KRinAZ

Hi, this is my 6th Cherokee and first possible transmission problem...the regular gears don't slip that I can tell, but the lockup doesn't do much anymore - cruising on the hiway with cruise control on - the engine speed goes up/down too much - kind of like I'm driving in 3rd instead of OD on the hiway (it does shift to OD normally though).

When I watch the rpm's and feel for each shift and when the tranny locks at steady cruise, I can still barely tell when it's trying to lock, but the engine rpm's vary to much under the light but varying loads (cruise control on) and it definitely isn't truly locked anymore.

The vehicle has a trans cooler, has 129k miles, I've owned the vehicle since 60k miles and have drained and filled the trans fluid ( 2qts 20oz's) at each oil change. The fluid has never smelled burnt and is always in good shape.

Never had a problem with an AW4 so haven't messed with them and don't know them that well, otherwise a very competent mechanic.

Any ideas , troubleshooting tips, possible solutions appreciated! - Kyle

mikEdub

More than likely your problem is with the oil pump. My jeep was having the same exact problems so I took it to the local transmission shop (not aamco) and they pressure tested it for me for free. Turns out the oil pump wasn't generating enough pressure (about 22psi low). So it would constantly go back and forth between 3rd and OD. I just put the new oil pump in about 30 minutes ago and now I'm procrastinating putting the transmission back in the jeep. I ended up paying $140 for a new pump.

Here is the guide for the AW4.
http://www.pirate4x4.com/tech/billav...AW4_manual.PDF

BlueXJ

I know this sounds bizarre but change the TPS and your transmission will stop slipping. It is actually not slipping it is locking and unlocking the converter. This is controlled through the transmission part of the ECU and gets the lock/unlock signal from the TPS.

98 JeepJeep

dont rule out a faulty SOLENOID......The TPS is expensive (50+) but it can be tested fairly easy......

mike37

I had that same thing
it was my brake peddle switch
I added a spring to hold the peddle up

try holding the peddle up with your toe for a few miles and see what happens

KRinAZ

OK, thanks for these tips - but let me state the problem clearer:

Shifting between 1,2,3 OD is all fine and there is no slip, but when the torque converter (TC) should lock up it doesn't. I can just barely tell when it tries to lock a couple seconds after shifting into OD, but it is no longer locked - the engine rpm's go up down just like it was in OD (with OD working correctly) without being in lock.

The brake switch is OK or I would not be able to keep the cruise control on - when the switch is engaged the CC disengages - and that that is all working fine.

I'm not sure how the lockup specific part of the trans and trans controller work or if there's anything I can fix or troubleshoot - any ideas?

I'm getting nervous driving the Jeep this way and it's my only vehicle - not sure if this is doing damage that will make the trans self-destruct.

- thx - Kyle

KRinAZ

BlueXJ mentioned the TPS - with the above added info is the TPS still a possibility? Is it possible to tell or troubleshoot this without replacing it? - thx - Kyle

KRinAZ

Checking the wiring diagram and the TPS - looks like pin 2 has the variable signal between pins 1 and 3

Measuring pin2 against pin 1 and pin 3 on my analog & digital VOM meters give nice smooth sweeps (analog)(no open or shorted spots) with these values (digital):

(Orange/Dark Blue wire) Pin1 to (Violet/White wire) Pin2 5.12 Kohms closed throttle to 470 ohms open throttle

(Black/Light Blue wire) Pin3 to (Violet/White wire) Pin2 125 ohms closed throttle to 4.8 Kohms open throttle

Pin1 to Pin3 5.14Kohms

Not sure what the ohm values should be, but it appears the TPS is working correctly - Kyle

mike37

my cruise would still work also
its not that hard to hold the peddle back with your toe for a couple of mills
just try it

KRinAZ

Thanks mike37 - didn't make any difference though - held the brake pedal up very firm but lockup still does not lockup

KRinAZ

By the way, the reason I'm describing this as the lockup slipping is because I don't get the normal rpm drop when the lockup [tries to] occur - there is the slightest blip in rpm when it used to lock. Based on that I don't think it's locking/unlocking - but that it can't lock when it tries/wants to.

On the solenoid - is there something typical to look for like an open circuit that would be seen on a VOM?

KRinAZ

OK, digging around on the 'net, I found some info on the wiring for the TCU and solenoid outputs.

It appears I've got a bad TCC solenoid (thanks much 98 jeepjeep for pointing me in that direction).

Here's what I found when measuring my jeep:

Harness wire, TCU connector pin, function:

blue/white stripe-C16-Sol 1

violet/white stripe-C15-Sol 2

white/black stripe-C14-Sol TCC

***

Ohm readings with digital VOM:

Wire Harness C16 reads 14.8 ohms

Wire Harness C15 reads 14.8 ohms

Wire Harness C14 reads 1 Kohms - TCC (lockup) solenoid looks open or a problem - should be 14.8 (actually 11-15 ohms) like the other solenoids

TCU C16 reads 11.75 Kohms

TCU C15 reads 11.76 Kohms

TCU C14 reads 11.75 Kohms

*****

By the way this is for an early 1996 XJ, not the later 1996 that may be more more like a 1997 FYI

I'll follow-up post again as soon as I get some solenoids and do the install - should be less than a week...

& thanks much! to all who contributed to this thread so far

syncview

probably your TCC solenoid then, you can almost confirm it by a help of a friend giving it +12V at C14, get under the jeep, keep your ear close to the oil pan, ask him to plug it, hear the solenoid's 'tuck' if it feels odd (not strong enough, or 'tucking' after intervals), you can also compare to other solenoids as well.. don't turn the engine on cause you don't need to.. let the shifter be in P as well. Maybe not the best way to check them, but still, could give you some surety.

KRinAZ

OK, replaced the TCC solenoid and the lockup works just fine again.

The solenoid replacement process is in other threads but to rehash:

My XJ sits a little over 8" above stock so access from underneath is easy.

Disconnected the battery.

Drained the warm trans fluid.

Sprayed WD40 into the trans filler tube union and let it soak while doing the following work - so that it would hopefully slide apart easily (it did).

Removed the crossmember, trans mount, and exhaust hanger (under the trans mount), then disconnected the exhaust at the header and held it to the passenger side of the vehicle with a bungee cord. Doing this made the pan very accessible so I could get at everything easily and clean the gasket surface well. Mine had been RTV'd the last time it was removed by whoever worked on it.

Removed the pan bolts except two toward the front of vehicle to catch the pan, wedged off the pan at the rear side and let it drain further (quite a bit more fluid), removed it.

Inspected the filter, had fine metal shavings in it - not enough to clog it (yet) but I did buy a filter/gasket in advance and glad I did. Replaced the filter, replaced the TCC solenoid - carefully finding a routing for the wire so it wouldn't rub on anything.

Measured wire harness C14 now reads 13.6 ohms - good! It was 1K in previous reading but that is bogus (I think meter was reading wire reluctance) - measuring the solenoid directly it is an open reading.

Cleaned the magnets in the pan, cleaned the pan, cleaned thoroughly the gasket surfaces and dried them with brake cleaner on a rag.

Greased the filler tube unions, re-installed the pan with the fiber (not cork) gasket in the filter/gasket kit, torqued the pan bolts in three cross passes up to 10 ft lbs.

Re-assemble everything else and fill with 4 qts Dex II/III and test drive - ahhh - lockup now works just like new.

Measuring the trans fluid after coming back - the 4 qts brought the hot measurement up to about 6oz from the max line - good by me.

This process would be the same for any of the three solenoids to be replaced - if you have a shifting or lockup problem measure the ohms at the wire harness - unless they are in the range of appx 11 - 15 ohms you have a solenoid (or hopefully not wiring) problem. Performing the measurement is quick and easy and should probably be verified/ruled out first.

Remember to disconnect the battery before disconnecting the TCU wire harness.

If you're in Phoenix, AZ, Get It Hard Parts (yes that's really the name of this trans parts store) had the solenoid and filter/gasket all for $75 including tax - and they deliver!

bufbarnaby

My `90 XJ AW4 OD feels like it is stuck on again even at low speeds.
Cable adjustment didn`t help...changed fluid also.
Is it worthwhile to get a new TCC solenoid ?
TPS is new , idles/runs fine.