Issue: 2020 8 Speed . RPM increase suddenly on down hills

[steverino]

Hi All,
Wondering if anyone has a similar issue or suggestions.
I have a 2020 JLUR Diesel with the 8 speed auto.

When going down a steep brumby trail section . RPM will go from 1000 to 2000 without me touching the gas.
Usually I am going slow just letting the engine coast. Speed is constant. Then RPM will jump. Sometimes it will come back
down and go up again. Sometimes I have to tap the break or gas pedal and the RPM will then go back down.
On one steep trail it was in 2nd. RPM = 1000, Speed and RPM was constant... or just slightly increasing. Then it jump to 3000 RPM.
A bit scary when a few feet to the right is..... a cliff.

Starting to do the dance with two dealers.

One of them said there was a speed sensor error code. They updated the power train software saying it was a bit old.
They said if it happened again bring it back and they would replace the "valve body".

It happened again so I took it back. They said there was no code this time so they could not replace anything.

It has done it in 2wd on pavement. Its not that often.

Off-road bump down hill sections it will do it a lot. I have had it increase RPM 10 times in one day.

Any ideas?

Sponsored

 

[beaups]

Sounds like it’s downshifting so it can engine brake as designed. Do you have hill descent control enabled by chance?

 

[steverino]

Sounds like it’s downshifting so it can engine brake as designed. Do you have hill descent control enabled by chance?

No it’s not downshifting. It stays in the same gear. Rpm goes up

 

[mwilk012]

No it’s not downshifting. It stays in the same gear. Rpm goes up

This is not possible without a major malfunction. You’re either right, or wrong, not sure which you would rather be in this case.

 

[steverino]

This is not possible without a major malfunction. You’re either right, or wrong, not sure which you would rather be in this case.

malfunction yes. Major No. There is no throttle cable on newer Jeeps. Just a bunch of sensor.
It it a matter of getting the dealer to replace the correct on.

 

[beaups]

malfunction yes. Major No. There is no throttle cable on newer Jeeps. Just a bunch of sensor.
It it a matter of getting the dealer to replace the correct on.

The throttle can't make the engine rev independent of gear regardless of it's design. You either have a major transmission failure or it's behaving as designed.

 

[mwilk012]

malfunction yes. Major No. There is no throttle cable on newer Jeeps. Just a bunch of sensor.
It it a matter of getting the dealer to replace the correct on.

I can’t tell if you’re being hopefully optimistic or just don’t understand how this works.

 

[Kristian]

Sounds like it’s downshifting so it can engine brake as designed. Do you have hill descent control enabled by chance?

Hill descent control only operates in 4L (At least on my 2020 Rubicon).

edit. Mine (8 speed auto) downshifts on hills all the time. The gear ratios are close enough together that if you're in drive the gear change can be hard to notice. And the dash display won't tell you.

If yours is an auto, try driving around in manual, where it cannot make such decisions for you. If it happens then, you have a problem.

 

[OzEric]

Have you had any new news on this issue, as mine is doing the same thing (21JLUR)?. In second or 3rd low just idling down a steep hill the revs will rise and fall continuously, irrespective of the grade. Doesn't seem to happen in 1st though. At first I thought it was some sort of off road clever thing, but its just annoying as it can speed up at the wrong time

Sponsored