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Shifting problems when hot
http://www.lostjeeps.com/forum/phpBB3/viewtopic.php?f=5&t=72712		 Page 1 of 1
Author:  Topan [ Mon Dec 03, 2012 8:02 am ]
Post subject:  Shifting problems when hot
Hi,
Since a few months I noticed that the transmission sometimes do not get into higher gear. It stays sometimes in 2nd or 3rd.
This happens after I have driven for some times uphill, on road or offroad. I never hammer my KJ, so it's always a smooth drive uphill. Because its uphill, the transmission is into lower gears.

When I got back to flat road and increase speed, the transmission refuses to get into higher gear. It last for maybe a mile. Ad then the higher gear gets in, and all is fine.

Could it be due to over heating ? I don't see any temperature gage increase.
Or quality of oil ?
Author:  Joe Romas [ Mon Dec 03, 2012 4:19 pm ]
Post subject:  Re: Shifting problems when hot
There are two normal instances where the TCM (transmission control module) is programmed not to go into over drive gears that are 4th and 5th on the CRD's transmission.
One is when the transmission is not warmed up like a mile or two on a cold morning.
Number two is when the transmission is overheated.

There is an abnormal instance where it will not go above 3rd gear and that is a "limp home" mode. Sometimes it will clear by shutting it of and restarting.
Have you had your fluid and filters changed? that's where I would start if the fluid level checks normal :JEEPIN:
Author:  Topan [ Tue Dec 04, 2012 2:50 am ]
Post subject:  Re: Shifting problems when hot
joe
Yes the trans fluid level is ok and the fluid is very clear.

As it happens after a uphill climb where the disks of the automatic transmission are slipping a lot due to changes of gears between 1st and 2nd back and forth, it is definitely due to overheating.
If this is a limp mode, how come there is no cell coming up ?

I have a trans cooler bypass, I have checked a few time it's temperature after a climb (using an IR temp. sensor) and I remember it was quite low. I will check again next time it happens.
Author:  racertracer [ Tue Dec 04, 2012 3:44 am ]
Post subject:  Re: Shifting problems when hot
Topan wrote:
joe
Yes the trans fluid level is ok and the fluid is very clear.

As it happens after a uphill climb where the disks of the automatic transmission are slipping a lot due to changes of gears between 1st and 2nd back and forth, it is definitely due to overheating.
If this is a limp mode, how come there is no cell coming up ?

I have a trans cooler bypass, I have checked a few time it's temperature after a climb (using an IR temp. sensor) and I remember it was quite low. I will check again next time it happens.


My transmission was overheating and the dealer replaced the transmission cooler, he said it was clogged.
Author:  Topan [ Tue Dec 04, 2012 7:47 am ]
Post subject:  Re: Shifting problems when hot
racertracer wrote:
Topan wrote:
joe
Yes the trans fluid level is ok and the fluid is very clear.

As it happens after a uphill climb where the disks of the automatic transmission are slipping a lot due to changes of gears between 1st and 2nd back and forth, it is definitely due to overheating.
If this is a limp mode, how come there is no cell coming up ?

I have a trans cooler bypass, I have checked a few time it's temperature after a climb (using an IR temp. sensor) and I remember it was quite low. I will check again next time it happens.


My transmission was overheating and the dealer replaced the transmission cooler, he said it was clogged.



He replaced the cooler which located underneath the air conditioning condenser ?
Really expensive and u need to remove everything, that's why some of us go for the options of bypassing this trans cooler when it leaks.
Author:  racertracer [ Tue Dec 04, 2012 7:57 am ]
Post subject:  Re: Shifting problems when hot
Yes, that is the one, located below the AC condensor. They also replaced the 2 hydraulic hoses that ran along side.
Author:  Joe Romas [ Tue Dec 04, 2012 10:04 am ]
Post subject:  Re: Shifting problems when hot
Topan wrote:

I have a trans cooler bypass


So do you have a external transmission cooler or have you just bypassed the cooler all together (I hope not)?
You could also push the OD button and turn off overdrive to eliminate some of the shifting as a work around.
Author:  Topan [ Tue Dec 04, 2012 10:33 am ]
Post subject:  Re: Shifting problems when hot
Joe Romas wrote:
Topan wrote:

I have a trans cooler bypass


So do you have a external transmission cooler or have you just bypassed the cooler all together (I hope not)?
You could also push the OD button and turn off overdrive to eliminate some of the shifting as a work around.


Yes I have bypassed the entire trans cooler, but of course I installed another cooler, like it is explained in many write-ups.... I always wanted to add a fan but I don't have the space, or let us say I never found a fan flat enough to fit.
Here is what I did in details :
viewtopic.php?f=5&t=62013

And agree, when speed is low enough I shift into 2nd which stop the trans to switch back and forth too much between gears, and on the road I push the OD button. But sometimes this is just not enough to avoid the over heating..... :banghead:
Author:  racertracer [ Tue Dec 04, 2012 10:43 am ]
Post subject:  Re: Shifting problems when hot
If you removed the original setup because of the small leaks deriving from the hose connection at the cooler. Then I suggest reconnecting them. I too had the small leaks, which occurred at the connecions and my mechanic just cleaned them and reseated them stopping the leak. make sure you clean any accumuated dirt from the connections.
Author:  Topan [ Tue Dec 04, 2012 1:22 pm ]
Post subject:  Re: Shifting problems when hot
I see what you mean but my leaks were coming from the lower part of the cooler, not good looking at all.
I will check that the new cooler by-passing the stock one is at reasonable temp.
Maybe try to find a fan flat enough to fit behind the grill.
Author:  Topan [ Tue Dec 04, 2012 1:22 pm ]
Post subject:  Re: Shifting problems when hot
I see what you mean but my leaks were coming from the lower part of the cooler, not good looking at all.
I will check that the new cooler by-passing the stock one is at reasonable temp.
Maybe try to find a fan flat enough to fit behind the grill.
Author:  racertracer [ Tue Dec 04, 2012 2:25 pm ]
Post subject:  Re: Shifting problems when hot
Topan wrote:
I see what you mean but my leaks were coming from the lower part of the cooler, not good looking at all.
I will check that the new cooler by-passing the stock one is at reasonable temp.
Maybe try to find a fan flat enough to fit behind the grill.


Mine were coming from there also.... and I thought that it wasn't related to the connectors at first but to a small hole in the cooler.

My mechanic said that it was the connectors leaking and that it was the force of the wind when driving that spread the fluid all over the cooler giving the inpression that a puncture hole between the cooler fins was at fault.
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