lockup change with tire swap???

[usetaboost]

Lockup never seemed to occur til about 55mph, and I had to let off the gas to get it to. Now after swapping to 275/40r17s it won't lock up at all? Only thing I can come up with that the lockup is set to occur at a certain tps voltage when the trans is in 4th gear, and with the shorter tires I'm not reaching that voltage since the car is going faster with the gas pedal in the same position. If I'm lucky the trans will stay in od but I can't get lu to happen at all.

 

[usetaboost]

Another lu related question. Does the car have to be in closed loop for the ecm to engage lockup?

 

[we4Mateo]

With a stock ecm, LU occurs below a TPS threshold and above a certain mph. The tires will change your true mph but not what the ecm sees so your speedometer and ecm should see the same speed regardless of what speed you are actually traveling. If LU is not occurring now, there is probably something else going on. Loose TCC solenoid wire? Maybe you are giving it more throttle at cruise with bigger tires and above TPS threshold?

I don't know about the close loop question. I think coolant temp and run time are the only ecm factors that allow LU.

 

[usetaboost]

The tps is .42 with key on. coolant temp was 168-170. It's never been easy to get it to kick in on its own. Always had to run it up in mph and let off the gas and then I could slow down 10mph or so and it would stay in lu

 

[we4Mateo]

Sounds like something else is going on and now coming to a head.

 

[usetaboost]

It's possible. Maybe the lockup switch finally fried out. I know whenever the trans got hot it would stick

 

[usetaboost]

Checked it at the aldl with key on and I have voltage, 11.90. WHen I push the brake pedal down the voltage drops to 11.60

 

[usetaboost]

just took it out. did a couple wot pulls and now the lu seems to work the way it did. Maybe the trans temp wasn't getting warm enough and not allowing lu?

 

[we4Mateo]

Seems weird to me. Maybe check pump pressures?

 

[usetaboost]

First time it's ever done that. It's got a transgo kit in it, just the standard one. I did swap the upshift spring, later to find out I shouldn't have. Maybe this has something to do with it?

 

[we4Mateo]

I don't know. Sorry