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Transmission overheat and "limp" mode

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13K views 5 replies 4 participants last post by  chris.muilenburg  
#1 ·
I'm so over this damn car already. I've had this obscure problem with it since 2017 and there's no known solution I've seen, so here goes one more attempt.

Whenever the Jeep is driven any distance for about an hour, the transmission overheat warning comes on, the Jeep enters into the "limp" mode throttling it back to 30/40 mph and it makes a high pitched whine. I know what all of it means, so I don't need a lto of explanations, and I do need to clarify THE CAR IS NOT OVERHEATING, since it seems most subjects regarding this always default to the car overheating.

I installed an additional supplemental radiator for the transmission line, which is connected in front of the standard radiator. I replaced the one and only valve which the parts catalog said would cause this overheat warning. I've had the transmission serviced, flushed, and refilled. But this problem always comes back in warmer weather, guaranteed.

I'm ready to scrap this thing if I didn't desperately need it!

Any outside-the-box ideas for this? Because I tried every obscure standard mechanical fix in the books and it hasn't worked.
 
#2 ·
As you've probably read, the whine / overheat / limp mode is almost always due to fluid foaming / cavitation which is a sign of overheating (not related to engine coolant temp) and/or the fluid level is too high. It doesn't take the fluid being overfilled by much to cause a problem.

What temperature is the transmission running at when limp mode happens?

Has the fluid level been checked and what level is it at temperature?


If you don't have something that reads trans temp, get a copy of CVTz50 - Apps on Google Play and an elm327 adaptor or something else like a scangauge II so you can keep an eye on it while you drive, and use it to check the fluid level against the chart below while it's running.

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Other things that can cause this are a dirty cooler filter (if the shop didn't know it existed and didn't change it) or a clogged "soup can" heat exchanger (#4 in diagram below).

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#3 ·
I run mine right at the minimum line. With the CVT, too little is FAR better than a TINY bit too much. The CVT fluid and BOTH filters need to be changed at least every 50 - 60k miles.
 
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#5 ·
In 2020, my CVT started overheating. I tried everything. Changed fluid and filters, bypassed the bypass valve, replaced the oil-to-water (soup can) cooler, flushed out the lines and trans cooler (blew air through them), and added an aux trans cooler. None of that helped. Then I read that if the fluid is overfilled that the pump will whip it into a foam and it won't be able to flow, which will cause it to overheat. I then changed it again but only filled it to the minimum. It's been 2 years since and hasn't overheated once.
 
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