PSA CHECK YOUR TRANSFER CASE

[Fast-n-Furious]

I wish they would just be more clear. Even the 392 supplement has the phrase "Track lock or limited slip" needs friction modifier. If they are writing a 392 specific manual they should just stick to what the 392 has. I also think GL-5 already has the friction modifier in it. I go through the same shit with my 2006.

Yup and now I’m reading through this JL forum thread to have a better understanding: https://www.jlwranglerforums.com/forum/threads/differential-oil-change.47318/

 

[Fast-n-Furious]

@Fast&Furious, our diffs on the 392 do not have limited slip differentials so no friction modifier necessary; ours are Tru-Lok, not Trac-Lok.

I topped off the diffs after finding them low from the factory ... thanks to @Robr651, and I used Lucas 75W90 Synthetic. Synthetic can be mixed with non-synthetic. The way this works is synthetic and non-synthetic can be mixed ... the properties of the non-synthetic are unaffected, but the extra properties of the synthetic are "diluted" by the non-synthetic.

I plan to run Lucas 75W90 Synthetic in front and rear diffs from the first fluid change onward. And while it is overkill, I will be changing the diff oil at 1,000mi, then again at 5,000, and then every 15,000. I plan to keep the diffs happy with clean fluid.

Thanks a lot with the information. I’ve never changed transfer and diff fluids so new to this topic. I’ve also read guys use 75w140 for rear diff and 75w90 front diff.

Now I’m thinking about doing the fluid change instead of top off.

 

[Fast-n-Furious]

Okay, I double checked the build sheet, they are Tru-Lok axles. Mine is the 2022 XR without the Tow Package, but I think all the 392s have the same M220 rear axle. According to the suggestions from that JL forum thread, we can use 75W140 for rear diff and 75W90 for front, OR 75W140 for both front and rear to get better protection, which is what I will probably end up with going.

 

[Viking Jeeper]

Okay, I double checked the build sheet, they are Tru-Lok axles. Mine is the 2022 XR without the Tow Package, but I think all the 392s have the same M220 rear axle. According to the suggestions from that JL forum thread, we can use 75W140 for rear diff and 75W90 for front, OR 75W140 for both front and rear to get better protection, which is what I will probably end up with going.

392 supplement specifies 75w85 F/R

 

[Robr651]

Hope this helps folks out who may not have the supplement / guide.

 

[Thankful]

Oil weight and brand are highly debated topics, for sure. The 75W140 is helpful in our diffs if they will be subjected to extreme stress such as towing. Otherwise, a good synthetic 75W85 or 75W90 will flow better and probably keep the diffs happier unless you expect significant stress on the diffs. Net, net, keeping the fluid fresh and clean is our best defense against wear.

 

[Fast-n-Furious]

Yes the 392 manual says 75W80. The DANA specifies 75W140. Some others commented it’s a MPG consideration that’s why Mopar recommends 75W80. But DANA doesn’t care about MPG.

 

[Viking Jeeper]

Yes the 392 manual says 75W80. The DANA specifies 75W140. Some others commented it’s a MPG consideration that’s why Mopar recommends 75W80. But DANA doesn’t care about MPG.

WTF

 

[Damnright]

Well....my transfer case was nearly 1/2 quart low. Secondly, the drain bolt was not torqued to spec and required several more turns

Thanks @Robr651 !!

 

[Electrified]

I live in H-Town where it is hot as h*ll for 8-9 months of the year. Is there a benefit to the 75W140 in hotter climates?

 

[stumblinhorse]

I live in H-Town where it is hot as h*ll for 8-9 months of the year. Is there a benefit to the 75W140 in hotter climates?

Yes. Regardless of towing. Heat is the biggest reason to run 75w140.

But no where does mopar/Jeep recommend 75W140 for a 392 m220, owners or service manual. No idea why they don’t, but so you have all the info possible.

 

[Electrified]

Yes. Regardless of towing. Heat is the biggest reason to run 75w140.

But no where does mopar/Jeep recommend 75W140 for a 392 m220, owners or service manual. No idea why they don’t, but so you have all the info possible.

Thank you.

 

[Fast-n-Furious]

Can you guys show me where the diff drain plugs are? I looked around underneath and only found the fill plugs on the pumpkins. No other plugs near the bottom of either front or rear diffs.

When I looked at the transfer case, it’s different from the video I posted earlier of a non-392 JL. The fill plug is on the left side instead.

 

[SCARd4Life]

Can you guys show me where the diff drain plugs are? I looked around underneath and only found the fill plugs on the pumpkins. No other plugs near the bottom of either front or rear diffs.

When I looked at the transfer case, it’s different from the video I posted earlier of a non-392 JL. The full plug is on the left side instead.

these are old school. drain by removing the diff cover.

 

[Viking Jeeper]

Can you guys show me where the diff drain plugs are? I looked around underneath and only found the fill plugs on the pumpkins. No other plugs near the bottom of either front or rear diffs.

these are old school. drain by removing the diff cover.

I looked the other day and found a drain plug on the rear (facing to the side) but not on the front axle. According to JL forum they stopped putting drain plugs on the front sometime in 2021.

Yes, just remove cover. These have a gasket now so no need to clean up all the old RTV for reinstallation. Even though I will remove the cover to change, I do wish there was a plug up front.

 

[Fast-n-Furious]

these are old school. drain by removing the diff cover.

Oh man, a little bigger project than I had imagined.

 

[Fast-n-Furious]

I looked the other day and found a drain plug on the rear (facing to the side) but not on the front axle. According to JL forum they stopped putting drain plugs on the front sometime in 2021.

Yes, just remove cover. These have a gasket now so no need to clean up all the old RTV for reinstallation. Even though I will remove the cover to change, I do wish there was a plug up front.

This just surprised me today. Mine is 2022 MY and I always thought there’s drain plugs there.

 

[Fast-n-Furious]

Big thanks to @Robr651. After reading your post I checked my Transfer Case and Diff fluid levels. Sure enough, you were right, they were all low. Diffs were half a pint low, each. Transfer case is low too but since I didn't have ATF+4 on hand to fill it today I'm unsure the exact amount. Since I have only 350 miles I should be just fine but glad to get these topped off during break-in. Thanks again.

Does your transfer case look like mine? The regular JL transfer case has fill hole on right, but mine is on left. Just to make sure I get things correct. Thanks.

 

[Robr651]

Does your transfer case look like mine? The regular JL transfer case has fill hole on right, but mine is on left. Just to make sure I get things correct. Thanks.

View attachment 7792

Yes mine looks like that and yes you have the fill hole circled. (One on the top)

 

[Fast-n-Furious]

Yes mine looks like that and yes you have the fill hole circled. (One on the top)

Thank you for confirming. I went to Jeep dealer today to buy a quart bottle of Mopar ATF+4. Talked to the parts guy and he told me that lots of JLs came to top off and usually 1/2 quart low, just as you had pointed out. I'll just need to get a pump and get it topped off.