Heat in rear end...

[jeepzj]

Thanks. I had factory filled 80W90 when I first bought the Jeep. Had it changed to the same fluid at 25K. Made no noise until I reached 45K at which time started making the same whoooosssh noise. When it reached 50K the rear started to rumble which turned out to be bad carrier bearings. Had the carrier bearings replaced under warranty and have been using 75W140 in the rear ever since but still had a slight whoooshh noise. I'm thinking the whooosssh noise is the ring and pinion? I guess my question is will the rear be any louder with 75W90 compared to using 75W140? If there is no significant change in noise then I would rather use the lighter weight 75W90 for better fuel economy and less heat. I suppose the level of protection would be the same? I do not tow or offroad ever.

[ August 15, 2005, 01:27 PM: Message edited by: jeepzj ]

 

[MolaKule]

The ring/pinion backlash/loading setup determines how much noise the diffy will make.

You might try our HDS-5 in 75W140. It has smoothed out and toned down a lot of differential noise problems.

 

[jeepzj]

Thanks. HDS-5 seems too thick. The K.Viscosity@40 C is 345 for HDS-5 75w140 compared to Amsoil Severe Gear 189.5.

 

[jeepzj]

quote:

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Originally posted by jeepzj:
Thanks. HDS-5 seems too thick. The K.Viscosity@40 C is 345 for HDS-5 75w140 compared to Amsoil Severe Gear 189.5.

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This has me thinking. How can there be such a big difference in Viscosity @ 40C with two different brands of gear oils both claiming to be 75w140? Specialy Formulation @ 40C is 345 compared to 189 for Amsoil. Am I missing something?

 

[MolaKule]

Depends on the viscosity of the starting base oil(s) used.

We start out with heavy base oils and then blend to target viscosity.

In my view, it's the 100 C figure that's important for performance differentials.

And our oils were tested down to at least -35 C and were still liquid, so we post very conservative figures for both ends of the temperature spectrum.

I have no idea what Amsoil uses.

Addendum: The figures listed were for some earlier fluids and needs updating. Our latest tests on HDS-5 75W140 show a 40 C vis of 287 cSt.

[ August 15, 2005, 05:18 PM: Message edited by: MolaKule ]

 

[jeepzj]

Will the thicker weight of a 75W140 make the rear end hotter or cooler? I'm currently using Amsoil Series 2000 75W140 but it's time to change out the fluid after 30K miles and was thinking of using the Amsoil Severe Gear 75W90 instead of 75W140. Any thoughts? Thanks.

 

[MolaKule]

Generally yes.

You might consider a mid-voscosity gear lube such as HDS-R.

 

[jeepzj]

"Generally yes" to what and will the thicker 75W140 quiet down a diff? Currently my rear diff goes "whooooooshhhh" with 75W140.

 

[MolaKule]

Sorry, generally the thicker fluids will run a bit hotter unless you have a large diff cover/case to dissipate the heat, becasue you are putting more Hp into the fluid to "churn" it or move it. That extra Hp, which is energy/time, translates into higher temps.

A thicker fluid will always deaden gear whine a bit.

quote:

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"whooooooshhhh" with 75W140.

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What does it do with 75W90???