I've read a bunch of posts here and elsewhere, but am curious. Will using 80W-90 in both axles for non-towing applications be suitable for me? I bought the correct viscosity gear oil by Lucas at NAPA and I feel robbed (even more after hearing not to use synthetic by nearly everyone).

75W-90 = $40/gal Valvoline
80W-90 = $20/gal Valvoline
75W-140 = $52/gal Valvoline

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2006 Jeep Liberty Limited 3.7

Just today I had a long conversation with the owner of a shop that only does regearing/rebuilding of differentials, axles, etc. He said that he NEVER uses synthetic oil in any axle that he works on. He only uses straight dino oil because he WANTS the thicker oil to stick to the gears and other parts - synthetic tends to not stick so causes more wear. He told me that he has rebuilt more differentials that used synthetic than for any other reason. Since differentials are not a pressurized system the dino oil is best because it will adhere to the metal where the synth will not adhere as well. He does use synth in his engines.

You'll save a ton of money buying the dino oil. Get a gallon of the 80W-90 for about 12 bucks and fill both the front and rear. You can go longer between maintenance too.

Bob

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2003 Liberty
- 3.7L V6, NP242 SelecTrac Transfer Case
- OME 927/948's, Bilsteins, JBA Gen 4.5 A-arms, JBA 1/4" top plate, 3-ring clevis, 2 extra rear isos
- Rubicon Moabs
- 4.10's, 265/70-16 Goodyear Duratracs
- 4X Guard Trans Skid, Modded BoulderBars, Mopar Engine, T-Case, Tank Skids, ARB bumper, Smittybilt 9500XRC winch

Thanks!

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2006 Jeep Liberty Limited 3.7

Thanks from me, too. I am getting ready to do all the fluids in my 2007. I bought it used in May with 42,000 miles on it and wanted to be sure that everything was up to date. This thread saved me from making a poor decision.

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--Prof

927/948 OME Springs - Bilstein Shocks - JBA Upper Control Arms - Rage Black Widow Roof Basket - Viper 3606V Alarm System

80w-90 for normal driving,use 85w-140 if wheeling or towing.Both are non-syn.

I've used the 85w-140 fluid in my rear diff before and let me warn you it's some thick. It took awhile to fill the diff.

I've since gone back to 80w-90 because I really don't tow that often.

sent from my Galaxy SIII & Tapatalk4 beta

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my trail & highway ride (and occasional tow rig)
04 Liberty Sport with a 2.5" lift, ProComp 245/75R16 AT's and two Hella700FF lamps (more accessories to come)

my trail queen
95 YJ with a RE 4" lift, 33" ProComp Extreme's, M8000 Winch, Lockrite Locker up front, Super35 in the rear and 4.88 gears

well sorry to steal the topic but i think it is useless to start another that will be almost same.... i got 5 gallons of free 75w90 diff oil shell spirax s6 axme is that ok for my diff???

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JEEP liberty 2005
completly stock but planning ome lift + mud tires
Daily driver

I use 85-140 all the time but then I tow some and am sort of hard on the throttle at times so need the extra good stuff
I've never used syn in anything I've had
engine yes diffs NO!!!

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MUDD'S MOTORSPORT'S We do IFS lift installs ,
03 OVERLAND EDITION /Kilby-Skidrow-Mopar-4XGuard skids/ 2.5 inch TOTAL CONTROL JBA coilovers -JBA Arms/MOABS-31 FALKEN WILDPEAK AT3W / 4.10's etc, 04 Kilimanjaro Edition loaded, plus 05 KJ limited

I use synthetic in every diff of the cars and suv's I own. I have never had a problem with it. The synthetic vs dino is stupid. If dino were so good then why do so many cars come factory filled with synthetic. The people that say dino is the best bet are old and stuck in there ways

I can tell you that if I were to run dino oil in my 500awhp 05 EVO it would not last long. Same with the diffs. Both my evo and Liberty run Redline shockprof in the diff's. (liberty front and rear. Evo in the rear, front and center diff's with light weight shockprof in the trans ) Before the evo I had a 92 galant vr4 that put down 562awhp and 484awtq. I ran Royle purple in the motor,trans diffs and Tcase. Never once did I see bearing or gear wear.

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05 Liberty CRD DD/ski slut
Lifted,hottune,Full exhaust
05 Mitsubish evolution SSL
450awhp/400awtq autocross slut

Stupid ???
Old and set in our ways ????

Talk to any diff builder in the US and you'll hear the same thing
So they're all old and set in there ways as well
You want the diff fluid to stick to the gears, not be flung off

Bragging about horsepower gets ya everywhere

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MUDD'S MOTORSPORT'S We do IFS lift installs ,
03 OVERLAND EDITION /Kilby-Skidrow-Mopar-4XGuard skids/ 2.5 inch TOTAL CONTROL JBA coilovers -JBA Arms/MOABS-31 FALKEN WILDPEAK AT3W / 4.10's etc, 04 Kilimanjaro Edition loaded, plus 05 KJ limited

Federal MPG standards,only reason why syn gear oils are used from the factory.Many are switching back to dino gears now since they can't get a diff to last more then 100k-150k using syn oil.Racing is far different then towing or offroading,much more stress is placed on the diffs in moderate+ wheeling then racing.When I'm in 1st gear and 4 low on the trail,say at 1000 rpm's and the 3.7 is making about 100lbs-ft of torque at said 1000rpm's my drivetrain is being subjected to 6600lbs-ft of torque.12 times the amount your tin boxes put out while racing.

Just think the high end aftermarket offroad diff builders state only use 85w-140 non-syn gear oil.Why is that in a axle that can cost over $10,000?

FWIW, I discovered the reason, at least A reason, Dino is preferred is the fact that synthetic rejects heat. If it can't absorb heat then it can't remove it from the gears then the gears can overheat.

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2010 KK Deep Water Blue,OME Liftplus 1",JBA 5.5 UCA ,Dynaflow cat back exhaust, Weathertech VV & mats,Mopar skids,Atthehelm front bumper, Smittybilt XRC 10, Rigid LED's,RL Skink Supersliders,Gecko Safari Basket Detroit Truetrac rear, E-Locker front, G2, Dana 4.10's

My car is 3300lbs and I launch the car at 6k building 10lbs of boost off the line and spin it to 8k.I put my diff through hell.

I'm willing to bet that most people that have issues with running synthetic are using
The cheap blends or cheap brands.

I only use
Royal Purple
Redline
Amsoil.

I have had had no issues with running those and will keep running them.

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05 Liberty CRD DD/ski slut
Lifted,hottune,Full exhaust
05 Mitsubish evolution SSL
450awhp/400awtq autocross slut

Nobody was telling you what you should run. I think they are not so receptive to the idea of anyone telling them what they should run. We old people who are stuck in our ways usually got to be that way for a reason. Mainly, by finding ways that worked and sticking with them.

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--Prof

927/948 OME Springs - Bilstein Shocks - JBA Upper Control Arms - Rage Black Widow Roof Basket - Viper 3606V Alarm System

The 3 worst gear oils ever to use.

Launching at 6k hurts CV joints and u-joints,not really gear sets until you start running full slicks.You just don't have the traction or torque to effect the gear sets yet.

I do run slicks 4 QTP
Axles and cv have Already been upgraded to drive shaft shop units.
Yes 6k launches do put a doo doo ton of stress on the diff. Seen lots of teeth ripped
Off ring gears.

But hEy to each there own. I will keep running what works for me.

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05 Liberty CRD DD/ski slut
Lifted,hottune,Full exhaust
05 Mitsubish evolution SSL
450awhp/400awtq autocross slut

I used to get my Liberty Limited serviced at the dealer = 100% Mopar synthetic every 15k to 20k. My pinion bearings went bad at 63k+ just outside the warrantee

I'm going to try to stay with regular gear oil from now on and see how it goes, currently at 170k.

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2002 Liberty Limited
2.5" Rusty's Coil Lift + OME 927 springs + 1/4" spacers
265x70 Revos
Warn 4x Floods
ARB bumper
TeraFlex extended front bumpstops
Rock Lizard Skink Super Sliders
Bosch Size 86 battery
Jeepin by Al's 4.5 UC Arms
Kryptonite Differential Cover
JBA Bolt on KJ Tri-Angulated 4 Link

Just changed out the fluids in both rear and front diffs, used 85w140 valvoline and my diffs have been thanking me ever since!!

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2006 Liberty KJ
- 3.7 V6 - OME 927/948 - Bilstein shocks - Teraflex bumpstops
- 245/75/16 Hankook Dynapro ATM - 1.25" Spidertrax Wheel Spacers
- Boiler's Roof Rack - CRS Rock Rails - All J Cargo Tray
- Cobra 75WSXT - 4 LED Roof Lights - Bed Lined Bumpers/Fenders