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Old 06-18-2009, 04:32 PM   #7 (permalink)
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Originally Posted by micondie View Post
I think I would need to put relays in the circuit to isolate the ECU form the TCL so the ECU wouldn't know about the manual switch. This would avoid the CEL. This would also allow me to wire the relay to either unlock on brake application or maybe on the 4-3 downshift.
Brake application, I can see, but there is an advantage to having the converter locked in any gear - 1:1 operation with the engine and transmission. There are lots of manual valve body options which allow (for race applications, granted) you to have lockup in every gear, without a manual switch. Those applications are for manual lockup though, where the lockup solenoid is controlled by fluid pressure and a valve.

Regardless of the control method, having lockup on demand will allow you to engine-brake (although not in DFCO) in any gear except 1st, which is a sprag-type gear.

If it were me, I'd probably try to find a way to de-activate it with the speed sensor (when it gets below a certain speed), so that I could have engine braking when I actually wanted to slow down, but after it gets into 2nd gear, below, say 22 MPH (where it usually shifts out of first), it would unlock before going into first (b/c it wouldn't make a diff if it was locked in first or not.)
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