Differential Fluid Question

brucebotti · Jul 25, 2009

I've got a question for you experts. The recommended fluid is 75w/90 GL5 fluid. I already have 5 quarts of Valvoline 80w/90 GL5 sitting on my shelf. Do you think it will be a problem to use it? It doesn't seem like it would be an issue.
Thanks,
Bruce

BjBnet · Jul 25, 2009

I'm changing it too....manual says 75/140 for the front and back if you tow a trailer which I do.
So I'm fine with the same fluid in front and back right? oh and it's synthetic.
Thanks

RageOfFury · Jul 25, 2009

FRONT AXLE (1.24L (2.6 pts.))
Mopar Synthentic Gear Lubricant 75W-140

REAR AXLE (2.08L (4.4 pts.))
Mopar Gear Lubricant 75W-90
or
Mopar Synthentic Gear Lubricant 75W-140 (Trailer Towing)

NOTE: Trac-lok equipped axles require 118 ml (4 ounces) of Limited Slip Additive be added to the lubricant.

belvedere · Jul 25, 2009

Bruce- Since you live in a cold climate, I'd go with some 75W90 synthetic.

Bj- You should be good to go!

BjBnet · Jul 25, 2009

thank you sir. I was just hoping I wasn't reading the manual wrong...
Man that oil is expensive, it's gonna cost me about $80....I bought 2 bottles yesterday which cost me over $40 with tax and I think I'll need 2 more to have enough for the rear.
Thanks again guys

brucebotti · Jul 25, 2009

Doesn't the manual say to use GL-5? Is synthetic mandatory, or just extra insurance?

Is 80w/90 okay versus 75w/90?

Thanks in advance!

Bruce

RageOfFury · Jul 25, 2009

brucebotti said:
Doesn't the manual say to use GL-5? Is synthetic mandatory, or just extra insurance?

Is 80w/90 okay versus 75w/90?

Thanks in advance!

Bruce

RageOfFury said:
FRONT AXLE (1.24L (2.6 pts.))
Mopar Synthetic Gear Lubricant 75W-140

REAR AXLE (2.08L (4.4 pts.))
Mopar Gear Lubricant 75W-90
or
Mopar Synthetic Gear Lubricant 75W-140 (Trailer Towing)

NOTE: Trac-lok equipped axles require 118 ml (4 ounces) of Limited Slip Additive be added to the lubricant.

Info taken directly from the KJ service manual.

tjkj2002 · Jul 25, 2009

brucebotti said:
Doesn't the manual say to use GL-5? Is synthetic mandatory, or just extra insurance?

Is 80w/90 okay versus 75w/90?

Thanks in advance!

Bruce

I've been doing alot of research and calling up different axle manufactures(aftermarket) and all recommend using non-synthetic only gear oil,more so for aftermarket High Pinion axles.Full synthetic gear oil makes the axle housing run cooler but the aftermarket axle makers(Currie and Hi9) say that that is due to the inability of the synthetic gear oil to draw the heat out of the gears/bearings.They only will warranty there stuff if dino gear oil is used,it makes the diff run a bit hotter but that is from the dino gear oil actually taking the heat out of the gears/bearings and transfering it to the housing which gets cooled by the air.

This seams to only effect gear oil for some reason,don't know why but when poeple that know more about diff's then I do say don't use full synthetic I will obey,then again I'm going to be running 2 high pinion axles soon and combined they cost about $10,000 so damn right I'm going to use the recommended fluids only.Take this info for what you want but if you want to please call Currie(714-528-6957) and ask them what they recommend using in there axles,or Hi9(219-287-7674,or 218-236-6737).

RageOfFury · Jul 26, 2009

tjkj2002 said:
I've been doing alot of research and calling up different axle manufactures(aftermarket) and all recommend using non-synthetic only gear oil,more so for aftermarket High Pinion axles.Full synthetic gear oil makes the axle housing run cooler but the aftermarket axle makers(Currie and Hi9) say that that is due to the inability of the synthetic gear oil to draw the heat out of the gears/bearings.They only will warranty there stuff if dino gear oil is used,it makes the diff run a bit hotter but that is from the dino gear oil actually taking the heat out of the gears/bearings and transfering it to the housing which gets cooled by the air.

This seams to only effect gear oil for some reason,don't know why but when poeple that know more about diff's then I do say don't use full synthetic I will obey,then again I'm going to be running 2 high pinion axles soon and combined they cost about $10,000 so damn right I'm going to use the recommended fluids only.Take this info for what you want but if you want to please call Currie(714-528-6957) and ask them what they recommend using in there axles,or Hi9(219-287-7674,or 218-236-6737).

Well that's what they recommend for their axles. Jeep recommends 75W-140 synthetic...I'd be more likely to follow what Jeep says than some aftermarket company.

Bikeflyer · Jul 26, 2009

Maybe dumb question, what is the difference between a "hi-pinion" and "stock" diff? How does this influence the mfg vs aftermarket engineering debate?

Powerslave · Jul 26, 2009

Hi-pinion housing, is what it is. The high pinion design allows the steering to run behind the axle and under the driveshaft.

Here is what a Hi Pinion DIFF looks like:

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Here you can see the difference in shaft placement:

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There is Low, Mid, and Hi pinion designations...

tjkj2002 · Jul 26, 2009

dentwizz said:
Maybe dumb question, what is the difference between a "hi-pinion" and "stock" diff? How does this influence the mfg vs aftermarket engineering debate?

Well since aftermarket suppliers make most of the OEM stuff(diff wise) I would trust them more.

RageOfFury · Jul 27, 2009

tjkj2002 said:
Well since aftermarket suppliers make most of the OEM stuff(diff wise) I would trust them more.

Why would Chrysler recommend synthetic gear oil then if it wasn't good?

For towing Chrysler recommends 75W-140 which is a synthetic fluid. If I want to follow the "experts" advice, what dino oil would they recommend as a substitute?

brucebotti · Jul 27, 2009

Thanks for the info. I guess where I was confused, was when I read that API spec GL-5 was needed. I looked at the dino gear oil I had, and it said GL-5, so I thought I was all set. I'm going to let it sit on the shelf, and go out and get synthetic with the GL-5 spec.
Bruce

tjkj2002 · Jul 27, 2009

brucebotti said:
Thanks for the info. I guess where I was confused, was when I read that API spec GL-5 was needed. I looked at the dino gear oil I had, and it said GL-5, so I thought I was all set. I'm going to let it sit on the shelf, and go out and get synthetic with the GL-5 spec.
Bruce

If your dino 80-90 is GL-5 certified you are good to go.

Why would Chrysler recommend synthetic gear oil then if it wasn't good?

How do you think they make money? By selling you parts

JJsKJ · Jul 27, 2009

I found differing opinions on the syn lube deal and also found some of these mfg's going by Old info on an old syn lube, Not more recent, better lubes. One axle MFG actually sells their own syn lube w/ their diffs and another gear MFG said Syn is fine as long as it meets spec. Also, those companies that said no on syn lube Couldn't provide testing data, etc. for their claims nor did they recently test other modern brands of syn lubes.

whatever.

bottom line reality is Good, Full synthetic gear lubes are better than dinos in diff applications. Read the Amsoil white paper on the subject and you will see which ones tested better than others. Of course if Your axle mfg says "do not use or no warranty" then I guess you gotta go w/ what they say right?

Powerslave · Jul 27, 2009

I am using 75W95 GL-5 in both diffs, Royal Purple synthetic, and in my Motorcycle rear shaft gear housing. This way, I'll know for SURE what's leaking without smelling it. I have a PS leak now...

Idaho08KK · Jul 27, 2009

I have to say that synthetic lubricants are superior to non synthetic. You get better lubrication, less lubricant break down due to wear and heat, and generally speaking, components last longer if synthetic lube is used(this applies more to engines than diffs.)
IMO, it is a safe bet to use whatever the manufacturer recommends. They either design it, test it, and build it, or they provide specifications to a 3rd party and have them manufacture the parts.
I would have to trust what a manufacturer says about their own products than what an aftermarket company had to say about them.

RageOfFury · Jul 27, 2009

Idaho08KK said:
I have to say that synthetic lubricants are superior to non synthetic. You get better lubrication, less lubricant break down due to wear and heat, and generally speaking, components last longer if synthetic lube is used(this applies more to engines than diffs.)
IMO, it is a safe bet to use whatever the manufacturer recommends. They either design it, test it, and build it, or they provide specifications to a 3rd party and have them manufacture the parts.
I would have to trust what a manufacturer says about their own products than what an aftermarket company had to say about them.

Amen!

So what would a Master Certified Chrysler, Dodge, Jeep Technicianwavey.gif recommend for the KJ's differentials?

Idaho08KK · Jul 27, 2009

Personally, whether towing or not, I would run 75w140 front and rear.

Differential Fluid Question

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