Yet another slipping AW4 question

I recently picked up a 1988 XJ. The P.O.'s 18 year old daughter was beating on it doing neutral drops and blew the rear axle pinion. Well, the pinion has been replaced and now the tranny is slipping. It only slips badly in D but can be driven by manually shifting the tranny. I am going to do a filter and fluid change to see if that helps but was wondering if anyone else had some ideas or do you think the tranny is toast?

Toyota Trans

The transmission uses internal solenoids to shift. You have to pull the bottom pan off to access them. They can be removed and tested individually. However, their function is to shift from one gear to the next. Talk to an agency mechanic that does lots of Toyota Truck Trannies as they often know about fixes other than replacement of whole trans. Good luck

Ok, did a little more investigation shifting through the gears and such as well as replaced the TPS with one from the bone yard. This is my findings.

D - Jeep shifts its weight forward but goes nowhere. There is also a grinding noise form the tranny area.

1-2 - Shifts into gear hard with a slight delay.

3 - Goes nowhere.

R - Shifts into reverse hard with slight delay. Also noted that the reverse lights come on maybe 2 second after the trans shifts into gear.

As I stated before the transmission can be shifted manually and does go into all gears including OD with slight slipping when up to speed.

The reverse lights make me think maybe the NSS but would that cause the other symptoms?

Start by digging out your multimeter and getting to the TCU under the right side of the dash. Verify that the TCU is getting +12volts on the yellow and red wires. If its not getting power, the tranny will give you 4th gear in (D) with no torque converter lockup and shift manually as you described. It might be as simple as a blown fuse.

If that checks out, then unplug the TCU and measure the resistance across the shift solenoids. Should be pins C14, C15, and C16 which my 88 FSM shows as the white with tan stripe, violet with tan stripe, and blue with tan stripe. The resistance should be 11-15 ohms.

The hard shifting might be needing to adjust the throttlebody-tranny cable, bad tranny mount, bad motor mount, sloppy u-joints, or a lot of slop in rear diff.

The reverse lights would be the classic NSS symptoms. http://www.go.jeep-xj.info/HowtoNSSrebuild.htm

For grinding from the tranny area, I would check that the torque converter bolts are tight and the flexplate are not cracked. Check that the bellhousing bolts are all tight as well.

lawsoncl said:

Start by digging out your multimeter and getting to the TCU under the right side of the dash. Verify that the TCU is getting +12volts on the yellow and red wires. If its not getting power, the tranny will give you 4th gear in (D) with no torque converter lockup and shift manually as you described. It might be as simple as a blown fuse.

If that checks out, then unplug the TCU and measure the resistance across the shift solenoids. Should be pins C14, C15, and C16 which my 88 FSM shows as the white with tan stripe, violet with tan stripe, and blue with tan stripe. The resistance should be 11-15 ohms.

The hard shifting might be needing to adjust the throttlebody-tranny cable, bad tranny mount, bad motor mount, sloppy u-joints, or a lot of slop in rear diff.

The reverse lights would be the classic NSS symptoms. http://www.go.jeep-xj.info/HowtoNSSrebuild.htm

For grinding from the tranny area, I would check that the torque converter bolts are tight and the flexplate are not cracked. Check that the bellhousing bolts are all tight as well.

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Well today I pulled out the multimeter and did a few checks. It seems I am getting 12 volts to the TCU. I also checked the resistance of the solenoids but I seemed to get much higher numbers then you sated. It seemed I got around 28 ohms instead of 11-15.......?
Also I strapped my CJ to the hitch on the YJ and tried to pull it up a slight incline and the tranny just slipped.
Any other ideas?

Re: Yet another slipping AW4 question.... HELP!

Pulled the pan and changed the filter today. Refilled it and at first it seemed that it was working better w/o the TCM plugged in. After plugging it in it still slipped the same as before. I unplugged it again an it is now driving like it was before. I did notice that grinding noise is more of a vibrating/buzzing noise that occurs when the tranny starts slipping. If you give it more gas as the tranny slips the Jeep starts vibrating. Any ideas? Torque converter?

It sounds like the clutches in the tranny are bad. The AW4 is a pretty durable, but the Neutral drops probably did it in. It is probably cheaper to buy a good used tranny and replace it than to fix yours.

If you're getting 28 ohms on the solenoids, the solenoid or the wiring to it is bad.

lawsoncl said:

If you're getting 28 ohms on the solenoids, the solenoid or the wiring to it is bad.

Click to expand...

X2 the resistance should not be that high unless there is a problem with the solenoid or the wiring is pinched and grounding somewhere.:dunno:

I'd inspect the ground strap from the driver's side back of the head to the firewall and make sure it's instact and not corroded.

Also, check the grounds at the passenger side of the engine block above the oil filter. There is also a ground wire that connects from here to the battery to "complete the loop".

I know when these were bad on mine, the torque converter would lock/unlock all the time when hitting small bumps or anything and the trans would seem like it's slipping as the TCU didn't know what to do.

Good point as the ground path for the solenoids is through the block.

Well I today I remove the ground strap cleaned the surfaces and reinstalled adding dielectric grease. When I got the Jeep the PO said that the battery cables had just been replaced. I removed the ground cable from the block, cleaned the surfaces, added dielectric grease and replaced the stud in the block with a bolt because I didn't like the way the stud was seating. The good news is I retested the solenoids and they all read 15.6 ohms. The bad news is that it had no effect on the functioning of the tranny. The clutches are still slipping. It seems worse with the TCM plugged in than disconnected.

Also I noticed 15.6 is still a tad high. When fixing the battery ground I noticed that the replacement cable is longer then stock. Could this be effecting the circuit resistance? My limited electrical background tells me it might.

NHscrambler said:

Well I today I remove the ground strap cleaned the surfaces and reinstalled adding dielectric grease. When I got the Jeep the PO said that the battery cables had just been replaced. I removed the ground cable from the block, cleaned the surfaces, added dielectric grease and replaced the stud in the block with a bolt because I didn't like the way the stud was seating. The good news is I retested the solenoids and they all read 15.6 ohms. The bad news is that it had no effect on the functioning of the tranny. The clutches are still slipping. It seems worse with the TCM plugged in than disconnected.

Also I noticed 15.6 is still a tad high. When fixing the battery ground I noticed that the replacement cable is longer then stock. Could this be effecting the circuit resistance? My limited electrical background tells me it might.

Click to expand...

When I short the test leads on most of my cheap DMMs they read about 1 ohm of internal resistance. Check and see what yours reads. Expensive meters have a knob on them for zeroing the meter, like FET analog meter. You could still be reading some ground wire and frame resistance between the tranny solenoids and the ground point you selected for the testing. Mine reads about 18 ohms on solenoid #3, that I recently tested, and I am sure it is just some poor wiring ground connections down at the tranny, but it is not causing me any problems. The solenoids are grounded well enough to work even with the extra 3 ohms of resistance.

The Engine sensors like the TPS and O2 sensor are much more sensitive to poor grounds that the tranny solenoids. IF you had 1 -5 ohms, or over 100 ohms reading on a tranny shift solenoid, I would say you have problem you need to dig into further.

Do you know what fluid was in it? If they had the wrong fluid in it, it might take more than fluid change to fix it, as it does not all drain out when dropping the pan. if not the fluid, sounds like the clutches.... got nailed.

Ecomike said:

Do you know what fluid was in it? If they had the wrong fluid in it, it might take more than fluid change to fix it, as it does not all drain out when dropping the pan. if not the fluid, sounds like the clutches.... got nailed.

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I am unsure what fluid was in it. I am guessing the wrong fluid due to the fact the tranny seemed to work a bit better the first minute or so after I changed it. I am pretty sure the clutches are shot but in a last ditch effort before I swap it out I am going to try a can of Trans X in the fluid run it for a bit then change the fluid out again and see if it helps.

Re: slipping AW4 question..... torque converter?

I am giving this one last bump. The tranny is out and a replacement will be swapped in tomorrow. I have worries about putting the same torque converter back in. Do any of the symptoms I listed sound like they could be from a bad T/C? Is there any way to physically tell if the converter is bad?

Re: slipping AW4 question..... torque converter?

NHscrambler said:

I am giving this one last bump. The tranny is out and a replacement will be swapped in tomorrow. I have worries about putting the same torque converter back in. Do any of the symptoms I listed sound like they could be from a bad T/C? Is there any way to physically tell if the converter is bad?

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I would replace the torque converter any time you swap or R&R service the tranny.

The Tranny TC can be tested per the ATSG manual on the AW4, but the installed tests are not conclusive as to the source of the problem if it fails.

There is a mechanical tool lock up test for the lose TC listed in the manual, but it only tests the lock up. A TC rebuild company could probably live test it on a machine, probably for the cost a rebuilt one.