'96 Jeep Grand Cherokee Front Axle Gear Oil, 75w-140 ok?

[CrazyJeeper]

I've got a 1996 Jeep Grand Cherokee with about 92,000 miles on it. From the factory the front axle was filled with 75w-90 dino gear oil. When I changed the fluid about 5 months ago, i put in valvoline 75w-90 dino gear oil. If anybody owns a grand cherokee would know, the axles tend to howl or make noise no matter what you do; even after a total rebuild they still tend to howl. Would I cause any damage to the front axle if I were to put in some Royal Purple 75w-140 gear oil in the front? Currently I have royal purple 75w-140 in the rear because that's what the factory fill in the rear axle was. I went to royal purple's web site and noticed that the viscosity of the 75w-90 and the 75w-140 was a big jump.

75w-90 cST @ 40*C is at 144.5
75w-140 cST @ 40*C is at 245.

I live in Long Beach, Cali so it never gets colder than 42* (during winter only) and I just dont want to put something in that could cause some damage to the spider gears. Any imput would be greatly appreciated. Seems as is alot of people on jeepsunlimited.com fill their front axle with 75w-140 without any negative experiences.

 

[Greaser]

The only reason Grand Cherokee rear axles howl is because D/C decided to go with the P.O.S Dana 44 aluminum rear axle...which is by NO means related to it's stout brother the cast iron Dana 44.They don't use the alloy rear any more but are using some other weird axle design..where you put all the bearing and seals on the axle shaft,then assemble the axle instead of installing the bearings and seals in the tubes first,then slide in the axle shaft...you have to see it to believe it...anyways..use the heavier oil out back but a syn. 75W-90 up front..it won't really ruin anything but isn't adding to your gas mileage lobbing that heavy oil around in the front diff.

 

[Jeffrey Behr]

I tend to agree with Greaser. The cast-aluminum axle housings that Jeep uses* are not as strong as the cast-iron versions. I bought a '99 Grandokee new and it started whining at around 5000 miles. The dealer replaced all the bearings at c. 8000 miles and it stayed quiet until I sold it this summer.

Try a synthetic 75-90 diff oil. I've used Red Line's gear and transmission lubes for decades with very good results.


* If I remember correctly, Jeep started using them when they went from the 35-series to the series-44 rear axle in the rear, to save weight, around your model year. I don't know if they use the aluminum-housing versions in the front.