limited slip question

[SGBARRACUDA]

Well today I decided to rotate my tires on my 03 DRW 3500, what a job that was. While i had the rear end in the air i decided to verify that my truck was a posi. Big surprize, when I turned one side of the duals the other side turned the opposite way! So I started it up ,put it in gear and figured I would try and stop one side from turning and that would prove my suspicion that I had a open rear and not posi, sure enough I was able to stop the one side with my foot! I double checked the info sheet in my glove box and sure enough it came with a limited slip rear! Does anyone know what type of posi the American Axle uses? Am I right in assuming that I have a non posi rear?

Also checked my ball joints and they are bad . 026 verticle play on the right side and . 023 on the left.

 

[JCleary]

I have been told it's a Torsen diff, meaning Torque-Sensing. These diffs are different in that they use gears instead of a clutch pack to create the limiting effect. They work only when both wheels have some traction. At that time, pressure is exerted on the gears, and they stop rotating at different speeds.



Here's a link to a long-winded explanation:



http://www.sonic.net/garyg/zonc/TechnicalInformation/TorsenDifferential.html



Basically, when one wheel is spinning faster than the other, but a load is still present (any time your tires aren't in the air) the gears will spread, or push against each other. This creates friction which causes both axle shafts to spin closer to the same speed. How much torque is transferred is based on the engineers' calculations.



They work very well as long as your wheels are in contact with the ground...



Theoretically.



My limited slip 2500 did a peg-legger around a corner the other day. Kind of surprised me.

 

[Jengle]

My 04 spins both quite well. Haven't done any pegleggers yet. Guess its still holding in at 36k. I got the 3. 73 LSD rear. No whine or other problems. Wait, I take that back. It is very good at the usual bunny hop, once it gets started. Need a set of ladder bars.

 

[Gypsyman]

Ditto on the bars...





or maybe a Kelderman 4 link!

 

[JHardwick]

I have been told it's a Torsen diff, meaning Torque-Sensing. These diffs are different in that they use gears instead of a clutch pack to create the limiting effect. They work only when both wheels have some traction. At that time, pressure is exerted on the gears, and they stop rotating at different speeds.



Here's a link to a long-winded explanation:



http://www.sonic.net/garyg/zonc/TechnicalInformation/TorsenDifferential.html



Basically, when one wheel is spinning faster than the other, but a load is still present (any time your tires aren't in the air) the gears will spread, or push against each other. This creates friction which causes both axle shafts to spin closer to the same speed. How much torque is transferred is based on the engineers' calculations.



They work very well as long as your wheels are in contact with the ground...



Theoretically.



My limited slip 2500 did a peg-legger around a corner the other day. Kind of surprised me.

nice link, I saved it in my favorites

 

[SGBARRACUDA]

The reason I ask is the other day I pulled a friend of mines wrecker out of the mud and while it took a few trys I did get him out. But he told me that only one rear was spinning? Is there a "road" test to verify this LSD is working?

 

[JCleary]

Perhaps the fact that one wheel was spinning indicates that in fact it is working. One wheel has to spin in order for the torque to transfer to the wheel with traction. It should transfer enough torque to provide forward motion, unlike a locker which always splits 50/50.



More spinning = more torqe transfer



I guess one way to check is to do a brake stand (automatic) or an aggressive take-off in 2nd gear on a manual. To avoid damage, I'd do it on gravel or dirt. With the Cummins you should have enough power to spin both rears.



Two black patches = working LSD

One patch = open diff



Anyone else have a suggestion? I know on the older limited slips you could spin one wheel with the axle lifted and the other would move the same way, but not on these.

 

[GerryDrake]

Count the tracks

30-35 mph on a dirt road, 3rd or 4th gear, I stand on it and look in the mirror. . 4 tracks, and I conclude it is working... (also, it doesn't go sideways)

 

[SBall]

I envy you guys!

Unfortunately my truck has the old LSD that uses clutch packs. I'm led to believe the helical-bevel differential in your new trucks is closely related to the torsens. The torsens are the most elegant approach to LSD, with no clutchs to wear out and transfer torque immediately. Torsens have this spec referred to as the bias ratio, which dictates how much torque is applied to the wheel with grip, as compared to the wheel that is spinning. For example, a LSD with a bias ratio of 5:1 suggests you'll have 5x the torque on the wheel with grip as you have on the wheel that's spinning. Consequently if you have tires with good traction, the Torsens work even better.

I have a Miata with a Torsen. With street tires, both rear wheels spin easily on snow and ice, but with Blizzack snow tires on the Miata, the traction is nothing short of amazing! Most car and truck manufacturers today prefer to add a few lines of software code to their anti-lock braking computers to implement traction control in a more cost-effective manner, in lieu of the more sophistacated mechanical solutions like the Torsens. Like I said before, I envy you guys with the newer rear axles.

 

[SGBARRACUDA]

Well I'm not so sure I like this approach to LSD, because when I was pulling the wrecker out it wasn,t that one tire was spinning while I was making forward progress pulling it out, I was standing still while it was spinning, which means to me that the non spinnong wheel was not aiding in the effort, wouldn't you say?

 

[p-Bar]

Well I'm not so sure I like this approach to LSD, because when I was pulling the wrecker out it wasn,t that one tire was spinning while I was making forward progress pulling it out, I was standing still while it was spinning, which means to me that the non spinnong wheel was not aiding in the effort, wouldn't you say?

I concure , with all the rain we have had in SO. Ca I backed up to my barn (mud driveway) just about got stuck and only 1 wheel would spin . What a bunch of crap. What would the dealer do to test??

 

[gsbrockman]

Here's a link to a long-winded explanation:



http://www.sonic.net/garyg/zonc/TechnicalInformation/TorsenDifferential.html

I required some Tylenol after reading that explanation. :-laf

Greg

 

[24vHO2004]

My truck would do the exact same thing. Sometimes it would and sometimes it wouldn't. The only problem is when I need both to move is the time when it wouldn't. However at 40,000 miles things seem to be better. I don't know if maybe it just had to break in or what. I was in a mud hole the other day that typically I would have needed 4 wheel to get out of, but both wheels were spinning and I moved pretty easily.

 

[p-Bar]

Well I guess I'll let it "Break In" Haha

 

[JVolpe]

Well at the track when I power brake a little boost both 315s spin at the same time. Same amount of rubber on both mud flaps and wheel well.

 

[NSperduto]

It's most likely an LSD, but the way the LSD operates in these trucks it's pretty much a waste of money especailly if you have 4wd, because when you really need the lsd to get out of a slippery spot, it doesn't work worth crap.



We just have 6 or 8 inches of snow last night. I have both truck parked in the long dirt driceway to my barn.

Anyway. The Dakota is the first truck in line, the ram is behind it. I snowblow the driveway, then clean off both trucks, get into the Dakota. it's in 2wd, start it, put it in drive, ease on the pedal and pull right out of the driveway with 0 tire slip at all.



I get in the ram in 2wd, start it, ease on the pedal and the wheel is spinning and I'm going nowhere. When I say nowhere, I mean, not even a foot. So I adjust the mirros so I can see the wheels and the left one is sitting there and the right one is spinning away. So I start rocking the truck to see if I could get it out of the spot, at one point I hear a small clunk type noise and now the left wheel is spinning and the right wheel is doing nothing. Which says to me the LSD is working. I sit there rocking it and I can't even get it out of it's parking spot. So I had to put it in 4wd, just to move.



At that there is why I say the LSD in these trucks sucks. The only thing I can try is going from the bfg long trails to the a/t's but I doubt it will make that great of a difference.



Nick

 

[SSage]

Our dually has never failed to spin all the rear tires on road or off. Maybe its a defect on some trucks, this is the best LS I've driven. I got stuck on a muddy hill two weeks ago. The rear tires spun at the same speed even though the drivers side rear had more traction. The truck was climbing an off camber hill with the drivers side taking most of the weight. The open front acted normal when the front left dug in stopping the truck while the right front was on hard ground doing nothing.



I wish Dodge would give us a selectable locker up front like the power wagon. I'm happy with the LS in rear so far. I can smoke the rears on pavement in turns pretty easy. I run off road at least once a month and the rear will fish tale, step out and such just like my locker equipped 98.

 

[FOXY005]

Found this on another Diesel site, and thought it would be of interest to all 3rd Gen Owners with LSD's









The following is a S. T. A. R. Center Case Report:

Report created Jan 6 2004

Updated Jan 13 2004



Customer says his trac-rite rear diff is not working?

GCK1: 01/06/2004

Recommendation/Solution

Review AAM Trac-rite diff characteristics. Rear diff is working or truck wouldn't move. It will overrun like standard diff if operating on extreme differernces in surfaces. (Ice under one rear tire with other tire on dry pavement. ) No further action.

:GCKI:01/06/2004

The 2003 heavey-duty Ram uses and American Axle helical differential or Trac-Rite. The Trac_Rite differential is different then Trac-Lok in that it uses helical gears (Trac-Lok uses clutches) to transfer power to the opposite wheel when slippage occurs. The transfer of power from wheel to wheel is torque sensitive and must have both wheels spinning (not stationary) to function. It is possible for the Trac-Rite differential to not send power to a wheel if is not spinning. Example: Accelerating from as stop and one wheel is on ice and the other on dry pavement. If accelerating to fast, the wheel on the ice may spin and never send power to the whell on the pavement side. A slower start may be necessary to start the vehicles momentum.

A written test procedure for Trac-Rite is not listed in the repair manual and the following points should be noted:

Testing the Trac-Rite differential while the vehicle is lifted and turning one wheel by hand, the opposite wheel will turn in the opposite direction. This is normal.

If the Trac-Rite assembly has and internal failure it will lock axles 100% side to side.

To test the Trac-Rite process, raise vehicle on appropriate lift, place into gear and accelerate quickly (hard launch). A second technician will witness both wheels turning at the same speed at the start of the acceleration.

Another test for Trac-Rite is to slowly drive vehicle in an open area and completely turn wheels to one direction and accelerate hard. . The vehicle will experience tire hop or shudder. This is normal. Trac-Rite differentials do not require friction modifier and should be used only with SAE75W-90 GL-5 synthetic fluid PN 05102232AA.

The Trac-Rite differential found in the American Axles may look like the helical gears have ground away the case. Six small half circles are noticable on the side of the differential opposite of the ring gear. These openings are desinged for oil flow and are not the result of the helical gears grinding through the differential. Please do not replace the differential case or any other part of the axle due to these openings.

Note: All American Axles require Mopar lube part# 05102232AA synthetic and does not use a friction modifier.

RAB40: 01/13/2004













Looks like both rear wheels must be rotating for it to operate properly , so not much help starting out on a slippery surface in 2WD.



Nothing like the old positraction with clutches the way I read it.

 

[SSage]

So, if one wheel has traction and one does not, the LS is just like an open diff? That does not make sense, when I pull onto pavement from a dirt shoulder I do not get the peg leg effect. I don't get much more wheel spin from one side when starting out on any surface. If I punch it with one side on gravel I still move with out gross wheel spin or the one leg feeling.



Am I'm unique? The LS works like an LS on my 03.

 

[JKlopp]

The limited slip in the new trucks works very well if you understand how to use it. It will act like an open if one wheel is on ice and has NO traction. Each wheels must have some traction to get the full effect or transfer of power to both wheels. The differential can not tell what is causing the apparent traction or load on each wheel. All you need to do is slightly set your emergency brake and the torque will be split to both wheels. It will closely match the traction of a locker. Try it, you'll like it, and just like a locker you will slide sideways.