd gear.