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  #1  
Old October 16th, 2003, 06:21
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Unhappy Yet Another AW4 Transmission Problem

I apologize if this seems a little long, but I am both asking for advice, and documenting a procedure I have not seen mentioned before. I have a 1998 XJ 4x4 4.0L AW4 Automatic with about 60000 miles. Early this summer, I dropped the pan on the tranny, changed the filter, and changed the fluid (With Dexron III/Mercron, of course). Everything seemed fine.

Now the transmission is acting very strangely, and slipping. When I step on the gas from a stop, more often than not the engine will rev, almost like it's in neutral. The Jeep will creep forward slowly, and then BANG, something engages, the jeep lurches, and I start moving. However, even at that point, the motor revs higher than normal, and it feels like the transmission is slipping. If I let off the gas just before it engages I can avoid the BANG, and drive it almost normally, but it still slips, especially starting on a hill. When I step on the gas on the highway, it feels like it's slipping, too.

It happened very suddenly. Two days ago, I drive to work in the morning, everything's fine. Drive home at night, big problems. This would seem to indicate it isn't a progressive problem related to, for example, the wrong ATF.

I stopped by the dealership, and ended up talking with a technician there (who reinforced the generally held view that AW4's are bulletproof.) He said many times the problem is related to the Throttle Pressure Sensor (?). What he was
talking about is described by AllData as a Throttle Valve. This has nothing to do with the TPS on the engine. The second cable coming off the throttle is a "Transmission Throttle Valve Cable." It goes down to the valve, located on the left hand side of the tranny, just forward and above the gear selector linkage.

I've never seen the throttle valve mentioned in previous posts about tranny problems. Paraphrasing the manual: The tranny throttle valve controls shift speed, quality, and part-throttle downshift sensitivity. If cable is too slack, it will shift early, and slip between shifts. If it's too tight, shifting will be delayed ( Revving the engine!? ), and downshifts will be overly sensitive.

Anyway, I followed the procedure to adjust the throttle cable: Make sure both the throttle and valve are in the fully closed (idle) position. Slide the cable clip off the throttle linkage. The manual said to use a small screwdriver to remove the retaining clip on the cable's bracket. Then you can adjust the position of the cable to make sure the end of the cable is centered over the
attachment stud on the throttle. Put the retaining clip back on to lock the cable (sleeve) in position, and reattach the end of the cable to the throttle. The tolerance is 1mm! The throttle valve has to be synchronized with the throttle, or else the transmission gets confused. My cable was too tight by
almost 1/4".

Manuals lie. The one I was following did not mention that on my '98, there is no longer a "valve lever" outside the transmission. It's internal. The cable just disappears into the tranny. It also did not mention that they made the adjustment even easier. All you do is disconnect the end of the cable from the throttle linkage, and PUSH DOWN ON THE METAL BUTTON ON TOP OF THE RETAINING CLIP. Then you can slide it to any position you need, and let go, and it's locked. I almost broke the connector with a screwdriver trying to remove it.

So, I take the XJ out for a test drive, and it seems about a 70% improvement. There's still slipping, but the problem with the engagement from a stop is almost gone - even uphill! I get the impression that the "throttle valve" is supposed to let fluid bypass the torque converter if you take your foot off the gas, and the moment you step on it, it sends fluid to the right places to make the Jeep go. This would make stopping easier, because there'd be less force coming from the tranny, and would prevent creeping when stopped. I have not confirmed this, though. And it doesn't explain the slipping.

Now the frustrating thing. I drove the Jeep to work this morning, and when it was cold, it seemed okay - still slipped a little, but didn't lurch when starting out. By the time I had been on the road for about 15 minutes it was as bad as before.

I'm at a loss! What now?? TPS? New Fluid? Throttle valve problems? I've seen mention of fuses, but the '98 owner's manual doesn't show a specific tranny fuse, and none under the hood were blown.

I've got MOPAR ATF on order ( The dealer didn't have any Dexron III, because "they always use ATF+3, and never had a problem." )
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  #2  
Old October 16th, 2003, 09:44
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8Mud 8Mud is offline
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There is a controversy I guess about ATF-3, ATF-4 and Dexron III (my Dodge/Jeep dealer says also ATF-3, all he has in the shop I guess). What does your manual say? Read a tech. posting about tranny fluids, www.allpar.com/fix/trans.html (you have to read about halfway down the page to get to the Jeep part). I changed the ATF3/4 out of my older AW4, to Dexron III, things really improved. The later Dodge trannyīs were designed to run ATF, the AW4 was designed to run Dexron II (at least the early models).
There was a notice from Jeep way back when, saying to watch what grades of Dexron you used, seemed there was a wide discrepancy, in what various manufactures considered to be Dexron, spec. Some of the Grand Cherokees had the 42 E tranny which used ATF-4.
That write up, about the clip and the throttle/tranny cable has been around a long time (they keep reprinting the same old nonsense). Itīs a Chevy cable at least in my XJ (early), but the newer sort, the (Chevy type) kick down cables havenīt had the swing clip since Corvettes of the 80`s.
I believe the type you have, is where you push a thumb sized release and the cable adjuster can be slid into the adjuster housing. The adjustment, as I understand it, is to let the adjuster slide all the way in, then with everything hooked up, with your thumb, open the throttle hard (to the stop), until the adjuster slides (ratchets) out as far as it will go. If you figure out you need a little more pressure, you can release it one more notch (but passing gear can be hard to find on occasion). The adjustment process Iīve given you, is for the Chevy, but the cable and adjuster are identical, Iīd surmise the adjustment process is also the same, for Jeep. If Iīm wrong, hopefully, somebody will jump in and correct me. Iīve never had to mess with the AW4 much, just replace the fluid on occasion.

I read your post again, something to look at, is the color of your fluid. If itīs slightly straw color or not bright Dexron red, itīs time to change. Burnt fluid slips and will gum up the valve body.
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  #3  
Old October 16th, 2003, 11:30
Tom R. Tom R. is offline
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As for the cable adjustment up by the T-body, the Haynes manual states to do it just as 8Mud stated. The transmission guy I've used recommended not to open the throttle with your thumb, but rather depress the gas pedal all the way down to ratchet the cable. I tried both and got varying results. What I do now, after adjusting the cable using either method, is drive it and determine how it shifts. If it shifts a little hard, then I make a fine adjustment by depressing the cable release and sliding the other plastic piece the cable runs through by hand. It's a minor adjustment and I find I can dial it in a bit better for smoother shifting.

I'm not convinced this specific adjustment will cure the shifting problems you're encountering, though. Sounds like something else going on, or perhaps it's something in combination with the cable adjustment. I'm interested to hear what you find out. Good luck,

Tom
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  #4  
Old October 16th, 2003, 21:00
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8Mud 8Mud is offline
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Tomīs right, there was an update (amendment) to that tranny throttle cable, adjustment, Iīd forgotten about (at least for Chev). They now recommend, using the gas pedal, pressed all the way to the floor, to ratchet out the adjuster. My mistake, getting old. Would probably be a good idea to adjust the throttle cable to get to the stop, then adjust the kickdown cable, best of both. A slightly loose cable (with Chev.) will give you slightly harder shifts. The tighter the cable gets the softer the shifts, my understanding is the cable is to reduce pump pressure (relieve some pressure) so the shifts donīt bang or shift to hard, at higher RPMīs/open throttle. Thatīs the way it works for the torqueflight and the TH series tranny, donīt know for sure with the AW4, havenīt made any tests.
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  #5  
Old October 17th, 2003, 07:17
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Thanks, folks, for the input.

Sorry, I should have mentioned that the fluid looks (and smells) fine. Also, I am retracting the statement that the transmission is slipping. I think my own paranoia, combined with my lack of experience troubleshooting automatics, convinced me that high RPM = slipping. With some experimenation, I've found that it doesn't appear to slip, just delay the shifting. Also, I shouldn't insert uninformed theories into this forum. The more I read about the Throttle Valve, the more it sounds like it does much more that what I described.

I should hit EBay for a Factory manual. I subscribed to www. alldatadiy. com for my Jeep, expecting the information would be accurate. That's where I got the incorrect TVC adjustment procedure. Between that, and some other customer service issues I've had with them, I don't think I'm going to renew. ( As a side point, the dealer's technician showed me a similar procedure as AllData on their computer - not the "push the button" one, so now I don't know WHO to believe. Of course - they also put the wrong spec fluid in all the AW4's, "and never had a problem"... )

After some Googling, I stumbled across this site where a guy swapped a Cherokee AW4 into his Wrangler:
http://www.stu-offroad.com/aw4

He happens to have the AW4 Service Manual:
http://www.stu-offroad.com/aw4/AW4_MANUAL.pdf

So, examining this from the perspective of as passive an observer as I can muster, there are three things in play here ( assuming the transmission itself does not have mechanical problems ):

1) The TPS - Reporting the throttle postion to the Transmission Control Unit.
2) The TCU - Making shift decisions based on the TPS and shift lever position, then operating the solenoids in the tranny.
3) The TV - doing some magic inside the tranny to make further decisions, based on the accuracy of the TV cable's adjustment.

It seems that the transmission THINKS the throttle is not open as much as it is. There are other sensors and switches involved, but I don't think they have much to do with the symptoms ( such as the switch that unlocks Torque Convertor when you hit the brakes.)

I tried some things on the way home last night. First, I disconnected the TPS. This made the motor rev WAY up - like 4500rpm, before shifting. I didn't even leave the parking lot like that. That kind of eliminates a fuse or the TCU as a problem. They obviously were getting SOME kind of signal from TPS.

Next, I did the adjustment on the TVC the way you've told me, and the way the AW4 Service Manual says (Push the release in, pull the cable back, open the throttle all the way, and let the release go). The end result was a cable that was about 1mm away from the original position before all this started ( I scribed a light line on the connector before I started playing.) So, the TVC seems to have been adjusted correctly.

Then, part way home, I deliberately mis-adjusted the cable too short (making the tranny think the throttle was open more than it was), and now the Jeep runs MUCH better. It doesn't rev as much - in fact it seems to lug a little before shifting, it doesn't downshift at the drop of a hat, and there is no sensation of slipping. The shifting got WAY better. It still wasn't right, but the engine revved only slightly from a stop, and the other gears were almost normal for timing, just harsher. This seems to indicate that the tranny is getting fed information that makes it think the throttle is NOT open as much as it actually is.

My money is on the TPS. I'll check it with a meter at lunchtime. Let's hope AllData is right about THOSE procedures... I'll report my success/failure.

MY KINGDOM FOR A SCAN TOOL!
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  #6  
Old October 17th, 2003, 07:41
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Runnin'OnEmpty Runnin'OnEmpty is offline
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Yukon, my money is also on a bad TPS. These things are almost a maintenence item. They will wear out at the lower end of the range, just where most throttle changes occur in day-to-day driving.

I assume you know how to check the TPS voltages. Make sure there is a SMOOTH transition from about 1v to 4v on the signal wire when the throttle is advanced. Don't forget to check the TPS ground wire. If you have a less than perfect ground, you can splice an extra wire in this circuit and run it to an engine ground. Jeeps seem to have a lot of trouble with the TPS grounding circuit.
Good luck.
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Old October 17th, 2003, 10:12
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Angry

Hmmm...Well, the TPS was spot on.

Low end was .9v, high end was 4.2v. Using an analog meter, there was NO hiccups in the meter over the range. Ground coming off the TPS connector was fine.

Next step, based on a conversation with a respected gearhead, is to disconnect the battery, let the computer forget all about this unhappy incident, and then try again with the TVC.

Then, do the fluid change like I already planned.

Whatever we do, we don't want to leave the TVC in a position that makes it compensate for / mask another problem.
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  #8  
Old October 19th, 2003, 07:41
Judd W. VA Judd W. VA is offline
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The Throttle Valve is a regulator of the pressure of the trans pump output. At idle you do not need high pressure through the trans because nothing is being applied, but hit the gas and clutches/band need engagement. Is a very good arrangement used by the venerable 700R4/4L60 and others.

The sudden jolt from sitting usually means the pump pressure has dropped too low causing a total trans 'shut down'. You need to tap the output on the side of the trans with a suitable gauge to see if the pump pressures outputted are correct according to specs. Is not hard to do really- just need the right gauge and fittings. Would be the best determining factor of all.

If you want real information on your trans, just buy a book from ATSG, Auto Trans Service Group. Go on line and get one generally for only $25 + shipping. Is the book the pros use. Make sure to get one for your later trans. Might have to get an earlier book then an upgrade if there have been many updates since.

I do believe the DexIII/Mercon is the ATF to use. Is not a Chry trans that would generally use ATF+3.
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Old October 19th, 2003, 17:02
bordn168 bordn168 is offline
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One of the first things I did when i bought my XJ was change the tranny fluid in my AW4. I checked with 3 or 4 different books and a couple of dealers and they said to use ATF+3 so that is what I put in and no problems came up.
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Old October 19th, 2003, 17:50
Judd W. VA Judd W. VA is offline
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Warning!!

If you have a 4.0 then you will have the AW-4 transmission and is designed to use Dexron III/Mercon. Is a Jap trans and is different than the Chrysler transmission. If you have the 2.5 engine with the 30RH trans then you use the ATF+3 fluid.

This is per my '98 FSM which isn't always correct, but this does make sense.
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Old October 20th, 2003, 08:57
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Markm80521 Markm80521 is offline
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That is correct. As I understand, the AW-4 is one of the better tranny's that came in the xj namely because it is a land cruiser tranny.
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Old October 21st, 2003, 10:26
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Just as an update, I started walking through the troubleshooting tree in the AW4 service manual and...

Did the "manual shift test" - unplug the TCM and see how it runs in "dumb" mode.

Without guidance from the TCM, the transmission is supposed to react to the shifter position as follows:

1-2 : Stay in 1st
3: Stay in 3rd
D: Stay in Overdrive.

This is good to know if you need to limp home. Just pretend it's a manual.

The tranny worked exactly as expected. But, I'm still getting the delayed engagement in 1st, and sometimes I CAN feel it slipping, in 1st and 3rd. The problem comes and goes - sometimes it pulls just fine, and other times it slips. When it slips, eventually it will go BANG and finally start pulling.

I'm going to follow the advice of Judd W (and the AW4 service manual) to check the transmission pressure. I just ordered a pressure test gauge, and will post my findings.

As for the fluid, the AW4 takes Dexron III/Mercon. I went to the dealer and asked for it, and they had to SPECIAL ORDER IT!! At first, they looked at me like I was from Mars when I refused to buy the ATF+3. They made an off-handed comment that their overhead lines in the maintenance bay had Dexron/Mercon available, but they don't make a point of putting it in the AW4's. When they top off an AW4, they use what every other Chrysler tranny uses - ATF+3. Unfortunately, the AW4 is a Japanese transmission that predates Chrysler acquiring Jeep. So that just adds to the confusion. The parts guy looked up the number in the owner's manual ( #4773590 ), and yes, indeed, that is a valid part number to get Mopar Dexron III/Mercon ATF. A technician looked up the service info on the XJ, and said the Xj 4.0L/Auto (AW4) didn't specify ATF+3 as a suitable substitute. (And yet, I get the impression they're going to keep on putting ATF+3 in the AW4's)

Regardless of individual experiences on this site, there are many sources that specify Dexron III/Mercon, and Jeep has not released a TSB stating ATF+3 is a suitable substitute. It seems that dealers may get lazy/inattentive, and put it in because other Chrysler products use ATF+3.

I'm not trying to dispute anybody's claims that ATF+3 will or will not work in the AW4, just pointing out that I have not found any printed evidence (from Jeep) that says ATF+3 should go in it. The owner's manual for my '98, the AW4 service manual, AllDataDIY, and other people here with FSM's all say it is supposed to use Dexron III/Mercon, with Dexron II as a subsitute if the other is not available (unless you have a 2001 XJ, in which case don't use Dexron II? AAAGGGHHH!!!).

People have pointed out that you should only get ATF that has a certification number on the back. All the posts I've read said that the certification number should start with a "D." The Mopar ATF I just bought had no certification!! :-) And the stuff I bought earlier this year at the local parts store had certification numbers starting with "G." I haven't a clue if its a valid number or not.

All I know is, if I had a vehicle still under warranty, and the transmission grenades, I'd want to make sure the tranny had the stuff specified in the owners manual, or a TSB stating a good substitute. Otherwise they may not honor the warranty.

And we won't even touch the subject of synthetics...
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Old October 21st, 2003, 16:35
Judd W. VA Judd W. VA is offline
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Isn't that interesting how the dang dealer does not even know what ATF it should be using in their various trans's?! There would have to be some real changes in the venerable AW4 that has used Dexron III for years in order to switch to the Chry fluid. It does seem the ATF+3 has quite substantially different slip properties than Dex III. Amazing.
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Old October 21st, 2003, 19:40
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This may sound like a dumb question, but are you checking the trans fluid while idling in neutral?If you are not, you are getting an incorrect fluid level reading and this may be the cause of all your problems........Just thought I would ask Good luck!!!
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Old October 22nd, 2003, 06:31
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Jeff -

Recently I haven't checked it while idling. Early in the summer I checked it that way, and it was just a little high after changing the fluid, but I left it that way. I guess I was too lazy to drain a little back out. All summer it's been fine. The level hasn't gone down (or up...) so I haven't bothered to check it while idling.

Wouldn't I feel like an idiot, if 5 months after changing the fluid, it starts acting up because it was too full?

My father was talking to a friend at the local garage who suggested putting a product called Trans-X into the tranny and running it for about 10 miles, then changing the fluid. He swears by the stuff. It's supposed to clean out varnish, deposits, etc from the transmission, and soften hard seals. He says many times they've used it to straighten out a squirrely transmission.

The bottle says to add it in a 10:1 ratio to the fluid. One older transmissions it says to leave it in permanently. I don't think a 6 year old AW4 tranny with 60,000 miles that's been regularly cared for qualifies as old or abused.

I'm naturally suspicious of adding anything foreign to the transmission, but since I don't plan to leave it in, I don't think it can harm it. Has anyone had experience with transmission additives?
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