rapid deceleration

[AdamSr]

The guy I got my 91 Caprice from swapped out the trans with a unit he said is out of a 96. When driving, once I let off the gas, the car decelerates like I hit the brakes. The car also gets horrible gas mileage. I knew this was going to be a drivable project, but all my project funds are being drained at the gas pump.

[sherlock9c1]

Well, for starters, the '91-93 Caprice used the 4L60E which shifted itself and the '94-96 Caprice used the 4L60E which shifts when the computer tells it to and the two are not compatible electronically, so you've got a possible problem right there.

It's likely that the transmission is not upshifting.

[KW Baraka]

Originally Posted by sherlock9c1

.......It's likely that the transmission is not upshifting.

Exactly my thoughts.

Adam..........Your tranny is in 1st or 2nd gear (regardless as to your actual speed), you're revving the hell out of the engine (accounts for poor gas mileage) and when you get off the throttle.....you essentually go into a state of torque braking.

Bottom line.....you need a 1991 to 1993 tranny.

KW

[1slow96]

Or a "stand alone" trans. management system.

[AdamSr]

How can I verify what trans is actually in the car? I'm going off what the previous owner told me, and he was a few fries short of a Happy Meal.

[ScottLC]

It was the 700r4 thru 1993. It became the 4L60e in 94(93 for some trucks) when GM started their new naming system. Just semantics in a lot of cases but for this trans it's also the addition of computer control. Yours should have a plug receptacle like this...



I assume with nothing plugged in to it. Or with a plug whose wires just trail off somewhere because he had nothing to connect them to.

A 700, which is what you should have in there, will only have a plug like this...



I think those are the only plugs on each but it's been years so if I'm wrong somebody will correct me.

[sherlock9c1]

I've seen 3-pin and 4-pin connectors on the '91-93 4L60s. Scott's pictures are helpful though; they look COMPLETELY different. If you can get the front of the car up on ramps or gently drive the front wheels up a curb, you can probably just slide right under the car and use a mirror and a flashlight to see what the plug looks like. It'll be on the passenger side, on the top of the valvebody area, towards the rear, facing upwards towards the body.

[ScottLC]

A 3 pin? Maybe I do remember seeing that. And DUH! I guess I could have told him where to look, too. Might have been helpful on my part.

[AdamSr]

So the car should have which, a 700r4 or a 4l60e?

[ScottLC]

It should have the small 4 plug 700 in it. If it's the big round plug then there's your problem.