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Transmission help after 2wd to 4wd swap

ljobbins

NAXJA Forum User
NAXJA Member
Location
SD County
I just finished swapping out transmissions 2wd to 4wd. I reused the torque converter from the 2wd that was working fine before I touched anything. The car shifts harshly between park, reverse, neutral, and drive. When I drove it up and down the street it would also not shift out of first through other gears. It would just rev up and never up shift. The 4wd trans came with all wires and everything still hooked up from the previous car. I only swapped over the torque converter and connected the wires. The fluid is all new and at the correct level with engine hot in idle. Anything that I might have screwed up or things to look for or check? I don’t know much about automatic transmissions and I don’t have tons of free time right now so please help me out.


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Try adjusting the throttle valve cable, this sounds like it might be misadjusted. You may have multiple issues but I think it's set too high causing harsh engagement.

https://www.naxja.org/forum/showthread.php?t=1015963

The not shifting between gears part may be something else, but should be tackled after this adjustment, which luckily takes about 30 seconds.

Edit: what year did the trans come from and what year is the Jeep?
 
I just finished swapping out transmissions 2wd to 4wd. I reused the torque converter from the 2wd that was working fine before I touched anything. The car shifts harshly between park, reverse, neutral, and drive. When I drove it up and down the street it would also not shift out of first through other gears. It would just rev up and never up shift. The 4wd trans came with all wires and everything still hooked up from the previous car. I only swapped over the torque converter and connected the wires. The fluid is all new and at the correct level with engine hot in idle. Anything that I might have screwed up or things to look for or check? I don’t know much about automatic transmissions and I don’t have tons of free time right now so please help me out.


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I have been down either this precise same road or one very similar. Actually, two roads.

Road #1: I bought what was represented to me to be a '98 4wd transmission. It was in fact a '97, or perhaps even earlier transmission. I took the trouble to have it rebuilt too. Paid a guy to mount the "new" transmission (and xfer case) into my 2wd XJ. got a call from him saying that the connector -- the one from the transmission to a place under the hood, near the rider's firewall, close to the heater blower would not work. Has maybe 6 or eight conductors. The one in the jeep was a different color than the one from the trans. No problem, I thought. I'll just fix the wires. WRONG. I will post a helpful thread at the end of this comment. The one had I read it, I could have saved about $2,000 all told.

Road # 2: When I plunked down money for a 'known' 2000 transmision and for its installation, even though the electrics looked OK (and as it turns out, were) I got pretty much the same symptoms as you got. This time the fix was simpler and lots cheaper: I live in North Florida where "mud daubers" (Sceliphron caementarium) ae commonplace, and one place they love to daub is/are transmission vent hoses. That produced for me the exact symptoms you are experiencing. When I would fill the transmission with fluid, a few quarts would go in until the air pressure in the transmission would permit no more to enter the transmission. To make things slightly worse, the fluid on the dipstick would show the trans to be overly full. But in fact, it has less fluid than it took to function properly. I cleared the vent hose, topped off the trans fluid and have not had a transmission issue since.

Back to raod #1: your '95 XJ almost certainly has a transmission (not the same as the engine ECM) computer, connector and associated wires that don't know what to do with an input shaft speed sensor signal Toward the end of production in '97, the AW4 sports such a sensor. And there are other differences as well. You can fix it with a manual shift kit, or you can shift it manually, if you don't really need second. BTW,, figuring which transmission you have takes about five seconds: Crawl under your XJ from the drivers side. About half way up on the transmission, no more than an inch or so behind the joint between the transmission, you will either see a hole in the transmission for a sensor, or you will see a boss for a sensor, but no hole for it to fit through. And there will be a boss for the little bracket that would secure the sensor to/in the transmission, if it had a sensor. That boss will NOT have threads cut in it.

Here's the thing: Perhaps whoever sold you the '95 transmission may have sold you a '98 transmission. If I prayed I'd pray for you a mud dauber scenario.

Here is an excellent thread on the AW$. The author gets to the problem you may be facing on the first page. Good luck, I do hope you have better luck than I did with a remedy to your issue. The Thread: https://www.naxja.org/forum/showthread.php?t=1053970

Lastly: If I had a nickel for every friend, collogue, enemy, etc who said: "Harold: if you wanted a 4X4 why didn't you just buy one?" Well had I followed their advice I would have enough nickels to fill the back of my shitbox, and enough to fill yours too. However many nickels there are in about $2500.
 
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Most likely not the dual sensor transmission because the wiring would not of plugged in. Low fluid is probably the most likely culprit, but checking the TV adjustment is not only a must do, it's something that really should be checked periodically anyway.
 
Most likely not the dual sensor transmission because the wiring would not of plugged in. Low fluid is probably the most likely culprit, but checking the TV adjustment is not only a must do, it's something that really should be checked periodically anyway.
I certainly agree on all counts. Three observations, however: The connectors may have been changed in the past, with what results, who knows. Second, an old transmission guy turned me on to the clogged vent line, which was my cure. I would never have found that on my own. Third: ALWAYS the most fertile ground to till when you're hunting an issue is the last thing you changed or worked on. I hope our OP has good luck with his issue.
 
Yeah I doubt this is a 98+ trans, but it takes 30 seconds to verify. Look for a speed sensor on the driver side right behind the bellhousing, IIRC it is nestled in behind the shifter cable bracket sorta. No sensor? Trans is correct for your year.

The mud dauber point is interesting.
 
If the wiring was changed to where it would plug in a 95 with no problems then it would work. As you already know, I have a 01 trans in my 95. You are probably on to something with the plugged vent or low fluid. Off chance the tcm isn't playing nicely but I really doubt it because everything related to 4wd is purely mechanical. Did you have to extend the harness to reach the speed sensor at the back of the t case?
 
If he stuck a 98+ trans in there with a 95 TCU, it would be upshifting way too fast (btdt). Is the rear speed sensor plugged in, right at the sensor? Unplug the trans computer and verify you can shift manually with the stick. Check the solenoid resistance to make sure the donor solenoids are good.
 
Won’t have time to work on it until Thursday night but that vent theory sounds interesting. I definitely thought that it would take more fluid than it did. But I’ll check everything when I get a chance.

I can say that I put them next to each other when I pulled the 2wd one and they matched up perfect. Same random holes empty, same wires and solenoids, same cable, everything looked identical. I did not know the condition of the solenoids or electronics, so I made sure that at least everything looked the same as the known good transmission.


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Both styles would look exactly the same except an extra plug on the driver side just behind the bell housing. But like I said, I have an 01 in my 95; if someone had already changed the wiring to make a late trans work in an earlier jeep then it would be hard to believe they didn't change the tail housing and reluctor wheel. Two other questions though; did you see the jeep it came out of, and how long has it been since it was on the road last?
 
Finally had 10 minutes to look at it. Fluid level triple checked. It’s full. Pulled the transmission fuse and it shifts fine manually. So that narrows it down to something electrical. I believe someone mentioned testing solenoids by testing ohms? Is that correct? And what am testing exactly? Since the jeep ran perfect with 2wd, I’m assuming the tcm is good. So it’s either the wrong wiring like some said or something else electrical. Help please.
009a7e8bc29da8844b95e8ac1e73220e.jpg

No sensors or connectors forward by the cable linkage.


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If the wiring was changed to where it would plug in a 95 with no problems then it would work. As you already know, I have a 01 trans in my 95. You are probably on to something with the plugged vent or low fluid. Off chance the tcm isn't playing nicely but I really doubt it because everything related to 4wd is purely mechanical. Did you have to extend the harness to reach the speed sensor at the back of the t case?


I did not have to extend the harness but it was a very tight stretch and I had to unwrap and move the cables in the engine bay to get enough length to connect it.


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Try adjusting the throttle valve cable, this sounds like it might be misadjusted. You may have multiple issues but I think it's set too high causing harsh engagement.

https://www.naxja.org/forum/showthread.php?t=1015963

The not shifting between gears part may be something else, but should be tackled after this adjustment, which luckily takes about 30 seconds.

Edit: what year did the trans come from and what year is the Jeep?


And I adjusted the tv cable per instructions. No change.


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connector_db5536b1b7ca648d94a258056578e5a5386a3d8d.jpg


Where to measure the solenoids. If S2 is bad, you won't get 2nd or 3rd gear. The rear speed sensor is the tan/blk wire. It should flip between 0 and 12 volts as the output spins (on a 95, it's a magnetic switch and 98+ it's a sensor that generates voltage spikes). The meter set for a/c should see something if you put the trans in gear and xfer case in neutral so the output shaft spins.
 
connector_db5536b1b7ca648d94a258056578e5a5386a3d8d.jpg


Where to measure the solenoids. If S2 is bad, you won't get 2nd or 3rd gear. The rear speed sensor is the tan/blk wire. It should flip between 0 and 12 volts as the output spins (on a 95, it's a magnetic switch and 98+ it's a sensor that generates voltage spikes). The meter set for a/c should see something if you put the trans in gear and xfer case in neutral so the output shaft spins.


E measured overload(no connection)
F measured 12.5 ohms
G measured 12.4 ohms


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Something that kinda of dawned on me and I’ll check it out later tonight. Maybe the transfer sensor is a different model than the original model for my year. Transfer case came separately from the transmission and I never thought to look at the year.


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Something that kinda of dawned on me and I’ll check it out later tonight. Maybe the transfer sensor is a different model than the original model for my year. Transfer case came separately from the transmission and I never thought to look at the year.


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The speedo sensor in the xfer case won't affect shifting. The trans computer is only looking at the output sensor at the back of the transmission and the throttle position sensor.

If I'm reading the diagram and your reading right, you have a bad torque converter lockup solenoid? I would have suspected the #2 solenoid for not upshifting into 2nd.
 
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