What's wrong with my transmission?

[kastein]

Could be... I would try unplugging the TCU to see if it still acted that way.

Another thing to try is adding an extra pint or so of trans fluid. My 98, right before I swapped it to an AX15, would slam into gear after a stop and sometimes slip its first 1-2 shift if the fluid was merely full rather than being about a pint overfull. Same symptoms as my 96 right before what I would guess was a serious fluid pump or TQ failure based on the sounds and lack of gears, though admittedly I never got a chance to tear that trans down before scrapping the jeep.

 

[jdougn]

Here's my experience with similar symptoms. Replaced the TPS with a new one from Oreilly. Still had problems so took it to a local transmission shop. The tech took it for a test drive. Got out on a back street, punched the throttle to the floor and held it. We're doing 75 mph down a city street but the tranny finally upshifts. He says it's the TPS. I tell him the TPS is new. He says ya didn't get it from the dealer did ya? The tranny shop had so many problems from new TPS (and other sensors) being bad right out of the box from any of the parts stores that they would only get them from the dealership. Replaced the TPS with OEM original and everything was fixed.

 

[jeremyj]

I've read about XJ's being picky about aftermarket sensors before. I never buy the cheapest parts; I usually get the more expensive ones that come with lifetime warranties. I won't argue against the superior quality of OEM, though.

My solenoid kit arrived today, so I'm going to install that this weekend. In the next week, I'll try to find time to pick up and install the cooler, too. If none of this helps, I'll try a Mopar TPS. If that doesn't work, I'll probably just drive it off a cliff.

It has been driving alright lately. Only once or twice have the gear changes been a little odd, but no signs of the total failure I experienced over the weekend. It's also been 15-20 degrees cooler, too.

 

[jeremyj]

So I installed the solenoids, as well as a new filter and fluid this weekend. Aside from having to drop the crossmember to remove the pan, all went well.

The fluid was dirtier than I expected, given how clean it looked on the dipstick. Everything else looked fine and the Jeep is shifting perfectly normal. I won't know how effective the new solenoids are until I go for a long drive, but I'm feeling (cautiously) optimistic.

 

[jeremyj]

UPDATE

Still not fixed. I'm feeling incredibly frustrated with this thing now. After a bit of driving yesterday, the converter decided to not stay locked up on the freeway again. Aside from changing out the converter itself, I'm pretty much out of ideas at this point.

New or replaced:

TPS
TCU
Solenoids
Fluid
Filter
Aftermarket transmission cooler added (inline)
Kickdown cable has been adjusted properly
Brake switch tested and works perfectly

After the solenoid job, I filled the fluid up to the appropriate level (Jeep running in neutral). Now, weeks later, the fluid is registering a bit high. I'll drain some back out, but I don't know if that could be causing the issue.

What the ****.

 

[jeremyj]

So this thing hasn't given me grief since last summer, but then decided to act up twice in two days, under different driving conditions, temps, and speeds. My latest attempt to remedy the issue involved disconnecting all four of the electrical plugs under the hood that run to the transmission (NSS, TCU, etc.), spray them out with electric parts cleaner, wipe them down, and then reconnect. This is yet another in a long list of suggested "fixes" for this issue. If this doesn't work, I can only think of two more options: Mopar TPS and a replacement torque converter. I'd really like to avoid dropping the tranny again.

I've been searching the web for a potential fix for these issues, for years. Literally. The threads always die without a solution. I hear multiple suggestions for a fix, all of them different, but no actual confirmation from the OP of the thread, saying the problem has been fixed. I thought I had mine fixed for a while, but I was wrong. Nothing seems to be working and I won't know for sure about my most recent effort until it acts up again.

 

[Ecomike]

NO!!!! The fluid level is measured in park with the fluid hot (after a long hard drive) and engine running!!!!

"After the solenoid job, I filled the fluid up to the appropriate level (Jeep running in neutral). Now, weeks later, the fluid is registering a bit high. I'll drain some back out, but I don't know if that could be causing the issue."

 

[Ecomike]

I would be concerned about the dents on the bent tubes in that photo.

So I installed the solenoids, as well as a new filter and fluid this weekend. Aside from having to drop the crossmember to remove the pan, all went well.

The fluid was dirtier than I expected, given how clean it looked on the dipstick. Everything else looked fine and the Jeep is shifting perfectly normal. I won't know how effective the new solenoids are until I go for a long drive, but I'm feeling (cautiously) optimistic.

 

[Ecomike]

I've read more than one person testing the resistance of the solenoids and finding them to be normal. They end up changing them anyway, and the problem goes away. I don't know what the deal is with this, but they can test normal and still be defective somehow.

Solid trash, like backed on varnish that peals off, think pealed paint chips, can clog up any of the valves, hydraulic or electric solenoids and cause intermittent operations.

I usually use a solvent based solution that dissolves varnish, like Trans-X (ages ago they used lacquer thinner as I recall) and it swells the seals that may be old and leaking, and can save a transmission that had fluid get too old and burned before it was replaced. Does not always work )some trash may lodge like metal bits that do not disolve or come loose), but my batting average with about 2-5 flushes using Trans-X is about 90% before I had to replace a valve body or transmission. One was fixed with a new valve body (Saturn), one was a used XJ swap (still have not rebuilt that one yet, round to it project-Renix 4WD AW4). One was a Dodge that was dealer rebuilt 6 times and tranny shop rebuilt once and I finally fixed it with Trans-X by myself.

It can get expensive flushing one 4-5 times. About $120 total doing it with Walmart Dex III and Trans-x.

Other options are a valve body swap or complete AW4 swap, using a known good JY tranny for you at this point.

What year is it? Can you find a Transmission TCU scanner/friend?

 

[blondejoncherokee]

what was it doing when it acted up ?

You could pull a JY valve body and install a transgo kit and new VB gaskets. multiple fluid drain and fills here and there to help it along. Maybe you have some crap built up in the VB?

I use trans -X in every pan change -about half a bottle- on a high mileage older XJ.

 

[Ecomike]

what was it doing when it acted up ?

You could pull a JY valve body and install a transgo kit and new VB gaskets. multiple fluid drain and fills here and there to help it along. Maybe you have some crap built up in the VB?

I use trans -X in every pan change -about half a bottle- on a high mileage older XJ.

Doing the combo sounds smart to me too.

 

[jeremyj]

Ecomike, I've checked the fluid with the Jeep in neutral, as well as in park, both when hot. I haven't noticed a difference in the level on the stick. Also, I've never seen those tubes in an AW4 that weren't bent or kinked. I don't know why, but they always seem to look a little beat and I've never heard anyone mention an issue with it. The Jeep is a '96 and I've tried two different TCUs with no change.

My issues are almost exclusively related to the torque converter not staying locked up, but only on random occasions. Sounds like I should try some Trans-X.

 

[Ecomike]

Years ago I installed a 12 volt (IRRC) LED light on the power to the TC lock up solenoid (#3-IIRC).

Then I installed a toggle switch in line as well, all on the output side of the TCU. Finally I installed a toggle switch on the power to the TCU.

All were a huge help on diagnostics as I was never sure before if it was the 3-4 th gear shift, the 2-3 rd gear shift or TC lock up that I was feeling and seeing on Tach and but-ometer gauges.

You could also add the earlier suggestion of a hot wire switched power wire to the TC solenoid by passing the TCU, which sounds like a great idea to me for your problem.

 

[jeremyj]

I'm not sure how I would wire in switches to the TCM and I'm not looking for a MacGyver fix. This thing is my daily driver and I just want it to function as it should, without a bunch of extra switches wired in.

It acted up again this morning, on my way to work. The issue has not only come back, but it seems to be more persistent. The overdrive won't engage unless I try to accelerate. Then it stays locked up until I give enough throttle to downshift into third gear. It's maddening.

 

[blondejoncherokee]

its super common to wire in a TC lockup switch. I had one in my old rig and loved it. it also fixed all my random TC lockup issues and cost about 5$ which was nice.

 

[jeremyj]

I'm assuming this switch would take the TCU out of the equation for the lockup, correct? So every time I'm cruising over 50 mph or so, I'd have to flip the switch, similar to shifting into fifth gear with a manual.

 

[old_man]

That depends. On mine I added a protection diode so either the TCU or the switch could force the lockup, without causing problems or destroying a TCU. It has been about 10 years since I did mine, so I would have to dig for the wiring.

 

[jeremyj]

That's the way I'd prefer mine if I did it. Everything works as it's meant to, but when the TC doesn't lock on its own, I'd just flip the switch and force it. I still would much rather just figure out what's going on and fix it appropriately.

Today I noticed that the TCU ground wires that attach to the block at the dipstick are totally covered in sludge from a leaky valve cover. I think I'll spray those down tonight and improve the connection to see if that does any good. Then I'll try pulling the NSS and VSS to clean them out and reinstall them.

 

[old_man]

That's the way I'd prefer mine if I did it. Everything works as it's meant to, but when the TC doesn't lock on its own, I'd just flip the switch and force it. I still would much rather just figure out what's going on and fix it appropriately.

Today I noticed that the TCU ground wires that attach to the block at the dipstick are totally covered in sludge from a leaky valve cover. I think I'll spray those down tonight and improve the connection to see if that does any good. Then I'll try pulling the NSS and VSS to clean them out and reinstall them.

Make sure and pack the NSS with dielectric grease or you will have corrosion problems.

 

[blondejoncherokee]

I'm assuming this switch would take the TCU out of the equation for the lockup, correct? So every time I'm cruising over 50 mph or so, I'd have to flip the switch, similar to shifting into fifth gear with a manual.

thats how I did mine.
I actually liked it in the hills (37s and one tons at the time, heavy cage, plating, etc ) turning off the TC made it easier to go up the steeper highway mountain passes on the way to the trails.