Green Diff Fluid? Huh?

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jls095

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I have a 2000 Jeep Cherokee and I have noticed a howl in 4WD. It only occurs in 4WD. As a first step I'm trying to isolate the issue between the front axle and transfer case.

I wanted to check the diff fluid level so I removed the plug. While the level was fine, the fluid was slightly brighter version of army green. What a surprise that was. When a garage replaced my TC, they may have put new fluid in the diff, but I didn't put green fluid in last time. Are there green diff oils out there? Or did the fluid I put in there magically turn green?

I'm trying to figure out if they put the wrong oil in and that's causing the howl.
 
Originally Posted By: Donald
Doesn't ATF go in the TC. It does in my 2001.

Mercruiser has outdrive gear lube that is snot green, but why would someone put boat lubricant in a car.


I'm referring to the front diff, not the ATF.

Also, front what I can tell about Shockproof Lightweight seems as though it's something a Jeep axle wouldn't exactly like...
 
So I just spoke to the garage. They did replace the diff fluid. He said he used Valvoline 75w-140.

1) I think that 75w-140 is an optional weight for my Jeep, but maybe the extra thickness isn't jiving with my diff. Thoughts?

2) He said that he doesn't know if it's green or not (he is indeed a moron). I've used Valvoline diff fluid before and it was not green so I seriously doubt that's what he used.
 
I was going to say Quaker State Greenoil SAE 90, 140 or 250, but the spec sheet lists them as brilliant yellow. Quaker State Greentech 5w-30 and 20w-50 are dyed green though.

Some gear oil has a greenish hue to it, maybe it's just the natural color of the lubricant. Could be signs of brass, copper or bronze corrosion too.
 
Which transfer case do you have? Since you can drive it fast enough in 4-hi to even hear a howl, I'm assuming an NP242. If its a 231.... don't DO that, and it won't howl- its a part-time T-case not meant for 4-hi on pavement. :)

Assuming NP-242:

Unless you have aftermarket locking hubs, NOTHING is turning in 4-hi that isn't also turning in 2-hi, but things are loaded differently so the source of the howl is something that gets load applied in 4-hi that it doesn't in 2-hi. In 4-hi, actual engine torque gets sent to the front diff, whereas in 2-hi the diff is spinning the front driveshaft, which is not connected to anything in the transfer case. That would point to the howl coming from either the front diff gears, front pinion bearing, or the center diff gears (NP-242 only) because they're loaded differently when in 4-Hi. My bet would be the front pinion bearings- the 2000s got the low-pinion front axle anyway, which loads the "weak side" pinion bearing when being driven versus how the high-pinion axle loads the "strong side" pinion bearing in forward motion. So now's a chance to replace it with a 99-prior high-pinon axle.
 
Originally Posted By: 440Magnum
Which transfer case do you have? Since you can drive it fast enough in 4-hi to even hear a howl, I'm assuming an NP242. If its a 231.... don't DO that, and it won't howl- its a part-time T-case not meant for 4-hi on pavement. :)

Assuming NP-242:

Unless you have aftermarket locking hubs, NOTHING is turning in 4-hi that isn't also turning in 2-hi, but things are loaded differently so the source of the howl is something that gets load applied in 4-hi that it doesn't in 2-hi. In 4-hi, actual engine torque gets sent to the front diff, whereas in 2-hi the diff is spinning the front driveshaft, which is not connected to anything in the transfer case. That would point to the howl coming from either the front diff gears, front pinion bearing, or the center diff gears (NP-242 only) because they're loaded differently when in 4-Hi. My bet would be the front pinion bearings- the 2000s got the low-pinion front axle anyway, which loads the "weak side" pinion bearing when being driven versus how the high-pinion axle loads the "strong side" pinion bearing in forward motion. So now's a chance to replace it with a 99-prior high-pinon axle.



It's a 231. I hear the howl driving 15mph in a straight line. I know not to use on pavement, etc.

I think that I'm going to change the diff fluid as the first step. Then if the howl persists I'm going to pull the front DS and see whether I can isolate the noise to the axle or the TC.
 
Originally Posted By: jls095
So I just spoke to the garage. They did replace the diff fluid. He said he used Valvoline 75w-140.

1) I think that 75w-140 is an optional weight for my Jeep, but maybe the extra thickness isn't jiving with my diff. Thoughts?

2) He said that he doesn't know if it's green or not (he is indeed a moron). I've used Valvoline diff fluid before and it was not green so I seriously doubt that's what he used.


Did they put 75w140 in the front diff? If so, I don't think that heavy of a gear oil is recommended. Not saying it's necessarily the cause of your issue, just mentioning.
 
I think BG products makes some green colored oils, but I don't remember for sure.

Many dealers use BG pruducts because BG the supplies the dealer with a AT flush machine, PSF flush machine, air intake cleaning machine, and oil system cleaning machine if that dealer agrees to only use BG chemicals.
 
I'm not sure what's happened in your case since there is no photos/extra data.

However, I have seen oils turn green during testing. Here's an example:

M9Gp61R.jpg
 
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