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1992 4L80E lock up in and out

52Chummins

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Location
Minnesota
Hello I am new to the whole forum scene.
I am having trouble with my 1992 Chevy 2500 plow truck with a 6.5 diesel.
The torque converter is coming in and out of lock up in third and fourth gear. If I baby it at 60mph I can get it to stay locked up. But if I touch the brake pedal going 60mph it comes out of lock up obviously, and goes back in and out multiple times without anything else changes.
I would appreciate any direction to go in. I know the TPS sensor and transmission are only a couple years old. The transmission was rebuilt by a reputable transmission shop. I adjusted the TPS.
 
what's your engine temp running? Lock up isn't commanded until the engine reaches 170*, maybe your right on the edge
 
The engine was at operating temperature. I’m not sure of the temperature exactly because I don’t trust the gauge, but it was going in and out of lock up after idling for 20 min and plowing for a half hour. Can I jump the temp sensor wires to make sure the sensor isn’t the problem?
 
The number one killer of these engines is temp. And the factory gauges are inaccurate more often than not. I promote old school mechanical temp gauge added in preference at the right rear head- the hottest spot of the engine. weather or not (like that pun guys?) that is the issue or only issue- I’ve no clue.

Something I recommend is adjusting the tps- 0.5 v at idle and 5v at wot. Having one come out of adjustment isn’t unheard of.
 
TPS, coolant temp sensor, and trans temp sensor are your 3 biggies to watch when your not getting lockup. With an electronic trans you really need a scanner to work on them and see what's going on. It could very easily be a flat spot in your TPS where it's not moving linearly.
 
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