Auto transmission overdrive issues please help!

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Flat black

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I have 1992 dodge ******* with an auto trans and it won't shift into the last gear of the transmission. It has high enough rpms and shifts into the other gears perfectly. I would appreciate any suggestions or thoughts to why it's doing this or how to fix it. Thanks.
 

reek

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could be your valve body is gunked up or possibly your OD shift solenoid. You could drop the pan and give it a quick clean, it's pretty simple and straight forward. just use a big table and keep track of all the small parts and what order they go in. I washed my valve body in gasoline and a bunch of 'silt' came out and it looks like new.

at the same time look at the filter and check the magnet see how much metal debris you are collecting. Also the snap ring on the a518 are know to break apart. that might be causing the shift issue as well. you'll probably find parts of the ring in your pan as well. You'll need a new pan gasket, I think they were still using cork in 92.
 

crazzywolfie

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have you checked the trans temp sensor? i think you need to jump it to bypass it but if it is not working properly it will prevent overdrive from being powered.
 
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Flat black

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Where is that located? Internal or external?
 

crazzywolfie

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should be on one of the transmission lines under the truck or at least that is how it was on my buddies truck.
 

crazzywolfie

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yes bypassing it would be unplugging it and making a jumper wire from 1 wire to the other. i believe the switch disconnects when it hits a certain temp taking power away from the overdrive solenoid. it is possible that it has gone bad. you could even just test for power at the overdrive solenoid connector. just make sure the key in in the run position. if the switch is working there should be 12+ at the connector. the computer grounds the solenoid when it feels you are at speed for overdrive.
 

Regularjay

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Your trans OD is controlled by the throttle position sensor (plastic doo-dad) on top of the pump and temperature sensors. Wont go into OD unless TPS is 70% or less and trans is warm enough but not hot. Most guys with OD problems report that the TPS is the issue, you can replace it, clean & adjust it or many use a potentiometer to bypass it. I would try clean & adjust 1st as it's free.
 
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Flat black

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Ended up being the gear in the side of the transfer case of the truck. Purchased a used one off a scrap yard and also a gear reducer from the net new and it worked slick! Trucks tack runs about ten over but that's because the gear reducer is made for different tires. It works though and that's what matters! Thx for all the help and info guys!
 

reek

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glad you got it sorted!
 
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