i recently replaced my ECM with a unit from the same year LG4 Firebird. the transmission shifted great with the old computer with the new one OD seems to be grabbing early. if it grabs and i just coast it seems come out but go back in and my RPMs drop to 1000. this is going about 30-35 i adjusted the TV cable, checked the fluid anything else? is this common?

i replaced the ECM because i was having problems with my CTS circuit and turned out to be ECM. now that the CTS is working OD might be kicking in but it felt like OD did before and my RPMs were 1500

 

The PROM / "chip" matters.

Does it shift 3 times?
Once, 2nd,
Twice, 3rd,
Third, 4th,
Thendoes it do a smooth reduction in RPM, lockup?

You can also (temporarily) unplug the 4 wire connector to observe shift behavior.

RPM is fun, but it may be working properly at 1000, 4th gear, locked up.
The chip can (fail to) control lockup. Determine whether you have it.

 

There's a difference between overdrive and TC lockup. There should be 3 shifts, and another "shift" that really isn't - it's the TC locking up. So I think what you may be describing is your first experience with this car of a "working" TC lockup? Which is controlled by the ECM you just replaced.

Does that sound right?

GD

 

To check to see if the torque converter clutch is working.... Go on the flat area of the freeway at apx. 65mph and at a steady speed depress the brake pedal slightly (enough to make brake lights to come on) and the rpms should go up about 150 - 250 rpm and drop that amount as soon as you let off the brake pedal.

 

The shifts are nice and smooth, I didn't count the number of shifts I will today though. I was told I did not need to swap the PROM since the new ECM has the same broadcast code FFA and was also removed from an 86 LG4. I did change out the PROM last night but have not driven her yet. I do not think my ECM has a Calpak .

In my experience with other vehicles OD it just felt like OD came in too early but I can see what your saying. Now the computer can see the actual temp it's commanding the trans to do stuff I didn't experience before. So the TC lock up is a separate event from OD? Altogether there will be 5 changes in the transmission?

I'll give that a shot. I never thought of that, that's gonna make the computer think I'm slowing down so it's taking it out of OD right?

 

No the brake thing is unlocking the converter.

There will be four events. You are already in first by moving the shifter to D. So a shift to second, third, fourth, and then TC lock. Four events.

GD

 

ok i drove her up my local highway. at 60 i slowly pressed the brake and the torque converter unlocked and RPM went up slightly. upon releasing it took a second but it locked up again

at 60 MPH i have about 1400 RPM. all shifts are smooth

does this sound like a healthy transmission?

 

With a CTS error the ECM wasn't locking the convertor. Now that it is working the ECM is now locking up the TCC. This is what is being felt once off the gas, TCC unlocks on a coast release, then re-locks once back on the go-pedal.

All in all I'd say it is working correctly.

Note that the only thing that is computer controlled in the 700R4/4L60 is the TCC lockup. All shifting is done via mechanical and hydraulic devices.

RBob.

 

can anyone tell me what rear end i have if my diff cover is 10 bolt? i wanna know if i have a stock rear end.

at 60 MPH my rpm is 1300 at 40 my RPM is 1000 and the car sounds and feels like its struggling to maintain that without dropping a gear

 

Yep sounds like a stock 2.77 or so. That's the aweful final drive my 86 TA had (but in the 9 bolt). Those are highway cruising gears. They suck for acceleration.

GD

 

thanks, im glad to hear nothing is wrong with my Trans Am and i can just drive her and save for some mods