Shifting Problems — Solenoids?
 

I've learned lots on here over the year I've been a Jeep owner, but I can't search out an answer to this question and am hoping you can help.

My 98 XJ (4.0) AW4 suddenly started not shifting out of first the other night. If I let up on the gas it would go up to higher gears, but if I didn't it seemed like it would probably redline without shifting. It threw a CEL, and the scan tool said P0700 (Transmission Control System), P0753 (Shift Solenoid A Electrical) and P0751 (Shift Solenoid A Performance or Stuck Off). Fluid looked fine.

After reading on here and elsewhere, I replaced the TPS first. No luck. It's shifting out of first now (a little late, but it does it), but *seems* to be skipping 2nd and going straight to 3rd. (If I put the lever in 1/2 it stays in 1). Besides the TPS replacement and an attempt at adjusting my throttle valve cable (it seemed to be fine), I haven't done anything else.

I did check the resistance of the solenoid circuits at the TCU, and they were within range. At least I *think* they were — it was hard to get a consistent reading.

Prior to this, I had 2-3 instances where it seemed to delay going into first gear in the last several months, but just a hesitation and no further problems.

At any rate, I'm stumped. Before I shell out the $200 and an afternoon's work to try the solenoids, any other suggestions?

Thanks!

Electrical connectors @ the transmission clean, dry and in good shape?

Mine is doing something similar. Someone told me to try resetting the computer but I haven't got to it yet

Radi, I need to get it up on some stands and take a better look at that. But I drove it to work this morning, and it was reliable — just skipping second, and seemed to be having trouble going into OD — still possibly a connection?

99, what do you mean by resetting the computer? I did disconnect the negative terminal for >30 minutes to clear out codes...

It sounds like you have a couple of sticky solenoids, but bad electrical connections, or a bad ground to the solenoids, or damaged wiring can mimic bad solenoids. If they don't have a solid 12V and good ground, their operation gets flaky. Make sure that isn't the problem before spending the money on solenoids.
The fact you did not get a consistent resistance reading on the solenoids makes me wonder about the wiring and connectors. The solenoids have a fixed winding, the resistance should be a stable value. Your DVM should settle on the ohms value and stay there. 8-12 or so.

You might try running a ground wire from the battery (-) to the transmission case, for test purposes. The solenoids ground through the transmission case, not the harness like the schematics suggest... which doesn't always provide a good connection.
Also verify the TCU has full battery voltage present, not something lesser.

Radi, that is very helpful, thank you. I'll get in and spend some quality time with the DVM.

I fixed mine, the neutral safety switch came loose and moved around when I shifted. Seems for for now cel went away and all. Ill let you know if anything else happens

There are other ways to check the resistance of the solenoids, but the best and most accurate way is to pull the pan and check them while attached to the valve body. Just pull the electrical connector and measure the resistance between the male spade terminal on the solenoid and the bracket. They all (three) should be between 11-15 ohms.

I had similar codes/symptoms and replaced mine last week (one read 167 ohms)...shifts like new again. If you're going to tackle it and need links/tips, etc. let us know.

If its only second gear, its not a solenoid.
In first gear solonoid 1. is on and 2. is off.
In third 1. is off and 2. is on. So if you have first and third they both work.
Second gear and OD both use the second brake clutch so this is probably your problem. Technically third does also, but the direct clutch is also applied so you might not notice if there is a second brake issue.
Both solenoids are also off in OD, so if you are having an issue with it, it is not solenoid related.

Well my problem wasn't actually fixed. My jeep just likes to mess with me I guess. I tried the kickdown cable adjustment and am going to clean all the connectors soon. Are there any connectors I should clean that I might overlook?

That is great info, thanks. I'll try to make certain on the drive home today, but I'm pretty sure I have first and third.

You say the second brake clutch is probably my problem — sorry for my cluelessness, but what is the second brake clutch?

It is one of the sets of clutches in the trans. So basically it sounds like its going to be an internal problem.

Thanks for the clarification. Boy, that is not encouraging.

Sorry, I wish I could tell you something better. The bright side is Aw4's are pretty cheap because they dont fail very often.

That's normal by the way. It'll eventually shift to 2 when the revs get high enough.

2'nd gear is where electrical deficiences often show themselves as it's the gear that requires both solenoids to pull in. If your #1 solenoid is drawing too much current (the one you are getting the codes on), the TCU may have trouble activating the second solenoid along with it. The TCU is current-limited.

Before you worry too much, drop the pan and check the solenoids. If they are not your problem, you aren't out much besides time. If they are the problem, you are 1/2 way towards fixing them ;)
You can also check the bottom of the pan for clutch material and other crud while you're at it.