limited slip on M35A2?

[stumps]

Whether operated by cams & gears (which some trucks, and even cars, used) or by clutches, they end up operating the same way- attempting to lock both axles together, but allowing some slippage so the vehicle can make tight turns without having a tire skidding. Positraction is GM's brand for it, just as Sur-Grip was Chrysler's.


Jim
​

Jim, I don't dispute what you say. I just wanted to point out (with this and my earlier post) that there are two vastly different systems that go under the name of limited-slip differentials. To lump them together is not, in my opinion, correct.

All of the car companies (that I am aware of) made a limited-slip differential that was simply a braking clutch that friction locked the right axle to the left axle at all times. Whenever the left axle turned at a different speed than the right axle, the clutch was forced to slip. No cams, no cones, no nothing, just a spring that set the clutch tension.

The power-loc, posi-traction, posi-loc, etc. are a different beast in that they make no attempt to lock the two axles together unless a --driven-- axle is spinning. They do not lock up at all in turns... no matter how tight, or how long you are in the turn. The mechanisms they use are somewhat different, but the similarities far outweigh the differences.

One common feature of the posi differentials is they are automatic, and the spinning wheel has to spin somewhat for the traction wheel to gain traction. The amount the spinning wheel has to spin varies depending on the internal configuration, but it always has to spin some.

The simple limited-slip differential will not always need a wheel to spin in order to give you traction in slippery conditions. I can easily see how it might be thought, by one not familiar with its internal construction, to never slip at all.

I am not arguing that these limited-slip and posi differentials are "lockers" in the sense that they manually hard lock the right axle to the left, but that the simple limited-slip, and the posi differentials are very different from each other.

I agree that it is incorrect to say a deuce has air "lockers" on the front differential. It doesn't. It simply has an air controlled clutch, on the transfer case that engages the open front differential. Nothing more. A better system than the automatic Sprag clutch (in my opinion), but not a locker.

-Chuck

OBTW, I didn't miss your link, I could see no point in following a link that showed me something I already knew.

 

[stumps]

they are still limited slip differentials (LSDs). there is no such product as "posi-traction" - it is the brand name given to a limited slip.

Posi-traction is a brand name given to a particular design used in a limited slip differential. As is Traction-Lok, Trac-Lok, Powr-Lok, and a host of others. All are named to sound similar. Ford's Traction-Lok is a simple spring loaded LSD. Dana's Trac-Lok, used in the 44, and 60 differentials doesn't seem to have any more to offer than Ford's Traction-Lok. The Dana 70/80's Power-Lok actually adjusts the torque to fit the situation, and was what I was attempting to describe without using the names of the parts, and diagrams.

you ever taken one apart? because what your describing doesn't exist in my Ford Dana 80 rear diff with OEM LSD.

Yes, and I suck rope at setting up differentials. It takes me all day, but I have done so successfully the couple of times I have needed to... As bad as my description was, your Dana 80 has the structure I was attempting to describe. Look at the ends of the mate shafts, and the V shaped ramps cut into the shaft openings in the differential case. When the wheels are not slipping and are driving straight ahead, the mate shafts drop into the bottoms of the V's and the clutch packs are disengaged (save for the belleville washers that apply some preload). When you are in a turn, the shafts stay in the bottoms of the V's keeping the clutch packs disengaged, but when the wheel slips and spins, the mate shafts ride up in the V's and put pressure on the disk pack, locking the axle to the differential case.

you are right, though - there are many many different methods in achieving "torque biasing", which is the technical method for 'limiting torque transfer' which is a fancy way of saying "limiting slip".

the basic style of spring loaded clutch pack type LSD (which you described first) is very simple, very straight-forward, and is what comes in OEM vehicles because it is cheap. also, they don't regulate or control torque transfer very well, which is why they hardly do anything at all.

Agreed, about all they do most of the time is make the wheels hop in sharp turns, and wear out the rear tires. But in a low torque slippery condition like ice under one wheel, and dry pavement under the other, they will let you drive right out like the ice wasn't there. You are out of luck if one wheel is slogging through deep mud, and the other is spinning in grease.

the more complex LSDs (which, one style, you described second) does a much better job at "torque biasing". there are many different methods (spring actuation, wedges, balls, cones, etc) for applying more torque per revolution, but they all are doing essentially the same thing.

but let's get back to 'torque bias'. this concept transmits a ratio of torque, not necessarily a force. you see, the simpler style of LSD only creates a certain amount of resistance. for example, say it takes 150ft-lbs of torqe to overcome the clutch pack on the simple LSD [and for the remainder of this post, i'm just using BS #'s for example sake]. that means that when a wheel loses traction, it will take 150ft-lbs of torque from the input torque and effectively transfer it (by resistance) to the wheel that has more traction. sometimes this is enough. often, it ain't jack and just gets you into further stuckness.

Yep! It is not enough torque for when one wheel is spinning, and the other wheel is slogging, like you get when you are plowing snow with one wheel, and the other wheel is spinning on some ice... there you are dead in your tracks. On the other hand, dry pavement on one wheel, and ice on the other, and you are golden.

...
diffs and traction aids are cool, and in some there's a lot of tech in them. ironically though, few have any "new" technology...

Clearly you have spent more time with LSD's than I have. I am a shade tree mechanic, not a pro. That doesn't mean I don't know how to turn a wrench... I have spent more than 30 years busting my knuckles... only that I know better than to try and earn a living at it. I took a different path.

Most of the major mechanical systems of cars seem to have frozen in time since the 1920's. There have been some incremental improvements, but any mechanic from the '30's would take one look at the major mechanical parts of today's cars, and feel right at home.

-Chuck

 

[greenjeepster]

You guys find some of the strangest stuff to argue over

 

[stumps]

You guys find some of the strangest stuff to argue over

Yeah, but we're having fun!

-Chuck

 

[BugEyeBear]

You guys find some of the strangest stuff to argue over

Its not so much "argueing" as it is establishing who is the "Deuce Alpha Male"!


(we really need a "popcorn" smiley here......)

 

[greenjeepster]

That would make me the deuce alpha male as I understand that a deuce does not have enough power to make lockers real effective and don't waste my time discussing them I just waste my time reading what you guys have to say about it

 

[mudguppy]

You guys find some of the strangest stuff to argue over

nah. at this point we are vehemently agreeing w/ each other.

 

[stumps]

That would make me the deuce alpha male as I understand that a deuce does not have enough power to make lockers real effective and don't waste my time discussing them I just waste my time reading what you guys have to say about it

Please help me to understand that! In first gear, low, my deuce could pull a house down. Why wouldn't it be able to effectively drive a locker? This is an honest question, explain it to me.

-Chuck

 

[armytruckdriverddsso]

I have a 68 GMC 1500 pick-up it has posi it drives completely different from limited slip like what was in my 98 Ford i had. It got stuck a the smallest chance. My GMC will plow past 4X4's

 

[greenjeepster]

haha, my evil plan to change the arguing topic worked.

Actually my logic is as follows:
Jeep Cherokee with 4.0 = 3000 lbs, 4 tires on ground, torque 300 ft lbs, hp 247. (numbers are not exact)

If somebody wants to build a trail rig with a Cherokee they usually will add lockers and replace the engine with a V8 in order to gain more torque.

Deuce with multi-fuel = 13500 lbs, 10 tires on the ground, torque 300 ft-lbs, hp 130.
(numbers not exact)

See the problems? You are putting 4 times the weight on less hp and equal torque. you are also powering 10 tires instead of 4 with less hp and equal torque. Essentially you can think about it as taking a Jeep Cherokee with a stock engine and lockers and reducing the effectiveness of the lockers by 4 X.

 

[stumps]

haha, my evil plan to change the arguing topic worked.

Actually my logic is as follows:
Jeep Cherokee with 4.0 = 3000 lbs, 4 tires on ground, torque 300 ft lbs, hp 247. (numbers are not exact)

If somebody wants to build a trail rig with a Cherokee they usually will add lockers and replace the engine with a V8 in order to gain more torque.

Deuce with multi-fuel = 13500 lbs, 10 tires on the ground, torque 300 ft-lbs, hp 130.
(numbers not exact)

See the problems? You are putting 4 times the weight on less hp and equal torque. you are also powering 10 tires instead of 4 with less hp and equal torque. Essentially you can think about it as taking a Jeep Cherokee with a stock engine and lockers and reducing the effectiveness of the lockers by 4 X.

Yes, but you are forgetting about the transmission. Put it in first gear, low, and you have torque galore. You are very slow, but if you can find some traction, you are moving. The lockers make the difference between a spinning wheel, and no traction, and some traction. The lockers mean the difference between moving and not moving.

All that V8 horsepower in the Jeep means one thing, and one thing only: You can go faster up a hill, or through the mud. I doubt the Jeep, even with the V8 can put as many foot pounds of torque out the rear axle as the deuce.

I don't know anyone who bought their deuce with the idea of winning a speed competition... but I know lots of guys that like the idea of not getting stuck.

My farm tractor has a grand total of 30HP, but I can pull a two bottom plow with it, and I can pull stumps out of the ground... it is slow, but it really pulls.. In first gear, my deuce is slower than my farm tractor is in first gear. And I can go even lower with the deuce by shifting the transfer case into low too.

-Chuck

 

[armytruckdriverddsso]

haha, my evil plan to change the arguing topic worked.

Actually my logic is as follows:
Jeep Cherokee with 4.0 = 3000 lbs, 4 tires on ground, torque 300 ft lbs, hp 247. (numbers are not exact)

If somebody wants to build a trail rig with a Cherokee they usually will add lockers and replace the engine with a V8 in order to gain more torque.

Deuce with multi-fuel = 13500 lbs, 10 tires on the ground, torque 300 ft-lbs, hp 130.
(numbers not exact)

See the problems? You are putting 4 times the weight on less hp and equal torque. you are also powering 10 tires instead of 4 with less hp and equal torque. Essentially you can think about it as taking a Jeep Cherokee with a stock engine and lockers and reducing the effectiveness of the lockers by 4 X.

This is right for driving on solid surfaces. If you are looking for traction on loss ground sand, snow, and mud, It will work fine that is why in national guard the added selectable air lockers. So we could unlock the diff's for HWY driving.

 

[mudguppy]

... that is why in national guard the added selectable air lockers. So we could unlock the diff's for HWY driving.

you got some info on these selectable lockers you keep talking about? because the only selectable lockers known for the deuce are 1) the norweigan deuces that require a lot of specialized parts and 2) ARB RD145 which have only been in existance for less than 2 years.


otherwise, i'm reaching for my flag...

edit: oh yeah, and i think there was a low pressure air-activated one made by a german company, but that's also in the last 5 years...

 

[greenjeepster]

Okay a couple of more points. First just because a military entity did it does not mean it is right. I am thinking of GIs with a jeep in a paper glider and then there was that rocket pack strapped to a guys back that they tried once

Secondly pull your specs on that tractor, or tell me what make and model it is so I can. At 30 hp I am betting it is a diesel which will mean that it is probably putting well over 1000 ft-lb at the motor. The multi-fuel is not a diesel, it is a compression ignition engine and they did not put out the torque of a diesel. They are much closer related to the diesel conversions that Buick had back in the same era as these trucks.

Also your deuce has a Power Divider on it between the two tandems. It, like a limit slip, is activated based on conditions of driving. It locks at a low speed and ties the two tandems together. It is there for crossing curbs and such. The axles are close together and when you get one set up on a curb or rock, log or what ever it lifts the other set enough that they will loose traction and the power would run to that axle. Now when you are running a 6x6 with a power divider and have limit slip or selectable lockers and you are moving slowly (idle speed) you are fine, But if you accelerate at all trying to get through soft sand or mud it disengages because of the increase in drive speed and you loose one of the tandems.

If you have the money and want to have the bragging rights that your deuce has lockers than by all means have at it. But they will not get you any farther than a deuce without them in the same circumstances.

 

[mudguppy]

wow, there's so many errors in this post....

... At 30 hp I am betting it is a diesel which will mean that it is probably putting well over 1000 ft-lb at the motor. ...

that is completely bogus!!! since Tq=(hp x 5252)/RPM, then RPM=(hp x 5252)/Tq. do the math and 30 hp with 1000ft-lbs crosses at 157 RPM. you need to show me a motor that will operate like that.

... The multi-fuel is not a diesel, it is a compression ignition engine and they did not put out the torque of a diesel. They are much closer related to the diesel conversions that Buick had back in the same era as these trucks. ...

no, it is still categorized as a diesel motor, since Diesel's design operates off of a compression ignition operating cycle. and the Buick abortion is also, categorically and functionally, a diesel.

... Also your deuce has a Power Divider on it between the two tandems. It, like a limit slip, is activated based on conditions of driving. It locks at a low speed and ties the two tandems together. It is there for crossing curbs and such. The axles are close together and when you get one set up on a curb or rock, log or what ever it lifts the other set enough that they will loose traction and the power would run to that axle. Now when you are running a 6x6 with a power divider and have limit slip or selectable lockers and you are moving slowly (idle speed) you are fine, But if you accelerate at all trying to get through soft sand or mud it disengages because of the increase in drive speed and you loose one of the tandems. ...

where did you get this stuff? take the top cover plate off of the top loader axle and you will clearly see that the input flange and output flanges are on the same pinion shaft. single piece, one shaft, no power divider, clutches or other voodoo.

someone has lied to you.

... If you have the money and want to have the bragging rights that your deuce has lockers than by all means have at it. But they will not get you any farther than a deuce without them in the same circumstances.

well, you obviously do not do much off-roading. because a 6x6 with open differentials is only 3 wheel drive. a 6x6 with locked diffs is true 6 wheel drive. this will get you farther than open diffs.

 

[greenjeepster]

wow, there's so many errors in this post....




that is completely bogus!!! since Tq=(hp x 5252)/RPM, then RPM=(hp x 5252)/Tq. do the math and 30 hp with 1000ft-lbs crosses at 157 RPM. you need to show me a motor that will operate like that.

Yes I should not have jumped off on this one. Comparing a farm tractor to a deuce is also pretty bogus. I am still interested what the torque rating is for his diesel tractor though and would love to see a you tube of it pulling stumps or powering six wheels.

no, it is still categorized as a diesel motor, since Diesel's design operates off of a compression ignition operating cycle. and the Buick abortion is also, categorically and functionally, a diesel.

look at the weight differences between a milti-fuel and a Cat or Cummings. The REAL diesel will be probably twice the weight easy. They are not the same animals. A diesel conversion is notoriously short lived much like the multi-fuel where a diesel will run 300-500 k miles between rebuilds. While they are technically a diesel just like a buick diesel conversion was, they are built lighter and cannot handle the torque that a real diesel can put out.

where did you get this stuff? take the top cover plate off of the top loader axle and you will clearly see that the input flange and output flanges are on the same pinion shaft. single piece, one shaft, no power divider, clutches or other voodoo.

someone has lied to you.

Okay I checked the NSN and it says "power divider not included" so lets scratch that I was told that they have one and from looking at the brake stand videos on youtube I assumed that that was enough to indicate that it did.

well, you obviously do not do much off-roading. because a 6x6 with open differentials is only 3 wheel drive. a 6x6 with locked diffs is true 6 wheel drive. this will get you farther than open diffs.

I was born off road and your above statement is like saying that an M37 and a stock Cherokee are both 4x4 so they will do as well as each other in a mud pit.

The deuce will do just fine on hard ground with lockers engaged as will one without. Get into a muddy situation where there is resistance against those 6 wheels and it is going to bog that engine out....

Think of it like a train locomotive, it can pull x amount of rail cars by its self, but you cannot double x without adding another locomotive. Essentially putting lockers on a deuce is doubling the work load to the engine. An engine that from design was under-powered to begin with.

 

[stumps]

Yes I should not have jumped off on this one. Comparing a farm tractor to a deuce is also pretty bogus. I am still interested what the torque rating is for his diesel tractor though and would love to see a you tube of it pulling stumps or powering six wheels.

You still aren't getting it! Torque is foot-pounds. When you add a reducing gear, like your differential, transfer case and transmission, you multiply the engine's torque by the gear ratio. There is an old guy named Archimedes (you may have heard of him) that said, give me a long enough lever, and I will move the earth.

Horse power is torque per second. It is a measure of how fast you can move things with your torque. My puny little farm tractor has a 30 HP gasoline engine. It is geared so that full throttle is a slow walking speed in first gear. It has as much torque as any 30HP engine, but because of its gearing, it can pull really hard, but only very slowly. A 300HP engine could pull as hard as my tractor, but 10 times as fast... or it could be geared to pull 10 times as hard, but just as fast.

look at the weight differences between a milti-fuel and a Cat or Cummings. The REAL diesel will be probably twice the weight easy. They are not the same animals. A diesel conversion is notoriously short lived much like the multi-fuel where a diesel will run 300-500 k miles between rebuilds. While they are technically a diesel just like a buick diesel conversion was, they are built lighter and cannot handle the torque that a real diesel can put out.

Someone is feeding you a whole lot of baloney!

The MF engine was built from a Continental diesel engine that was used in farm tractors made by Oliver, and after the merger, White. In the Oliver/White tractor, the engine was 17 to 1 compression ratio and turbocharged, it puts out 220HP, at 2200 RPM all day long. Farmers put 10,000 hours on that engine easily. The MF engine weighs in on the heavy side of 1600 lbs. Comparable horsepower CAT engines are much lighter. The only thing standing in the way of the MF engine putting out 300-400 HP is the high compression ratio.

Okay I checked the NSN and it says "power divider not included" so lets scratch that I was told that they have one and from looking at the brake stand videos on youtube I assumed that that was enough to indicate that it did.

No, sorry. The deuce has two rear axles that are simply daisy chained together. Each axle has a shaft that passes the power straight through to the axle following it. If you wanted to, you could couple a dozen axles together. I am told that there were military trailers with driven wheels available that coupled to the output shaft of the deuces rear axle.

I was born off road and your above statement is like saying that an M37 and a stock Cherokee are both 4x4 so they will do as well as each other in a mud pit.

The deuce will do just fine on hard ground with lockers engaged as will one without. Get into a muddy situation where there is resistance against those 6 wheels and it is going to bog that engine out....

Nope! It is all about speed. If I put the deuce in first gear, and the transfer case in low, full throttle is about the same speed as a little old lady in her walker. You could submerge the deuce in mud in first gear low, and it would spin all three axles all day long.

Horsepower is an indication of how --fast-- you can lift a weight, or push a load. If you are willing to move slowly, and are geared accordingly, you can move a tremendous load with very little horsepower.

Torque is mathematically derived from horsepower, and vice versa. You can turn great horsepower at high speeds into great torque by gearing the engine down. For instance: If you take a 300HP engine that develops 150 ft-lbs of torque at 4000 RPM, and put it through a 2 to 1 gearbox, you get a 300HP engine that develops 300 ft-lbs of torque at 2000 RPM. Put it through a 4 to 1 gearbox, and you get a 300HP engine that develops 600 ft-lbs at 1000 RPM.

-Chuck

 

[mudguppy]

... look at the weight differences between a milti-fuel and a Cat or Cummings. The REAL diesel will be probably twice the weight easy. They are not the same animals. A diesel conversion is notoriously short lived much like the multi-fuel where a diesel will run 300-500 k miles between rebuilds. While they are technically a diesel just like a buick diesel conversion was, they are built lighter and cannot handle the torque that a real diesel can put out. ....

LDT-465
Displacement: 478 ci / 7.8L
weight: 1650 lbs

Cat C7
Displacement: 441 ci / 7.2L
weight: 1425 lbs

Cat C9
Displacement: 567 ci / 9.3L
weight: 1650 lbs

Cat 3126
Displacement: 439 ci / 7.2L
weight: 1590 lbs

Cummins ISC/6CTA
Displacement: 506 ci / 8.3L
weight: 1630 lbs


look, i'm not arguing in favor of the multifuel - i think it's less-than-adequate in terms of reliability and service life and puts out insufficient power (hp & tq) for the size of the engine. it is what it is, and that's why i plan to repower my deuce w/ a 5.9 Cummins.

you have to admit that lockers and tire speed have no corelation at all. yes, the more traction you have the more strain you put on the motor. and w/ a motor that puts out tiny amounts of power, well, that's what all those gears are for. you don't need wheel-speed to get through every situation. if you have traction and the time to find it, a deuce and it's gears will get through.

 

[Recovry4x4]

Laymans terms or, words from an off roader. My deuce stuck on a muddy hill with 3 wheel ends spinning in the mud offers almost no resistance to the drivetrain. Adding lockers would only direct that power to the other 3 non spinning ends. I can assure you that in low range and first gear, the deuce has adequate power at the wheel ends to spin them. Add 10,000# to the truck and then perhaps it will limit power. I know that my 20,000# + wrecker sure lets you know its heavier when you try to spin the tires.

 

[stumps]

Thank you for digging up the correct weight on the MF engine. I will edit my post to reflect your number.

look, i'm not arguing in favor of the multifuel - i think it's less-than-adequate in terms of reliability and service life and puts out insufficient power (hp & tq) for the size of the engine. it is what it is, and that's why i plan to repower my deuce w/ a 5.9 Cummins.

In the White tractor, the engine the MF was derived from lasts basically forever. Plowing is a tough job, the White engine is rated to put out 220HP at 2200 RPM continuously.

I am certain that the MF's problems with reliability stem from a couple of things. First, a turbocharged 22 to 1 compression ratio is a brutal thing to do to an engine. Virtually all turbocharged diesels are in the 17 to 19 to 1 range. Second, the MF piston is a heavy thing. Third, the oil filters should never have been mounted upside down, and above the oil pan. The MF engine runs 12+ seconds with air being puffed through its bearings before the oil filter canisters fill up and provide oil pressure, and Fourth, the Fuel Density Compensator's tendency to leak and dilute the oil kills bearings.

It would be interesting to modify an MF engine back to the tractor engine it once was. It would put out 80 more horsepower and should last 500,000 miles easily. I personally think fixing the oil filter drain back problem will do the most towards making the MF a 500,000 mile engine.

you have to admit that lockers and tire speed have no corelation at all. yes, the more traction you have the more strain you put on the motor. and w/ a motor that puts out tiny amounts of power, well, that's what all those gears are for. you don't need wheel-speed to get through every situation. if you have traction and the time to find it, a deuce and it's gears will get through.

I think that 90% of the time just having the other three wheels contributing in a slippery situation would do the trick.

-Chuck