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I have a '90 W150, 318 auto. As of late, the overdrive has been acting "goofy".
By this I mean it isn't shifting like it should, it keeps going in and out of O.D. at 45 to 55mph, it used to shift up, and stay there until I gave it some throttle. It seems to be ok for the first few miles, then it gets worse as it warms up, to the point I have to manually take the O.D. off. The truck shows 95,000 but I really don't know the actual. My fluid is very clean looking, and smelling, and has never used any
I've replaced the easy/cheap parts (sensors-the TPS, sensor in rr. end, & sensor in transfer case), somebody told me it's probably an adjustment of the O.D. bands/clutch? In any case I'm very not familiar, I was wondering.....before I take it to who-knows-who....trans. shop, if I drop the pan, is the adjustment something that I could do with the proper instruction??? Frankly, I'm scared a shop will tell me "sorry Johnny, it's wasted......you need a total re-build" bend over.....etc. Please advise if you can.Thanks, John Verbison, MI
 

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good. morning
my truck is doing exactly the same thing, did you ever find out what the issue was? I just put in A new transmission and its doing what you described
 

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. . . my truck is doing exactly the same thing, did you ever find out what the issue was? I just put in A new transmission and its doing what you described . . .
What is vehicle model year and engine? This determines the particular transmission used. Have you replaced the transmission and the same slipping behavior is still occurring or are you contemplating replacing the transmission as a fix? I will respond to the older post and relate information which should help with your similar issue.

You have the Chrysler A500 / 42RH transmission in your vehicle. It is hydraulically controlled and hydraulically shifted. The only electronic control is the overdrive engagement solenoid which is controlled by the PCM (powertrain control module) After engine temperature reaches a minimum threshold and other speed conditions reached, the PCM energizes the overdrive engagement solenoid circuit. This allows hydraulic pressure in the transmission to simultaneously disengage the direct drive clutch and engage the overdrive clutch. The override switch on the instrument panel opens the circuit so the PCM will NOT activate the overdrive engagement solenoid. this keeps the transmission in 3rd gear at highway speeds.

There are 2 bands and multiple clutches in the transmission. The attached chart shows which elements of the transmission are in use with different positions of the transmission gear selector and actual gear utilized in the transmission. Adjusting the front and rear bands will not have an effect on this slipping in 4th gear / overdrive. From the chart you will see that both the front and rear bands are NOT engaged in 3rd gear or 4th gear. So the bands are not the source of the slipping. The front and rear clutches are both engaged in 3rd gear and 4th gear so they are not the source of the slipping. So that leaves only the 4th gear overdrive clutch as a possible culprit along with low fluid pressure in the overdrive clutch circuit.

Rectangle Font Slope Line Material property

I believe the overdrive housing can be removed with the transmission in the vehicle and that serviced separately? You would need to find a knowledgeable transmission repair facility and determine if that is a viable option.
 

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great information thank you, had a 3 speed with OD in it 2 pin connector, bought a rebuilt trans with od and lockup converter it came with 3 pin connector. Not using lockup on it as my original setup only had 2 wires lock up wire coming out of trans is not connected....
 

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I'm trying to visualize how you have a 3-pin connector coming out of the transmission, and mating it with a 2-pin connector in your truck harness. They won't mate and latch.
Nevertheless, you want to make sure you have the correct wires from harness to transmission. The center contact is 12V, and on either side are the grounds for overdrive and for lockup torque converter.
Sometimes intermittent overdrive function is caused by the overdrive/lockup solenoid pack coming loose. It's inside the pan, screwed to the right side of the valve body, and there is a cardboard gasket. The screws can come loose, and then some fluid leaks internally around the valve body instead of being contained in the passages to the solenoid. The fix is to drop the pan and tighten the 3 screws, then reinstall pan and fill fluid.
 

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I bought the correct plug 3 pin For transmission and left the lock up wire not connected and spliced the other 2, i will drop pan and check out 3 screws hope that’s the issue
 
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