Jeep Wrangler Forum banner

1 - 20 of 30 Posts

·
Registered
Joined
·
240 Posts
Discussion Starter #1
Hey Jeepers! Alright, having issues with the gear oil recommendations! I have a 2012 JKU Manual, D30 in front, D44 in rear. I do NOT Tow but I am lifted and running 35s. Looking to change diff fluid, Jeep Manual states 80W-90 Front, 80W-90 Rear unless towing then use 75W-140. Im wanting a FULL Synthetic, all i can find in a Full Synthetic is a 75W-90, is that ok? Also i stated i do not tow but are the 35s, steel bumpers, alum fenders, **extra weight considered "towing"?? As you can tell im a bit confused as to what i should fill with, any advice, opinion, or help is always greatly appreciated!
 

·
Registered
Joined
·
708 Posts
I've heard some people advocate for non-synthetic for gears specifically, but never really saw a convincing argument. My general sense is that gears aren't terribly picky compared to say your engine about the exact oil you use.
 

·
Registered
Joined
·
926 Posts
3" lift here with 35's been using Amsoil full synthetic 80 90 since I bought it in 2013 got both dana 44's but can't say enough about Amsoil it's great stuff...might be overkill but I change it once a year in the summer just to be safe (peace of mind).
 

·
Registered
Joined
·
725 Posts
3" lift here with 35's been using Amsoil full synthetic 75 90 since I bought it in 2013 got both dana 44's but can't say enough about Amsoil it's great stuff...might be overkill but I change it once a year in the summer just to be safe (peace of mind).
Going to run Amsoil in my diffs - are you running Amsoil 5W20 engine oil?
 

·
Registered
Joined
·
240 Posts
Discussion Starter #7
3" lift here with 35's been using Amsoil full synthetic 80 90 since I bought it in 2013 got both dana 44's but can't say enough about Amsoil it's great stuff...might be overkill but I change it once a year in the summer just to be safe (peace of mind).
$15 a quart?
 

·
Premium Member
Joined
·
3,652 Posts
75W90 full synthetic will be fine.
^ this.


I've heard some people advocate for non-synthetic for gears specifically, but never really saw a convincing argument. My general sense is that gears aren't terribly picky compared to say your engine about the exact oil you use.
Synthetic only makes sense for gears if you live in very cold ( <0F/-18C) or very hot (>110F/43C) climate IMHO. Or if you tow heavy trailers.
 
  • Like
Reactions: kodgil58

·
Registered
Joined
·
926 Posts
Going to run Amsoil in my diffs - are you running Amsoil 5W20 engine oil?
No I use Pennzoil full synthetic because....like you said the quarts cost 14 each at my local store here in Texas and a full fill up of pennzoil oil 5w20 is like 26 dollars at walmart good stuff. Put some amsoil in your diffs it's worth it good luck finding it that's probably the hardest part I also use lubelockers in my diff covers or you can use the regular stuff.
 

·
Registered
Joined
·
363 Posts
75 or 85 140 non synthetic is all you need.

there are competition jeeps running tons of HP on 40s with bigass axles that don't even use synthetic lol. it really isn't needed or helpful.
 

·
Registered
Joined
·
240 Posts
Discussion Starter #13
You aren’t driving some type of high performance vehicle. Put brand name gear oil of your choosing in the axles.
True, guess i just get caught up in all the hype of "use this or your JKU will blow up" Long as im changing it should be better than not
 

·
Registered
Joined
·
8,924 Posts
Valvolene has a 75/140 syn gear oil ---- it was only about a buck more at Wallyworld.

But, every time I've changed my gear oil, I found chunks of gear the size of dimes. So I'd fill the pumpkins back up and take the beast to the dealer for a new LSD.

...sigh...
 
  • Like
Reactions: kodgil58

·
Registered
Joined
·
240 Posts
Discussion Starter #15
Valvolene has a 75/140 syn gear oil ---- it was only about a buck more at Wallyworld.

But, every time I've changed my gear oil, I found chunks of gear the size of dimes. So I'd fill the pumpkins back up and take the beast to the dealer for a new LSD.

...sigh...
I went with 75w-90 Full Syn Valvoline for both axles, i dont tow and no LS, i pray i never see chunks of anything in my oil.
 

·
Registered
Joined
·
1,226 Posts
Interesting that Currie Enterprises specifies dino oil.

Lubrication Requirements - 9-inch rearends use a high-offset hypoid gear design that requires a sever duty gear oil with API GL-6 rating. Use of oil not meeting the GL-6 rating will damage the gears and bearings and void the Currie Warranty.
 

·
Registered
Joined
·
363 Posts
same as my spider 9 in the TJ - the True-hi Nine center section with Arb locker specifically states non synthetic 85-140
 

·
Registered
Joined
·
725 Posts
No I use Pennzoil full synthetic because....like you said the quarts cost 14 each at my local store here in Texas and a full fill up of pennzoil oil 5w20 is like 26 dollars at walmart good stuff. Put some amsoil in your diffs it's worth it good luck finding it that's probably the hardest part I also use lubelockers in my diff covers or you can use the regular stuff.
Thanks. Decided on PUP 5W20, but will Amsoil the diffs.
 

·
Premium Member
Joined
·
6,975 Posts
Check the tags on the diffs. The owners manual and most references for my '03 TJ Rubicon call for 80W90 in front and rear diffs, but just had them serviced and the tags on the diffs called for 75W140 Synthetic. Spicer/Dana know best.
 

·
Registered
Joined
·
363 Posts
if you had a towing package then it could say 75w140 to be safe .
"Many well known high-end axle builders like Currie and Dynatrac will void the warranty for their extreme use axles if they discover it had a synthetic gear lube inside when it comes back in for warranty repairs. Yes, that is true.

Currie's extreme-use axle manufacuring facility, for example, was getting some unexplained and totally unexpected R&P gear and bearing failures from some if their customers running their axles in extreme competitive conditions where there should have not been any problems. After much testing that ultimately required they custom build a special axle housing so they could measure temperatures at the ring & pinion gears themselves, they discovered the gears were running much hotter when bathed in a synthetic gear lube. They were totally shocked because when they measured the temps of the differentials filled with synthetic gear lubes, they were cooler.

They and labs finally discovered that the reason the differential cases were cooler when filled with synthetic GL-5 gear lube was that the synthetic was not extracting (sinking) the heat out of the gears nearly as well as the conventional gear lubes were doing. Yes, that is true and I got the inside info on it after calling and talking with John Currie a year or two ago.

At that point, Currie and other axle manufacturers began changing their warranties to require only the use of conventional gear lubes. Once they did that, their failure rates went back down to where they should have been. Currie now only sells conventional gear lubes for their axles as well, they won't even sell synthetic gear lube any more.

Note that these were all extreme use axles so for normal lighter duty axles, you wouldn't see that kind of failure rate with synthetic gear lubes.

I now run strictly conventional 85W-140 Torco GL-5 gear lube in my axles since learning that.

The below is from Currie's axle assembly instruction sheet:

"Step 5) Final Details: Installing the unit in the vehicle varies per car so we will not cover that here.
Once the unit is installed however, you will want to remove the pipe plug in the driver’s side of the
gear case to fill the unit with oil. The unit has a 3 quart oil capacity - do not put any more than 3
quarts in the unit or it will leak out. You will want to use only a good name brand 85-140 weight gear
oil such as 9-Plus oil, Torco, Kendall, or Valvoline. Never use any type of synthetic oil, synthetic
blend oil, store brand oil, or Sta-Lube brand oil." "
 
1 - 20 of 30 Posts
Top