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Discussion Starter #1
I never got to ask this while here and I never saw a post regarding the color that I had in my diff. I got the 2wd 2500 and I believe its the 10.5 axle, we bought it with 150k but the previous owners didnt care for it so I think the fluid in the diff was easily over 50k miles.

The color when I changed it awhile ago was a dark green color, which Ive never seen before for diff/gear fluid. It smelled nasty like usual for gear fluid, I was told it could be due to water getting into the diff hub or some contamination. We never had any rear axle noises or whines at all luckily. What would cause for it to be this contaminated green color? I replaced it with synpower 75w90 until the fluid dripped out of the fill hole. Its been about 30k since the fluid change, should I do it again?
 

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50k miles is nothing if all is well in a diff and using good fluid. Green though? Maybe algae? Yes. Shouldve changed after 1000kms. Or for the more OCD or beer drinking excuse type tear down axle wash every part, pressure wash axle, blast with brake clean, blow out with air and reassemble. Or change the fluid a couple times. Did you remove the diff cover? To get a look at the face of the ring gear and let it properly drain?
 
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Discussion Starter #3
50k miles is nothing if all is well in a diff and using good fluid. Green though? Maybe algae? Yes. Shouldve changed after 1000kms. Or for the more OCD or beer drinking excuse type tear down axle wash every part, pressure wash axle, blast with brake clean, blow out with air and reassemble. Or change the fluid a couple times. Did you remove the diff cover? To get a look at the face of the ring gear and let it properly drain?
I did remove the cover, But I have no idea if it was bad or good. Sounds like it could be well over 100k then for that fluid..... wouldnt suprise me, my PS fluid once drained and settled in a bottle it was sludgy at the bottom so I knew the owners before were horrible.
 

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Likely Redline gear lube.
 
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All Redline gear oils (diff and manual trans) are clear/light yellow.

I'm thinking that someone dumped in a green rear axle fluid additive.
The popular Ford Traction-lock (clutch type) rear axle additive I use in my 5.0L Mustang and previous Ford trucks is dark green.

If you are towing heavy, changing the rear axle fluid at 30K miles or less is a good idea.
But if you are not towing or hauling heavy, you can let it go for quite a while.
 
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Discussion Starter #7
All Redline gear oils (diff and manual trans) are clear/light yellow.

I'm thinking that someone dumped in a green rear axle fluid additive.
The popular Ford Traction-lock (clutch type) rear axle additive I use in my 5.0L Mustang and previous Ford trucks is dark green.

If you are towing heavy, changing the rear axle fluid at 30K miles or less is a good idea.
But if you are not towing or hauling heavy, you can let it go for quite a while.
Huh Ive never seen green fluid before, I dont tow much we have only towed once with a trailer with a truck on it. I wanted to change it once more since I want to play it safe.
 

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Gear lube’s were greenish when I had my shop in the early 70s. Maybe you got some left over 50 year old stuff!
 
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Discussion Starter #9
Gear lube’s were greenish when I had my shop in the early 70s. Maybe you got some left over 50 year old stuff!
Could be, it came from a indian farmer in norcal, but they never changed the air filter/fuel filter and ps fluid so maybe it wasnt changed by them.
 

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Discussion Starter #10
All Redline gear oils (diff and manual trans) are clear/light yellow.

I'm thinking that someone dumped in a green rear axle fluid additive.
The popular Ford Traction-lock (clutch type) rear axle additive I use in my 5.0L Mustang and previous Ford trucks is dark green.

If you are towing heavy, changing the rear axle fluid at 30K miles or less is a good idea.
But if you are not towing or hauling heavy, you can let it go for quite a while.
We wouldnt need those additives in our rear end, so maybe they were mistaken and thought it needed that extra cushion or they possibly thought it was an lsd and it needed an additive for that.
 
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We wouldnt need those additives in our rear end, so maybe they were mistaken and thought it needed that extra cushion or they possibly thought it was an lsd and it needed an additive for that.

Agreed, there are tons of guys mistakenly dumping limited slip axle additive into their non-clutch type locking Chrysler /AAM differential.
 
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Discussion Starter #12
I will be changing the fluid again just due to removing any left over contaminants in the axle that was left over because I know that green ooze was sticky and thick so I couldnt get it all off the corners and such..... I did have small amounts of dirt or rust fall in the casing last time but I did my best to wipe them out (lesson learned) so I will be pressure washing it before I open it next time around. I will post pics of it once done. I will be using 75w90 again and may just stick with the syn power again since its worked this far.
 

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IIRC, I tried ?Castrol? non syn in my 97 D80 and it was green, so I wouldn't be surprised if there are still green gear lubes out there. I strongly recommend UOA for gear lubes. I had some of that crap that claim to be the first syn., in my 97, that was depleted on additives at 12300 miles already and the gear teeth turned dull gray and were singing.
 
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