Front Diff oil change

DOC4444 · **Posted:** Fri Sep 23, 2011 12:01 am

So it takes 1.6 quarts? Is the current wisdom 75-140 synthetic or 75-90 dino? Is there a drain plug or does the cover need to come off so I will need a gasket?

Thanks,

DOC

jeepdan · **Posted:** Fri Sep 23, 2011 8:38 am

There is a drain plug which is screwed into aluminum

,so be careful. I don't think that you could remove the cover if you wanted to without dropping the diff. Not sure if the MPG savings is there to justify the extra cost of synthetic.

Hoosier CRD · **Posted:** Fri Sep 23, 2011 5:27 pm

DOC4444,

I plan on going with the Severe Gear Synthetic EP Lubricant 75W-90 Amsoil myself. This has been strongly suggested by a good friend that is quite knowledgeable about lubricants. In fact, he is an Amsoil distributor.

Use this in the rear too if you have a posi. BTW, if you do have a posi, be sure to add the lubricant modifier from a Ford dealer; costs about $5.00 and is also recommended by Auburn Differentials.

Hoosier CRD

tjkj2002 · **Posted:** Fri Sep 23, 2011 6:45 pm

Hoosier CRD wrote:

DOC4444,

This has been strongly suggested by a good friend that is quite knowledgeable about lubricants. In fact, he is an Amsoil distributor.

Makes him know almost nothing about oils but trying to line his wallet with your $$$.No locker/LSD company recommends synthetic,heck Detroit only recommends dino.

Hoosier CRD · **Posted:** Fri Sep 23, 2011 9:11 pm

tjkj2002 wrote:

Hoosier CRD wrote:

DOC4444,

This has been strongly suggested by a good friend that is quite knowledgeable about lubricants. In fact, he is an Amsoil distributor.

Makes him know almost nothing about oils but trying to line his wallet with your $$$.No locker/LSD company recommends synthetic,heck Detroit only recommends dino.

Here is what the Auburn Gear Installation Manual states about lubricants:

"The Auburn Gear limited-slip differential design has been extensively tested with high quality
non-synthetic 80W90 hypoid oils treated with GM or Ford friction additives (3 oz. of additive
will treat 1 quart of oil). To avoid differential clutch chatter (noise) and for optimum
performance, use the oil and additive described above. Use of other additive and oil types may
cause differential clutch chatter.
- Ford Part Number: C8A219B546A
- GM Part Number: 1052358"

Actually tjkj2002, my friend is alot more knowledgeable about oils than you give him credit. I've checked with him this evening and he firmly supports his position on synthetics in differentials, regardless of what Auburn says. For Auburns, use non-synthetic, all others, unless stated otherwise, synthetics are okay.

I will be adding the Amsoil Severe Gear 75W-90 to both the front/rear diffs on my KJ. You are welcome to do as you wish with yours. But denegrating my suggestion and my friend's integrity will stop right here.

Hoosier CRD

ATXKJ · **Posted:** Sat Sep 24, 2011 11:45 am

I'd be very interested if your friend has Data - i.e. something with numbers - measurements???????
not at all interested in Opinions.

although I will give Tj credit - that's the first time I realized Detroit had a preference on Synthetic vs Dino
Corporations have resources to test stuff and have legal warranty repercussions if they're wrong.....

tjkj2002 · **Posted:** Sat Sep 24, 2011 8:30 pm

Hoosier CRD wrote:

Actually tjkj2002, my friend is alot more knowledgeable about oils than you give him credit. I've checked with him this evening and he firmly supports his position on synthetics in differentials, regardless of what Auburn says. For Auburns, use non-synthetic, all others, unless stated otherwise, synthetics are okay.

I will be adding the Amsoil Severe Gear 75W-90 to both the front/rear diffs on my KJ. You are welcome to do as you wish with yours. But denegrating my suggestion and my friend's integrity will stop right here.

Hoosier CRD

Call Currie and ask what to use in there diffs,then call Hi9 and ask them what gear oil to use in there diffs.Both make diffs that see more extreme conditions then most will ever and yes both only recommend dino 85w-140 or no warranty.For a low pinion axle you may get 100k trouble free miles but if you ran dino you will get 200k-300k trouble free miles.Synthetic is only good in a forced oiled system(like your engine and trans) but a splash oiled system everything that makes syn good makes it very undisireable.

Hoosier CRD · **Posted:** Sun Sep 25, 2011 5:24 am

ATXKJ wrote:

I'd be very interested if your friend has Data - i.e. something with numbers - measurements???????
not at all interested in Opinions.

although I will give Tj credit - that's the first time I realized Detroit had a preference on Synthetic vs Dino
Corporations have resources to test stuff and have legal warranty repercussions if they're wrong.....

Short answer is "Yes". What data would you like to see, ATXKJ?

Hoosier CRD

Hoosier CRD · **Posted:** Sun Sep 25, 2011 5:38 am

tjkj2002 wrote:

Hoosier CRD wrote:

Actually tjkj2002, my friend is alot more knowledgeable about oils than you give him credit. I've checked with him this evening and he firmly supports his position on synthetics in differentials, regardless of what Auburn says. For Auburns, use non-synthetic, all others, unless stated otherwise, synthetics are okay.

I will be adding the Amsoil Severe Gear 75W-90 to both the front/rear diffs on my KJ. You are welcome to do as you wish with yours. But denegrating my suggestion and my friend's integrity will stop right here.

Hoosier CRD

Call Currie and ask what to use in there diffs,then call Hi9 and ask them what gear oil to use in there diffs.Both make diffs that see more extreme conditions then most will ever and yes both only recommend dino 85w-140 or no warranty.For a low pinion axle you may get 100k trouble free miles but if you ran dino you will get 200k-300k trouble free miles.Synthetic is only good in a forced oiled system(like your engine and trans) but a splash oiled system everything that makes syn good makes it very undisireable.

tjkj2002, I think that I know what you are saying here. Yes, severe duty applications like the one's where Currie, Hi9 and Auburn are oft used are just that--severe duty. But here's a question that needs answering: If you have a severe duty application, why in the world would anyone go 200K-300K before changing the fluid? Any fluid!?! With the cost of about three quarts of diff lube being what it is, i.e. not that much, I'd change it before each event if it were that critical. Too, in severe duty applications, i.e. racecars or rock crawlers, thorough teardowns are frequent--be it for preventative maintenance or failures. Fluids get changed then too.

As ATXKJ has asked, I'll gather some data and we'll go from there.

Hoosier CRD

ATXKJ · **Posted:** Mon Sep 26, 2011 8:26 pm

Hoosier CRD wrote:

Short answer is "Yes". What data would you like to see, ATXKJ?
Hoosier CRD

Actually that's a good question - because the folks saying Synthetic is not good - generally don't give a reason, I wonder if Eaton would give a reason?

So the quick response would be just lifespan data on differentials Dino vs Synthetic - probably under high stress conditions.

I'm not sure what oil property would distinguish between pressure lubricated vs splash oiled.

CATCRD · **Posted:** Mon Sep 26, 2011 9:45 pm

ATXKJ wrote:

Hoosier CRD wrote:

Short answer is "Yes". What data would you like to see, ATXKJ?
Hoosier CRD

Actually that's a good question - because the folks saying Synthetic is not good - generally don't give a reason, I wonder if Eaton would give a reason?

Reason: they don't want to bother doing the testing.

ATXKJ wrote:

So the quick response would be just lifespan data on differentials Dino vs Synthetic - probably under high stress conditions.

See previous reason. It's easier for the OEM to just say "don't use it".

ATXKJ wrote:

I'm not sure what oil property would distinguish between pressure lubricated vs splash oiled.

Short answer: none.

ATXKJ · **Posted:** Tue Sep 27, 2011 1:54 pm

CATCRD wrote:

ATXKJ wrote:

I'm not sure what oil property would distinguish between pressure lubricated vs splash oiled.

Short answer: none.

I'm not sure that's totally true - pressure lubricated normally has a filter, splash lubricated doesn't - so if you have contamination - in a pressure lubricated - the filter cleans it up. in a splash lubricated - it's only cleaned - when you change the oil.

so if someone drives through a mud hole - that contaminates the diff - who's more likely to change the oil?
and who's more likely to rationalize a reason not to change the oil?

the guy who spend $20 on Dino - or the guy who spent $50+ on synthetic?

so a cheaper oil - might make the diff last longer - if the person is more willing to change it......

CATCRD · **Posted:** Tue Sep 27, 2011 6:09 pm

ATXKJ wrote:

CATCRD wrote:

ATXKJ wrote:

I'm not sure what oil property would distinguish between pressure lubricated vs splash oiled.

Short answer: none.

I'm not sure that's totally true - pressure lubricated normally has a filter, splash lubricated doesn't - so if you have contamination - in a pressure lubricated - the filter cleans it up. in a splash lubricated - it's only cleaned - when you change the oil.

so if someone drives through a mud hole - that contaminates the diff - who's more likely to change the oil?
and who's more likely to rationalize a reason not to change the oil?

the guy who spend $20 on Dino - or the guy who spent $50+ on synthetic?

so a cheaper oil - might make the diff last longer - if the person is more willing to change it......

I agree with that, but contamination is not an "oil" property - intrinsic to the oil. Like viscosity or viscosity index.

tjkj2002 · **Posted:** Tue Sep 27, 2011 6:25 pm

CATCRD wrote:

I agree with that, but contamination is not an "oil" property - intrinsic to the oil. Like viscosity or viscosity index.

All that junk data amsoil puts out really has nothing to do with real world abuse.

If you actually understand how a diff works and how it is lubed you do not want a free flowing gear oil there like synthetic,the properties that make synthetic great in a forced oil system are major flaws in a splash oiled system.

ATXKJ · **Posted:** Tue Sep 27, 2011 7:55 pm

tjkj2002 wrote:

the properties that make synthetic great in a forced oil system are major flaws in a splash oiled system.

Name one.

Actually I think the differential folks don't know why - I think the places that are really seeing problems are small shops without the resources or ability to analyze why.

tjkj2002 · **Posted:** Tue Sep 27, 2011 8:14 pm

ATXKJ wrote:

tjkj2002 wrote:

the properties that make synthetic great in a forced oil system are major flaws in a splash oiled system.

Name one.

Actually I think the differential folks don't know why - I think the places that are really seeing problems are small shops without the resources or ability to analyze why.

Fee flowing,what you do not want in a diff,more so if you have a high pinion axle.I wouldn't call Currie small by anymeans.

ATXKJ · **Posted:** Tue Sep 27, 2011 9:08 pm

Currie's web says they have 50 employees
I would call that small , Moser too

Eaton - 'Detroit' is a 13.7 Billion/year company with 73,000 employees.

Mobil oil is 11 B/Quarter - they probably has more Phd's have studying oil than Currie has employees.

That doesn't mean that Currie hasn't seen a problem - but I'm sure they didn't put a dozen Engineers and a million dollar budget on identifying and solving the problem.

Free flowing - is a measure of viscosity - and a viscosity index - the measure of change in flow characteristics over temperature. There are also Dynamic and kinematic viscosity's and different SAE measurements for Gear oil vs Engine oil. Those known, there are standard SAE tests for them.

the only reason Synthetic vs Dino viscosity would be better on forced oil vs splashed oil would be if one didn't met the spec.

now - for me - I'm not racing - I'm not towing - I'm not even driving very fast and at Jeep's oil change intervals I could use anything on the market and not have problems.
although I still like to know why Currie thinks it's a problem
(and Eaton's web now says - use the auto manufacturer's oil recommendation)

tjkj2002 · **Posted:** Tue Sep 27, 2011 9:35 pm

ATXKJ wrote:

now - for me - I'm not racing - I'm not towing - I'm not even driving very fast and at Jeep's oil change intervals I could use anything on the market and not have problems.
although I still like to know why Currie thinks it's a problem

Look at your own avatar pic,extreme conditions.Call Currie and ask.

DIESELIB · **Posted:** Wed Sep 28, 2011 10:42 am

Not wanting to cause any more problems....but here's my input:
Actually you're BOTH right..... the main reason companies like Currie recommend DINO oil as compared to synthetic is because it typically provides better "cling" properties...meaning that, in a rock crawler for example, at LOW speed operation it keeps a thicker film of oil on the parts which translates to more protection..... HOWEVER...if a constant flow is available,such as highway use or drag racing, the SYNTHETIC will give better performance results through better lubrication AND less drag loss due to a freer flow...
just my 2cents...
Tom

67Customs · **Posted:** Wed Sep 28, 2011 11:36 am

DIESELIB wrote:

Not wanting to cause any more problems....but here's my input:
Actually you're BOTH right..... the main reason companies like Currie recommend DINO oil as compared to synthetic is because it typically provides better "cling" properties...meaning that, in a rock crawler for example, at LOW speed operation it keeps a thicker film of oil on the parts which translates to more protection..... HOWEVER...if a constant flow is available,such as highway use or drag racing, the SYNTHETIC will give better performance results through better lubrication AND less drag loss due to a freer flow...
just my 2cents...
Tom

That makes more sense than any explenation I've heard on this topic. I've serched the internet for hours, prior to this thread, trying to come up with an answer as to why someone told me that using Mobil 1 Synthetic 75W-40 is hurting my gears driving to work and back (with the occasional off road trip and towing duty). Nobody seems to have a clear answer other than such and such company recommends dino. Well, Toyota recommends 0W-20, but the engine isn't going to blow up if you use 5W-30.

Front Diff oil change

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