Putting together a 4:1 (teralow)

[kleake]

OK, here's an experiment for you. Park your Jeep on Moab or Sierra rock. Engage low range, bring the RPM's to 3,500. Side-step the clutch.

The chain in 4 to 1 case sees 47% more torque than the 2.72 case.

I would be willing to take that challenge and disagree with you..... The chain and everything after it would see exactly the same either way because your tires are spinning by that rpm... But,,, everything before the reduction would see less stress....

If you can turn your tires, it isn't going to matter how much reduction you have from the chain out to the wheels as they are already at their maximum traction/load.... Now if you was to pin a tire where it would not rotate at all,,, and you bring the rpm to 3500,,,,, then there would definitely be a difference,,, and I'll bet it would be a broken axle, driveline or your tranny or clutch is slipping.....

Put some engineering into it,,,,, if it takes 1000 ft lbs of torque (at the yoke) to break all 4 of your tires loose,,, tell me your input torqe to accomplish this with the reduction of each?

 

[BRIANHO13]

I would be willing to take that challenge and disagree with you..... The chain and everything after it would see exactly the same either way because your tires are spinning by that rpm... But,,, everything before the reduction would see less stress....

If you can turn your tires, it isn't going to matter how much reduction you have from the chain out to the wheels as they are already at their maximum traction/load.... Now if you was to pin a tire where it would not rotate at all,,, and you bring the rpm to 3500,,,,, then there would definitely be a difference,,, and I'll bet it would be a broken axle, driveline or your tranny or clutch is slipping.....

Put some engineering into it,,,,, if it takes 1000 ft lbs of torque (at the yoke) to break all 4 of your tires loose,,, tell me your input torqe to accomplish this with the reduction of each?

OH MY GOD
Lower gearing does increase torque.....it also lets you get to the engines peak torque at a lower speed (MPH) Seriously do some research, you are arguing with people much smarter than you (apparently)......seriously look up what lower gears do to torque. You obviously will be surprised.

 

[kleake]

I am not arguing that lower gears don't increase torque available,,, because that is the whole purpose of them. What I am arguing,,, (or actually discussing because I am not getting stressed out over this as the fundamentals are highly needed in order to understand drivetrain stress), is the fact that "having" more torque available, does not mean you are going to "use" more in the same application.

If you are "apparently" smarter than me,,, do the math.... If it takes 1000 ft lbs of torque at the yoke to break all 4 of your tires loose,,, how much torque is being input in each case?

 

[kleake]

Assuming it takes 1000 ft lbs to spin all 4 tires in a given situation

4 low before - 1000\2.72\3.8 = 96.75 ft lbs at the engine
4 low after 4:1 - 1000\4\3.8 = 65.79 ft lbs at the engine

Either way, the 1000 ft lbs are all it takes to spin all 4 tires,,, effectively no extra strain on the chain than you had before the 4:1 kit....

 

[GSequoia]

Okay Kleake I'll try to put down what I've been trying ot say the whole time...

You can't always spin the tires!

If your tire is wedged or you're on rock with lots of traction (common) you could easily be hitting the gas and going nowhere; that's when stuff breaks, that's when the chain will stretch.

 

[Root Moose]

Assuming it takes 1000 ft lbs to spin all 4 tires in a given situation

4 low before - 1000\2.72\3.8 = 96.75 ft lbs at the engine
4 low after 4:1 - 1000\4\3.8 = 65.79 ft lbs at the engine

Either way, the 1000 ft lbs are all it takes to spin all 4 tires,,, effectively no extra strain on the chain than you had before the 4:1 kit....

Your argument is correct IF (note, big IF) you are able to break traction at the wheels.

Your assumption is that you have the power to break traction already. This is where you are going wrong. Also consider that the 4:1 will allow you to go places that you may not have attempted with the original case gearing.

The point the others are making is that in a rock crawling environment you may be surprised to see all four wheels on the ground, locked diffs at both ends, and low range with first gear stall the vehicle because you can't break traction. Cross axled and a wheel wedged between rocks is not the place to side step the clutch.

Anyway, do the wide chain. You've got the case apart, do it.

 

[kleake]

Okay Kleake I'll try to put down what I've been trying ot say the whole time...

You can't always spin the tires!

If your tire is wedged or you're on rock with lots of traction (common) you could easily be hitting the gas and going nowhere; that's when stuff breaks, that's when the chain will stretch.

I couldn't agree with you more,,,, and that explains my point as well..... The 4:1 kit isn't going to add stress on the chain except in this exact scenario, and odds are that it will only last a second and something else is going to break... If you are going to go wide open throttle when your tire is wedged, then something will break. Most of the time, you will never use enough throttle to push things to that limit, so yes, your maximum torque is higher with the kit,,, but more than likely you are going to have more than needed to twist an axle or break a joint way before you reach that max even with the stock t-case.

With that said, the amount of torque required to turn that tire is exactly the same, you only achieve that torque limit with less strain on engine and transmission. That is why I say the chain is under no more load with the 4:1 as it was before. If you up your traction, the traction will directly effect the chain, not the 4:1 kit..... So if you need the wider chain,,, then you needed it before the 4:1 kit.....

Bottom line,,, I am not saying it is not advantageous to go to the wider chain,,,, but the 4:1 kit is not the reason,,, it is ultimate traction that you have....

 

[CW]

I am fairly certain the chevy np231c has wide chain. I'll look it up in the books when I go to work tomarrow to verify. It also has the 6 planetary that the np241 has. Both should interchange with the np231j. I'm going to do this set up along with a 32 spline output shaft with a 231 doubler and see how long it holds up. I can get the parts real cheep and when I break the 231 with 7.4:1 gearing I'll spring for a d300.

 

[CRASH]

But you are overlooking the second variable, engine stall. With a 2.72, and perfect traction, the engine will simply stall before reaching it's torque peak. With a 4-1, in the same situation, you are reaching higher into the torque peak of the engine, and therefor placing more stress on the chain.

I couldn't agree with you more,,,, and that explains my point as well..... The 4:1 kit isn't going to add stress on the chain except in this exact scenario, and odds are that it will only last a second and something else is going to break... If you are going to go wide open throttle when your tire is wedged, then something will break. Most of the time, you will never use enough throttle to push things to that limit, so yes, your maximum torque is higher with the kit,,, but more than likely you are going to have more than needed to twist an axle or break a joint way before you reach that max even with the stock t-case.

With that said, the amount of torque required to turn that tire is exactly the same, you only achieve that torque limit with less strain on engine and transmission. That is why I say the chain is under no more load with the 4:1 as it was before. If you up your traction, the traction will directly effect the chain, not the 4:1 kit..... So if you need the wider chain,,, then you needed it before the 4:1 kit.....

Bottom line,,, I am not saying it is not advantageous to go to the wider chain,,,, but the 4:1 kit is not the reason,,, it is ultimate traction that you have....

 

[kleake]

But you are overlooking the second variable, engine stall. With a 2.72, and perfect traction, the engine will simply stall before reaching it's torque peak. With a 4-1, in the same situation, you are reaching higher into the torque peak of the engine, and therefor placing more stress on the chain.

When was the last time you stalled your tires on your XJ? When you did,,,, did you floor it??? I have never seen a situation where the 4.0L didn't have enough torque to turn the tires.... In perfect traction, you are correct, but that is what I am trying to say.... I don't know of any XJ yet that can get enough traction to stall on any reasonable size tire.... Now if we are talking 37" or above,, sure,, you could get that good of traction,,, but you better have some good axles and driveshafts cuz you are going to be breaking some stuff..... The NP231 is a very strong unit in stock form, and can handle much more torque than most XJ's can get the traction for.

I agree with your theory,,, but what I am trying to say is that it is highly unlikely you are ever going to be in a scenario to stall hard enough that 2.72 can't get it turning.. If you do, that is the one time it would be advantagous to go to the wide chain,,,, but how often is that in reality,, is it enough to make the upgrade worth it? If so, then cool, do it..

 

[CRASH]

When was the last time you stalled your tires on your XJ? When you did,,,, did you floor it??? I have never seen a situation where the 4.0L didn't have enough torque to turn the tires.... In perfect traction, you are correct, but that is what I am trying to say.... I don't know of any XJ yet that can get enough traction to stall on any reasonable size tire.... Now if we are talking 37" or above,, sure,, you could get that good of traction,,, but you better have some good axles and driveshafts cuz you are going to be breaking some stuff..... The NP231 is a very strong unit in stock form, and can handle much more torque than most XJ's can get the traction for.

I agree with your theory,,, but what I am trying to say is that it is highly unlikely you are ever going to be in a scenario stall hard enough that 2.72 can't get it turning.. If you do, that is the one time it would be advantagous,,,, but how often is that in reality,, is it enough to make the upgrade worth it? If so, then cool, do it..

Even with 85 to 1 gearing and 35" tires, I can stall my 4.6 liter stroker.

Have you seen the size of the rocks on our extreme trails? They are large, have tons of available traction, and we break a lot of parts.

That said, my previous 231 held up to a LOT of abuse with an HD output shaft and regular 2.72 gearing. I hated the sloppiness of the chain, and this was mostly due to having much of my gear reduction in front of the chain, and having a manual transmission. New chains don't really help this feeling, and the additional gearing, in my instance, caused a lot of chain wear.

 

[kleake]

Even with 85 to 1 gearing and 35" tires, I can stall my 4.6 liter stroker.

Have you seen the size of the rocks on our extreme trails? They are large, have tons of available traction, and we break a lot of parts.

That said, my previous 231 held up to a LOT of abuse with an HD output shaft and regular 2.72 gearing. I hated the sloppiness of the chain, and this was mostly due to having much of my gear reduction in front of the chain, and having a manual transmission. New chains don't really help this feeling, and the additional gearing, in my instance, caused a lot of chain wear.

How many miles did you have on that chain? You said you break alot of parts,,, say,,,, an axle? If it breaks at 500ft lbs of torqe,,, then you put a 4:1 in,,, that same axle will still break at 500ft lbs correct? So the chain didn't see any more torque than before,,,, you just didn't have to work so hard to do it....

Don't get me wrong, I would love to put in a 4:1 kit in mine for slow crawling, and ease of getting over an obstacle,,, but the chain won't actually see more stress due to it... In perfect traction, sure, it could, but most of us will never see perfect traction...

I don't remember how much the wider chain kit cost, but if I remember right it was above $200. It could definitely be worth it in some rigs,,,, but not most... If I was running 37" tires and D60's,,, and putting in a 4:1,,,, I would consider doing the wide chain at the same time,,,, but it would be due to traction I plan to have, not because of the 4:1...

 

[CRASH]

Have you ever come up to a steep verticle ledge, climbed it with the front axle, and then had to "bump" the rear up? Often, one bump doesn't do it, and you begin to bounce a little as you apply power. This bouncing occurs at 2,500 - 3,500 RPM (in my case). Now you have situation where the chain goes from seeing no torque (wheels in the air) to perhaps 300 ft/lbs (my case) in a split second when the tires make contact. When the tires catch, the 4 to 1 multiples my 300 ft/lbs 47% more than the old 2.72.

Can we at least agree on this?

 

[kleake]

Have you ever come up to a steep verticle ledge, climbed it with the front axle, and then had to "bump" the rear up? Often, one bump doesn't do it, and you begin to bounce a little as you apply power. This bouncing occurs at 2,500 - 3,500 RPM (in my case). Now you have situation where the chain goes from seeing no torque (wheels in the air) to perhaps 300 ft/lbs (my case) in a split second when the tires make contact. When the tires catch, the 4 to 1 multiples my 300 ft/lbs 47% more than the old 2.72.

Can we at least agree on this?

hehe,,, yes,,, I would agree with that..... Although, I would hope you are not applying all 300 ft/lbs of torque when they catch though!!! My guess, you would only be at about half throttle when you do this... If you are at full throttle when they grab,,, and they grab hard,,, that's probably when you'll hear that loud bang!!!

Crash,,, I agree with your theory,,,, the catch in this whole thing depends entirely on traction.... If you can get the traction, yours is more true,,, if you can't get that much traction, the wider chain isn't an issue....

 

[CRASH]

If you are at full throttle when they grab,,, and they grab hard,,, that's probably when you'll hear that loud bang!!!
.

Yes, I've heard the bang often. It's usually my 8.8. Again.

 

[kleake]

Yes, I've heard the bang often. It's usually my 8.8. Again.

Curious,,,, you are breaking your Ford 8.8?

 

[CRASH]

Curious,,,, you are breaking your Ford 8.8?

Two broken housings and a broken ARB.

 

[BrettM]

Two broken housings and a broken ARB.

and yet he keeps band-aiding it.... I expect a Hi9 with the links next winter

 

[CRASH]

and yet he keeps band-aiding it.... I expect a Hi9 with the links next winter

LP60....I put too many miles on my rig for a TrueHi9, or HP 60 for that matter.

 

[kleake]

LP60....I put too many miles on my rig for a TrueHi9, or HP 60 for that matter.

I'm curious now,,,, I've been thinking of going to the 8.8 and hadn't heard much bad about them but now?? What size tire are you running?