RPMs limited in 4L reverse?

[Almost]

And here is where they Planetary gears can be used in any direction with the same torque handing ability either way - as long as the thrust surfaces are the same on each end.
I don't know where the never tow in reverse comes from......

Just what I have seen being repeated time and time again in these groups. If you google "why you shouldn't tow in reverse" you will be inundated with pages and pages of this being asked across all vehicle forums and off-road forums. But to your point, this might be an old myth stemming from the days of manual transmissions and straight-cut gears being weaker and people just sending it too hard in reverse.

Sponsored

 

[ShadowsPapa]

Just what I have seen being repeated time and time again in these groups. If you google "why you shouldn't tow in reverse" you will be inundated with pages and pages of this being asked across all vehicle forums and off-road forums. But to your point, this might be an old myth stemming from the days of manual transmissions and straight-cut gears being weaker and people just sending it too hard in reverse.

Understand that the people saying all of this stuff are ordinary untrained people - guessing, or repeating what they saw in another forum (sound familiar?!) They aren't mechanics, they saw something in a forum, they posted it in another forum, someone else googles and now sees that in 2 forums so it must be fact.
It IS myth perpetuated by untrained "forum experts" who know stuff simply because they read it on an RV forum.
Google isn't always your friend.
I can tell you about a first-hand experience with such crap -
In the mid-1990s, I put together my pages on rust removal using electrolysis. I had the chemistry in there, warnings on safety, what to do and what not to do. I was raised with the understanding that the Hindenburg incident was due to the hydrogen in the envelope - it was in every book, it was talked about in school, everyone "knew" it was due to the hydrogen.
So I put in my write-up a bit about the Hindenburg and hydrogen - as that's what I had always seen.

Along comes a NASA propulsion engineer who thought - meh, that doesn't wash. He did an in-depth study of the air ship and the events of that day.
He proved it wasn't the hydrogen at all - it was the coating put on the fabric of the envelope. He discovered that it was coated with a substance that contained some of the ingredients for GUN POWDER. Once a spark was even close - there was no putting it out and the fabric burned so bloody hot it melted metal. Hydrogen wasn't even a factor.

I see his study and go to my pages to make corrections. But it was too late. I found over a half-dozen COPIES of my text out there on other sites. In a couple of months, it grew to over a dozen. And it was almost word-for-word, including a word I had spelled incorrectly on my electrolysis page. That misinformation was on over a dozen other sites. Anyone who looked up the process and was posting it in forums or whatever would be perpetuating that incorrect information.

I saw it on the internet, it MUST be true! 10 people said it, that means it's an indisputable fact.

A guy came to the AMC forum talking about transmission throttle pressure vs. governor pressure. He had the relationship backwards. I tried to explain the correct relationship and he jumped and started calling me a hack, and worse. He said he KNEW all about transmissions and further, he linked to a page where he got his "facts" from.
Some owner of an AMX rebuilt his transmission in his driveway and posted about it on his web site. He put this crap in there about the pressures and how an automatic shifts.
Here I am, college trained on transmissions, years of experience in a pro shop making a living at it, and yet I was the bad guy.
That clown read about automatics on a web site put up by a guy who ONE TIME worked on his transmission, it happened to work (he was lucky, that's all) and so it must be true.

 

[Maximus Gladius]

OP, were you in 4L because you wanted the lockers? You have the 2021 JTR, like mine and you can have rear locker in 4H. I did a video (not on YouTube) where I jacked all 4 corners up off the ground, initiated front and rear lockers in 4H.

PM me and I’ll send you the vid.

 

[Limestone]

To all who have responded, thanks for your interest. If other folks could try 4L reverse and see if it is rpm limited, that would be great.

 

[Maximus Gladius]

To all who have responded, thanks for your interest. If other folks could try 4L reverse and see if it is rpm limited, that would be great.

Mine is limited just as you are experiencing

 

[Limestone]

Mine is limited just as you are experiencing

Thanks for checking! Did you also find that if you let off on the accelerator a bit and then try to accelerate again it would further limit from 3500 rpm to 2500 rpm?

 

[Maximus Gladius]

Thanks for checking! Did you also find that if you let off on the accelerator a bit and then try to accelerate again it would further limit from 3500 rpm to 2500 rpm?

Yes. It felt like I wasn’t going anywhere fast. I was actually trying to pull someone out of the snow bank and had put the truck in 4L lockers. After trying and wanting more speed, I remembered the lockers in 4H and once I engaged that, the truck had the power and speed and walked that other vehicle out.

 

[Limestone]

Yes. It felt like I wasn’t going anywhere fast. I was actually trying to pull someone out of the snow bank and had put the truck in 4L lockers. After trying and wanting more speed, I remembered the lockers in 4H and once I engaged that, the truck had the power and speed and walked that other vehicle out.

Very similar to my experience!?
I was pushing through fresh snow down a narrow road. I was solo. The hill exposure changed more to the north and the snow became much deeper very quickly. I had to reverse about 1/2 mile to reach a turn around point. At 3500 rpm I was doing ok, but when I slowed a bit and the rpms got limited to 2500, it felt like the truck was about to stop at any moment. I didn’t know what was going on. If I stopped, I didn’t know if I could get started again, so I just maintained the 2500 rpm for about 1/2 mile until I reached the turn around point at the top of the hill. I was quite the ecperience.

 

[ChrisNLA]

Understand that the people saying all of this stuff are ordinary untrained people - guessing, or repeating what they saw in another forum (sound familiar?!) They aren't mechanics, they saw something in a forum, they posted it in another forum, someone else googles and now sees that in 2 forums so it must be fact.
It IS myth perpetuated by untrained "forum experts" who know stuff simply because they read it on an RV forum.
Google isn't always your friend.
I can tell you about a first-hand experience with such crap -
In the mid-1990s, I put together my pages on rust removal using electrolysis. I had the chemistry in there, warnings on safety, what to do and what not to do. I was raised with the understanding that the Hindenburg incident was due to the hydrogen in the envelope - it was in every book, it was talked about in school, everyone "knew" it was due to the hydrogen.
So I put in my write-up a bit about the Hindenburg and hydrogen - as that's what I had always seen.

Along comes a NASA propulsion engineer who thought - meh, that doesn't wash. He did an in-depth study of the air ship and the events of that day.
He proved it wasn't the hydrogen at all - it was the coating put on the fabric of the envelope. He discovered that it was coated with a substance that contained some of the ingredients for GUN POWDER. Once a spark was even close - there was no putting it out and the fabric burned so bloody hot it melted metal. Hydrogen wasn't even a factor.

I see his study and go to my pages to make corrections. But it was too late. I found over a half-dozen COPIES of my text out there on other sites. In a couple of months, it grew to over a dozen. And it was almost word-for-word, including a word I had spelled incorrectly on my electrolysis page. That misinformation was on over a dozen other sites. Anyone who looked up the process and was posting it in forums or whatever would be perpetuating that incorrect information.

I saw it on the internet, it MUST be true! 10 people said it, that means it's an indisputable fact.

A guy came to the AMC forum talking about transmission throttle pressure vs. governor pressure. He had the relationship backwards. I tried to explain the correct relationship and he jumped and started calling me a hack, and worse. He said he KNEW all about transmissions and further, he linked to a page where he got his "facts" from.
Some owner of an AMX rebuilt his transmission in his driveway and posted about it on his web site. He put this crap in there about the pressures and how an automatic shifts.
Here I am, college trained on transmissions, years of experience in a pro shop making a living at it, and yet I was the bad guy.
That clown read about automatics on a web site put up by a guy who ONE TIME worked on his transmission, it happened to work (he was lucky, that's all) and so it must be true.

Sorry, been dabbling in machine shop, worked on transmissions for years, and have had to study different gear types.
Your info is quite flawed (and I know the reasons they only use the straight cut gear for reverse - having rebuild many dozens of transmissions)

They are as strong either direction - it's just that the thrust is in different directions (the AXIAL loading varies)
The thrust may be forward in one case, and the gear thrown back on the shaft in another.
But there can't be any difference in strength because the teeth are identical on both sides.
Check the machinery handbook for the details.
Helical gears are STRONGER. There's actually more surface area, the load is spread out.

Here - from the experts -

And here is where they are used - and why -

They handle higher loads and greater speeds.

Planetary gears can be used in any direction with the same torque handing ability either way - as long as the thrust surfaces are the same on each end.
I don't know where the never tow in reverse comes from......

Straight cut gears are still used for reverse gears in manual transmissions.
Automatics use helical gears.

This shows reverse in one of the transmissions I worked on, plus the helical gears inside.

I have heard similar claims before, but not about the transmission, it was about the ring and pinion gear in the axle being weaker in a certain direction. Of course, this depends on high pinion or low pinion, and I believe some other variable - but the argument was made that you could be more likely to strip a ring and pinion gear because when pulling in reverse, the ring and pinion is trying to pull apart from one another (again, depending on LP/HP, etc. orientation) under high load, whereas traveling forward, the cut of the gears pulls them toward each other.

Granted, this was extreme cases / forces. Do you see any validity to that claim?

 

[ShadowsPapa]

I have heard similar claims before, but not about the transmission, it was about the ring and pinion gear in the axle being weaker in a certain direction. Of course, this depends on high pinion or low pinion, and I believe some other variable - but the argument was made that you could be more likely to strip a ring and pinion gear because when pulling in reverse, the ring and pinion is trying to pull apart from one another (again, depending on LP/HP, etc. orientation) under high load, whereas traveling forward, the cut of the gears pulls them toward each other.

Granted, this was extreme cases / forces. Do you see any validity to that claim?

You'd have to have a heck of a reverse pull, a lot of torque, to destroy the typical differential in reverse.
However, it's said that the Ford 9" has a slightly different cut to the gears to give them incredible strength and going reverse with them can be problematic under heavy torque situations as the reverse side/coast side is more straight up. A lot of people put those differentials under drag cars. They are tough as heck, and the Ford quick-change punkin allows for fast gear changes at the track by replacing the whole center section while the housing stays in the car. Simple pull the axles out to disengage the side gears, swap centers, put axles back in - you now have a different ratio.

Anyway, the thrust on the pinion does change in reverse and most can't handle the same torque "in reverse" but you'd really need to pull hard to break most of them.
Like you said - there are so many variables - LP, HP, make, gear cut (example, the Ford) ratio, whatever.

I've always figured it was safer to pull or "tow" forward anyway - you can see where you are going, and the rig is behind you if something cuts loose.

 

[Limestone]

So far only Maximus Gladias has responded to the original question that was posted. I’m sure that all who responded had good intentions, but those responses have not addressed he original question so I’ll try again.
When my gladiator is in 4L REVERSE, the rpms are limited to 3500, and if I let off on the accelerator a bit, the rpms are further limited to 2500. Has anyone else experienced this in their gladiator? Is this “normal” for all gladiators. If you can, just put your truck in 4L Reverse, see what happens and report back.
Best wishes to all!

 

[ShadowsPapa]

Just to clarify for those looking on and who want to test this -
He was in Off Road + mode.
That's only Rubicon (perhaps Mojave???)
So don't bother taking your Overland, Sport, Sport S, Overland High Altitude or anything else out and trying it.
And when you try it, be in 4L with OFF ROAD + engaged.

OR+ de-gains the throttle and since it's likely connected, only a JT with OR+ can try to duplicate his experiences.

No use me trying as I don't have Off Road +

 

[Limestone]

Just to clarify for those looking on and who want to test this -
He was in Off Road + mode.
That's only Rubicon (perhaps Mojave???)
So don't bother taking your Overland, Sport, Sport S, Overland High Altitude or anything else out and trying it.
And when you try it, be in 4L with OFF ROAD + engaged.

OR+ de-gains the throttle and since it's likely connected, only a JT with OR+ can try to duplicate his experiences.

No use me trying as I don't have Off Road +

True, I was in Off Road+ when I first experienced the rpm limiting in 4L reverse, but have since noticed the rpm limiting by just putting the truck in 4L reverse, no Off Road+, no lockers, no other changes. Sorry I didn’t clarify this earlier.

 

[Limestone]

True, I was in Off Road+ when I first experienced the rpm limiting in 4L reverse, but have since noticed the rpm limiting by just putting the truck in 4L reverse, no Off Road+, no lockers, no other changes. Sorry I didn’t clarify this earlier.

Maybe I still am still failing to describe the situation fully. When I put the truck in 4L Reverse (no off road+, no lockers, no other changes) and then begin to back up, once 3500 rpms is reached, the truck will not go any faster. If I let off on the accelerator a bit and then try to accelerate again, rpms are further limited to 2500. The ground speed of the truck at 3500 rpm in 4L Reverse is about 6mph, and at 2500 about 5mph. These are my results on a level gravel road.

 

[DankjeeP]

Mine is limited just as you are experiencing

"Because of the additional gear reduction when in low range, engine RPMs should be kept under 2500 (remember the planetary is turning at 4 times that rate 2,500 x 4.0 = 10,000 RPM). Severe transfer case damage can occur if this RPM warning is not observed "

Sponsored