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  #1  
Old February 24th, 2020, 16:26
Agreen Agreen is offline
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Delayed 2-3 shift

Let's see if anyone else has fixed this issue before. And before you go commenting on what fixed yours, read the list of things I've already done.

1998 Sport 4.0 4WD AW4
335,xxx miles

I bought this in 2014 with 230,xxx miles on it and it's had this issue since I bought it.

Under normal throttle conditions, it holds 2nd gear for way too long. 1-2 shift is right on time. Around 2200 to 2400 rpm. 2-3 shift will hold until well after 3000 rpm, sometimes close to 4000. When it shifts, there is no delay. It shifts nice and crisp, but it's just late. 3-4 is right on time as expected, and so is lockup. No issue with downshifts. I can make it upshift to 3rd by slightly backing off the throttle, and I've kind of gotten used to doing it, but it's just not right.

-Fluid level is perfect.
-Always used Dex III
-Fluid is bright red, does not smell burned
-TPS has been checked, and checked, and checked. It's perfectly in spec and operates smoothly through the range.
-The throttle cable adjustment has been done several times. I've even tried playing with it in different directions, but it either drags the shifts out or makes it take forever to shift, so it's been set back to where it should be.
-I have pulled the transmission completely apart and completely overhauled it. I did this about 30k miles ago because I actually converted it from 2wd to 4wd. The 4wd donor trans was in unknown condition, so I used everything from the 2wd except the 4wd output shaft and extension housing. It works well, but the original problem persisted. I also wanted to freshen things up in there since it had over 300k miles on it. Turns out when I pulled the 4wd trans apart to get the output shaft, it was pretty badly burned.
-I also installed a Trans-go HD2 kit while the trans was apart. I used the truck setting, not race. I installed the 1st gear hold as I do a lot of off-road driving and I like the 1st gear hold feature. The trans shifts more firmly now, but still has the original delayed 2-3 shift.
-I have checked the wiring, all grounds, and the harness going to the transmission.
-I put a multimeter on the wires going to the transmission to see if it's calling for 3rd gear. Solenoid #1 is supposed to deenergize, allowing line pressure to shift the 2-3 shift valve to move against spring pressure and shift to 3rd. The TCM doesn't call for 3rd gear until the moment it shifts. In other words, it's not the solenoid or shift valve hanging up, it's the TCM calling for a delayed shift. I even dropped the pan a few days ago and swapped solenoids #1 and 2. I checked their resistance and they were 12.7 and 13.4 ohms. It shifted the same after I swapped their places.

The only thing I can think of is that the TCM has some sort of bias resistor that has drifted over the years and THOUSANDS of miles of use. I've seen resistors (or other electronic/electrical components) change values due to age before, and I'm thinking this is what's happened. Should I take the gamble on a junkyard TCM? Is there ANYTHING that I've missed that I should look at?

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  #2  
Old February 24th, 2020, 20:35
Runnin'OnEmpty's Avatar
Runnin'OnEmpty Runnin'OnEmpty is offline
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Re: Delayed 2-3 shift

I like your theory of an electronic part drifting out of spec in the TCM.

Even though the TPS tests OK, that doesn't mean it performs in real
world (while driving) conditions. It too could have drifted out of spec.

I would replace the TPS. They're relatively cheap.
If no change, then I'd replace the TCM...Diagnosing has been done,
now it's time to throw parts at it. LOL.
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  #3  
Old February 25th, 2020, 04:10
Agreen Agreen is offline
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Re: Delayed 2-3 shift

Yeah I'm not doing that. I'd rather grab a 200k mile TPS from a junkyard than use a "new" one. Throttle sensors and O2 sensors are the 2 things on XJs that are brand particular, and if you have a good one, you're better off keeping it. The same thing goes for shift solenoids. Aftermarket solenoids are a real crapshoot, and I've rarely seen them go bad, but often replaced based on suspicion.

I have a scan tool hooked up and can watch it in real time as I drive. I can (and have done this several times) data log(ged) the TPS. There's absolutely no data to prove that it's causing any issue. The only thing that makes sense is the TCM at this point.
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Old February 25th, 2020, 04:33
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cruiser54 cruiser54 is offline
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Re: Delayed 2-3 shift

try unplugging the tCU, spraying out all the contacts and plugging it back in.
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  #5  
Old February 25th, 2020, 19:13
lawsoncl lawsoncl is offline
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Re: Delayed 2-3 shift

You've been pretty thorough in your testing, so I assume verified good supply voltage and low impedance ground at the TPS, and good continuity to the TCM. I can't image anything "drifting" inside the TCM that wouldn't cause more than just a late 2-3 shift. Trying a junk yard TCM can't hurt. I'd halfway wonder about the rear output speed sensor, but you're not seeing an issue with 3rd-4th gear right? The front and rear speed sensor are the same part number, so you could swap them and see what happens.
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  #6  
Old February 26th, 2020, 04:24
Agreen Agreen is offline
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Re: Delayed 2-3 shift

The only problem I've had is with 2-3. I'd think that if it were an issue with in vs out speed sensors that it would cause an issue with all gears because it's common to all of them. Each shift point is decided by separate bias networks that are variable based on TPS voltage. Resistors can change value over time with heat, which is what I'm thinking has to have happened. I won't be able to get to the yard for a TCM for a little bit though.
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  #7  
Old February 26th, 2020, 19:56
lawsoncl lawsoncl is offline
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Re: Delayed 2-3 shift

I'm skeptical that an 1998 is using analog circuits to decide on the shifting. I'm pretty sure it would be digitizing the shaft speeds and using a formula or lookup table from there. Supposedly with the right reader, you can talk to the TCM and see the solenoid state and rpms.
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  #8  
Old February 28th, 2020, 10:54
Agreen Agreen is offline
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Re: Delayed 2-3 shift

I sure wish I could find the schematic for the TCM. I searched through the FSM and haven't found it yet.

You're probably right. There's little chance the TCM is entirely analog. I'm still going to swap the TCM to see what it does. There's got to be some analog stuff in it though. SMT components are still being used in electronics, so it's still not too farfetched to think it's something not solid state causing my problem.
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  #9  
Old February 28th, 2020, 11:09
RCP Phx RCP Phx is offline
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Re: Delayed 2-3 shift

Your not likely to find much as the TCM is proprietary just as the PCM.
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  #10  
Old February 28th, 2020, 14:12
Agreen Agreen is offline
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Re: Delayed 2-3 shift

I just swapped it with one from the local junkyard. Doesn't seem to have solved it.

I'll be pulling the in/output speed sensors soon to see if they have metal accumulation and probably swap them.
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