99 cj won't hold overdrive

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Feb 8, 2021 | 01:56 PM
  #1  
Hi all, new to the forum. Just my jeep doesn't want to hold over drive i have checked all that i could find on the net. The trans cooler lines are all good no leaks and no codes. Cleaned the NSS. now it goes into over drive just doesn't hold the gear in only works once after i start the jeep from resting worm or cold. Decided to try and change the filter and add a little type f for a flush when i saw this at the rear most solenoid not sure if it is supposed to look this way or not.


Anyone with experience with these 4 speed transmissions please help a guy out. If they aren't supposed to be this way any suggestions on where to get a new one. The local junk yard doen't get xj's or older zj's very often.
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Feb 8, 2021 | 02:05 PM
  #2  
What does it do exactly? Go for OD then hop back into 3rd?

Have you checked that your Throttle Valve (TV) cable isn't too tight? It's the cables that runs to the throttle body and down to the transmission.
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Feb 8, 2021 | 10:44 PM
  #3  
Quote: What does it do exactly? Go for OD then hop back into 3rd?

Have you checked that your Throttle Valve (TV) cable isn't too tight? It's the cables that runs to the throttle body and down to the transmission.
Yeah, I checked the TV cable multiple times.
it goes into overdrive only once each time i start it. It will go in to OD for maybe 1000 feet at about 45 mph then go back to 3rd if i excellerate obviously it would happen sooner. It won't go into OD again after it kicks out of OD. Without a restart. Also changed the filter / fluid, and all 3 solenoids today with same results.
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Feb 8, 2021 | 11:33 PM
  #4  
I had a little trouble with the OD...actually torque converter lockup, the solution I found that worked was good grounds.

Yep, no kidding. Clean the grounds where they connect to the engine block just aft of the alternator on the passenger side.

Once you get them clean (take them off and check the wires and clean the terminals), look right beside the transmission dipstick tube at the aft of the engine.

There will be two connectors there. Unlatch the gray one. Take a pick and scratch the contacts as they may have oxidized over the years. Plug it back together and try your XJ out!

It solved my problem, hope it solves yours!
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Feb 8, 2021 | 11:55 PM
  #5  
further to the above,

measure the resistance of each solenoid, and from the engine bay connector to ground as well

It should be < 15 ohms

the solenoid is different than the other 2, but should not look burned

it can be replaced for not very much
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Feb 9, 2021 | 07:16 AM
  #6  
On the older XJ's you find the Transmission Control Module (TCM) stuck to the back/underside of the passenger dash, I'm not sure if it moved on the 97+.

If you were to unplug it and do a test drive, it should indicate a mechanical fault or electrical. If the issue remains it's mechanical, if it goes, electrical. On a 99 this will throw an engine code when the TCM is disconnected. When disconnected you will have to select 1-2 for 1st, 3 for 3rd and D for 4th/OD.
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Feb 9, 2021 | 09:42 AM
  #7  
With the engine computer unplugged, he won't get the torque converter lockup, which some people refer to as OD. Aside from grounds, the usual suspect for upshifting or downshifting at the wrong time is a bad TPS sensor. Also check the brake light signal, because if the trans computer thinks you have your foot on the brake it will unlock the torque converter.
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Feb 9, 2021 | 02:07 PM
  #8  
Quote: On the older XJ's you find the Transmission Control Module (TCM) stuck to the back/underside of the passenger dash, I'm not sure if it moved on the 97+.

If you were to unplug it and do a test drive, it should indicate a mechanical fault or electrical. If the issue remains it's mechanical, if it goes, electrical. On a 99 this will throw an engine code when the TCM is disconnected. When disconnected you will have to select 1-2 for 1st, 3 for 3rd and D for 4th/OD.
It did. The TCM for 97-01 is mounted under the dash on the driver side, by the right knee.
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Feb 9, 2021 | 05:27 PM
  #9  
Quote: It did. The TCM for 97-01 is mounted under the dash on the driver side, by the right knee.
Thanks for clarifying.
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Feb 9, 2021 | 06:40 PM
  #10  
Yes, those crossover tubes are bent like that. They go to/from the pump.

(You can see them clearly at 33:41)
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Feb 9, 2021 | 06:41 PM
  #11  
Yes, those crossover tubes are supposed to be bent like that. They go to/from the pump.

(You can see them clearly at 33:41)

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Feb 10, 2021 | 12:41 AM
  #12  
Quote: It did. The TCM for 97-01 is mounted under the dash on the driver side, by the right knee.
So is the '96
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