2nd Gen Non-Engine/Transmission can't believe napa doesn't carry......

[shendren]

80w-90 gear oil (synthetic) for my truck..... all they carry is the 75w-90... ...



not much selection in the gear oil out there. i would like to use castrol. i thought i saw something out there from joe d. on castrol being pretty good. where does one get castrol gear oil? i would like to use something that is easily found on the shelf. . rather that go to a mail order brand...

 

[QRTRHRS]

Assuming this is for your rear?

Scott, why do you want 80-90? A good portion of us are using either 75-90 or 75-140 for the really heavy towers. Castrol sythetic GL5 is pretty commonly found but I don't recall the weights. Joe D usually speaks of Castrol GL4 which is harder to find and more expensive when you do. Try about 54 bucks a gallion as one of the better prices. Daimler only wants Castrol GL4 in the 5sp transmission. Joe has written extensively about this.



You need to do a search in the drivetrain or accessories forums on rear lubricants. There will be far more input then you ever wanted.

 

[shendren]

why do i want 80w-90?



cause the service manual calls for it.....



i'm not real familiar with gear oil so i thought i'd go for what was called for. the only thing i can find is valvoline on the shelves... . are most of you using valvoline? and is 75w-140 for the hotter weather like here in florida?



thanks. scott

 

[Rammin On]

Scott ...



Put 75-140w in there ... . your rear will be happy you did . . with as much running as you do ... this is a better choice . . I run Valvoline semi-syn in both of mine with excellent results. I don't want to start an oil war ... so use your favorite brand ...



Keith

 

[nickleinonen]

gear oil to gear oil... there is nothing all that different between. putting in one brand at 75w90 or another brand ad 80w90 isn't going to make a difference. unless you are towing real heavy, i wouldn't run the 75w140. that's too heavy. you loose fuel economy just slightly [on other brands/engine combos] if you have the LSD, look for something that is rated for it, or just buy the mopar LSD additive [suppose to be good stuff... ] for it. check out walmart. they have all kinds of stuff. i got my castrol syntec 75w90 there on sale. was gonna use mobil1 next on my 'hoe but since i will probably sell it soon, gonna hold off. don't like the smell of gear oil that much to change it for the potential buyer

 

[redram]

Gear Oil is NOT all the same.



the reason you are having difficulty finding a "synthetic" 80W90 is that the synthetic basestocks have better low temperature fluidity. This means that most mineral (conventional) gearoils would act like an SAE 80 weight when cold as compared to a synthetic acting like an SAE 75 weight when cold.



This is a good thing as the oil will flow to the bearings much easier on a sub freezing morning.



In my Owner's and Maintenance Manual, Chrysler recommended the synthetic 75W140 for any application involving towing or heavy duty. I don't know about others, but I consider my 96 12 valve to be "heavy duty" even when it was un-modified.



The difference in fuel mileage between the 75W90 and 75W140 is going to be very minimal, in fact I doubt that you could accurately document it on anything but a high dollar test rig running only the differential.



and again,

oil is not oil is not oil. If you believe they are all the same, I've got some property for sale that is "only under water once per year" that I'll let you have for cheap!

 

[MJawsman]

A few years back when the Dana 80 came out, I spoke with a Dana engineer in the light axle division. He said the things to do on that axle were to frequently check backlash and use 75-140 gear lube. That's what I run even though I don't tow a lot or all that often. Never had any problems even in sub zero Minnesota. Just my $. 02