5000 miles Front/Rear diff fluid + T-case fluid check results

KuntryRube

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Just echoing a couple of people's PSA about checking your fluids:

CHECK YOU FLUIDS!!!


Just because yours is new doesn't mean jack. There has been a few new ones that have reported to have their gear oil in poor state i.e. dark color, low volume, and/or burnt smelling. I just completed my checks for my front and rear differentials and my transfer case's fluids. I will post the pictures below. Staring with the good/normal. The front diff was a bit low but not by much. Using a hex key I measured it out to be half an inch low. I don't know how much fluid it needed but it didn't need much at all. I put in some Royal Purple 75w-140 and within two seconds, it poured out. Before I had topped it off, I sampled some of the fluid from the hex key and the color was greenish and light. Not concerning in the least. It smelled like typical gear oil. Now on to the T-Case.

Before I begin, I do want to mention that my 392 is on 37s with no lift. For those wondering, yes I am able to comfortably get underneath the vehicle without feeling too cramped. I was even able to bypass the stock transfer case skid plate. All I needed was a 8 inch extension and a ratchet. Keep in mind though of the exhaust that's right next to your work area. Be smart, wait until your car has cooled down. I used my cooled down exhaust as a arm rest while I was ratcheting. I was pleasantly surprised that the fluid was nice and fresh. It was reddish pink and completely full. That's typical of all ATF fluids. Seeing two of my mechanical boxes in good condition was a relief. Now for the rear.

Here was where I didn't like the results. It was BLACK and smelly. It smelled like 50/50 dirt and gear oil. I am being 100% honest. It really smelled earthly like mud. The fluid level was the same as the front but I know they have different capacities so it's safe to bet that it was lower than the front diff. The first image is of the drain plug. There's some gooey gray goop that has congregated on the end and it appears to be mettalic in nature. I'm guessing this is normal.

PXL_20230609_225420002.jpg


Below represents the color of the fluid. If it was this dark in such a small quantity collected as shown on the paper towel, imagine in a clear cup.
PXL_20230609_220912516.jpg

PXL_20230609_221234704.jpg

PXL_20230609_221844090.jpg
PXL_20230609_221852031.jpg


I did take it out on some trails but no way it would be that dark. Do yourself a favor and check your fluids and if necessary do a drain & fill. I might just save your from a headache in the future.
 
Agree totally, I added fluids to everything in the Jeep when it got to me From the dealer, everything was low. Power steering, coolant, atf+4, brake fluid and diffs. I changed the rear diff at 4k and similar it was dark and needed changing. I assume it will be much better now. I did use 75w-85, since the manual says to use that only. I will check the 8HP75 now that I have a little fluid left over from changing it on my JGC.
 
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Same here, replaced the diff fluids at 7500 miles, very dark and unpleasant. I used 75W-140 too, both front and rear, been running fine.
 
Same here, replaced the diff fluids at 7500 miles, very dark and unpleasant. I used 75W-140 too, both front and rear, been running fine.
I would have also but the owners manual has a bunch of stuff that looks to be a way for Stellantis to get out of warranty. Premium fuel, oil changes every 6 months and 75-85 diff fluid. In the past they thay used words like recommended it is different in the 392 manual.
 
I would have also but the owners manual has a bunch of stuff that looks to be a way for Stellantis to get out of warranty. Premium fuel, oil changes every 6 months and 75-85 diff fluid. In the past they thay used words like recommended it is different in the 392 manual.
I'm with you and I've been very careful too, not as careful as you are though. When I decided to fill with 75W-140, it was based on the following:
 

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Just echoing a couple of people's PSA about checking your fluids:

CHECK YOU FLUIDS!!!

Just because yours is new doesn't mean jack. There has been a few new ones that have reported to have their gear oil in poor state i.e. dark color, low volume, and/or burnt smelling. I just completed my checks for my front and rear differentials and my transfer case's fluids. I will post the pictures below. Staring with the good/normal. The front diff was a bit low but not by much. Using a hex key I measured it out to be half an inch low. I don't know how much fluid it needed but it didn't need much at all. I put in some Royal Purple 75w-140 and within two seconds, it poured out. Before I had topped it off, I sampled some of the fluid from the hex key and the color was greenish and light. Not concerning in the least. It smelled like typical gear oil. Now on to the T-Case.

Before I begin, I do want to mention that my 392 is on 37s with no lift. For those wondering, yes I am able to comfortably get underneath the vehicle without feeling too cramped. I was even able to bypass the stock transfer case skid plate. All I needed was a 8 inch extension and a ratchet. Keep in mind though of the exhaust that's right next to your work area. Be smart, wait until your car has cooled down. I used my cooled down exhaust as a arm rest while I was ratcheting. I was pleasantly surprised that the fluid was nice and fresh. It was reddish pink and completely full. That's typical of all ATF fluids. Seeing two of my mechanical boxes in good condition was a relief. Now for the rear.

Here was where I didn't like the results. It was BLACK and smelly. It smelled like 50/50 dirt and gear oil. I am being 100% honest. It really smelled earthly like mud. The fluid level was the same as the front but I know they have different capacities so it's safe to bet that it was lower than the front diff. The first image is of the drain plug. There's some gooey gray goop that has congregated on the end and it appears to be mettalic in nature. I'm guessing this is normal.

View attachment 22457

Below represents the color of the fluid. If it was this dark in such a small quantity collected as shown on the paper towel, imagine in a clear cup.
View attachment 22458
View attachment 22461
View attachment 22459View attachment 22460

I did take it out on some trails but no way it would be that dark. Do yourself a favor and check your fluids and if necessary do a drain & fill. I might just save your from a headache in the future.
How many miles did yours have on it when you did the above checks?
 
How many miles did yours have on it when you did the above checks?
It's in the subject title, buddy - 5000ish miles. You might wanna check yours if you haven't yet. If you do, let people know its condition.
 
I changed mine out at about 10k miles and was equally nasty. I used Royal Purple gear oil to replace.
 
My two cents on the 75-140 weight:

I have a 4runner with East Coast Gear 3rd members with 4.56 gears. East Cost specifies that you must run Lucas Extreme Severe 75 - 140 fluid or they will not warranty them. I've had those gears in there for right at 20,000 miles now, changed at 500 miles (break in) and again around 5000. I haven't checked them again since (they are probably due) but when I drained them at 5000, the fluid in both looked like new, was still gold coming out. That's good enough for me.

My '24 Sarge Green is on order, I will probably swap the fluid out at 500 miles and go with Lucas just based on that experience.

As for the OEM rec for a lower weight, I have to wonder if that's tied to an attempt to increase MPG, sort of like the 0w-20 oils they spec for Toyota. That stuff is like water. I bet there's an impact on MPG tied in there somewhere that is either driven by the Feds or the Manufacturers trying to bump the number...
 
My two cents on the 75-140 weight:

I have a 4runner with East Coast Gear 3rd members with 4.56 gears. East Cost specifies that you must run Lucas Extreme Severe 75 - 140 fluid or they will not warranty them. I've had those gears in there for right at 20,000 miles now, changed at 500 miles (break in) and again around 5000. I haven't checked them again since (they are probably due) but when I drained them at 5000, the fluid in both looked like new, was still gold coming out. That's good enough for me.

My '24 Sarge Green is on order, I will probably swap the fluid out at 500 miles and go with Lucas just based on that experience.

As for the OEM rec for a lower weight, I have to wonder if that's tied to an attempt to increase MPG, sort of like the 0w-20 oils they spec for Toyota. That stuff is like water. I bet there's an impact on MPG tied in there somewhere that is either driven by the Feds or the Manufacturers trying to bump the number...
No idea why they do stuff, but the 392 is the only engine model wrangler that doesn’t say use 75w-140 for towing…. All others do. Even the ones with exactly the same m220 rear axle. Doesn’t make sense. But denying warranty doesn’t make sense either.
 
Definitely going to 75W-140 in mine...Dana 44 HD should be Dana 44 HA...Half Ass...Dana dropped the ball on these axles as far as I am concerned...
 
Coming on a public forum and posting you are not following a manufacturers recommendations or requirements for a vehicle under warranty is not a good practice to ensure your issues will be covered in the future.
 
Coming on a public forum and posting you are not following a manufacturers recommendations or requirements for a vehicle under warranty is not a good practice to ensure your issues will be covered in the future.
How could they possibly tell what type of oil you put in your differential? I just had a NEW rear axle put under my 2018 JL under warranty and I told the Service Manager I had changed the gear oil 3x’s and was running 75W-140, he replaced it without hesitation…
 
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How could they possibly tell what type of oil you put in your differential? I just had a NEW rear axle put under my 2018 JL under warranty and I told the Service Manager I had changed the gear oil 3x’s and was running 75W-140, he replaced it without hesitation…
That fluid is recommended for that model.

How could they tell you didn’t use SRT 0W-40 or 93 octane or zf8 in the transmission? One way, look on jeep392.com ;)
 
That fluid is recommended for that model.

How could they tell you didn’t use SRT 0W-40 or 93 octane or zf8 in the transmission? One way, look on jeep392.com ;)
Actually factory is 85W-90…I changed it and ran it until I made sure it had enough damage so they would have no choice but to replace it…the main thing they checked was my PCM for a hack…didn’t find it…
 
Actually factory is 85W-90…I changed it and ran it until I made sure it had enough damage so they would have no choice but to replace it…the main thing they checked was my PCM for a hack…didn’t find it…
Owners manual for that year and model indicates 75w-140 is acceptable for towing. Again the owners manual for the 392 does not say that.
 
Owners manual for that year and model indicates 75w-140 is acceptable for towing. Again the owners manual for the 392 does not say that.
Strange they would do that? Wonder what their reasoning is for not allowing 75W-140 to be utilized in the same Dana 44 HD as I had in my JL Sahara? Only difference is Locker vs LSD...everything else is the same...Dana 44 HD...the bearings were shot in mine...
 
Owners manual for that year and model indicates 75w-140 is acceptable for towing. Again the owners manual for the 392 does not say that.
From my 2018 JL Sahara Jeep Manual: Doesn't say 75W-140 at all for the M220 = Dana 44 HD......window sticker attached for review...I can say this with FULL confidence as well as soon as I put the Royal Purple 75W-140 in the Dana HD44 it ran MUCH quieter and did not "pop" near as much as it did with 85W-90 + Friction Modifier...the Royal Purple 75W-140 does not require Friction Modifier...
 

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