Tranny issues with the Jeep

Nick1994

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Took my Jeep out off-roading yesterday to Widowmaker at Sycamore Creek. It's a huge sandy wash and some off-road obstacles. I did some hill climbs and was pretty hard on it, shifting to 4H & 4L a lot, which means I put the transmission in neutral to do so (automatic AW4). I noticed it wasn't accelerating real well but waved it off and continued. Then I started playing with the shifter, even if I manually downshifted it wouldn't go to 1st and it still couldn't even break the rear wheels loose in 2wd in the dirt (normally it could roast them). So it was stuck in 3rd gear. I had reverse though. No 1st, 2nd, or OD. I checked the fluid and it was 1/2" over the Max line. Fluid looks good, doesn't smell burnt. I drove home 50 miles or so on the highway with it in 3rd gear, even full throttle up to 75 and letting off it wouldn't shift. I got home and let it sit for 20-25 minutes and started it up and drove it a mile or two, it shifted perfectly. I've never had shifting problems before, it's actually one of the smoothest and best transmissions in a car I've driven. I did a drain and refill of the transmission 4 or so years ago, and then maybe 2 years ago I changed the transmission pan gasket, while that was dropped it got a new filter too. It doesn't get a whole lot of miles. I'm guessing a shift solenoid? Or the transmission overheated from hill climbs and being hard on it? It's got a small tranny cooler. Also, I used my cheap little WiFi scan tool and no codes. Here's the hill I was climbing a lot, and also some sand driving. [Linked Image]
 
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Originally Posted by MrMoody
Staying in 3rd would have to be ECU/TCU. Probably limp mode from overheating.
Agreed; once it cooled down it went back to normal. High fluid level can occur when the fluid gets really hot, as IIRC automatic trans fluid does expand with temperature.
 
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Maybe you overfilled when you changed it and when it gets hot and expands it's even more overfilled and causing issues. shrug
 
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Went into Limp mode for sure... This is common with all Chrysler transmissions if there is a problem such as high temperatures.
 
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Originally Posted by MrMoody
Staying in 3rd would have to be ECU/TCU. Probably limp mode from overheating.
Doesn't it stay in 2 in limp mode?
 

Nick1994

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I didn't shut it down out there since I was alone, and the starter just started to crank a little slow recently. Another thing for the list.
 
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It got hot and stuck its self in limp mode. It didn't reset out of limp till you turned it off. If you had turned it off earlier for a few minutes it would have shifted normal on the drive home. Time for some more cooling!
 
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Originally Posted by Chris142
It got hot and stuck its self in limp mode. It didn't reset out of limp till you turned it off. If you had turned it off earlier for a few minutes it would have shifted normal on the drive home. Time for some more cooling!
/\ This! Sounds like you need a bigger cooler. Im not sure about your year Jeep but mine has a tranny high temp light.
 
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Originally Posted by demarpaint
Originally Posted by MrMoody
Staying in 3rd would have to be ECU/TCU. Probably limp mode from overheating.
Doesn't it stay in 2 in limp mode?
Depends on the model of vehicle. Some are Gear 2 some are Gear 3.
 
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The AW4 is not a Chrysler transmission, it is basically the Toyota A340 found in the Tacoma. It is a fairly robust transmission, but it does tend to run on the hot side, even with just normal driving. Sand hills climbs like that could've definitely made it run too warm. I'd definitely get a good sized transmission cooler on it, and you can skip the "heat exchanger" in the radiator where the trans lines normally route to and just run them directly to the cooler since you are in Arizona. Since it got hot, might be a good idea to change the trans fluid. I just use regular Coastal Dex III from Autozone in mine and it shifts perfect.
 
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I've seem them overheated pretty bad on the trails before - to the point that they are shooting fluid out the dipstick and never seen that happen. They don't have a "limp mode" from overheat / mechanical failure; only when they lose communication with the NSS or the TCU (which should be under the dash). It's possible that one of the solenoids got stuck. I would really recommend a transmission cooler. They can run extremely hot. I'm considering adding a second one to mine as mine will get hot to the touch on the return side if I'm rock crawling on a hot day.
 
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Originally Posted by jeepman3071
I'd definitely get a good sized transmission cooler on it, and you can skip the "heat exchanger" in the radiator where the trans lines normally route to and just run them directly to the cooler
I never, ever recommend this unless the aftermarket cooler is absolutely huge, like 30,000 GVWR rated. Every bit of cooling helps - including the heat exchanger in the radiator.... so don't bypass it.
 
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A clutch fan out of a 4 banger Jeep can give you healthy air movement, and as easy as swapping parts.
 
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Originally Posted by Linctex
Originally Posted by jeepman3071
I'd definitely get a good sized transmission cooler on it, and you can skip the "heat exchanger" in the radiator where the trans lines normally route to and just run them directly to the cooler
I never, ever recommend this unless the aftermarket cooler is absolutely huge, like 30,000 GVWR rated. Every bit of cooling helps - including the heat exchanger in the radiator.... so don't bypass it.
If you drive it where it gets cold. If not there is no benefit to be gained with faster warm up from the heat exchanger. If I had an external trans cooler, I would bypass it just to avoid the risk of the trans and coolant getting mixed.
 
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Originally Posted by StevieC
Originally Posted by demarpaint
Originally Posted by MrMoody
Staying in 3rd would have to be ECU/TCU. Probably limp mode from overheating.
Doesn't it stay in 2 in limp mode?
Depends on the model of vehicle. Some are Gear 2 some are Gear 3.
Thanks.
 
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Originally Posted by jeepman3071
The AW4 is not a Chrysler transmission, it is basically the Toyota A340 found in the Tacoma. It is a fairly robust transmission, but it does tend to run on the hot side, even with just normal driving. Sand hills climbs like that could've definitely made it run too warm. I'd definitely get a good sized transmission cooler on it, and you can skip the "heat exchanger" in the radiator where the trans lines normally route to and just run them directly to the cooler since you are in Arizona. Since it got hot, might be a good idea to change the trans fluid. I just use regular Coastal Dex III from Autozone in mine and it shifts perfect.
Even when Chrysler sources stuff outside their own engineering department they always either have it built to their specifications as needed or have software / fail-safes programmed in. It's about not having to pay out on Warranty Claims. Further just because it's not storing codes you can read doesn't mean it's not storing diagnostic information the dealer scan tool can access about the history of when it was in limp mode or when some sort of fault occurred. Chryslers are quite good at storing a lot of information for their own diagnostics. Not even my dad's expensive Snap-On tool can access all of this data and it can see just about everything a dealer can. I know first hand as the Throttle plate had an intermittent issue on my my Fleet Caravan (now my dad's van) the first week I got it. It wasn't setting a check engine light and had nothing stored as checked by my dad's Snap-on tool as I had him check it out so I would have more information to go to the dealer with when I took it in. They read and found that the ECM was aware of it and was monitoring it before setting a hard/soft code. Again there were no hard/pending codes in the system when we scanned it with the Snap-On tool which isn't some e-bay special. It has the ability to do almost everything the dealer can including key-fob programming and it was over $10K when he purchased it.
 
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I had a Comanche with the AW4 transmission. that thing was amazing. I did add a transmission cooler, and hauled our boat, snowmobiles 10's of thousands of miles. other than fluid changes, the trans was great, even at 175k miles when I sold the truck. add a cooler.....
 

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Originally Posted by StevieC
Originally Posted by jeepman3071
The AW4 is not a Chrysler transmission, it is basically the Toyota A340 found in the Tacoma. It is a fairly robust transmission, but it does tend to run on the hot side, even with just normal driving. Sand hills climbs like that could've definitely made it run too warm. I'd definitely get a good sized transmission cooler on it, and you can skip the "heat exchanger" in the radiator where the trans lines normally route to and just run them directly to the cooler since you are in Arizona. Since it got hot, might be a good idea to change the trans fluid. I just use regular Coastal Dex III from Autozone in mine and it shifts perfect.
Even when Chrysler sources stuff outside their own engineering department they always either have it built to their specifications as needed or have software / fail-safes programmed in. It's about not having to pay out on Warranty Claims. Further just because it's not storing codes you can read doesn't mean it's not storing diagnostic information the dealer scan tool can access about the history of when it was in limp mode or when some sort of fault occurred. Chryslers are quite good at storing a lot of information for their own diagnostics. Not even my dad's expensive Snap-On tool can access all of this data and it can see just about everything a dealer can. I know first hand as the Throttle plate had an intermittent issue on my my Fleet Caravan (now my dad's van) the first week I got it. It wasn't setting a check engine light and had nothing stored as checked by my dad's Snap-on tool as I had him check it out so I would have more information to go to the dealer with when I took it in. They read and found that the ECM was aware of it and was monitoring it before setting a hard/soft code. Again there were no hard/pending codes in the system when we scanned it with the Snap-On tool which isn't some e-bay special. It has the ability to do almost everything the dealer can including key-fob programming and it was over $10K when he purchased it.
And of course the other really nice thing WiTech gives you is the ability to do software updates, which often folks aren't aware of. Each has its release notes as well, indicating what has been fixed/addressed.
 
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