toasterknight

99 4L AW4 4wd

I am still working through my issues, but have narrowed one issue down enough to feel comfortable asking for advice.

In drive, while accelerating, my trans will up shift what i consider too early, though this may just be me, ending up with the jeep always being about 1500 rpm after shifting. When it shifts into 4th, as soon as I hit 45 it will lock the torque converter unless I'm am on the throttle almost to the point where it would stay in 3rd.

When cruising, if i need to accelerate it will not unlock the torque converter until after shifting down to 3rd. When you let off the throttle completely it will unlock, however if you barely keep on the throttle, it will keep the converter locked. I was able to keep it locked in that situation, down to about 900 rpm or 30 mph.

The fluid in it may be 20k old. It still smells fine and is the proper color. It has md3 in it. Chevron ATF MD3 if my memory is correct. I was dumb when it was changed and had the filter done at the same time.

I believe that is everything that has been done to it as well as all the symptoms. I may have forgotten something some please ask.

jpmarine6786

Locking the converter at 45 is normal.
Forcing it to lug by barley keeping on the throttle once it's locked is something mine also does. I don't see anything weird here.

toasterknight

It won't unlock the torque converter unless it downshifts is the primary weird behavior. I was trying to list all of the odd behavior in case it helped diagnose. When I say lightly on the throttle I mean light enough that had it been the brake it wouldn't have turned the brake lights on.

jpmarine6786

Ya mine does it too. It doesn't make any sense to me. Obviously the computer programming for the AW4 is very simple. Once the converter is locked, it won't unlock unless the brake pedal is pushed or it downshifts.

toasterknight

It really sucks where I live. We have too many hills. I was hoping it was something wrong and someone had advice.

jpmarine6786

I would just lock out OD.

toasterknight

I can't do that without being at 3000 rpm. The highway is 65 between work and home.

Radi

If it's stacking the gears and you end up lugging the engine you might make sure the TV cable adjustment is correct. There's a few threads around here addressing it. The TPS also has a lot of input into shifting and TC lockup.

eta: here's one:
https://www.cherokeeforum.com/f2/free-quick-fix-41821/

cruiser54

Find the connectors for the trans info superhighway. Clean them. Tip 10 of my Tips but not sure on the 99 if it's the same.

You could have a bad TPS also.

jpmarine6786

My dads 04 LJ with the 42RLE does the same thing. Once it's in OD it won't unlock the converter until it downshifts or the brake pedal is pressed. My TV cable is adjusted. I honestly think we are all overthinking this.

jpmarine6786

So I did some fooling around on my off hour. So. Mine will let it stay in OD TC locked till around 35, then the rpm drops too low and even a little throttle forces a downshift. I also pulled the TV cable all the way out, and pushed it in as much as the adjusted would go. It didn't make any difference in the shift points, all it did was change the speed at which the shifts happened. So my conclusion is that the computer has a very simple "If, Then" programming setup. Thus, there's no hard downshift set till the rpm drops below a certain speed, kinda like when you're coming to a stop and the transmission automatically downshifts with the drop in your speed.

So kinda like
If (RPM = 2000) and (TPS =<50%) And (Vehicle speed =< 20 mph)
Then gear = 1st.
This is a very simple example but I think you can get what I'm saying.

toasterknight

I will look into that when I get home tonight. I think the tps is fine. I replaced it in the past with an echlin unit, and my scan tool shows it functioning correctly. It is reading the closed throttle slightly higher than the mopar unit, 18% vs 14%, but the behavior of the trans didn't change with that swap.

I adjusted the cable again this morning. My slight vibration I thought was unrelated is less now. On the way to work it still wasn't unlocking. I will see home it behaves on the way home in regards to staying locked at lower speeds.

cruiser54

Will it unlock if you slightly depress the brake pedal?

toasterknight

Yes it does.

cruiser54

Go with Tip 10 and see what happens.