All automatic transmission JK owners should read this! regarding overheating trans
09-22-2010, 05:43 PM
#21
JK Jedi Master
being a new automatic owner.. my previous 3 jeeps were all 6 speeds.. (1 TJ and 2 previous JKs). I have noticed the cause of the overheating...
automatic transmission torque converters by nature make LOTS of heat.. modern automatics are outfitted with Locking torque converters.. so effectively the converter is "locked out" and there is direct connection from engine to transmission input shaft similar to when a clutch on a manual is let out and engaged for driving....
the Jeep automatic is a 4 speed overdrive transmission with a locking torque converter..
like any transmission when you need a little extra power to climb a hill or to pass, etc you need to downshift your gears... in a manual you downshift and go.. the Jeep automatic plays a trick instead...
if you need just a little extra power, the jeep will leave the transmission in 4th overdrive gear and will simply unlock the torque converter.. which will raise the RPMs on the engine about 500-600 so that you are making a little more power from the engine.. (into its power band)...
this is great for a real short time and works good.. however the trans is making LOTS of heat during this time.. the computer on the jeep is not programmed smart enough to re-lock the transmission until you let down on the throttle requiring less load from your engine... instead it continues to make heat until it overheats....
the way it SHOULD work is that the transmission would recognize a couple things:
1] that it would see an extended time of unlock converter.. and make a downshift to 3rd gear and then re-locl the converter and run in 3rd till you no longer need the extra power
2] that it could do the above if it notices the trans temp is rising too high..
I am confident that this would alleviate some of the issues with these transmissions.. this would all be a computer flash change and not need any hardware...
the other thing would be that they could allow converter engagement in 2nd gear as well for those that get hot oil when offroading and never make it to 3rd gear where the converter can lock-up....
whats funny is the old GM 4L60E transmission from the early 90s would lock its converter solid if it overheated....
-Christopher
automatic transmission torque converters by nature make LOTS of heat.. modern automatics are outfitted with Locking torque converters.. so effectively the converter is "locked out" and there is direct connection from engine to transmission input shaft similar to when a clutch on a manual is let out and engaged for driving....
the Jeep automatic is a 4 speed overdrive transmission with a locking torque converter..
like any transmission when you need a little extra power to climb a hill or to pass, etc you need to downshift your gears... in a manual you downshift and go.. the Jeep automatic plays a trick instead...
if you need just a little extra power, the jeep will leave the transmission in 4th overdrive gear and will simply unlock the torque converter.. which will raise the RPMs on the engine about 500-600 so that you are making a little more power from the engine.. (into its power band)...
this is great for a real short time and works good.. however the trans is making LOTS of heat during this time.. the computer on the jeep is not programmed smart enough to re-lock the transmission until you let down on the throttle requiring less load from your engine... instead it continues to make heat until it overheats....
the way it SHOULD work is that the transmission would recognize a couple things:
1] that it would see an extended time of unlock converter.. and make a downshift to 3rd gear and then re-locl the converter and run in 3rd till you no longer need the extra power
2] that it could do the above if it notices the trans temp is rising too high..
I am confident that this would alleviate some of the issues with these transmissions.. this would all be a computer flash change and not need any hardware...
the other thing would be that they could allow converter engagement in 2nd gear as well for those that get hot oil when offroading and never make it to 3rd gear where the converter can lock-up....
whats funny is the old GM 4L60E transmission from the early 90s would lock its converter solid if it overheated....
-Christopher
Here is some additional info for you, related to how you said it should work:
1] That's exactly what the O/D Off button will do.
2] If the driver is paying attention, he will turn off the O/D until the need passes.
"the other thing would be that they could allow converter engagement in 2nd gear as well for those that get hot oil when offroading and never make it to 3rd gear where the converter can lock-up...."
The overheat shift schedule delays 2-3 shift, 3-4 shift, allows 3rd gear lock-up at a lower mph.
The super-overheat shift schedule allows 2nd gear partial lock-up; it will not unlock at all above 22mph unless the throttle is closed, or at WOT kick down to 1st.
When my transmission temp begins to rise while wheeling, I can make it come back down by managing the O/D button, the t-case lever, and the transmission selector lever.
Around town, my O/D is always off.
On the highway, if the downshift from O/D seems to be delayed on a hill, I just turn off O/D until the top of the hill.
My transmission has never overheated (no aux cooler).
Like said in the post below, an aux cooler is recommended in the factory service manual.
Last edited by ronjenx; 09-22-2010 at 05:55 PM.
09-22-2010, 05:45 PM
#22
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Spartan99 - you need to find a new dealer because the one you have is a complete d-bag with absolutely zero understanding of the law. In the meantime, you might suggest that your dealer actually read the owners manual that came with your Jeep, especially the part that recommends installing an aux. tranny cooler.
Very first mod I made to my Jeep was an aux. cooler and I'd love to see a dealer prove doing so harmed the Jeep.
Edit: see later posts. I was wrong...the aux. tranny cooler reference is in the service manual and does not appear to be in the owner's manual. Sorry for the bad info.
Very first mod I made to my Jeep was an aux. cooler and I'd love to see a dealer prove doing so harmed the Jeep.
Edit: see later posts. I was wrong...the aux. tranny cooler reference is in the service manual and does not appear to be in the owner's manual. Sorry for the bad info.
Last edited by Sharkey; 09-23-2010 at 02:27 PM.
09-22-2010, 06:31 PM
#23
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09-22-2010, 06:36 PM
#24
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ISo I decided to stop dealing with the screwballs at the Jeep Dealerships and call Jeep direct. I explained my situation with some entry level customer service guy, and he asked what Jeep could do to make things better - I replied, "take back my Jeep for a 6-speed." He wasn't sure if he could do that, so escalated my case to a higher level.
I later received a call from a lady that had enough power to help me solve the situation.
I explained the problem to her, and she assured me that Jeep was determined to solve this problem, whatever that would end up meaning
I later received a call from a lady that had enough power to help me solve the situation.
I explained the problem to her, and she assured me that Jeep was determined to solve this problem, whatever that would end up meaning
But! in order to save me troubles in the future -
what exactly do I need to do or say in order to get the dealership to install (and cover under warranty ) the tranny cooler? for free course.
09-22-2010, 08:11 PM
#25
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09-22-2010, 08:28 PM
#26
JK Super Freak
Yes you're right the manual DOES recommend a cooler. I've read that as well. Which is why it makes no freakin' sense that Jeep won't install it and cover it, let alone provide one oem.
And did I mention that when I spoke with Chrysler, I mentioned my Death Wobble, and of course, according to lady I spoke with, she had no record of dw ever being reported.
It's become a joke to me now. They still gotta fix my Jeep though. that's no joke.
And did I mention that when I spoke with Chrysler, I mentioned my Death Wobble, and of course, according to lady I spoke with, she had no record of dw ever being reported.
It's become a joke to me now. They still gotta fix my Jeep though. that's no joke.
09-22-2010, 08:29 PM
#27
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'08 JK Service Manual excerpt-Auto-trans overheating
For those of you heading to your dealer about the overheating issue stated in this thread, I decided to do a little research myself.
I have the complete set of factory (shop) service manuals for my '08 JK (which I also have an auto-trans).
I scanned and converted to PDF, two pages that I found a bit interesting. I tried to attach it but it's too large a file (201KB). PM me and I can email it if you'd like.
If the dealer mechanic reads the DTC codes, if code # P0218 has been set, then the transmission has been in an overheated state. It appears to me that Chrysler is recommending an additional cooler in some cases, based on this service manual diagnostics section in the manual.
For me, I haven't had the issue (yet) even after some hard wheeling in Moab in some very hot weather (over 100). I do know that my dealer flashed the computer a few years ago as part of a tech bulletin related to the Hot Oil message. No issues......but I'm thinking now of also adding a cooler, but I too have the lifetime power-train warranty and worry about impacting that.
Hope this helps.
I have the complete set of factory (shop) service manuals for my '08 JK (which I also have an auto-trans).
I scanned and converted to PDF, two pages that I found a bit interesting. I tried to attach it but it's too large a file (201KB). PM me and I can email it if you'd like.
If the dealer mechanic reads the DTC codes, if code # P0218 has been set, then the transmission has been in an overheated state. It appears to me that Chrysler is recommending an additional cooler in some cases, based on this service manual diagnostics section in the manual.
For me, I haven't had the issue (yet) even after some hard wheeling in Moab in some very hot weather (over 100). I do know that my dealer flashed the computer a few years ago as part of a tech bulletin related to the Hot Oil message. No issues......but I'm thinking now of also adding a cooler, but I too have the lifetime power-train warranty and worry about impacting that.
Hope this helps.
09-23-2010, 05:16 AM
#28
JK Super Freak
You have the 42RLE pegged pretty well.
Here is some additional info for you, related to how you said it should work:
1] That's exactly what the O/D Off button will do.
2] If the driver is paying attention, he will turn off the O/D until the need passes.
"the other thing would be that they could allow converter engagement in 2nd gear as well for those that get hot oil when offroading and never make it to 3rd gear where the converter can lock-up...."
The overheat shift schedule delays 2-3 shift, 3-4 shift, allows 3rd gear lock-up at a lower mph.
The super-overheat shift schedule allows 2nd gear partial lock-up; it will not unlock at all above 22mph unless the throttle is closed, or at WOT kick down to 1st.
When my transmission temp begins to rise while wheeling, I can make it come back down by managing the O/D button, the t-case lever, and the transmission selector lever.
Around town, my O/D is always off.
On the highway, if the downshift from O/D seems to be delayed on a hill, I just turn off O/D until the top of the hill.
My transmission has never overheated (no aux cooler).
Like said in the post below, an aux cooler is recommended in the factory service manual.
Here is some additional info for you, related to how you said it should work:
1] That's exactly what the O/D Off button will do.
2] If the driver is paying attention, he will turn off the O/D until the need passes.
"the other thing would be that they could allow converter engagement in 2nd gear as well for those that get hot oil when offroading and never make it to 3rd gear where the converter can lock-up...."
The overheat shift schedule delays 2-3 shift, 3-4 shift, allows 3rd gear lock-up at a lower mph.
The super-overheat shift schedule allows 2nd gear partial lock-up; it will not unlock at all above 22mph unless the throttle is closed, or at WOT kick down to 1st.
When my transmission temp begins to rise while wheeling, I can make it come back down by managing the O/D button, the t-case lever, and the transmission selector lever.
Around town, my O/D is always off.
On the highway, if the downshift from O/D seems to be delayed on a hill, I just turn off O/D until the top of the hill.
My transmission has never overheated (no aux cooler).
Like said in the post below, an aux cooler is recommended in the factory service manual.
granted i havent had my JK auto in the mountains yet.. but when I had 6 speed JK's I always downshifted to 4th or 5th gear and left it there until i was out of the hilly terrain... so it makes perfect sense to do the same with the auto and give it a fighting chance.....
I see it as being easier on the drivetrain to have the RPMs up at 2800-3000 rather than constant up and down shifting.....
-Christopher
09-23-2010, 08:27 AM
#29
JK Super Freak
I'm going to remind the dealer about the cooler being recommended in the manual. I'll pay for it if I have to. Don't like doing that, but whatever. I just want the warranty to remain intact.
09-23-2010, 09:12 AM
#30
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But, your right, I might have had a ding and missed it. So, I am wondering if I need a code to have them fix it, do I need proof. I have had that recall done, so I am pretty sure if I had trip it, it is gone now since the flash. And that light has not come on since. I checked my tran oil, the other day, cherry red and no burnt smell. Not that is a ture test.
I got it used, so I don't have the lifetime warrently. But, If can get something fixed from them and have it covered, then why not.