American Axle Limited Slip with photos

[sag2]

OK, I did a search using "limited Slip" and went back to 2004. I didn't see any posts with a good explanation of how the TracLock differential works. Many bad mouth it, but once you see and understand how it works, you will see that the torque handling is probably superior to a clutch design. Also once you see how it works, you will understand why it requires special fluid WITHOUT friction modifier, PN 05102232AA.
I couldn't get my markup program to work, so I'll just have to explain it best I can. Sorry for the fuzzy photos, didn't have my camera with me at school so had to use my phone.
The first photo shows the two helical gears, the two "brakes" that are the silver piece at the end of each gear, and one side gear that the axle goes through. There is a second side gear that the other axle splines to. The helical gears (6), and the brakes (6) reside inside the carrier. If there is no difference in wheel speed, all the pieces rotate together with the differential housing.



The next photo shows the parts in the differential. Note that the side gear meshes with only one of the helical gears (there are three such sets), and the brake has a clearance cut out so the side gear misses it. At the top of the photo is where the opposite side gear would be, and it meshes with the other helical gear and misses the brake.


The third photo shows just the brake installed in the differential. Note the relief notch cut into the brake. It is in the hole to the left, and the notch is in the 2 o'clock position. That allows the oil film to get out from between the helical gear and the brake so the helical gear will stop trying to rotate. This is where the proper fluid comes in. In order to work, the gear has to "punch through" the fluid film on the brake and stop the spinning. Friction modifier is slippery and it keeps the brake from working properly.

Now this is how it works. Picture one wheel (side gear) spinning on a loose surface. The helical gears are spinning opposite directions, and they want to push each other apart (each one toward their respective brake). If there is some resistance to rotation (the other wheel has some traction, vehicle brake applied slightly) they want to push apart really hard. That stops the rotation of the helical gears (because they are pushing hard on the differential brake) and essentially "locks" them together. Since they are locked together, and the side gears are in mesh with the helical gears, both side gears and the axles have to spin at the same speed. And the more resistance applied to both wheels makes the helical gears push that much harder against the brake, allowing lots of torque to be passed through to the axles.

I hope this was a clear enough explanation, if not ask away.

 

[Yo Hoot]

My only question is if the oil sheers away won't the ends of the helical gears/brakes wear out quick?

Thanks for posting this. Actually the correct name is TracRite GT. Here is the AAM page with a cutaway pic...

American Axle & Manufacturing (AAM) - TracRite® Axle Differentials

#ad


TRAC-RITE DIFFERENTIAL.....

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 heavy-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 noticeable 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

 

[steved]

While they don't "require" LSD modifier, sometimes it is added to prevent chattering. I ran 85w140 Royal Purple for many miles (I believe about 150k) and recently changed to 75w140 Schaeffers #267... immediately experienced LSD chatter. After researching on this forum, it was noted that DCX would add LSD modifier for those owners/trucks experiencing chatter. I acquired two 4-ounce bottles of LSD modifier from a local Dodge dealer because I have an extra capacity cover, and added only one... it hasn't chattered since. There was almost no debris visible on the magnet, and the Royal Purple I drained looked like new after 150k.



I also found that my Trac-Rite did not function (at all) until three years after I bought the truck... in 2007, I was towing well over 10k and within 100 feet of the place we loaded the trailer I experienced a loud "snap" from the rear differential... the LSD has performed flawlessly since (and as good as the trac-loc and power-loc used in the Dana's).

 

[Yo Hoot]

While they don't "require" LSD modifier, sometimes it is added to prevent chattering. I ran 85w140 Royal Purple for many miles (I believe about 150k) and recently changed to 75w140 Schaeffers #267... immediately experienced LSD chatter. After researching on this forum, it was noted that DCX would add LSD modifier for those owners/trucks experiencing chatter. I acquired two 4-ounce bottles of LSD modifier from a local Dodge dealer because I have an extra capacity cover, and added only one... it hasn't chattered since. There was almost no debris visible on the magnet, and the Royal Purple I drained looked like new after 150k.



I also found that my Trac-Rite did not function (at all) until three years after I bought the truck... in 2007, I was towing well over 10k and within 100 feet of the place we loaded the trailer I experienced a loud "snap" from the rear differential... the LSD has performed flawlessly since (and as good as the trac-loc and power-loc used in the Dana's).

I'm confused. Why was it working for three years?

 

[steved]

I'm confused. Why was it NOT working for three years?

I assume you meant to say that...



I never had any posi-traction "action" for the first three years I owned the truck (from new) until I towed heavy that one time... has worked great ever since. I had it to the Dodge garage three times regarding no operation... there is no real "test" to verify it is working correctly. I can tell you it was a night and day difference going from it not working to when it started working...



I can only assume something was "hung up" in the Trac-Rite differential and needed that load/torque to pop it free???

 

[Yo Hoot]

Yes that's what I meant. Take a look three posts up. It explains how to determin if it's working. I use Redline 75-90. I can lay posi routine. Notice the type of lube they recommend... . GL5 75-90. Redline does contain additive though but it works for me.

 

[steved]

It only states that it will lock solid if it malfunctions... mine would only spin one wheel or the other before the "snap". I can lay two strips at will currently, since it snapped. I don't know if they ever tested it... just gave me the "it works fine" answer.



I was using RP 85w140 at that time, the same fill I only recently drained... so it was not the gear oil.



Like I said, I feel something was hung up in mine; and it took that load to place enough "torque" on it to break it free. Probably an abnormal situation. If you read early posts of mine, you would find where I stated I felt the Trac-Rite was useless (because it most likely wasn't working)... since it started working correctly, I feel it was a good replacement for the Dana options.

 

[steved]

As for the chatter... it seems hit/miss with these trucks. I didn't have it until I switched to Schaeffers... and then I got it bad (felt like two pieces of rubber sliding past each other).

 

[mhsmith57]

What about an electronic differential lock for my 2005 3. 73 11. 5" AA limited slip differential? Wish Dodge included a locking differential in thier trucks rear ends, don't want to buy a 4x4.

Mark

 

[AH64ID]

I am a huge fan of the OEM LSD, it works better than any other LSD I have driven. . In fact until I drove this LSD I wouldn't own an LSD, and would have paid to have one removed, they are useless and unpredictable on ice.

While they don't "require" LSD modifier, sometimes it is added to prevent chattering. I ran 85w140 Royal Purple for many miles (I believe about 150k) and recently changed to 75w140 Schaeffers #267... immediately experienced LSD chatter. After researching on this forum, it was noted that DCX would add LSD modifier for those owners/trucks experiencing chatter. I acquired two 4-ounce bottles of LSD modifier from a local Dodge dealer because I have an extra capacity cover, and added only one... it hasn't chattered since. There was almost no debris visible on the magnet, and the Royal Purple I drained looked like new after 150k.



I also found that my Trac-Rite did not function (at all) until three years after I bought the truck... in 2007, I was towing well over 10k and within 100 feet of the place we loaded the trailer I experienced a loud "snap" from the rear differential... the LSD has performed flawlessly since (and as good as the trac-loc and power-loc used in the Dana's).

As for the chatter... it seems hit/miss with these trucks. I didn't have it until I switched to Schaeffers... and then I got it bad (felt like two pieces of rubber sliding past each other).

Based on the helical design there is no physical way what you encountered was chatter. I would guess that something in there didn't like the Schaffers, and I wouldn't run it if it makes a helical LSD make noise. Chatter is uneven slipping of clutch disks, and as there are no clutches in the OEM LSE, you can't have chatter.



I have no doubt that additive fixed your issue, or that you had a friction issue in your axle, but its not chatter and I would blame the fluid, not the LSD.

 

[Yo Hoot]

What about an electronic differential lock for my 2005 3. 73 11. 5" AA limited slip differential? Wish Dodge included a locking differential in thier trucks rear ends, don't want to buy a 4x4.

Mark

I believe there is one available for the 10. 5" rear but not ours.

 

[p-Bar]

ARB has the 11. 5 out for the Dodges now.

 

[AH64ID]

With the weight of these motors the locker in the front would be far more effective. And you can get the 9. 25 elocker. .

 

[steved]

Based on the helical design there is no physical way what you encountered was chatter. I would guess that something in there didn't like the Schaffers, and I wouldn't run it if it makes a helical LSD make noise. Chatter is uneven slipping of clutch disks, and as there are no clutches in the OEM LSE, you can't have chatter.



I have no doubt that additive fixed your issue, or that you had a friction issue in your axle, but its not chatter and I would blame the fluid, not the LSD.

You need to do a little research before you make uneducated claims... :-laf You obviously have no idea how ANY LSD operates... if it has a clutch (or shoe in this case), it can chatter.



I've explained this way too many times before... not wasting my breath again.

 

[steved]

With the weight of these motors the locker in the front would be far more effective. And you can get the 9. 25 elocker. .

Hmm, lets place even MORE stress on the weaker of the two axles...

 

[AH64ID]

You need to do a little research before you make uneducated claims... :-laf You obviously have no idea how ANY LSD operates... if it has a clutch (or shoe in this case), it can chatter.

I've explained this way too many times before... not wasting my breath again.

I've done plenty of research on it, it shouldn't chatter. Its the beauty of a helical gear LSD. Probably the reason that the manual states in bold that friction modifier isn't necessary, its not; if you chatter you have other issues.

But we also disagree on the weight of oils to run in the axle, and I've done my research there too, for all I know the 140 wt helps induce the chatter?? Don't know since you ran the redline without issue??

Hmm, lets place even MORE stress on the weaker of the two axles...

If driven correctly its not an issue... I have seen plenty of times where a rear locker in a pickup is useless as there is less weight on the rear end, throw the tq of a diesel in there and the situation gets worse.

I have ran more locker/e-locker/LSD combo's than I recall, but there are very few I will continue to run. My preferred setup is open, selectable that defaults open, or helical gear.

 

[sag2]

bump to top

 

[rbattelle]

Based on the helical design there is no physical way what you encountered was chatter.

Generally speaking, I would agree, except to say the improbability of chatter is based on the use of brake shoes rather than clutches, not because of the helical nature of the gearset. Symantics, I suppose.

if it has a clutch (or shoe in this case), it can chatter.

This is an interesting thing to think about, actually. The basic question here is, can the brake shoes in this differential chatter? And, if so, would we expect it to sound the same as chatter in a traditional plate-type clutch arrangement?



Although I find it unlikely that the brake shoes in this thing would chatter, I am willing to accept that it's possible.



If we accept that they can - and do - chatter under the right circumstances, however, it seems unlikely that the sound would be anything like a traditional plate-type clutch pack, which makes you wonder whether the operator would correctly identify the sound as LSD chatter.



I like these torque-biasing differentials! Here's a simple explanation of how they work.



I think a lot of people hate them because they forget that the product of anything and zero is zero!



-Ryan

 

[sag2]

They do chatter, and it is because of a slip/stick of the brake "shoe" portion of the helical gear. That is why the correct lube is important in this diff.

 

[rbattelle]

They do chatter, and it is because of a slip/stick of the brake "shoe" portion of the helical gear. That is why the correct lube is important in this diff.

Fair enough, I believe you!



-Ryan