stevedolce

hi--need some help please. about 3 days ago i noticed my jku transmission slipping when i first pull out of my driveway or garage at work. i checked my fluid and i was pretty dry(must have a leak some where)--on the way home my check engine light came on. got home and filled up about .5 quart of ATF+4 and now my dipstick looks goor but engine light is still on. most of the time slipping comes from low fluids..right?

i'll know more in the AM when my jeep is cold

any ideas?

ronjenx

Yes, low fluid is a common cause of slipping.

When you checked the fluid level, was the transmission warm, in park or neutral, with the engine idling?

stevedolce

Yep--warm and in park. Hope my check engine light turns off soon. Could that come on due to low fluids? Or could that be a sign of a bigger issue?

ronjenx

Check for codes. See what triggered the light. While it's hooked up, you can clear the code and turn off the light.

Otherwise, most codes take three good trips to turn off the light.

bombout800

A common mistake where some people drive while the transmission is super cold can cause it to slip. If it's really cold out and you don't give the trans some time to build up a little heat it will give you trouble. I would let it get good and warm before driving it. Try letting it idle for a few mins before driving it. Let the trans fluid get to around 100 degrees. Not saying you, but some people think it's okay to beat the heck out of a cold transmission. It's not. If it's really cold where you are letting it idle for a few mins will led the trans fluid warm a little.

stevedolce

OK-made it to work. i let the jeep warm up as usual--maybe 5-10 minutes. pulled out of driveway and first gear seemed OK, but 2nd slipped. waited about 10 seconds at stop sign and then 2nd engaged. drove jeep to work happily. (about 40 miles). last night i put about .5 quart in. after driving to work my dipstick was still low(engine was hot, ran thru gears). should i put another .5 quart in?

i also got the following errors:

P0944 loss of hydrolic pump prime (basically means low fluid--right?)P0732 gear ratio error in 2nd
P0731 error 1st

i'm running super chip with the tow tune FYI
it's a 2011 JKU auto.


P0306 cylinder 6 misfire(i'll deal with this later)

stevedolce

5 quarts--
so putting in .5 isn't that much of a dent--huh?

karls

There are folks who put in an additional 2 qts of fluid to assist with losing gears on steep climbs. I won't comment as to if it's good or not for the transmission but looking at the logistics of the situation- it would work.

I've got a manual so my fluid level is not subject to experimentation.

stevedolce

i'm going to dump the other .5 quart in.

a transmission 101 question:

why does it act normal after a shift or two? what happens to the fluid?

ronjenx

Cold fluid isn't a prime factor with your transmission slipping. I start mine as low as -30°F, with warm-up of less than a minute. The best way to warm up a vehicle is to drive it.
I do take it easy until the fluid temp begins to climb. I see no evidence of any bad transmission behavior when it's really cold.

Cold fluid does take up less room in the sump, so if you have low fluid level, it will be even lower until it warms up.
That can cause slippage. You mentioned more than once you have low fluid in the sump. Bring the level up to spec and go from there.
The trans controller is programmed with different shift schedules based on start-up temperature. Here is a clip from the chart:

[TABLE="class: MsoNormalTable"]
[TR]
[TD] Schedule

[/TD]
[TD="width: 280"] Condition

[/TD]
[TD="width: 434"] Expected Operation

[/TD]
[TD][/TD]
[/TR]
[TR]
[TD="width: 82"][/TD]
[TD="width: 280"][/TD]
[TD="width: 434"][/TD]
[TD][/TD]
[/TR]
[TR]
[TD="width: 82"] Extreme Cold

[/TD]
[TD="width: 280"] Oil temperature at start-up below -27° C (-16° F)

[/TD]
[TD="width: 434"] Park, Reverse, Neutral and 2nd gear only (prevents shifting which may fail a clutch with frequent shifts)

[/TD]
[TD][/TD]
[/TR]
[TR]
[TD][/TD]
[/TR]
[TR]
[TD="width: 82"] Cold

[/TD]
[TD="width: 280"] Oil temperature at start-up above -25° C (-12° F) and below 2° C (36° F)

[/TD]
[TD="width: 434"] - Delayed 2-3 upshift (approximately 22-31 mph)

- Delayed 3-4 upshift (45-53 mph)

- Early 4-3 costdown shift (approximately 30 mph)

- Early 3-2 coastdown shift (approximately 17 mph)

- High speed 4-2, 3-2, 2-1 kickdown shifts are prevented

- No EMCC[/TD]
[TD][/TD]
[/TR]
[TR]
[TD][/TD]
[/TR]
[TR]
[TD][/TD]
[/TR]
[TR]
[TD="width: 434"]

[/TD]
[TD][/TD]
[/TR]
[TR]
[TD="width: 434"]

[/TD]
[TD][/TD]
[/TR]
[TR]
[TD="width: 434"]

[/TD]
[TD][/TD]
[/TR]
[TR]
[TD="width: 434"]

[/TD]
[TD][/TD]
[/TR]
[TR]
[TD="width: 82"] Warm

[/TD]
[TD="width: 280"] Oil temperature at start-up above 2° C (36° F) and below 27° C (80° F)

[/TD]
[TD="width: 434"] - Normal operation (upshift, kickdowns, and coastdowns)

- No EMCC[/TD]
[TD][/TD]
[/TR]
[TR]
[TD][/TD]
[/TR]
[TR]
[TD][/TD]
[/TR]
[/TABLE]


Overfilling the transmission isn't a good idea as that can cause other issues, including foaming and discharge out the vent or dip stick tube, either of which can lead to a fire.

Here is a picture showing the fluid level at different temperatures. If you have no way to see the sump temperature, buy or borrow an infrared temp gun and point it at the transmission pan after it has been driven for a while and is as warm as it's going to get.
I have done this and the gun agrees with the temp gauge within a few degrees.