So I have been going through my new to me 06 and getting some maintence done. Timing belt with all the pulleys, oil change(rotella T6), serp belt, hayden 9205 fan clutch and 11 blade fan mod, new thermostat and front hub bearings. My next thing I want to get done before winter sets in is the diffs and the tranny/transfer case oil due to it being right at 100k. The tranny and transfer oil should be ATF+4.. no problem there. After searching here for the diffs they should be 75-90 front and 80-90 in the rear or 80-140 if towing alot(I dont). Why the difference between 75 and 80 for the front and back? Not wanting to start a huge oil debate(like I did in a motorcycle forum once, dont wish to relive that) any recomendations for what to put in them? Dino or synthetic or doesnt really matter?

Thanks!

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2006 Silver CRD, Samco hoses, GDE Eco tune, K&N filter, Powerstop Rotors and pads.

Do not know why the difference from front to back weight wise. I know synthetic is what they call for in the 05. I use synthetic in both units. Also do use good grade trans filters. Some of the cheap flat filters will split in use and can damage the trans. I use Mopar trans filters.

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2005 CRD Limited

Plain old dino 80w-90 gear oil(non-syn) would be the best for you and cheap.If you want to spend $17+ per qt for syn gear oil do it but remember it must be changed every 12k-15k.Dino gear oil will last longer and better protect your diffs for 1/3 of the price if not more.


The one and only time synthetic oil is worse then dino oil.

I followed your advice on the dino gear oil in my drain and fill this past weekend. I am just curious as to why you recommend not using the synthetic gear oil. I haven't been able to find any evidence that the conventional is any better than syn, actually I haven't seen anything to support the dino over syn decision, though I admittedly haven't read the entire internet.

Well that works good then! Figures I walked right by some Rotella 80w-90 tonight.... have to stop back tomorrow.

Thanks!

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2006 Silver CRD, Samco hoses, GDE Eco tune, K&N filter, Powerstop Rotors and pads.

Think what do they say makes syn better? Then truely understand how your diff operates and is oiled and you will find all the properties that make synthetic's "better" is the worst oil for your diff.Every wonder why gear oil changes are 12k-15k for syn? It does not hold up in diffs with small capacity.They only recommend syn gear oil for the extra 10th of a mpg it gives you so they can raise there mpg average to meet federal regs.

I could go on and on and I'm sure others will chime in saying the complete reverse but when I dropped $4200 on a rear diff and Currie stated use only dino 85w-140 as syn gear oil will destroy the diff and void the warranty and this from more years of experiance then I've been alive I'd have to take there word.Plus at $4.99 a qt compared to $17.99 a qt is a big statement.

Interesting... I have used synthetic gear oil for many years, and hundreds of thousands of miles in every vehicle I have ever owned, and not one failure while using it. I didn't change it that often, either. I did, however, have a failure while using dino gear oil. I guess I'd better dump the synthetic, I may destroy something... Seriously though, you are not going to destroy your rear axle, or front diff using synthetic, I can assure you. You also don't need to change it that often, unless you are towing heavy loads all of the time, or otherwise pushing your axles to the max, which most don't. I have 75w140 Mobil 1 synthetic in the rear of mine as I do some towing once in a while, and I think it is probably better protection. In the front diff, I use Mobil 1 synthetic 75w90. I know others that have used this for a long time, and no failures. To each their own.

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Mike Rausch
Bear, Delaware
2006 Liberty Sport CRD 253K

I understand how a diff operates. Synthetics are recommended because they remain stable for longer periods of time, they also usually have higher quality additive packages in them and have. Though the temperature extremes are not that which motor oil sees, things such as shear forces likely are. Are the film strengths of conventional higher? IU routinely change my diffs every 10-15k anyway, just as a point of maintenance.

I posed the question on Bobistheoilguy.com to see what the lubrication experts have to say.

I have the same in my jeep for near 2 years now with no issues

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2006 Liberty CRD Limited Deep Beryl Green Metallic Clear coat, Fumoto valve, MH ProVent (removed), GDE Eco tune,
OME 790/948 springs, OME struts, OME N132L shocks, Jeepin by Al A-arms, Hercules Terra Trac AT2 245/75R16
Weeks Stage 1 EGR delete, 5 volt steel glow plugs

If I recall corrctly, bobistheoilguy had an oil test that showed convential diff/gear oil was better suited than synthetics. I'm a die hard user of real synthetic oils in an engine but will stick to conventional for diffs.

Regular changes and changes after water immersion are more important than what type of gear oil you use.

Because of the recommend frequency(often)This oil change I used a oil extractor for the rear. And also used conventional oils for front and rear.

I asked the question at BITOG:


http://www.bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Main=183754&Number=2760505#Post2760505

Not trying to be negative, so don't get me wrong, but all I read over there were opinions and anecdotes. Plenty of that here. Did I miss something? If this sounds sarcastic, it isn't.

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Matt B.

05 Limited CRD. Bought it new. 112k on the clock now.

GDE Eco-tune, rear differential drain plug (drilled and tapped the pumpkin), transmission pan drain plug, Fumoto oil valve, fuel filler neck restriction removed, front hitch, Hayden fan clutch, Sears P1 battery since 08, Mobil 1 5w40, 5 volt glow plugs, DIY timing belt at 109k

You are correct, not too much in the way of hard facts. I would have expected a link to some test results or something of the sort.

One of the most sought after 9" center section,notice what they post in big black letters 3 times on the page.

http://truehi9.com/oilingsystem2.html

I see that. I am just curious as to why they say recommend the conventional. I don't care one way or the other what the right answer is, I just want to know the reasoning behind the choice.

I have a theory. High end off road axles see an odd combination of high horsepower and low speed. The answer could lie in that.

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Matt B.

05 Limited CRD. Bought it new. 112k on the clock now.

GDE Eco-tune, rear differential drain plug (drilled and tapped the pumpkin), transmission pan drain plug, Fumoto oil valve, fuel filler neck restriction removed, front hitch, Hayden fan clutch, Sears P1 battery since 08, Mobil 1 5w40, 5 volt glow plugs, DIY timing belt at 109k

I called Currie and asked - they didn't have much data beyond - 'we tried it and axles break more with synthetic.'

my Theory is that conventional oil has better heat transfer than synthetic -
it's a guess because I've never seen data on that -
I have seen lots of other data and synthetic always comes out better or equal.
heat transfer problems would cause bearing/seal failures.

and that would only be an issue if you're really stressing the axle - which tends to happen a lot for Currie's competition stuff.

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2005 CRD
stuff
Skeptic quod gratis asseritur, gratis negatur