75W -vs- 85W Gear Lube

EugeneTheJeep06 · **Posted:** Tue Mar 14, 2006 10:33 pm

I'm going to change my diff oil tomorrow and all I could find at the local autoparts stores were quarts of 85W gear lube and I know the libbys call for a 75W lube. Long story short is it a bad idea to use the 85W lube, could it damage anything and whats the real difference between 75 & 85W oil.
Thanks !! :wink:

FreedomKJ · **Posted:** Thu Mar 16, 2006 8:15 pm

This reply is a little late, but the KJ calls for 75W-140 synthetic. You may be able to get away with running a heavier oil, but I'd recommend against it.

75W-140 syn is available from many online dealers and Wal-Mart also sells it.

EugeneTheJeep06 · **Posted:** Thu Mar 16, 2006 8:48 pm

Thanks for the reply, after some heavy searching I found the 75W oil.

PitViper · **Posted:** Thu Mar 16, 2006 9:38 pm

Most dealers should have the oil in stock.

Edwin · **Posted:** Fri Mar 17, 2006 7:00 am

FreedomKJ wrote:

This reply is a little late, but the KJ calls for 75W-140 synthetic. You may be able to get away with running a heavier oil, but I'd recommend against it.

75W-140 syn is available from many online dealers and Wal-Mart also sells it.

Actually, the front takes only 75w-140 syn. The rear takes 75w-140 syn. if you tow. You don't have to use syn on the rear diff, if you don't tow.

LibertyCRD · **Posted:** Fri Mar 17, 2006 9:46 am

Actually the front takes 80W90 gear oil. And the rear takes 75W90 unless you tow...then it says to use the 75W140. I'm going to use a synthetic blend in mine because the pure synthetic is $17.00 per quart and that is insane.

krazz1e · **Posted:** Fri Mar 17, 2006 11:28 am

I use 80w90 except when I had my locker that required expensive stuff.

I know you all like syn, but I like to buy cheap and change often.

Jeepjeepster · **Posted:** Fri Mar 17, 2006 11:43 am

I use 75w-140 full syn in the front and rear. My dad knows this guy and bought us a 5 gal bucket of castrol for $80. Great deal if you ask me.

Edwin · **Posted:** Fri Mar 17, 2006 6:57 pm

LibertyCRD wrote:

Actually the front takes 80W90 gear oil. And the rear takes 75W90 unless you tow...then it says to use the 75W140. I'm going to use a synthetic blend in mine because the pure synthetic is $17.00 per quart and that is insane.

My manual says 75w-140 syn. only in the front.

LibertyCRD · **Posted:** Fri Mar 17, 2006 8:35 pm

That's odd because my wife has a 2004 Sport, and mine is a 2005 Sport, and both of our manuals call for 80W90 synthetic for the front diff.

Jeepjeepster · **Posted:** Fri Mar 17, 2006 11:46 pm

Edwin wrote:

LibertyCRD wrote:

Actually the front takes 80W90 gear oil. And the rear takes 75W90 unless you tow...then it says to use the 75W140. I'm going to use a synthetic blend in mine because the pure synthetic is $17.00 per quart and that is insane.

My manual says 75w-140 syn. only in the front.

Mine does too.

FreedomKJ · **Posted:** Sat Mar 18, 2006 12:01 am

Hmm. My owners manual and the Jeep Service manual for '03 both say 75W140 syn for the front.

Edwin: You are correct about only requiring 75W140 syn in the rear if you tow. I tow only occasionally, but I figure that offroading puts stresses similar to towing on your diff so that's good enough for me.

JJsTJ · **Posted:** Sat Mar 18, 2006 12:11 am

LibertyCRD wrote:

That's odd because my wife has a 2004 Sport, and mine is a 2005 Sport, and both of our manuals call for 80W90 synthetic for the front diff.

Amsoil's application guide shows the 80w-90 for the front diff on the CRD but also inlcudes 75w-90 as an alternative.

the1jferg · **Posted:** Sat Mar 18, 2006 12:14 am

If you change it often enough you can use vasoline.

If you are gonna water wheel, don't waste your money on Syn because you should be changin it.

If you gots one of them thar no-slips, you'll find it a bit quieter with heavy stuff. Heavy in summer, lighter in winter.

I think two bottles of 90w = 180w

white04kj · **Posted:** Mon Mar 20, 2006 10:31 am

Alright, at the risk of sounding dumb, I'm really lost. I've heard of people using 75W-90 front and rear, and in this thread people are using all sorts of different weights apparently. I'm just wondering if I should just go by what the manual says or what? Thanks.

Eddo · **Joined:** Thu Jul 07, 2005 7:01 pm **Posts:** 1214

Two basic viscosities of gear oil. Heavy and Light

Light
80w-90 (almost always non-synthetic)
75w-90 (almost always synthetic)

Heavy
85w-140 (almost always non-synthetic)
75w-140 (almost always synthetic)

Check your owners manual for what fluid to use, but in reality it doesnt make too much of a difference, not as critical as getting the correct viscosity for motor oil.

camper · **Posted:** Tue Mar 21, 2006 10:20 pm

I use valvoline 85w-140 mineral gear oil (non-synthetic) in front and rear and I change it fairly regularly.....I have powertrax no-slip in the rear and detroit true-trac in the front.....I guess that may be contrary to owners manual instruction but I haven't had any problems and I'm not concerned that I will.....jeep's not gonna warranty my differentials anyway.....

I get in some water on the trails and I've found the rear stays pretty well sealed but my front does take on some water and gets milky....so I don't see the value of more expensive synthetic if I'm just gonna change it out all the time....

JJsTJ · **Posted:** Tue Mar 21, 2006 10:31 pm

camper wrote:

I get in some water on the trails and I've found the rear stays pretty well sealed but my front does take on some water and gets milky....so I don't see the value of more expensive synthetic if I'm just gonna change it out all the time....

I Agree and I sell Amsoil Synthetic lubes. If you play in the water a lot, save the money on Syn and just change the fluid more frequently. Now you Desert wheelers Need to contact me for some good stuff though!! :wink:

LibertyCRD · **Posted:** Thu Mar 23, 2006 10:44 am

I just changed my front and rear diff. fluid last night for the first time. And I checked my owner's manual once again to be sure, and it does say 80W90 for the front diff, and 75W140 for the rear if you tow (which I do).

I used Valvoline synthetic blend. It's cheaper than full syn, but better quality than non-syn.

jdumont · **Posted:** Sat Mar 25, 2006 6:15 pm

I am also pretty lost with this fluid type conversation. My 02 manual says under recommended fluid in the diff section "Mopar gear lubricant or equivalent thermally stable API-GL5 grade." It then goes on to say if you tow to use 75W-140 Syn. It never says what to use if you dont tow....

75W -vs- 85W Gear Lube

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