Braking/deceleration and ESS question-

[TheDerb]

I went from a Sport Manual to a Rubicon Automatic. I've never daily driven an automatic vehicle before.

First thing I noticed is that the ESS "moves" the truck quite a bit more in my new truck vs the Sport Manual when the truck turns back on. Not quite to an "I think my engine mounts are loose" level, but more than I would expect considering I'm moving from a truck with the same engine. I'm sort of assuming it is because the engine is immediately hooking up with the transmission and going into gear, which is causing more mechanical movement, thus leading to the truck "shuddering" more than I am used to.

Anybody have an experience on this?

Then let's talk about the brakes: the brakes in this Rubicon seem to work just fine, but there are intermittent situations where the brakes feel like they are on the verge of ABS kicking in- even though it is stopping at the same interval and at the same speed it should. There is definitely more play in these brakes than there was in the Sport Manual.

Anybody know if this is typical?

I'm hoping this saves me from having to drop it off at the dealer for either of these issues. Thanks in advance!

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[Mr._Bill]

I think what you are experiencing is normal. I turn off ESS, except when I forget, but it shudders some for me on restart. The brakes will feel different, since the clutch is not released and there is power being applied while trying to stop.

Unless there are error codes stored in the computer, or you have an issue you can reproduce, the dealer likely won't be able to do much for you.

 

[TheDerb]

I think what you are experiencing is normal. I turn off ESS, except when I forget, but it shudders some for me on restart. The brakes will feel different, since the clutch is not released and there is power being applied while trying to stop.

Unless there are error codes stored in the computer, or you have an issue you can reproduce, the dealer likely won't be able to do much for you.

That's quite a good take. Thanks for that! I didn't even think about the clutching/braking relationship.

 

[ATL_Rubi]

So fun fact, our trucks have EBD, or Electronic Brake force distribution. It modulates the braking between the front and rear axles based on external and internal factors to avoid instability. I can 100% feel when the jeep is grabbing more front brake than a more even split.

Antother factor is BAS, Brake Assist System, which senses emergency braking and applies "optimum" pressure to the braking system in addition to ABS as needed.

Those two factors could be contributing to your perceived sense of the ABS almost kicking in, it could be the system doing it's work. For the shudder, it's normal, it's equalivent to turning on a manual engine on while in gear, the transmission is applying drag on the engine and the engine is outputting force thus shuddering the transmission as it kicks itself back into gear.

 

[mdyucca]

The shudder is one of the reasons why I don’t like the ESS in the Jeep. I had a Toyota with auto start system and it was seamless no shudder and no battery problems.

 

[ShadowsPapa]

I have no shudder at all. The engine IS starting and immediately loaded with an automatic, however, so will feel different.
To me it's like starting my 73 with the TF727 and the NSS not working and the shift linkage not quite adjusted correctly - you put your foot solidly on the brake, hit the key, it starts - it's in gear so as quick as that transmission pump supplies pressure to the clutches and bands, that engine is loaded and the car is ready to go. Really spooky with cold carburetors and it wants to fast-idle when it starts.
This is nothing compared to that...........

I had a Toyota with auto start system and it was seamless no shudder and no battery problems.

Very different vehicles - and the battery issues are not ESS, they are crap MOPAR batteries. Even the 4xe with only ONE battery - the main 12v battery, has a huge number of battery failures. That's proof positive that the 12v batteries go south in Jeeps even with no ESS because there is no ESS in a 4xe. All the 12v battery does is drive the standard electronics - radio, HVAC, cooling fan, lights and so on.

I guess I'm a bit wondering what the heck this "shudder" is that some refer to. I've never noticed it in any Jeep I've ever owned that had ESS. It's an engine starting, and it's in gear as quick as hydraulic pressure is built in the transmission which can be before all 6 are firing evenly.
It does no damage.

I'm sort of assuming it is because the engine is immediately hooking up with the transmission and going into gear, which is causing more mechanical movement, thus leading to the truck "shuddering" more than I am used to.

With the engine off, the pressures in the transmission drop, once the engine is turning a certain amount the pressures build again and it's a load on the engine. The engine may not be quite up to speed when the pressures are built up. I'd have to research how these specific transmission are pressurized - but they have to assume you have taken your foot off the brake and are onto the accelerator now so they've got to be able to have that thing solidly in gear as quick as a human can react.

There's no damage - these systems have been in use for a few years and there's problem with them. GM used it, BMW used it, as have others (BMW even uses the ZF transmissions, as do others). Grand Cherokee has had these systems since roughly 2016 and no issues.

We're so used to things we fully understand, and seem to fear what we don't.

 

[Charles 236]

The automatic transmission in the Gladiator is pressurized by an accumulator that builds pressure and holds it during an ESS stop. This pressure allows almost instantaneous transmission engagement when pulling away from the stop.

 

[ShadowsPapa]

The automatic transmission in the Gladiator is pressurized by an accumulator that builds pressure and holds it during an ESS stop. This pressure allows almost instantaneous transmission engagement when pulling away from the stop.

I wondered - and now it seems I've seen that somewhere before - perhaps in tech info about the transmission itself.
They have to have a way to allow pretty much instantaneous take-off from a stop.
It also explains why the JT feels a whole lot like my car when starting it in other than N or P, but in that case it relies on the engine spinning the TC which in turn turns the pump. But the pressure build-up is extremely fast as once that engine fires, you can feel the car "lurch" against the brakes.
So these do it one better by not letting the pressure get to full 0 psi during a stop, holding a residual pressure, ready to go. Once that engine starts I can hit the gas and GO. That's what I like about it. No lag.

Thanks for the update/info

 

[TheDerb]

I have no shudder at all. The engine IS starting and immediately loaded with an automatic, however, so will feel different.
To me it's like starting my 73 with the TF727 and the NSS not working and the shift linkage not quite adjusted correctly - you put your foot solidly on the brake, hit the key, it starts - it's in gear so as quick as that transmission pump supplies pressure to the clutches and bands, that engine is loaded and the car is ready to go. Really spooky with cold carburetors and it wants to fast-idle when it starts.
This is nothing compared to that...........


Very different vehicles - and the battery issues are not ESS, they are crap MOPAR batteries. Even the 4xe with only ONE battery - the main 12v battery, has a huge number of battery failures. That's proof positive that the 12v batteries go south in Jeeps even with no ESS because there is no ESS in a 4xe. All the 12v battery does is drive the standard electronics - radio, HVAC, cooling fan, lights and so on.

I guess I'm a bit wondering what the heck this "shudder" is that some refer to. I've never noticed it in any Jeep I've ever owned that had ESS. It's an engine starting, and it's in gear as quick as hydraulic pressure is built in the transmission which can be before all 6 are firing evenly.
It does no damage.



With the engine off, the pressures in the transmission drop, once the engine is turning a certain amount the pressures build again and it's a load on the engine. The engine may not be quite up to speed when the pressures are built up. I'd have to research how these specific transmission are pressurized - but they have to assume you have taken your foot off the brake and are onto the accelerator now so they've got to be able to have that thing solidly in gear as quick as a human can react.

There's no damage - these systems have been in use for a few years and there's problem with them. GM used it, BMW used it, as have others (BMW even uses the ZF transmissions, as do others). Grand Cherokee has had these systems since roughly 2016 and no issues.

We're so used to things we fully understand, and seem to fear what we don't.

Thanks for the great response!

 

[Charles 236]

I wondered - and now it seems I've seen that somewhere before - perhaps in tech info about the transmission itself.
They have to have a way to allow pretty much instantaneous take-off from a stop.
It also explains why the JT feels a whole lot like my car when starting it in other than N or P, but in that case it relies on the engine spinning the TC which in turn turns the pump. But the pressure build-up is extremely fast as once that engine fires, you can feel the car "lurch" against the brakes.
So these do it one better by not letting the pressure get to full 0 psi during a stop, holding a residual pressure, ready to go. Once that engine starts I can hit the gas and GO. That's what I like about it. No lag.

Thanks for the update/info

I have wondered about the long term durability of the accumulator, since I used to perform Recall 685 back in the '90s, and a major point of failure in the Bendix 10 ABS (this system combined anti-lock braking and hydraulic boost for the brakes by using the ABS pump) was the accumulator. Hopefully the ZF eight speed has a much better accumulator than the Bendix 10. So far, I haven't seen or heard of any failure specific to the ESS in this transmission.

 

[ShadowsPapa]

I have wondered about the long term durability of the accumulator, since I used to perform Recall 685 back in the '90s, and a major point of failure in the Bendix 10 ABS (this system combined anti-lock braking and hydraulic boost for the brakes by using the ABS pump) was the accumulator. Hopefully the ZF eight speed has a much better accumulator than the Bendix 10. So far, I haven't seen or heard of any failure specific to the ESS in this transmission.

Same transmission as used in the WK in the last few years, or is it? I know we've had 3 ESS Grand Cherokees (if my count is right?? Maybe only 2.........) Very reliable vehicles.

 

[Charles 236]

Essentially the same, there might be a few minor differences.

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