Transmission ECU

[abovenbeyond]

Hi all,
Does the '91 305 use the 4l60 for a trans?

And if so is it a transmission controlled electronically?

Here is why I ask, would the ecu from a 9C1 work in my civie model?

And if so, what would be the benefits of switching?

[silicon212]

Yes it uses a 4L60. A 4L60 is the same as a TH700R4. The computer only controls torque converter lockup, as it does on all TH700R4 transmissions. The 4L60E transmission is the electronic controlled unit, and it didn't see use in the Caprice until 1994.

The ECM between the civilian and 9C1 models is the same - the difference in programming is the only difference. If your 9C1 model has a 305 in it (many did in 1991), the ECM will be the same with the same chip, same programming.

[abovenbeyond]

Hi Silicon,
So if I understand you correctly, my 91 (non 9C1) ECM and the 9C1 (350 or 305) are the same physically, but programmed differently?

Would the be any benefit in searching down a ECM for a 9C1 with the 4L60?

What was the difference?

[silicon212]

Originally Posted by abovenbeyond

Hi Silicon,
So if I understand you correctly, my 91 (non 9C1) ECM and the 9C1 (350 or 305) are the same physically, but programmed differently?

Would the be any benefit in searching down a ECM for a 9C1 with the 4L60?

What was the difference?

The ROM tables are a little different due to the displacement differences between the two engines, and for no other reason. The 305 program actually runs the timing a little more agressively than the 350 program does, however the 350 program pulses the injectors a little more (to give more fuel for the increased displacement).

There is no such thing as a '9C1' ECM, they're the same in every car of that model year.

The transmission does not matter unless you get a later model PCM, which would require the 4L60E trans, along with an L99/LT1 engine.

[abovenbeyond]

Ahh ok, I think I understand.