Interesting evolution of engine breaking

[Valpan]

Hi, I’m a fellow jeeper from Switzerland.
In may 2020 I traded my YJ 4.0 manual for a brand new JL 2dr 2.0... I know, I should have bought a stick shift but in Europe, that’s unavailable...

The first kilometers were amazing ! The power, the comfort, made me really happy with my purchase.

I use my Jeep for a daily commute of 40 kilometers but more importantly, 1000m of elevation ! And every evening, going home, descending from the Alps, I spent my whole trip pressing this freacking brake pedal.

And when I used my offroader on mountain trails, I just had to heat up those breaks everytime the trail went even slightly downhill !

It felt like, even when downshifting manually, the ECU would give just a little bit of gas letting me roll down the road like a rollercoaster. For proof, the instant fuel consumption would climb, indicating that fuel was beeing injecting with my foot completely off the gas.
And then came a random night, shift ending, bottom on the heated seat, snow falling gently, covering the road... I lined up for the first grade and suddenly, my trans downshifted and I barely used the brakes for the all descent !
I looked at the odometer and it showed 8020km.

Having a formation as a car technician, I imagine a break-in map was programmed in the ECU to end after some definite distance and that apparently that distance was 8000km.

Does anyone of you know if my thoughts are right ?

Now, I barely use the break pedal, my fuel consumption went down and I am even happier with the JL !

ps: I just got a 2 inches lift (50mm) Old Man Emu suspension kit with adjustable lower control arms waiting in the garage! Mounting in two weeks...
ps 2: sorry for the « spelling mistakes » english is not my first language

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[Obi.Wan.Shawnobi]

So the "transmission coasting" between shifts, was an issue I had with my 2015 Cherokee. It was soo bad that it became an issue, resulting in me trading it in and having to sell my old wrangler too as equity to get out of that new car.

I also have the 2.0. What I do is put it into manual mode at the crest of the hill and always down shift 2 gears into 6th. Then from there I may down shift again. If you do this while applying the brakes, do you still get the surge? At an 8% grade I find 5th gear usually holds 65mph (don't know the km equivalent).

I guess all I'm trying to say is, don't free roll down hill while shifting casually into the proper gear to give to enough driveline torque.

The ZF transmission is used in a lot of applications between many manufactures. It's the TCM programming that is probably the issue. If it feels unsafe, have the dealership refresh the TCM. Best of luck.

 

[Valpan]

Hi, thanks for your reply.
Fortunately the problem solved itself after the odometer reached 8000km.

Now, everything’s fine and sometimes I even need to put some throttle while going downhill.

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