How do I test TCM/solenoids?

96 4dr. 4.0L AW4 4WD.

My jeep has recently developed a shifting problem. When I put the selector in D, it seems to shift through all four gears. However, it is shifting from first to 2nd "later" than it used to. (at a higher RPM) If I shift to 1-2, it doesn't shift out of 1st.

I replaced the TPS today, no change. I knew it couldn't be that easy.

I disconnected the TCM. It worked exactly as expected without a TCM. (1st, no 2nd, 3rd & 4th had to "manually" shift to get those.)

So could the "4" gears I think it's using actually be 1,3,4 and TC lock? would that explain the late shift out of 1st?

If anyone has had this experience or has any insight as to what I can test/replace next, I'd really appreciate the help.

-Eric

I swear that i searched before posting that thread. Honest!

Of course AFTER I asked the previous question, I found this:
http://www.transonline.com/transdigest/magazines/1997-10/Shift%20Pointers/index.html

I'll break out the meter tomorrow.

I tested recently using that link and it worked perfectly. Correctly diagnosed a bad solenoid. My symptoms were different (had a 4th gear start in D). I think you're on the right track, but I'm sure the AW4 experts that helped me will jump in. Also check the throttle valve cable... http://www.naxja.org/forum/showthread.php?t=1015963&highlight=throttle+cable+wow

96PAXJ said:

96 4dr. 4.0L AW4 4WD.

My jeep has recently developed a shifting problem. When I put the selector in D, it seems to shift through all four gears. However, it is shifting from first to 2nd "later" than it used to. (at a higher RPM) If I shift to 1-2, it doesn't shift out of 1st.

I replaced the TPS today, no change. I knew it couldn't be that easy.

I disconnected the TCM. It worked exactly as expected without a TCM. (1st, no 2nd, 3rd & 4th had to "manually" shift to get those.)

So could the "4" gears I think it's using actually be 1,3,4 and TC lock? would that explain the late shift out of 1st?

If anyone has had this experience or has any insight as to what I can test/replace next, I'd really appreciate the help.

-Eric

Click to expand...

I'm not sure if you already found this out, but in 1-2 the shift to 2 is very much higher than most expect, around 4000 to 4500 RPM iirc.
Your hypothesis about 1/3/OD/TC lockup sounds reasonable, but I'm not entirely sure.
Checking solenoids - measure em (see page 3 of the article you linked for nominal values, thanks for the link, all I knew was that they should be in the under-20-ohm range) and see what you get.

If you're adventurous, you can find out if it's the TCU for sure by wiring up a toggle switch to 12V for each solenoid wire, then throw it in D and take a drive. See http://www.greatlakesxj.com/tech/aw4shiftmod.html for a table of which switches should be on and off for what gears. TC lockup solenoid is easy, turn the switch on to lock the TC, just don't do it in first or second gear.

Thanks for the speedy replies.

I have been reading about the TC lockup switch. I think it's something I'd want to install permanently anyway. I guess now a good time to do that.

I adjusted the TV cable a while back. That firmed up the shifting nicely. No real difference other that.
Just can't quite figure out the no 2nd in 1-2.

I'll post what I find with the meter tomorrow.

I forgot to add that she's got 187,000 miles on her. I guess a little shifting problem shouldn't be a big surprise.

That makes me think...
How's the fluid? Filled to the proper level? Good and red, or burnt and black/brown?

It leaks a little. I keep it topped off. She has had a small drip at the transcooler (those quick connect things) for 2 years. What drips out is nice and red. regardless of my readings tomorrow, I should probably pull the pan and look around some.

Well, I tested the solenoids. #1=11.6 ohms, #2=11.4 ohms, #3=11.3 ohms. All within specs.
I wired in a lighted toggle to manually lock the TC.

Seems like everything is fine except for 2nd gear. 2nd is there when the selector is in 3 or D. But no 2nd when it's in 1-2.

I guess I can live with this. My biggest concern was that I was losing gas mileage/overworking the transmission if 2nd gear or TC lock weren't working in "D."

Thanks again for all the help.

Eric

Yeah, that's behavior just as it left the factory - it actually will hit 2nd if you get to like 3500-4500rpm. If you want, you can wire up an override switch and put it in 2nd whenever you want... the page I linked with the solenoid table has instructions further up.