2 pages of hashing it out... all for what? Bottom line is the owner's manual specifically says to use synthetic...and if you don't, they can deny warranty if they want to when your stuff blows up.

BTW... after all my years worth of experience with GM, Ford, and Chrysler... only Chrysler has had numerous differential problems on many of their 4x4s. So the bit about them using "timken and spicer" parts isn't worth a hill of beans.

The Ram 1500 is Chrysler's cash cow. Go visit a dodge truck forum sometime and see how many guys have had their rearends grenade. It's almost epidemic.

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2005 Stone White KJ Limited CRD 4x4
Off-Road Pkg
Trac-Lok
Emu 790s/948s
Skyjacker H7088s rear/Bilsteins front
15x7 Black Rock Lobos/31x10.50 Firestones
GDE HOT Tune + TCM Tune
Euro TC
CB radio
Thrush Turbo muffler
AEM DryFlow filter

It does not specify only to use synthetic in the owners manual and 12k-15k drain intervals are in force.

And why do you think so many rear diffs have blown up? Nissan had the same issue on the Titans also.It's the type of gear lubed used,yep synthetic is the common factor in all of those trashed diffs.

You are hilarious, you really are, but the owner's manual does state synthetic 75W-90 or synthetic 75W-140. I don't know why you pretend to be an expert on the CRD.

You need to learn that repeating a thing over and over is not what makes it true. You made the statement that syn gear oil doesn't transfer heat as well, so the burden of proof is on you to back that up with some data. You seem to ignore the data I provided that refutes that. And you say that somehow this rule doesn't apply to syn motor oils? They're made from the same base stocks genius.

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05CRD: GDE Hot ECU & TCM tunes, Provent, Cat filter, Facet lift pump, TransGo kit, Florida TC, Samcos, stainless brake lines, HDS thermostat, Renegade light bar,
RL super sliders, Bilstein adjustables, Al's Gen 4.5 Arms, 235/85-16 Duratracs, DTT rear, Elocker front, EVIC+TPMS, Turbo timer, McNally pillar gauges, Weeks Stage II kit.

Think it simply could be a poorly designed differential on Chrysler's part. My brothers differential in his '98 Dodge Ram 1500 broke a few teeth off the spider gears which then messed up some other stuff. I know for a fact that convential gear lube was used in it.

This is like arguing whether a car runs better if it's painted blue versus red. It's probably the design, or someone didn't do the preload or shimmed it exactly as needed.

This falls in the same realm as engine oil. As long as it is quality stuff, the most critical factors are that it has the proper amount in it and it was changed at some frequency.

My owners manual does not state any syn to be used.I have given proof,call the axle manufacturers for there "wording".

Oh and forced lubrication is not the same as a "splash" lubricated system,2 totally different requirements for proper lubrication.

Half this debate is over my head, but I can contribute this much. Straight from the 2006 FSM:

Axle Differential (Front):
Mopar Gear & Axle Lubricant (SAE 80W-90) or equivalent.

Axle Differential (Rear):
Mopar Synthetic Gear Lubricant (SAE 75W-90) or equivalent. For trailer towing, the lubricant should be replaced with Mopar Synthetic Gear & Axle Lubricant (SAE 75W-140) or equivalent. Models equipped with Trac-LokTM require a limited-slip additive.

So yes, the manual DOES recommend synthetic for the rear differential.

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2006 Jeep Liberty CRD, Limited
GDE Eco Tune, GDE TCM Tune, Bauer 203* Tstat, Amsoil EaA 201 Filter, Clean MAP, Samco CAC Hoses, Magnaflow Muffler #12226.
New Mopar Fuel Filter, K&N Filterminder, Fumoto Oil Drain Valve
225/75R16 Hankook Dynapros

I've heard this before too. Some of the testing used is different too. However, I don't know the details. Can you explain? Do you have any references to journal or SAE papers? Will be peer reviewed and the least biased of the available sources. Spare us the testimonials and sales sheets from manufacturers.

Seriously Troy; are you going to hold on to this one?

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Manure green 2005 CRD sport4x4, GDE Hot tune, Cat Gut, OE skids, Draw tight hitch, Duramax lift pump, 160K on multiple varieties of fuel, XM radio, Escort live with Redline, fog light mod, GPS, Icom IC7000 all band radio call sign KC9QPF, Grabber AT2s on Soft 8s, FIA grill blanket.

I'm still waiting for an explanation on why back in the day, we NEVER EVER changed rearend grease and NOTHING happened to it in 100K miles.

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2006 Sport CRD

Could the Aztecs have known, that in 2012 after a 4 year experiment, our country would cease to exist?

The 05 manual states to use 75-140 synthetic for front and 75-90 for rear(for towing 75-140 synthetic.
I use 75-140 synthetic front and 75-140 dino rear.
Seems the specs change from year to year

Hrm... I wonder why this is. Are the components slightly different or does it even really matter? Looking back over this thread, I notice that a lot of the more-knowledgeable-than-me folks on here are using non-spec fluid weights, front and rear.

I honestly don't know what to use... For someone who does little to no towing and doesn't plan on changing his diff fluids until 50k (about 15k from here)

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2006 Jeep Liberty CRD, Limited
GDE Eco Tune, GDE TCM Tune, Bauer 203* Tstat, Amsoil EaA 201 Filter, Clean MAP, Samco CAC Hoses, Magnaflow Muffler #12226.
New Mopar Fuel Filter, K&N Filterminder, Fumoto Oil Drain Valve
225/75R16 Hankook Dynapros

Because "back in the day" the average 350 V8 in your "Chivalay" pickem-up put out maybe 180hp? The 1/2 ton truck of today probably can out-haul a 3/4 ton from 25 years ago. The speed limit was 55mph. People weren't towing enormous 5th wheel trailers or huge boats and campers nearly as much, and wheel/tire sizes have gotten pretty absurd.

What hasn't changed much? The axles. As far as I can tell, a 1/2 ton truck still has the same basic axle they've had forever. Looking under a Tundra or Titan pickup it looks like a joke - this little skinny axle that looks like it came off a '75 Datsun B210.

So now we have these big, heavy 1/2 ton trucks running 350-400hp STOCK, pulling far larger loads at higher speeds and with big, heavy rims and tires. That poor wimpy little diff doesn't have a chance, and with the source of the gears and bearings likely being China or India, I'm not surprised they are turning into a pile of metal chips.

I used to work in a quick lube in college in the early 90's. We checked every rear end for fluid level and condition. MANY of them were either foaming badly, milky, or had turned into this evil smelling black goo. Didn't matter what brand or model, all had issues. The fact that none had blown up yet was simply due to the fact that a Ford 9" behind a 300 CID six could probably run dry and not burn up.

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'02 Jetta TDI Wagon 5 spd (mine)
'10 Outback (her's)
'05 CRD Sport (hangar queen)

I don't do scientific papers,most do not apply to real world.

Dyno gear oil was used "back in the day",and syn is most used today in diffs.

Far from it,besides toyota and nissan which suck anyways.The diffs of today are different,not that they are weaker they just have to be lighter to meet CARB standards.Less material means less ability to cool and in a splash lube system you do not want synthetic otherwise you burn up the bearings.I most regardes the older trucks and FSJ's are 25%+ heavier then today's trucks and SUV's.

No, my day was in the 1960's and we had over 150 HP vehicles. It didn't matter if the rearend was in a Boss 302, or a Superbird. The speed limit was 70 everywhere 2 lane or 4 lane.

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2006 Sport CRD

Could the Aztecs have known, that in 2012 after a 4 year experiment, our country would cease to exist?

Uh yeah...think the engineers and scientist just whip something up and put it in the application or something? There's a lot of testing that goes into this stuff. If there was a correlation to a particular product accelerating damage to things, that company would be getting sued.

Just because it's in a scientific or engineering paper doesn't mean the whatever it is doesn't apply to the real word...something that ignorant people like to spout. The question is: when does it apply to the real world? There are things developed for or by NASA that eventually trickle into applications in the real world. There's also a lot of information written in the patent literature which doesn't necessarily get published elsewhere. But you know...this probably doesn't apply to the real world either.

Believe it or not...and I'm guessing not...the base lube stock is just a carrier. Mineral oil and synthetic oils in and of themselves don't supply sufficient lubricity. I've seen this for myself when doing a 4-ball wear test with mineral oil...and no, the "doesn't apply to the real world crap" doesn't apply here either because if it doesn't lubricate sufficiently in a 4-ball wear test, it isn't magically going to perform better in the real world differential either. The additives do the real work. There's a pretty good chance that many of the same additives are used in both types of oils. The "viscosity is too thin" argument is lame. If the viscosity weights are written to be the same for both types, then they are the same for the temperatures at which they were measured. The difference is that the synthetic is going to have a flatter viscosity curve over a span of temperatures relative to that of the conventional meaning that it doesn't get as thick as a conventional in the extreme cold nor does it get quite as thin at extreme heat as the conventional. That whole heat transfer argument is weak too...the base stock is going to be the controlling factor here and sadly they're going to be for all intents and purposes equal...and no, if some engineer or scientist measures them and gets the same exact number in the lab, they're not going to perform magically different in a differential either.

I just love conversing with people who are proud to be ignorant. It's even better than listening to tapes of "Daily Affirmation With Stuart Smalley".

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Manure green 2005 CRD sport4x4, GDE Hot tune, Cat Gut, OE skids, Draw tight hitch, Duramax lift pump, 160K on multiple varieties of fuel, XM radio, Escort live with Redline, fog light mod, GPS, Icom IC7000 all band radio call sign KC9QPF, Grabber AT2s on Soft 8s, FIA grill blanket.

The basic issue is that while synthetics are universally better than dino for almost everything, they have trouble with "shear strength". For example, when I was a regular around the Indycar garages ten years ago, Penske, who was sponsored by Mobil One, put dino oil (Swepco moly) in Mobil One bottles to put in their gearboxes (transaxles). I believe there has been a recent development in synthetic gearbox oils that has finally addressed the problem, but it is not generally available to the automotive market yet. I think it is only available from an English company called Silkolene.

In any case, the shear strength problem that synthetics have had specifically with hypoid applications answers the question about why, before synthetics, we "never changed" diff oil and they "never" seemed to fail.

Redline is a very popular product with racers. When my fellow Formula Ford competitors started swithching over to Redline for their Hewlands over 10 years ago, the sales of R&Ps for Hewlands tripled. I have always used a trick dino hydraulic oil (Case Hytran) in my FF transmissions and never had any significant R&P wear.

Regarding the CRD, we are still under a DCJ ESP, so I ONLY use the synthetic they require.


DOC

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2005 KJ CRD Ltd Detroit TrueTrac Bilsteins G2 GDE "HOT" ECU GDE TCM "Tow Tune" "euro" TC SEGR Weeks Elbow New HG at 130K ARPs Clean CAT aFe Filter Magnaflow Exhaust EHM Cumminos In-Tank Lift Pump Hayden Fan Clutch Nylon Fan VH Enabled with GDE lower shutoff point Recalibrated Temp Gauge Tekonsha Prodigy Sears P-1 ZDDP

Thanks for posting this...first mention of the "actual problem." Given the issue around the shear strength, I wonder how much difference in where there is between what most of us do using the Jeep as a commuting vehicle versus that of racing or lot of heavy duty towing for the various types of oil.

KD,

In hypoid applications, it is a function of a combination of pressure, shear and the force throwing the oil off the gears. A towing application with a relatively small R&P could be much more challenging than a racing application. The bottom line is that Swepco 203 (dino base with moly) has traditionally provided maximum protection for ring and pinions. it is possible that Silkolene has come up with something synthetic that is as good or better than Swepco 203, but that is not clear even to John Grubb at J&J Racing, one of the premier racing gearbox experts in the world. (Just checked with him.)

If we keep the Jeep past the ESP, I will probably switch to Swepco when the warranty expires. (It is compatible with clutch type limited slips, but some may require an additive. Check with your LSD maker.)

DOC

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2005 KJ CRD Ltd Detroit TrueTrac Bilsteins G2 GDE "HOT" ECU GDE TCM "Tow Tune" "euro" TC SEGR Weeks Elbow New HG at 130K ARPs Clean CAT aFe Filter Magnaflow Exhaust EHM Cumminos In-Tank Lift Pump Hayden Fan Clutch Nylon Fan VH Enabled with GDE lower shutoff point Recalibrated Temp Gauge Tekonsha Prodigy Sears P-1 ZDDP