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Got an 89 4zei auto trans.When the trans is cold it wont shift up past third and wont coast when you let up on the gas.When its warm it shifts all the way up to OD no problem.Changed the fluid and washed out the filter but no change.what else should I be looking for?
 

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I hate to say it, but that's the way this transmission is designed to run. There is a sensor on the pass side of the intake that tells the tranny computer when to allow it to shift into OD. The only thing to check is the engine thermostat. If it is stuck open, the engine will take longer to warm up, and thus it will take longer for the transmission to let itself shift.

-Tad
 

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I notice there two sensors, next to each other , the one on the left, looking at the engine, is the coolant temp switch , connect to the temp gauge on the dash, what is the other sensor?
 

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The other sensor is the same kind of sensor, but it's used by the transmission. It keeps the tranny from shifting into OD before the engine is warmed up. It is part of the emissions control system in the sense that a warm engine runs cleaner, so by keeping the engine in 3rd, it will warm up faster than if it shifts into OD right away.

-Tad
 

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Tad you are genius, I think you might have narrowed down the problem for me. My transmission keeps on going to overdrive and back down to third at cruising speed. may be this sensor is screwing up. Do you have any suggestion for testing the sensor, how about once the engine is warmed up disconnecting and grounding the sensor wire?
 

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I checked the sensor, it closes as soon as engine warms up (17-18 Ohms readings), but after driving for a mile or so at 30-40 mph the overdrive light start to flash at a very set intervals and continues until the vehicles comes to complete stop. The transmission shifts ok. I have not tried the high speed yet. Well stay tuned
 

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[offtopic]
Hey FW, I like your choice of username. The 190 was a much more graceful looking aircraft than the Messers.

But, I'm a great fan of the British (DeHavilland?) Mosquito.
[/offtopic]

Cheers,
 

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I agree. British plane are nice to look at but hellish models to fly. Believe it or not the easiest warbirds to fly are P47 thunderbolt and FW series. Now help me with my trans problem. Next on schedule is to test trans. oil temp sensor. I read somewhere that when the oil temp. goes high the TCM prevent the trans from going to OD.
 

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Well It was the TCM modules. Thanks to our administator Tad and Conman for all their help. Once I changed the TCM everything started to work fine. So remember if you have removed the valve cover make sure it is grounded. That is the grounding for the condensor. :lol:

1989 Trooper II LS.
 
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