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Manual Shift option wears out transmission

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Maximus Gladius

Maximus Gladius

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I think a possibility for all my warranty replacements of components is that when the component is made on the assembly line and the QC employee does their “tap test” like we do when picking out a watermelon, and it doesn’t sound quite right, it goes on to the Canada bound conveyor belt I’m im the guy that gets it.
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It's not using the auto-manual feature. It's just horrible luck/inept service (maybe?). I had a manual replaced once and the shop forgot to close it up. I drove it for a day and had gear oil everywhere. S**t happens.

Back when I had a Golf in manual variety, I abused the f out of it. I didn't replace my brake pads until around 60k, and I only did it because I wanted some vented rotors. I replaced my front hub bearings before my brakes.

Using compression braking has been around a lot longer than the modern auto-manual transmissions. There's nothing wrong with doing it.

The only difference between auto and manual is the trigger point. The computer still runs everything.
 

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I think a possibility for all my warranty replacements of components is that when the component is made on the assembly line and the QC employee does their “tap test” like we do when picking out a watermelon, and it doesn’t sound quite right, it goes on to the Canada bound conveyor belt I’m im the guy that gets it.
Sorry, had to laugh at this comment. Are you sure there isn't someone at the dealership that hates your guts and is taking it out on your Jeep?!
 

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I guess what we would need to see for a true non-guessing theory is a video of you driving in your driving style.

When I was a teenager 43 years ago, I had a 1966 Mustang with a 3 speed. I just loved to drop it into second from third at about 45 MPH, drop the clutch, and listen to the tires chirp. All was well and good until I did it at 60MPH one day, and bang! Busted second gear all up, and that, in turn, shredded the rest. So, I technically wasn't doing anything the transmission wasn't designed for, but I was doing something out of spec for it. I told my Dad I just downshifted into second to slow down but I left out the detail of going 60 MPH when I did it :)

I don't see how this could be accomplished though with this transmission as it just won't downshift if you are outside of safe ranges determined by the computer.

I guess it is possible if someone was super hard and pushing the downshifting to the limits that it could cause issues over time.

Much like I am sure if you ran the RPM's up to red line EVERYTIME you shifted that it most undoubtedly would cause premature engine wear. The engine is designed to hit the red line safely but I would guess not on every shift.
 
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Flyboy2109

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Wow, This is how I have driven my 1994 Suburban for years, manually dropping gears to slow and tow. Shocking that a Jeep "trail built" tranny cannot handle it. It shouldn't be referred to as "abuse". I consider it normal transmission operation. How about driving down Pikes' Peak or any mountain pass? I would be downshifting to save the brakes and not have them fade.

Sidelight: I have a '23 Sport S manual. It holds back very poorly even with downshifts, the rpm climbs quickly downhill. There is essentially no engine braking with the manual, why is this? My '90 Dakota and every other manual I have had engine brake well, it is why I bought a stick. And now I have two manual tranny recalls to deal with, oh boy. Disappointing.
 

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Sorry, had to laugh at this comment. Are you sure there isn't someone at the dealership that hates your guts and is taking it out on your Jeep?!
It wouldn’t surprise me BUT…all these people that I’ve dealt with face to face have been 5 stars. The others I don’t see have made some mistakes but I’ve never been an ass to them.
 

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EXACTLY.

Either way, kinetic energy of the vehicle is being reduced by converting it to heat energy. What do you want taking all that heat: pads & rotors or a transmission?

Not quite, in the tranny and engine some becomes heat but mostly it is converted to mechanical energy expended to hold back the vehicle counter to gravity, the brakes convert the energy to heat.
 
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Let’s say for the sake of argument, that manual shifting to slow down is a very bad thing and abusive. Let’s put that aside for a min to talk about those that have “blow by” ( air blows out the oil fill cap when engine is on and cap is off) and perhaps these people don’t use manual shift to assist in slowing down (negative compression) and those that don’t have “blow by” because they do use manual shift to slow down. ?? I think this is a substantial topic.

Blow by is air forcing itself through the rings and back out the PCV valve. Maybe this air escaping through the rings is from the rings having mostly been worn by positive compression and not worn by enough negative compression.

I did not have blow by in the first engine and I certainly don’t have it in the second. Could the escaping air be going on during the soft computer controlled engine negative compression during normal slowing down as a pose to manually shifting the slowing down causing much higher breaking in and wear on the negative pressure of the rings?? I’m truly blowing this out my a$$ but it’s a fantastic idea explaining the need to break in rings, not only by driving it like you stole it (positive compression) but also by stronger negative engine compression - manual shifting to assist in slowing down.
 

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I guess what we would need to see for a true non-guessing theory is a video of you driving in your driving style.

When I was a teenager 43 years ago, I had a 1966 Mustang with a 3 speed. I just loved to drop it into second from third at about 45 MPH, drop the clutch, and listen to the tires chirp. All was well and good until I did it at 60MPH one day, and bang! Busted second gear all up, and that, in turn, shredded the rest. So, I technically wasn't doing anything the transmission wasn't designed for, but I was doing something out of spec for it. I told my Dad I just downshifted into second to slow down but I left out the detail of going 60 MPH when I did it :)

I don't see how this could be accomplished though with this transmission as it just won't downshift if you are outside of safe ranges determined by the computer.

I guess it is possible if someone was super hard and pushing the downshifting to the limits that it could cause issues over time.

Much like I am sure if you ran the RPM's up to red line EVERYTIME you shifted that it most undoubtedly would cause premature engine wear. The engine is designed to hit the red line safely but I would guess not on every shift.
Yup. We're speculating.
So is the OP.
Maybe folks missed the parts where he admitted the reasons for failure of #1 and #2 (bad out of the box, DOA) and then #3 had a whine from day one?
Why is anyone even bothering to connect this to anything but the various causes already outlined?
This is a nothing burger here.
#1 - "glycol contamination"
#2 - "DOA"
#3 - "Whine from the beginning indicating abnormal planetary gear situation - resulting in high iron in the testing. I take that as a "DUH". If you have a whine, you will have high iron content after a while because the whine itself indicates abnormal conditions.

Why is this even a question?

Let’s say for the sake of argument, that manual shifting to slow down is a very bad thing and abusive. Let’s put that aside for a min to talk about those that have “blow by” ( air blows out the oil fill cap when engine is on and cap is off) and perhaps these people don’t use manual shift to assist in slowing down (negative compression) and those that don’t have “blow by” because they do use manual shift to slow down. ?? I think this is a substantial topic.

Blow by is air forcing itself through the rings and back out the PCV valve. Maybe this air escaping through the rings is from the rings having mostly been worn by positive compression and not worn by enough negative compression.
You are speculating based on being a non-mechanic?
Sorry, but the last paragraph I quoted here is laughable.
There's no difference in "wear" because no matter what, the forces above the piston greatly out-measure the forces below.
Downshifting you are putting the engine in sort of a compressor mode - the pressure above is higher than the pressure below.
Running the engine for power - the pressure above the piston is greater than below.
If you had a pressure below the piston to cause substantial improper wear - you'd be blowing oil out the seals.
Negative compression? Huh? You mean more pressure in the crankcase than in the chamber? Not happening (except in the intake stroke and even then the difference is negligible)
I spent months, years, learning rings and pistons for performance use, and in college and you aren't even close. it's going to be interesting how many armchair mechanics jump on this one.
Man, this is getting as twisted as some soap opera plots.

Not quite, in the tranny and engine some becomes heat but mostly it is converted to mechanical energy expended to hold back the vehicle counter to gravity, the brakes convert the energy to heat.
Yeah, sorry, I'm getting a kick out of some of the 'guessing" going on that's so far off the mark the bullets are going into the air.
The transmission gears are ALWAYS engaged, unlike a manual. Those planetary sets never disengage.
They have to handle the full HP and torque of that engine. Imagine pulling a heavy trailer up a hill or mountain, the stress they are under.
When downshifting the same gears, still fully engages, are transferring the energy from the moving vehicle back to the engine where it's being used to run the engine as a compressor. It's lost to motion in making the mass of the engine parts to move, and against compression like your air compressor motor spins the compressor - requiring HP to do so.

I can again say - this is a nothing-burger. Thousands of people, perhaps tens of thousands, manually shift automatics every day - some on the drag strip, some just because, and some because they live in mountains and it's just a normal thing to use engine braking.
It's not a big deal and I'm speaking as a mechanic.
It's only a big deal if you use the transmission to try to send that energy back to the engine too quickly - you downshift and see an extreme change in engine RPM. Then you are trying to dissipate more HP than the transmission was designed to handle.
It takes HP to make a truck go from 0 to 60 and it takes HP to make it go from 60 to 0
It takes more HP to go from 60 to 0 faster than you got up to 60 because HP is work done over time. As long as you downshift and don't exceed the HP limits of the transmission (500 in this case) it's just not a problem.

Refer back to the OP's own statements -
1 didn't fail because of downshifting
2 didn't fail because of downshifting
3 was already failing

This is pure unadulterated speculation based on a lot of misunderstanding of physics and transmissions (and engines when i start to see "ring wear by negative compression. What the heck is that even??)

Wow, This is how I have driven my 1994 Suburban for years, manually dropping gears to slow and tow. Shocking that a Jeep "trail built" tranny cannot handle it. It shouldn't be referred to as "abuse". I consider it normal transmission operation. How about driving down Pikes' Peak or any mountain pass? I would be downshifting to save the brakes and not have them fade.
Yeah, I'm sitting back smiling, at times almost laughing, the made up stuff, the trying to figure things out with no background in physics or engines (or transmissions)

I went down Pike's Peak and honestly, used the transmission the whole way. And - the transmission temperature didn't rise above normal. Maybe folks missed where I explained how these are programmed to downshift 2 gears to maintain speed going down a steep hill if you use the brake pedal just right?
When I got to the check point I was waved through pretty quickly. My wheels weren't even warm. (yeah, I checked) (we stopped for a short break and the gift shop)

Think of taking these things through some of the toughest areas that some of these guys do - transfer case in low, axles locked, engine running higher RPM for torque - think there's not some hefty forces there?

Again, though - refer back to -
1 didn't fail because of downshifting (glycol)
2 didn't fail because of downshifting (DOA(
3 was already failing (whine from day one - totally totally explaining the high iron!)

Why was downshifting even brought up when it was known it didn't cause any failures to date?
 

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Now that’s a pretty bold statement to make and post this thread saying it but now that I’m just past 4000k kms on my warranty replaced 4th auto transmission, …I decided to try driving this one a little differently to see if the manual shift feature, (I used a lot only for slowing down) had a significant roll in bringing about my third transmission’s demise and pump failure at only 32k kms.

As it was becoming apparent that the third transmission was experiencing problems and noted by the oil analysis lab to change the oil and filter because the IRON wear was too high, I had much time to critically think what could possibly be causing it’s failure. The 4th tranny was put in and I decided to not use the manual shift to assist in slowing down (which my brake pads benefited from) greatly and I wanted to see what impact this would have on the transmission in the wear department.

The first oil analysis proves the transmission is healthy right out of the gate and the second report was done at 3950k kms, pretty much at the same kms the third transmission report was done and we can see a HUGE reduction in wear not using the manual shift.

I’ve thought long and hard about this and the numbers don’t lie. Cause and effect law applies here and we can see this. I’ll be pulling samples and getting analysis reports at the same times as the third transmission to see if this theory holds true.

My conclusion is this 850RE transmission should not use the manual shift feature for slowing down if we can see expedited wear as a result. Now that said, I would use it if I’m coming down a mountain pass and I don’t want to burn the brakes out so there’s times it’s needed but it was far to easy for me to use it often in the city to slow down. It’s a cool feature so I used it. But I have also been able to not use it and be ok too. I figure brake pads are cheap andI’m still on my first pair at 80k kms.

(first image is 4th tranny)
(Second image is 3rd tranny)

IMG_1873.png


IMG_1875.png
I look at it just like a manual transmission and drive it accordingly when it comes to manual mode. While the clutches serve somewhat different functions between the AT/MT, they are in effect similar materials and serve a similar purpose. I would never use the clutch as a brake to SLOW down, rather I use the brakes then downshift to retard speed.

The wisdom is that both clutch and brake are consumables, but the latter is far easier and cheaper to replace so it behooves the driver to sacrifice the brakes over clutch. Since the clutch(es) only wear when actuating or releasing, if you slow the truck until it downshifts to desired gear then lock it in manual, the clutches are static and not incurring wear.
 

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Yup. We're speculating.
So is the OP.
Maybe folks missed the parts where he admitted the reasons for failure of #1 and #2 (bad out of the box, DOA) and then #3 had a whine from day one?
Why is anyone even bothering to connect this to anything but the various causes already outlined?
This is a nothing burger here.
#1 - "glycol contamination"
#2 - "DOA"
#3 - "Whine from the beginning indicating abnormal planetary gear situation - resulting in high iron in the testing. I take that as a "DUH". If you have a whine, you will have high iron content after a while because the whine itself indicates abnormal conditions.

Why is this even a question?


You are speculating based on being a non-mechanic?
Sorry, but the last paragraph I quoted here is laughable.
There's no difference in "wear" because no matter what, the forces above the piston greatly out-measure the forces below.
Downshifting you are putting the engine in sort of a compressor mode - the pressure above is higher than the pressure below.
Running the engine for power - the pressure above the piston is greater than below.
If you had a pressure below the piston to cause substantial improper wear - you'd be blowing oil out the seals.
Negative compression? Huh? You mean more pressure in the crankcase than in the chamber? Not happening (except in the intake stroke and even then the difference is negligible)
I spent months, years, learning rings and pistons for performance use, and in college and you aren't even close. it's going to be interesting how many armchair mechanics jump on this one.
Man, this is getting as twisted as some soap opera plots.



Yeah, sorry, I'm getting a kick out of some of the 'guessing" going on that's so far off the mark the bullets are going into the air.
The transmission gears are ALWAYS engaged, unlike a manual. Those planetary sets never disengage.
They have to handle the full HP and torque of that engine. Imagine pulling a heavy trailer up a hill or mountain, the stress they are under.
When downshifting the same gears, still fully engages, are transferring the energy from the moving vehicle back to the engine where it's being used to run the engine as a compressor. It's lost to motion in making the mass of the engine parts to move, and against compression like your air compressor motor spins the compressor - requiring HP to do so.

I can again say - this is a nothing-burger. Thousands of people, perhaps tens of thousands, manually shift automatics every day - some on the drag strip, some just because, and some because they live in mountains and it's just a normal thing to use engine braking.
It's not a big deal and I'm speaking as a mechanic.
It's only a big deal if you use the transmission to try to send that energy back to the engine too quickly - you downshift and see an extreme change in engine RPM. Then you are trying to dissipate more HP than the transmission was designed to handle.
It takes HP to make a truck go from 0 to 60 and it takes HP to make it go from 60 to 0
It takes more HP to go from 60 to 0 faster than you got up to 60 because HP is work done over time. As long as you downshift and don't exceed the HP limits of the transmission (500 in this case) it's just not a problem.

Refer back to the OP's own statements -
1 didn't fail because of downshifting
2 didn't fail because of downshifting
3 was already failing

This is pure unadulterated speculation based on a lot of misunderstanding of physics and transmissions (and engines when i start to see "ring wear by negative compression. What the heck is that even??)



Yeah, I'm sitting back smiling, at times almost laughing, the made up stuff, the trying to figure things out with no background in physics or engines (or transmissions)

I went down Pike's Peak and honestly, used the transmission the whole way. And - the transmission temperature didn't rise above normal. Maybe folks missed where I explained how these are programmed to downshift 2 gears to maintain speed going down a steep hill if you use the brake pedal just right?
When I got to the check point I was waved through pretty quickly. My wheels weren't even warm. (yeah, I checked) (we stopped for a short break and the gift shop)

Think of taking these things through some of the toughest areas that some of these guys do - transfer case in low, axles locked, engine running higher RPM for torque - think there's not some hefty forces there?

Again, though - refer back to -
1 didn't fail because of downshifting (glycol)
2 didn't fail because of downshifting (DOA(
3 was already failing (whine from day one - totally totally explaining the high iron!)

Why was downshifting even brought up when it was known it didn't cause any failures to date?
The ECM/TCM engine breaking algorithms are excellent in this truck. The first time I experienced it in action was crossing the Big Horn range between Buffalo and Ten Sleep. With three people, a bed full of cargo and a 2,500lb trailer the truck would hold speed with only minimal braking before curves.

That was the moment I realized how much engineering work went into making the Gladiator a solid tow vehicle. I have perhaps preternatural fear of abusing clutches, probably something to do with learning to drive in a stick and old Dad being militant about his XJ. As a result, I cannot bring myself to use downshift to slow, only to use the gears to hold speed after scrubbing speed by brake.

Right or wrong, multiple manual vehicles over my life and no clutch issues. I leave the clutch wear to my wife ;)
 

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Refer back to the OP's own statements -
1 didn't fail because of downshifting
2 didn't fail because of downshifting
3 was already failing

This is pure unadulterated speculation based on a lot of misunderstanding of physics and transmissions (and engines when i start to see "ring wear by negative compression. What the heck is that even??)
Are you saying that this thread is click-bait?
 

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Are you saying that this thread is click-bait?
Trying to explain something that doesn't exist? Yeah, sort of LOL
It's 100% based on false or faulty assumptions, trying to make a pattern where none exists.
 

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(and engines when i start to see "ring wear by negative compression. What the heck is that even??)
negative compression = explosive expansion. So rings getting so much pressure from combustion they scrape against the cylinder wall, leading to premature wear. I mean, this 3.6L is so damn powerful it's shredding transmission, why not engines, too?

duh.

:CWL:

Years ago there was an argument amongst the unintelligent around the phrase "you can't make an engine bigger by making it smaller." Apparently no one was familiar with the phrase "boring out" or "bored over."

I'm not one who knows all the technical terms, nor born with a natural mechanical aptitude, but I can definitely smell it when someone's burnt the popcorn.
 

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negative compression = explosive expansion. So rings getting so much pressure from combustion they scrape against the cylinder wall, leading to premature wear. I mean, this 3.6L is so damn powerful it's shredding transmission, why not engines, too?

duh.

:CWL:

Years ago there was an argument amongst the unintelligent around the phrase "you can't make an engine bigger by making it smaller." Apparently no one was familiar with the phrase "boring out" or "bored over."

I'm not one who knows all the technical terms, nor born with a natural mechanical aptitude, but I can definitely smell it when someone's burnt the popcorn.
Yeah, but boring it doesn't make the engine smaller. It's the same physical dimensions with increased displacement.

On the other hand, the tardis is bigger on the inside than it is the outside
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