open vs limited slip diferentials.

[buddyIam]

I have read about differentials overheating. Is this a problem 'almost' exclusive to limited slip?

My new vehicle will be used a great amount of time on steep 2 lane winding mountain roads. I would expect that would cause higher than normal wear.

I have never needed a limited slip, but do plan on a lot of beach camping so will be buying a 4x4.

Would I be better off with a air locker etc. How do the air lockers act on patchy snow/ice covered roads?

I think adding a air locker after purchasing a limited slip truck would be a expensive way to go about things so any information on the air locker, such as lifespan vs a limited slip diff would be appreciated.

I just would like to stress other than emergency like situation(unexpected mud or snow) my only purpose for the 4x4 would be a few miles of beach driving. Even in the beach camping, 4x4 is only needed on the first approach to the wet sand and the U-turn and approach to the campsite.

I will be getting some sort of differential control and if I decide to camp deeper in the dunes I may install an air lock on the front.

I believe it is Eaton that makes a electric locker. What do you guys know about those and other locker.

Thanks in advance.

[Grit_dog]

Don't worry about getting a lsd axle. They are not problematic and will help you in the areas you describe. Especially if you're looking at 5500 trucks, ATs pretty heavy duty. I have yet to crack the rear diff open on dozens of trucks I've had with up to 150 k on them, except to change the oil.
If you're looking at lighter Fords 250/350 ( not sure if it's offerd in the 450/550 trucks), the e locker offered on the newer Fords is AWESOME! One of the best OE features of late IMO. Had one on my old 2013 F250 company truck up in ak and it worked great. Only works up to 20 mph then unlocks but it was sweet. Used it most every day in the winter just to drive up the driveway. With the Ford I could lock the rear and drive up in 2 wd, empty bed. Would have to shift my Dodge into 4 wd if I didn't take a run at it.

[buddyIam]

Oughtsix

Why would you say that? You don't have a clue what roads I have traveled. But i will tell you.
The places I camp only have access because of logging roads. From these logging roads I travel in 1 or 2 miles and camp in dispersed areas. These are basically jeep/4x4 trails. With some areas narrow enough that you must fold in your mirrors.
I camp in altitudes from 7000 to 9000 feet.
Because the forests are thinned occasionally the logging roads are well maintained in most cases. It is part of their logging permit to maintain these roads for public access in BLM/national forest.

In fact in popular dispersed camping areas the logging companies must come in and remove felled trees and widow makers left over from the winter.

That is my experience in California. Yours may differ.

In fact you should have said you don't have a clue about what I know.

[Wes_Tausend]

...

JIMNLIN,

Thanks for the info.

If I understand correctly, the Torsen type diff responds exceptionally well to slight braking to cause a torque transfer (began loading the helical worm-gears). To keep the front brakes from dragging to no use, the parking brake may be slightly engaged temporarily. If you ever do have a chance to experiment, I would be interested in hearing the results. Of course this is far from worry-free automatic engagement, but in a bind, perhaps a good card to hold if it works.

Reference:
www.ut.ngb.army.mil - HMMWV

Wes
...

[JIMNLIN]

By the exposed end-view of the ring-side helical worm-gears, and the adjacent gray bearing cap for the matching worm-gear set, we can conclude that JIMNLIN likely has the same helical gear set-up in his 2500 Ram. This is the highly touted, and bulletproof Torsen type differential that the military AM General HMMWV uses, so it was interesting to hear that it commonly slips with one wheel on ice. Now true, a Torsen type diff is essentially and open diff that relies on substancial gear drag to transfer torque to the wheel with traction; but in contrast, low friction Spider gears found in ordinary open diffs very easily allow one wheel to slip.

Yeah the Trac-rite was very controversial when introduced in the new '03 Dodge HD trucks. Lots of cussin and discussin threads on the subject on Dodge/Cummins forums at that time.

This from STAR Group;

The following is a S. T. A. R. Center Case Report:
Report created Jan 6 2004
Updated Jan 13 2004
STAR Group: Trans Core
Created by: G. Knapp
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 wheel on the pavement side. A slower start may be necessary to start the vehicles momentum. "
............................................................

The '01 Dodge/Cummins I had with the Dana 70 and I believe it was the Trac-Lok ??? worked great....just like the G80 GM while sitting still in the above conditions.

[Wes_Tausend]

JIMNLIN wrote:
Dodge went with the Trac-Rite GT which is a helical gear locker with the new '03 AAM 11.5" axles. Worthless piece of junk I've ever owned.
Now when sitting at a stop sign with one wheel on ice and the other on dry pavement your stuck with the wheel spinning away on ice. For this unit to work both wheels have to be turning.
In fact the owners manual says to apply the parking brake lightly so the Trac-Rite to work.
However the Trac-Rite is great for leaving two long black marks on dry pavement.

Now what the 4500/5500 uses I have no idea.

Bedlam wrote:

JIMNLIN wrote:
Now what the 4500/5500 uses I have no idea.

Ram uses the Dana S14-111L axle on these trucks. I do not know if Spicer makes the the LSD or someone else.

http://www.dana.com/wps/wcm/connect/dext2cv/commercial+vehicle/home/products/drive+axles/s110

http://www.dana.com/wps/wcm/connect/dext2cv/commercial+vehicle/home/products/drive+axles/s130

Thanks for the info, JIMNLIN, and thanks for the links Bedlam.

From Bedlam's 4500/5500 link, a photo:


By the exposed end-view of the ring-side helical worm-gears, and the adjacent gray bearing cap for the matching worm-gear set, we can conclude that JIMNLIN likely has the same helical gear set-up in his 2500 Ram. This is the highly touted, and bulletproof Torsen type differential that the military AM General HMMWV uses, so it was interesting to hear that it commonly slips with one wheel on ice. Now true, a Torsen type diff is essentially and open diff that relies on substancial gear drag to transfer torque to the wheel with traction; but in contrast, low friction Spider gears found in ordinary open diffs very easily allow one wheel to slip.

The G80, on the other hand, will supposedly lock up on ice, at 100 rpm max slip. Since the G80 uses a positive pawl engagement, there have been cases in the past where a rapid initial slip and violent engagement have broken these parts. They may be more robust, or softened by clutches, now. Note, at one time the breaking strength of Gleason Torsen diffs was a downside, but that has largely been overcome, since purchase by Eaton (Tru-Trac). The Torsen tech is either licensed now, or the patent has run out, as Dana is apparently using the principle.

Wes
...

[Bedlam]

JIMNLIN wrote:
Now what the 4500/5500 uses I have no idea.

Ram uses the Dana S14-111L axle on these trucks. I do not know if Spicer makes the the LSD or someone else.

http://www.dana.com/wps/wcm/connect/dext2cv/commercial+vehicle/home/products/drive+axles/s110

http://www.dana.com/wps/wcm/connect/dext2cv/commercial+vehicle/home/products/drive+axles/s130

[oughtsix]

buddyIam wrote:
My favorite camping spots are 1 or 2 miles of poor dirt road off of secondary roads, (much worse that logging roads.). Thunder storms can blow in, in a flash. But clear out just as fast. You can get snow just about any time of the year.

You have NO CLUE what a 10 year old logging road looks like. :S

[JIMNLIN]

Dodge went with the Trac-Rite GT which is a helical gear locker with the new '03 AAM 11.5" axles. Worthless piece of junk I've ever owned.
Now when sitting at a stop sign with one wheel on ice and the other on dry pavement your stuck with the wheel spinning away on ice. For this unit to work both wheels have to be turning.
In fact the owners manual says to apply the parking brake lightly so the Trac-Rite to work.
However the Trac-Rite is great for leaving two long black marks on dry pavement.

Now what the 4500/5500 uses I have no idea.

[RCMAN46]

I love all this mis information about the G80 from those who have never had or driven a truck with a G80.

If anyone is interested do a google search and get educated.

In most normal driving the G80 is an open differential.

It locks only when there is a difference of rpm between the two rear wheels of about 100 rpm (approx. 11 mph) at speeds below 30 mph.

With normal driving without full/heavy throttle the G80 will be a true open differential.

I may be wrong but I believe the only locking rear end that was offered with the Duramax was the G80.

[lbrjet]

I agree with Fordlover on the Ford LS, pretty much worthless.

[Fordlover]

limited slips are nearly useless in my experience (especially in fords). If you are in a really tight spot, they tend to act like open diffs, just spinning the tire with the least traction. My choice would always be: (in order from best to worst)
Locker
computer controlled Brake actuated traction control
limited slip
open diff

This is a bit of an over simplification, but it hits the high points. The G80 seems to act like a true locker, far more than a LSD. Not sure which it truly is though.

[Wes_Tausend]

carringb wrote:

ScottG wrote:


The "drag" is so minimal it is inconsequential or non existent - oil separates them and technically they do not touch. When they are not locked up there is nothing holding them back - they just freewheel. Other wise they would wear out quickly.
They do not get engaged until a ratio is met. Not even a little bit and it make no discernible heat.
What makes heat is heavy loading and lots of power - or abuse.

Personally I would never own a truck, especially a 2WD, without some form of LSD. Had one once and got stuck in the most ridiculous places.

Maybe you are confusing various limited slip and locker differentials. The most common LSD is a clutch-pack style. The friction surfaces are always in contact as long as there some pre-load (there usually is, and more can be added by adding extra clutch discs), and friction increases as torque through the differential increases.

I'm not saying anybody should skip on LSD for this reason. I'm just stating that it can add extra heat vs an open diff. I have observed in my vehicle, that curving 2-lane roads increase MY differential temps substantially over the same grade roads without curves.

Bryan,

I think you are right as usual. Looking a little closer, Scott is partially correct too. While both GM and Ford generally still use spring-loaded LS (limited slip) with some constant curvy-road drag, GM apparently does use a more positive locking mechanism in their Eaton G80, which might be an option. I found a good G80 article here that appears knowledgeable.

I suppose either a pin/ramp locking system (never seen one) or the above G80 might not generate excessive clutch-slip heat. The pin/ramp locker does have one other disadvantage identical to the Detroit Locker. The driving wheel is always on the inside of the curve when turning (outside ratchets/freewheels faster). This means that the inside rear tire is trying to turn the rear axle opposite of the desired steering direction which I found a debilitating nuisance in greasy mud. If the G80 truly locks, a similar steering problem could result with the inside tire trying to push the front straight during turns. But the G80 mechanism supposedly allows an axle difference of about 100 rpm pre-engagement which shouldn't affect turns. The G80 also supposedly entirely disengages over 30 mph. Maybe the G80 would not be too bad on highway glare ice if it allows one rear tire to spin as a warning, while the other maintains direction as does an open diff. My Ford Trac Locks sucked.

I don't know what Dodge/Ram uses, but my first guess would be constant spring/bevel gear loading which would heat as you say, and side-slip on ND icy interstates. Maybe Scott can enlighten us which type his truck(s) use(s).

Wes
...

[time2roll]

I have Eaton TrueTrak in both axles described a bit above as 'Torsen'.

These work incredibly well in sand, mud, snow etc. The huge difference is that TrueTrak both transfers torque and differentiates at the same time. This is noticed most when turning. Other lockers and limited slip attempt or do lock axles causing wheel slip and loss of lateral traction.

TrueTrak causes NO steering issues on the front. It just works. Yes all four wheels spin if I am on soft sand, mud, ice etc and hit the throttle.

Huge improvement from the OEM limited slip rear and open front axle. I can run with the ATVs in the mild dunes at Pismo Beach. No way with OEM set up.

Absolutely no maintenance or control system to fail and will outlast the truck.

[Sport45]

buddyIam wrote:
Carringb,

Is that the reason I hear of the limit slip diffs getting Hot? Would they get hot enough to cause poor lubrication in the type of mountain roads I am driving. It can be above 95 degrees even at 7500 ft occasionally. And of course well into the 100's in the foot hills. And this would be slow going in the areas of the hairpin turns.

It appears the Rams are all limit slip but a Ford with 4.10 for open diff is available.

I certainly don't like the idea of a external cooler.

It also appears that the Manufacturers make it almost impossible for you to pick a truck with everything you want. 🙂

I believe you are worrying unnecessarily. 99.9% (or more) of us don't monitor axle temps and don't have problems with them. Even on winding roads there's not enough difference in wheel speeds to make limited slip clutch action a significant contributer to temperature. Most of the heat is generated from the ring and pinion gears.