AW4 is slipping when warmed up, any thoughts?

Hi, I'm new to the forum and have searched but I can't find a similar problem to the one I'm having. I only have 100k on the odo and the 96 XJ with 31s has never been towed with. I can only drive for about 30 minutes and then my tranny starts to slip, when I come to a stop, then accelerate it slips bad and will hardly move. I have to shift into 1st gear to get it moving again and then manually shift it to get it up to highway speeds. I can also feel it slip between 3rd and OD, it drops into 3rd too easily and doesn't hold OD as it should. I've already changed my filter and fluid, which made my shifts smoother. The new fluid is kind of burnt and looks more like motor oil light brown, not red. When I'm stopped and apply the brakes and the gas at the same time the jeep just slips, forward and reverse both. The only gear that still has some power is 1st. When I allow it to cool overnight it's fine again and drives and shifts smoothly. Could I have an overheating issue or worse? No check engine lights so I'm guessing there isn't any codes to read. Sorry for the long post.

I will ad to this that when i say "slipping" I meen the engine revs up normally but the Jeep doesn't move. it feels just like a bad clutch on a standard. Anybody????

you should install a tranny cool as cheap insurance, only approx. $50 and they do nothing but good for the AW4

anti-slip products for trannys work well from what i hear, but that will only be a bandaid for any problems you might have

I'm planning on draining the fluid and adding the anti-slip with some new tranny fluid tonight. A tranny cooler is a good idea and i plan on using this jeep to pull my small boat around so I'll do that too, along with a temp gauge. I've located a used tranny in the area but i'm hoping it doesn't come to that.

Well the tranny was slipping on the way to work again this morning so I messed with it a little. When I came to an intersection I left it in OD and floored it, it slipped like it normally does and the jeep moved a little but didn't down shift into 2nd or 1st like it should have, and the engine didn't want to rev past a certain point almost like it didn't have any power. When I moved the gear lever down to 1-2 it took right off and got me up to speed. I'm wondering if this could be something other than a bad tranny, like a plugged cat converter? Would a plugged cat get worse when warmed up? The jeep seems to run fine, no smoke or smell. The cat looks very old and rusty.

i wish someone else would help you out, i know how frustrating tranny trouble can be

i don't know much in the way of auto, but you could possibly check the voltages coming from the TCU to make sure its not bad....FSM says input voltage should be 5.0V and output 4.2V, but i always thought you checked individual wires......anyway, a search should pull that test up quick

fyi, normal operatin temp for the AW4 is approx. 130F to 176F ala the fsm, a temp guage would help you see if your fluid is getting overheated

wish i could help you out more, but i dont know much

Try getting a full trans fluid change - and not just the pan.... get the whole lot drained out (incl. the trans pump, cooler etc....), you'll be surprised at what a complete change of new fluid can do for an AW4. FWIW, I had slipping problems in my 93' 2 door (esp. first thing in the morning), and they disappeared as soon as I had the trans fully flushed out and replaced with Dexron/Mercon.... Oh BTW, there's been pages of discussion about what fluid to use on this forum, and the general consensus was that no matter what the current Chrysler manuals say, make sure you get Dexron !

Best of luck with it and let us know how you go.

did you change the speedometer gear when you went to 31 in. tires ?
vehicle speed sensor is used by the tcu to set shift points .
there is a write up on the gojeep home page to find the right gear for your
tire size / gear ratio .

if the fluid looks and smells burnt , then as previously mentioned get
a fluid exchange done .

final thought , my 96 did something very similar :
trans would work great driving around town , 10 minutes at highway speed
and it would kick out of o/d .
finally one day it dropped into neutral as i slowing for a stop .
coasted into a parking lot checked the fluid which showed several
quarts overfilled . let it cool down and eased it home .

it came down to a combination of a bad tps ( had a "dead" spot )
and a failed turbine ouput speed sensor , drivers side of trans under the
transfer case shift bracket ( two wire white connector )

hope this helps .

sw_mi_xj said:

did you change the speedometer gear when you went to 31 in. tires ?
vehicle speed sensor is used by the tcu to set shift points .
there is a write up on the gojeep home page to find the right gear for your
tire size / gear ratio .

Click to expand...

this is spobi.

the aw-4 has its OWN speed sensor.

it does NOT use the speedo sensor located at the transfercase.

the aw-4 has its OWN speed sensor.

it does NOT use the speedo sensor located at the transfercase.[/QUOTE]

really ? that's cool ,
so then dont refer to this from an aw4 diag . manual

SPEED SENSOR
Speed sensor, mounted in adapter housing or extension
housing, is an input device consisting of speed sensor rotor and speed
sensor. Speed sensor rotor is mounted on transmission output shaft.
Input signal is delivered from speed sensor to TCM with each
revolution of transmission output shaft. The TCM uses input signal for
controlling transmission operation.

sw_mi_xj said:

the aw-4 has its OWN speed sensor.

so then dont refer to this from an aw4 diag . manual

SPEED SENSOR
Speed sensor, mounted in adapter housing or extension
housing, is an input device consisting of speed sensor rotor and speed
sensor. Speed sensor rotor is mounted on transmission output shaft.
Input signal is delivered from speed sensor to TCM with each
revolution of transmission output shaft. The TCM uses input signal for
controlling transmission operation.

Click to expand...

That writeup appears to be confusing the tranny output shaft speed sensor with the vehicle speed sensor. The tranny output shaft sensor cannot be changed. The vehicle speed sensor which can have its gear changed is located in the xfer case tail housing (or the tranny tail housing if a 2wd). There is no connection from the speedo sensor to the TCU. Wouldn't make sense to do so since the xfer case changes the gear ratio anyway. The AW4 output shaft speed sensor is on the drivers side of the tranny under the transfer case shift linkage bracket and is connected to the TCU.

The TCU doesn't care about vehicle speed. The shift points are determined by output rpm and not vehicle speed. You can prove this by putting the xfer case in neutral and the tranny in drive and watch it upshift. In pre-1997, the TCU only measures the output shaft and figures the input shaft speed based on what gear its in. Later AW4s have an additional input shaft speed sensor to directly measure the input. This really helps diagnositics as the TCU can now tell if either shaft sensor is bad or if the tranny is in the wrong gear.

BTW, if that sensor is bad it will either not upshift at all (no signal - typical) or perhaps upshift randomly (erratic signal).

I had a similar problem with mine shortly after I got her. It seemed that it was serviced at a jeep dealership just before I bought it (at 120,000 miles) and the morons put Chrysler ATF in it instead of Dexron III. I unhooked the return line to the trans from the radiator cooler and flushed the old crap out by running the engine until the flow of fluid started to slow, shutting off, refilling with Dexron III, running the engine... repeated until clear crap was replaced by red stuff. Took about 12 quarts IIRC. Then I dropped the pan and replaced the filter. Also added a B&M Supercooler downstream of the radiator cooler. Haven't had any issues since. FWIW, I just used Castrol Dex III, nothing fancy.

It sounds to me most like you have a leak somewhere. That would cause the slipping, the overheating & burnt oil. Take a close look at the oil supply/cooling lines & the seals front & rear. Even after you changed the oil/filter, it wouldn't be long before the symptoms reappear.

Otherwise, the internals in your tranny may have gone bad.

IMO a problem with the electronic control of the AW4 would NOT cause slipping--it would shift rough or not at all, you would lose gears, etc., but it would not slip like that. That's my non-professional opinion FWIW.

I suggest you take it to a tranny shop & pay them to remove the tranny & look for leaks. It'll cost a lot, but if they know their stuff they'll figure out what's wrong & still charge less than the dealership.

I went thru something like this with a torque converter problem. The tranny shop pointed out that the AW4 is a very tough tranny--its internals are less likely to melt & fall apart than the typical Chrysler tranny. They guessed right away that it was a leak. In the process they discovered that a bushing between the t-conv & the engine output shaft had worn, causing the t-conv to wobble & thereby causing a leak from the front of the tranny.

lawsoncl said:

The tranny output shaft sensor cannot be changed.

yes it can be changed on a 96, that is what was wrong with mine .


The TCU doesn't care about vehicle speed. The shift points are determined by output rpm and not vehicle speed.

ok then try this , put the wrong vss " speedo " gear in yours , and take it for a drive. that is a shared sensor between the tcu and engine computer .

Click to expand...

i was just trying to help the guy out , sharing my experience with the same
type of problem .
but what do i know , i have only done this for the last 25 years .

pull the pan and check the filter, a friend of mines was clogged so bad that it just started slipping and the next day it wouldn't move in his driveway, once the filter was clean and the fluid changed it runs fine

sw_mi_xj said:

i was just trying to help the guy out , sharing my experience with the same
type of problem .
but what do i know , i have only done this for the last 25 years .

Click to expand...

Hope you don't think I wasn't busting your balls. I was just passing on what I learned when I swapped a 99 AW4 in my 89 MJ. I did seem odd that the AW4 diag you have had the sensors confused.