Diff Oil Confusion

[Mangate]

I am approaching oil changes for diffs and have been checking recommended viscosities.
The front diff 186FIA (Model 30) uses 75W140 until 2005 when it changes to 80W90 in the FSM. Did they change anything, other than the recommended oil? Should I put the 80W90 in my 2002 KJ?

The 2002 FSM has 2 rear axle options, the 198RBI(Model 35) uses 75W140, this axle disappears from the FSM from 2003 onwards.
The 8.25 axle uses 75W90, and is the only axle listed from 2003 onwards.

How do I know which axle I have? I seem to remember something about a sticker on one of the axle tubes, but I can't read what was printed on there.

 

[AlexKJ]

I also have a little confusion here... my manual says that I should put 80W90 in the 8.25... ¿what should I do? ¿75W90 or 80W90? ¿is the difference negligible?... Maybe the next time I'll put synthetic 75W140 all around... It´s a little expensive, but what the heck!

Cheers

 

[Dave]

My 05 FSM says 80-90w for the front. For the rear 75-90w except if you are towing use 75-140w. Front takes 2.6 pints and rear takes 4.4 pints. I bought 4 quarts of Valvoline syn 75-140 and was planning to do both with that for the sake of simplicity. Havn't done it yet.

If you can't read the axle tags try the dealer and ask for a build sheet and you will need to give them the last 6 numbers of your vin#. It is instant and free. They pull one all the time when they service vehicles when they need to see what came from the factory in your jeep. Or you can go to the jeep website under owners and e-mail them and ask for it and you will get one that way.

Hope this helps.
Dave

 

[JeepJeepster]

I use Castrol 75w-140 SYN in the front and read diffs..

haha, how does he make those upside down ¿..

 

[offroadohio]

Its easy to tellt he rear axles apart.

Look at the dif cover ( nearly identical) on the 8.25 the axle houses extends just a LITTLE past the bottom corners of the cover. on the 35 it does not.

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Dana35

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8.25

I have never seen a 35 in a liberty, although I'm sure they exist, they are probably very rare ( a good thing)

My 07 calsl for 75x140 in the rear regardless of towing or not, if towing it calsl for full synthetic. The front calls for 75w90

 

[jeepkj02]

I've used both 75w90 and 80w90 in both front and rear diffs with no problems. For the most part, 80w90 is dino oil and 75w90 is syn.

 

[JJsKJ]

I run 75w110, Full Syn in All my Jeeps in both diffs.

 

[Mangate]

Thanks for the input. I think I'll go with the 75W90 or 80W90 (isn't much difference there) in both diffs.