Is it downshifting,.. or?

[jerjon]

New 23' Mojave auto. 900miles,.
I'm noticing when I begin to break, or break and in some cases break again an let off the pedal..it feels as if it downshifted or continues to apply breaking after letting up.. as if it down shifted yet the numbers indicated on dash has not dropped to a lower gear to justify the slow down.. Any takers on this?

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[Lunentucker]

"brake"

 

[ShadowsPapa]

New 23' Mojave auto. 900miles,.
I'm noticing when I begin to break, or break and in some cases break again an let off the pedal..it feels as if it downshifted or continues to apply breaking after letting up.. as if it down shifted yet the numbers indicated on dash has not dropped to a lower gear to justify the slow down.. Any takers on this?

Yes, these sense and apply a downshift depending on how you brake or apply the brake pedal.

I LOVE it - we live in a hilly area so when I hit the brake pedal with the right pressure, then let up, it downshifts and slows me going down hill without having to ride the brakes. These are smart transmissions (smart trucks for that matter)
Mine usually shows the downshift although it takes a second or two for the display to catch up.
It could also be that the TC has locked so you have engine braking as well.

You want something with automatic braking - drive a 4xe and let up on the gas. I can come to a complete stop without apply the brakes until the last 10 feet when it's in regen mode.
THAT takes getting used to.
But for the Gladiator - I bet what you are experiencing is normal - either a downshift or the TC is locking due to relaxed torque requirements.

 

[jerjon]

Yes, these sense and apply a downshift depending on how you brake or apply the brake pedal.

I LOVE it - we live in a hilly area so when I hit the brake pedal with the right pressure, then let up, it downshifts and slows me going down hill without having to ride the brakes. These are smart transmissions (smart trucks for that matter)
Mine usually shows the downshift although it takes a second or two for the display to catch up.
It could also be that the TC has locked so you have engine braking as well.

You want something with automatic braking - drive a 4xe and let up on the gas. I can come to a complete stop without apply the brakes until the last 10 feet when it's in regen mode.
THAT takes getting used to.
But for the Gladiator - I bet what you are experiencing is normal - either a downshift or the TC is locking due to relaxed torque requirements.

Ok good! I was hoping this wasn't a,.. just me issue.. spelling sure that's just me..
Wish the dash would catch up faster, but the tc lock up one would think is directly related to a down shift?

 

[Gren71]

With only 900 miles maybe its related to the new pads? Its been a while but I remember feeling like my pads held just a moment too long have a routine brake application. ?‍

otherwise im with papa, it definitely down shifts when it thinks it needs to while braking.

 

[BearFootSam]

New 23' Mojave auto. 900miles,.
I'm noticing when I begin to break, or break and in some cases break again an let off the pedal..it feels as if it downshifted or continues to apply breaking after letting up.. as if it down shifted yet the numbers indicated on dash has not dropped to a lower gear to justify the slow down.. Any takers on this?

It's the TCM programming implementing a maximum engine braking mode, perhaps related to tow/haul. Making some observations on a 12 mile, 5,400' downhill grade I've noticed something interesting: If I start from manual shifting at the top, I need to be in 4th gear to hold 40-45mph. However, if I leave it in auto and let then make some firm brake applications to scrub speed to the same range then let off the brake, the transmission will sit in 5th gear while holding 40-45. In manual mode 5th gear would be too high for sufficient engine braking.

What I glean from this is that the TCM's downhill mode (not sure the technical term) is utilizing methods other than gearing alone to moderate speed. I'm quite sure it's not the transmission brakes or clutches, because (a) this would cause horrific wear, and (b), the transmission temperature falls while coasting down. If I have been on the unpaved ridge road up top, I might start the downgrade with a trans temp of 190*f, which the other day fell to 176*f by the time we'd gotten down (ambient temps in the upper 40's). I'd be really curious how this is achieved, is it via the torque converter or is it an engine mapping change? I've even considered it's a combination of maximizing parasitic loads while locking the TC. The AC compressor, alternator and that 850w fan could in aggregate apply a substantial load.

 

[ShadowsPapa]

It's the TCM programming implementing a maximum engine braking mode, perhaps related to tow/haul. Making some observations on a 12 mile, 5,400' downhill grade I've noticed something interesting: If I start from manual shifting at the top, I need to be in 4th gear to hold 40-45mph. However, if I leave it in auto and let then make some firm brake applications to scrub speed to the same range then let off the brake, the transmission will sit in 5th gear while holding 40-45. In manual mode 5th gear would be too high for sufficient engine braking.

What I glean from this is that the TCM's downhill mode (not sure the technical term) is utilizing methods other than gearing alone to moderate speed. I'm quite sure it's not the transmission brakes or clutches, because (a) this would cause horrific wear, and (b), the transmission temperature falls while coasting down. If I have been on the unpaved ridge road up top, I might start the downgrade with a trans temp of 190*f, which the other day fell to 176*f by the time we'd gotten down (ambient temps in the upper 40's). I'd be really curious how this is achieved, is it via the torque converter or is it an engine mapping change? I've even considered it's a combination of maximizing parasitic loads while locking the TC. The AC compressor, alternator and that 850w fan could in aggregate apply a substantial load.

I love that feature in our hills and winding roads. I don't have to downshift or hold the brakes to keep it from gaining speed. The proper application of the brake pedal (firm push and let off) and it goes into that mode for me. Handy as heck. My brakes should last fairly long since I don't have to keep feathering them - or downshift myself- to prevent gaining speed in some of our steeper hills. It's especially nice heading to the south end of Powers Drive -a steep incline heading into a highway with a steep drop on the other side. It handles going down that hill in winter fine. More than one person has lost it in the winter going down that thing. Jeeps handle it fine.

 

[Dp7]

As a long time manual driver, I personally hate engine braking... I have always done what everyone says you shouldn't do and is even illegal in some jurisdictions.. if I'm not applying gas, I shift into neutral. Obvs that is a much more clunky thing to do with an automatic, so I don't... but, I wish I could set mine up to not syphon my kinetic energy while coasting.

It seems really simple to me... if your engine, transmission, alternator, etc. all have a limited number of rotations before having to be rebuilt/replaced, why would you want to increase the rotations on those parts? Worn out brakes and rotors are cheap and easy to replace.

 

[ShadowsPapa]

. if I'm not applying gas, I shift into neutral. Obvs that is a much more clunky thing to do with an automatic,

So you are trying to save wear and miles on one thing by wearing out synchronizers and clutch release bearings and other parts?
As a decades long mechanic, seems to me to be 6 of one, half a dozen of the other. Unless you do a drastic downshift, the "added rotations" or wear is minimal.
I've had something with a manual transmission since i started driving in the early 1970s and everything I've had has gone the distance, even with me doing mild downshifts.
Last thing in the world you want to do around here is be in neutral on our hills - totally less control if something goes wrong like a deer or something popping into the road (often, the trees and brush are right up to the shoulder) - there's 0 time to react.
My current manual transmission vehicle - my SX4, has all but 200,000 miles on it.

 

[Dp7]

Last thing in the world you want to do around here is be in neutral on our hills - totally less control if something goes wrong like a deer or something popping into the road (often, the trees and brush are right up to the shoulder) - there's 0 time to react.

I'm in deer-crossing country, so I get what you're saying... but, in neutral (or even in a high gear) using brakes alone to slow down... you're already basically riding the brake pedal, so, unless you're in the middle of a turn, you're gonna be locking it up, but you'll get there sooner if you've already got steady pressure on the pedal. If you're in the middle of a turn then it won't matter either way, you just gotta plow through that stupid thing.

 

[BearFootSam]

As a long time manual driver, I personally hate engine braking... I have always done what everyone says you shouldn't do and is even illegal in some jurisdictions.. if I'm not applying gas, I shift into neutral. Obvs that is a much more clunky thing to do with an automatic, so I don't... but, I wish I could set mine up to not syphon my kinetic energy while coasting.

It seems really simple to me... if your engine, transmission, alternator, etc. all have a limited number of rotations before having to be rebuilt/replaced, why would you want to increase the rotations on those parts? Worn out brakes and rotors are cheap and easy to replace.

I'm fairly certain the ZF design attempts to reduce coasting drag for fuel efficiency unless the driver expresses intent to reduce speed. What Bill and I are referring to is the transmissions aggressive engine braking mode. Normal downhill coasting the truck will gain speed. After a hard brake application to hold speed on a downslope the transmission will take the hint and increase the engine braking effect nearly eliminating the need to ride the brakes.

If you apply a little throttle the retard function quits and the truck will start accelerating again if the slope is steep enough.

I grew up on manuals and of all the autos I driven this is without question the best of them. Heavily loaded, or towing on rough ground is very tough on a clutch unless it's really robust. You are going to be in low range or slipping the clutch a lot. With two feet the automatic is going to be smoother and kinder to the driveline in such conditions.

 

[Dp7]

I'm fairly certain the ZF design attempts to reduce coasting drag for fuel efficiency unless the driver expresses intent to reduce speed. What Bill and I are referring to is the transmissions aggressive engine braking mode. Normal downhill coasting the truck will gain speed. After a hard brake application to hold speed on a downslope the transmission will take the hint and increase the engine braking effect nearly eliminating the need to ride the brakes.

If you apply a little throttle the retard function quits and the truck will start accelerating again if the slope is steep enough.

I grew up on manuals and of all the autos I driven this is without question the best of them. Heavily loaded, or towing on rough ground is very tough on a clutch unless it's really robust. You are going to be in low range or slipping the clutch a lot. With two feet the automatic is going to be smoother and kinder to the driveline in such conditions.

That just doesn't seem to be what I'm experiencing. Just recently I was driving down a fairly steep hill near my home and I was having to give it gas to maintain 55mph. It stood out to me because I was like ... this is crazy, why am I slowing down? On this same stretch of road I would shift into neutral and coast to 65+ on my old JL. I also have a JLA and I don't recall experiencing such aggressive engine braking, but I don't drive it very much (Wife's Jeep). Maybe it's something to do with the JT being a 2024 or that it has the tow package?

That being said, I agree that the Wrangler/Gladiator auto is the best I've ever driven. Shifts are smooth and downshifts are quick to respond. It does seem like the Gladiator is a little slower to upshift than the Wrangler, but I've chalked that up to it being 700lbs heavier.

 

[BearFootSam]

That just doesn't seem to be what I'm experiencing. Just recently I was driving down a fairly steep hill near my home and I was having to give it gas to maintain 55mph. It stood out to me because I was like ... this is crazy, why am I slowing down? On this same stretch of road I would shift into neutral and coast to 65+ on my old JL. I also have a JLA and I don't recall experiencing such aggressive engine braking, but I don't drive it very much (Wife's Jeep). Maybe it's something to do with the JT being a 2024 or that it has the tow package?

That being said, I agree that the Wrangler/Gladiator auto is the best I've ever driven. Shifts are smooth and downshifts are quick to respond. It does seem like the Gladiator is a little slower to upshift than the Wrangler, but I've chalked that up to it being 700lbs heavier.

Maybe it’s still breaking in? The zF 8 speeds have a initial learning and adaptation phase. I wouldn’t be surprised if it also programmed to avoid high load scenarios for the first x,000 miles. I’m speaking from current experience at 33k.

Id love to read a document describing the logic and modes of operation for this transmission. In a manual you always know exactly what you’re going to get. Even a dumb automatic is mostly predictable. This transmission though catches me off guard. Predominately in a positive way. Such as the hill braking mode, I can feel and recognize it but I would like to understand what conditions prompt or deactivate it? Or why is it up shifting rolling up the drive at 7mph under steady throttle? Is it the initial acceleration, slope angle, engine load?

 

[biplaneguy]

It seems really simple to me... if your engine, transmission, alternator, etc. all have a limited number of rotations before having to be rebuilt/replaced, why would you want to increase the rotations on those parts? Worn out brakes and rotors are cheap and easy to replace.

When you use the brakes, it's using mechanical friction to absorb the vehicle's energy, causing wear of the pads and discs, increased heat to the wheel bearings and seals, etc. When you use engine braking, it's using fluid friction and the work of pumping air, which does not (directly) cause wear, and the excess heat is easily handled by the cooling system (coolant and oil).

 

[Badunit]

What often gets me is when it downshifts hard when I am braking, like when slowing for a speed bump or stopping at a light. It is like I slammed on the brakes for no good reason. It happens all the time unless I remember to lighten my pressure on the brake pedal right before it would do it.

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