1998 ZJ 4.0 sudden reverse problems. - JeepForum.com
 
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post #1 of 5 Old 07-01-2020, 08:00 PM Thread Starter
thapropellerguy
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1998 ZJ 4.0 sudden reverse problems.

So out of nowhere my Jeep now bucks when in reverse and won't move on it's own. What I mean is when I would typically go from drive to reverse you feel and hear it engage and the engine would move with the gear selection, and then when releasing the brake it would reverse on it's own. So what I have going on now is shifting into reverse and not really feeling or hearing it engage, it wont move under it's own power, and will buck and shudder when pressing the accelerator to back up.

I had to replace the governor sensor and solenoid last year, and ever since it would throw a code every so often that I have to clear of which came on again when the reverse issue started. Forward gears seem to have no issues. Any ideas?


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post #2 of 5 Old 07-02-2020, 02:27 AM
Timo_90xj
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Reverse is engaged through the manual shift valve on the valve body, and the rear band is applied when reverse is selected.

Check rear band adjustment and that the rear servo works properly and has no leaks. You need to remove the fluid pan for band adjustment, and having issues with the reverse I highly suggest dropping the valve body so you can do the air test to see if servo works, there are no leaks and that the rear band tightens around the rear drum.
If air test reveals leaks or some other issues, you need to fix the issues. If it's just the band adjustment being loose, you might get lucky adjusting it.
If the rear band has failed, tranny needs to come out and pulled apart.

1998 Grand Cherokee 5.9 LX daily driver, 1.75" BB, 32" KM2s, HPD30 Eaton e-locker/D44a stock LSD, 4.56 gears, custom- fabbed tube bumpers and tube fenders,...


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1990 XJ Limited (4-door), 4.0 I6, AW4, NP242, ***rolled and totalled @ 165k miles***

***Under construction***
1990 XJ (4-door), 4.0 I6, AW4, NP242, PBR 42" tires, Unimog 404 portal axles, 110" WB, full cage + uniframe completely rebuilt, front 3-link + panhard / double triangulated 4-link rear,... ***SOLD***
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post #3 of 5 Old 07-02-2020, 03:02 PM Thread Starter
thapropellerguy
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Quote:
Originally Posted by Timo_90xj View Post
Reverse is engaged through the manual shift valve on the valve body, and the rear band is applied when reverse is selected.

Check rear band adjustment and that the rear servo works properly and has no leaks. You need to remove the fluid pan for band adjustment, and having issues with the reverse I highly suggest dropping
the valve body so you can do the air test to see if servo works, there are no leaks and that the rear band tightens around the rear drum.
If air test reveals leaks or some other issues, you need to fix the issues. If it's just the band adjustment being loose, you might get lucky adjusting it.
If the rear band has failed, tranny needs to come and pulled apart.
Thank you for your advice. New development, wants take off in neutral almost like a second drive selection and my dash lights are good haywire.

Better late than never.
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post #4 of 5 Old 07-02-2020, 03:54 PM
jtec
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might want to check the shift cable adjustment.
And trouble starting - shifter is in N - no issues?

Lights going haywire OK got ask what lights, do you have any to chekc codes- you mentioned there being codes just grasping at straws. but why not check first.

Timo_90xj - gave a suggestion above- I think you headed that path sorry not always easy.

When I see the price of OEM I think aftermarket.
When I see the quality of aftermarket I think OEM.
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post #5 of 5 Old 07-02-2020, 10:23 PM
Timo_90xj
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Yeah, wanting to take off in neutral could indicate a simple thing like having the shifter cable adjusted incorrectly. It's easy enough to check before tearing into transmission internals.
But, getting multiple issues at the same time unfortunately often indicates bigger problems. Start diagnosing from the easy & obvious possibilities, if that path fails then start looking deeper into it.

1998 Grand Cherokee 5.9 LX daily driver, 1.75" BB, 32" KM2s, HPD30 Eaton e-locker/D44a stock LSD, 4.56 gears, custom- fabbed tube bumpers and tube fenders,...


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1990 XJ Limited (4-door), 4.0 I6, AW4, NP242, ***rolled and totalled @ 165k miles***

***Under construction***
1990 XJ (4-door), 4.0 I6, AW4, NP242, PBR 42" tires, Unimog 404 portal axles, 110" WB, full cage + uniframe completely rebuilt, front 3-link + panhard / double triangulated 4-link rear,... ***SOLD***
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