2nd Gen Non-Engine/Transmission Limited Slip Diff???

[Sarge]

I had the Diff fluid changed at the dealer recently for the recommended synthetic blend as I tow heavy often. The question is, how do I know if the LSD is working? Right after the change I went to a parking lot and did the "figure 8" test, but heard/felt nothing. Is there another test to tell if my diff is working properly? I made sure that the work order listed the friction modifier when I picked it up. Any help is appreciated. Sarge

 

[TowPro]

the best way to check it is lift both rear wheels off the ground, put the truck in Neutral, have somebody hold one wheel, and turn the other wheel. If it turns the drive shaft its not a posi.



Now the real question is "how much pressure does it take to make the posi clutches slip". I have heard as little as 35psi is OK in Dodges mind, but I can't find that thread so not 100% sure.



On my 2002, I was stopped on a hill, trying to go up the hill.

One set of rear wheels is on ice, and the other set is on dry and I hit the fuel, the one set will spin, but the posi will grab enough that the truck will also start to go forward.



Now if both wheels are "near" equal traction, they both will spin.



The rear builders have to come up with a compromise when building posi rears. If the clutches are to tight, the rear will cause one tire to squeal or feel like its skipping during dry traction turns, if its to loose it will let one wheel spin while standing still in low traction conditions.



Dodge will get more complaints from a rear that is to tight as you would feel it every time you turn, so they go on the loose side.



If you feel inclined, you can remove your posi carrier, and change the order of your clutch plates for more traction, at the expense of noise and strange feelings while turning in the dry.

 

[Gary - K7GLD]

Apparently, there is a spec whereby ONE wheel is held stationary while measured torque is applied to the other to measure the LS clutch slippage point - problem is in knowing what the "proper" torque figure is, and having the proper equipment to apply and measure it...



Many owners switching to alternate differential lubes, synthetics especially, just pour the stuff in, and if they don't get any LS "chatter" in turns, assume all is well - when in fact, the superior slipperyness of the synthetic has rendered their LS differential absolutely worthless as far as LS action is concerned.



A fairly decent "grassroots" test of LS differential action, is to place ONE rear wheel on a loose surface - wet, grassy, gravel, etc - and the other on a good dry surface, and then try to take off aggressively. If you get clear evidence of fairly equal traction to BOTH wheels - but no objectional "chatter" in other circumstances, things are probably OK. If after changing out LS differential lube, you detect annoying grabbing or chatter from the differential in sharp turns on dry surfaces, you probably need to add some of the DC spec LS friction modifier to obtain proper LS action...



I'd give you odds MOST owners haven't a CLUE as to whether their LS is operating properly or not...

 

[jtisdale]

And I'd bet...

Most owners dont know if they have one, or if they do, dont care if it works or not.

From my 01 service manual... note this may differ by year

With one wheel on the ground, and one off, if the torque is less than 30 ft. lbs or more than 200ft. lbs (to turn the tire in the air), the factory LSD should be serviced.





My 95 had a great LSD, you could whip donuts in that thing all day long. My 01 is a lot weaker. It seems to load and unload often. The dealer and I both checked it, and it lets go at almost 195ft. lbs. (either tire)

 

[Berrigan]

I heard you take 2 pieces of kitchen type wax paper and put it under one rear wheel. Then put a 2x4 in front of a front tire. Then try to drive over the 2x4. The rear tire with the wax paper should not spin if LS is working and you should be able to go over the 2x4. I never tried it though.

 

[Gary - K7GLD]

"Most owners dont know if they have one, or if they do, dont care if it works or not. "



HEH HEH HEH...



IF they were hitched to 7000 lbs or so of RV, and had to back up a 10% grade into an RV space with one wheel out in loose dirt and the other on pavement, I bet they'd start "caring", REAL quick! :-laf :-laf :-laf



BEEN there - DONE that - LOTSA times!



And THAT is why proper LS action IS important to THIS owner!

 

[KatDiesel]

I test mine.....



Floor it... . yep two black marks its working. Oo.

 

[Greg Boardman-RIP]

I agree with Kat... ... ... Rmm Rmmm EEERRRRRRRHHHHHHHH!!!!!!

 

[Sarge]

Gary, that's my point exactly. With 12k of fiver following me down the road, I'd rather not find out the hard way... .....

 

[One Old Dog]

I'm With kat Floor it.

 

[gitchesum]

Originally posted by KatDiesel

I test mine.....



Floor it... . yep two black marks its working. Oo.

4 marks here. Yep, it works

 

[TowPro]

Gary, I bet if you tried this in your new Dodge Posi you would be disappointed. Unless the dirt was real dry.



the next problem with this "limited" slip rear is once the clutches start to slip, as in when your stuck, they get hot and slip even worse.



They should define Limited Slip as "in NEAR EQUAL traction conditions, both wheels will attempt to turn. "

Originally posted by Gary - KJ6Q

"Most owners dont know if they have one, or if they do, dont care if it works or not. "



HEH HEH HEH...



IF they were hitched to 7000 lbs or so of RV, and had to back up a 10% grade into an RV space with one wheel out in loose dirt and the other on pavement, I bet they'd start "caring", REAL quick! :-laf :-laf :-laf



BEEN there - DONE that - LOTSA times!



And THAT is why proper LS action IS important to THIS owner!

 

[Gary - K7GLD]

I seriously doubt a stock LS is ever gonna perform like a true locker, and at the same time function as a reasonably "normal" differential - BUT, I *have* had occasion to "test" mine while towing our 5er when one wheel was in grassy mud and the other on packed gravel/dirt - AND on an uphill grade... Mild spinning of the muddy side for about a foot, then hauled right on out, somehing I would have had significant problems with in my older no-LSD '91...



It may NOT be the greatest - but it's a dern sight better than NONE - and even BETTER when it actually WORKS!

 

[Big Dawg]

I've got the limited slip on mine and had an experience with it the other day. I was on the beach in Daytona the other day when traffic stops right in front of me. When it starts again my rear wheels are in loose sand. I let off the clutch and get the chatter/grab which shakes the truck pretty good. I try taking off in 1st 2nd and 3rd and finally get loose in a few seconds. I'm guessing this is the LS trying to make up it's mind which wheel has the traction which neither one did so it just went back and forth from one wheel to the other. 500 foot pounds of torque didn't help matters either. Well LS is better than no LS and there are better alternatives out there... HOWEVER... I am NOT my own warranty station.

 

[Extreme1]

Big Dawg, that was probably wheel hop caused by leaf spring twist.



The service manual describes a test as above where you jack up one side and try to turn the other with a torque wrench (truck in neutral). You could do it yourself with a torque wrench, just add the length from the center of the wheel to the lug your twisting into the equation. (Use a lug that is at the three o'clock position).



After installing my LSD last year along with some super slippery synthetic lube, I began to notice binding of the LSD on sharp turns after a few hundred miles. I never did do the figure 8's.



This is the very same LSD that Okie-Go removed because it didn't work good enough for his application. I only had to add 1 ounce of the Mopar friction modifier to stop the binding on turns.



This newer LSD has the plates assembled in a different order than the older units, the change over was probably around '98 or '99. Re-ordering the plates would increase the friction surface area by about 50% (if my memory is correct). It is an afternoon job and doesn't require any special tools besides a torque wrench and a service manual.



Personally, I prefer to leave mine "loose" as vitually all of my towing miles are in the winter and I never take the truck off road enough to need it. Pulling my trailer on icy roads can get more exciting than the race I'm going to with a "tight" LSD.

 

[Big Dawg]

Extreme 1...



Yes I believe that you are right about the wheel hop. I did want the LS when I got my truck because I figured it was better than the alternative. By the way... whats wrong with doing donuts on the ice while towing a trailer. Where's your sense of adventure man?



I'm too stupid to be my own warranty station but I'm still smarter than those bag of rocks that work at the Dodge warranty station.

 

[Gary - K7GLD]

Hey - what can be more exciting than seeing the rearend of yer ride go past you as you spin helplessly on a slick surface - we spend good money for that sort of thrill at the amiusement parks... I've had a couple of close calls with limited slip differentials when I got too aggressive on poor surfaces - nearly got me killed...

 

[Big Dawg]

Gary...

Did you see the photos of the guy's truck that lost it and had a head on with a semi? Man that's a good one to keep in mind when driving on the ice 73's

 

[Extreme1]

Originally posted by Big Dawg

Where's your sense of adventure man?

I take care of that when I get my trailer to the track. I race an Arctic Cat F7 on ice in a cross country kind of environment. Very adventurous!

 

[Chris N5CWM]

It goes something like this..

Ssssssssss-smoke em!