96 GC transmission swap, part 3, limp home mode - JeepForum.com
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post #1 of 19 Old 11-13-2019, 07:01 PM Thread Starter
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96 GC transmission swap, part 3, limp home mode

Got the transmission and transfer case all in, hooked up, topped off ATF, fluid looks good, took a couple test runs. From park it goes into gear nice and quick, pulls good, no noises. But takes off in second gear, won't shift above that. Put shifter in low, takes off good and shifts into second just fine when manually shifted, won't upshift when manually shifting into drive. All the sensors and control hookups looked the same from the old to the replacement transmission, everything plugged right in, shift linkage exactly the same. The OD button has no effect on it, wind it out some while in second gear didn't do anything

Did the ignition key sequence to pull codes, got a 12, then 37, then 45, then 55. No check engine lights are on.

Any suggestions? What to check? Old transmission worked fine, made lots of noise though. Would there be any differences in the transmissions in the same year? Was told the replacement was a 96 and it all looked identical.

Earlier posts:
https://www.jeepforum.com/forum/f13/.../#post40780799
https://www.jeepforum.com/forum/f13/.../#post40782553

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post #2 of 19 Old 11-13-2019, 07:10 PM
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I think the 96 used a 46re what year is your zj?

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post #3 of 19 Old 11-13-2019, 07:23 PM Thread Starter
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This is a 96 ZJ GC Laredo, 4.0 inline six. The casting numbers on the top of the case were the same, if that actually means anything. Everything on the transmissions looked the same.
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post #4 of 19 Old 11-13-2019, 07:53 PM
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Maybe one of the shift solenoids is bad? Hmm what year did the donner come from? Maybe the tcm is different? The zj did use 5 different automatics

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post #5 of 19 Old 11-13-2019, 09:06 PM Thread Starter
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Maybe I need to dig a little deeper. Where is the ID tag or numbers on this transmission? This does seem like an electrical deal.
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post #6 of 19 Old 11-14-2019, 02:50 AM
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That I don't know

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post #7 of 19 Old 11-14-2019, 02:59 AM
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Quote:
Originally Posted by tom3 View Post
But takes off in second gear, won't shift above that. Put shifter in low, takes off good and shifts into second just fine when manually shifted, won't upshift when manually shifting into drive.
I'm suspecting it's actually starting off in 3rd gear when in drive, not second. When you select 1st gear, it's actually in 2nd. This is very common if some or all of the transmission solenoids or sensors fail.

Do this: when stationary (not moving at all), select neutral. Then quickly select 1st gear from neutral, no stopping in between. See if it now starts in first; then manually select second, does it upshift? Then select OD, does it now upshift?


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I think the 96 used a 46re what year is your zj?
Negative, only the '98 5.9 used a 46RE; '96-'98 5.2 used 44RE, '93-'98 4.0 42RE, and early-build '93 4.0 came with the AW4. '93-'95 5.2 used 46RH.

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Maybe one of the shift solenoids is bad? Hmm what year did the donner come from? Maybe the tcm is different? The zj did use 5 different automatics
Solenoid and/ or sensor failure is a possibility, and a fairly common cause for no shifts in drive.
As for a TCM, there is no such thing in the '96-'98 ZJs; engine- and transmission control are both in the PCM (powertrain control module).

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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 #8 of 19 Old 11-14-2019, 03:07 AM
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Quote:
Originally Posted by Timo_90xj View Post
I'm suspecting it's actually starting off in 3rd gear when in drive, not second. When you select 1st gear, it's actually in 2nd. This is very common if some or all of the transmission solenoids or sensors fail.



Do this: when stationary (not moving at all), select neutral. Then quickly select 1st gear from neutral, no stopping in between. See if it now starts in first; then manually select second, does it upshift? Then select OD, does it now upshift?









Negative, only the '98 5.9 used a 46RE; '96-'98 5.2 used 44RE, '93-'98 4.0 42RE, and early-build '93 4.0 came with the AW4. '93-'95 5.2 used 46RH.







Solenoid and/ or sensor failure is a possibility, and a fairly common cause for no shifts in drive.

As for a TCM, there is no such thing in the '96-'98 ZJs; engine- and transmission control are both in the PCM (powertrain control module).
Ah im used to my 94 it has a ecu tcm combo, glad I didn't send him on a chase for parts that don't exist

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post #9 of 19 Old 11-15-2019, 01:19 PM Thread Starter
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Another test drive. Tried the quick shift from neutral to first, starts off in first, shift to second, goes into second, shift to drive, stays in second. And in in drive it will actually start off in first sometimes, and I can hear it downshift when stopping, and shift to second, but not always. Still not going into third.

Got out my old Xray scanner and checked codes, got a handful.
p1757 Governor pressure not equal to target at 15-20psi
p1762 governor pressure sensor voltage too low or high
p0748 pressure control solenoid electrical
p1765 transmission 12v supply relay control circuit fault

So this is pointing to something but I'm not sure what or where? Any of you point me in the right direction?
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post #10 of 19 Old 11-15-2019, 02:11 PM
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Bad shift solenoid or bad solenoid control? (Whatever that may be)

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post #11 of 19 Old 11-15-2019, 03:16 PM
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I honestly don't know if it's actually even possible not to have 3rd gear with governor sensor or solenoid fault, but the limp home mode in D should give you 3rd gear only with the governor sensor and/ or solenoid failed.

I'm not saying this is a mechanical fault without further diagnosing, but I have a bit of a gut feeling that you might've gotten a faulty transmission. I've never tested it myself, but try unplugging the tranny main connector @ transmission. Fire up the Jeep and go for a test drive; with manual shifts you should have P-R-N-3rd-2-1. I'll do my best to dig around the factory manuals I've got on my computer, but not guaranteed to be able to fully help - I unfortunately don't have the powertrain diagnostic manual.

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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 #12 of 19 Old 11-15-2019, 03:47 PM Thread Starter
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I'll try the unplugged sensor/solenoid. Seems like there should be some way to make this a manual shifted transmission but probably need a valve body change to do that. And I'll see if I can get some voltage readings that make sense. Always hated automatic transmissions, married 15 years before the wife finally talked me into one. And then it was an Olds Delta 88, low mileage one owner. Trans went out and turned out it had a Vega spec. transmission in it from the factory. No way GM should put that little tranny in a V8 Olds. Just my luck.

And thanks for the comments, appreciate the help!
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post #13 of 19 Old 11-15-2019, 03:57 PM
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Yeap, you gotta pull & modify the valve body for these to be manual shifted. Not really that expensive, IIRC ~170$. Transgo TFOD-HD2 gives you automatic shifts in D, and will manually hold 1-2-3 & shift into 1-2-3 @ any speed or any RPMs.

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 #14 of 19 Old 11-15-2019, 07:53 PM Thread Starter
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Pulled off the big connector on the solenoid, lost some skin. Took a drive and now have reverse, 2nd, and drive (3rd). No first and no overdrive but it is driveable at least temporarily. Sort of like an old Powerglide from back in the day. Have to start off in first or second shift position, then shift into drive, or it will actually take off in drive. So the transmission itself seems to be ok. Might do a fluid change and swap the solenoid out of the old transmission later on.
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post #15 of 19 Old 11-15-2019, 08:22 PM
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Quote:
Originally Posted by Timo_90xj View Post
Yeap, you gotta pull & modify the valve body for these to be manual shifted. Not really that expensive, IIRC ~170$. Transgo TFOD-HD2 gives you automatic shifts in D, and will manually hold 1-2-3 & shift into 1-2-3 @ any speed or any RPMs.
Are you saying that doing that I could put it in 2 and it would go into 2nd like a stick? If so would this work on a 94 42re?

94 ZJ 4.5" on 31s
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