Rear end temp

I have a 8.75 rear end with 430 gears, auburn carrier and Strange axles. It seems to be getting very hot Does anybody know the proper running temp of this set up. Thanks

oley340 said:

I have a 8.75 rear end with 430 gears, auburn carrier and Strange axles. It seems to be getting very hot Does anybody know the proper running temp of this set up. Thanks

Click to expand...

Hello oley340,
Without some more information as to what the drive train is being subject to during your Temperature concern its a little hard to provide a answer, but here is a general rule of thumb.
The following is could be considered average.
During normal / to lite aggressive street driving you could expect to see temperatures around 120 deg to 175 deg F.
During oval track racing it would be expected to see 175 deg F to 250 deg F. (Note at one mile and above type speedways we see more like 300 + deg F with a lube pump and cooler installed)
During Drag racing its more like ambient temperature to 150 deg F. (short runs and cooling down between rounds).
The relationship between temperature and type of use has a lot to do with the following,
Is the gear set, bearing's, and seals new or used?
Are the parts in your rear end name brand like U/S gear, Strange, Timken ?
How was the rear set up (Back Lash, Pre-Load) ?
How old are the fluids?
Types of rears such as Detroit locker, Trac-Loc, Clutch pack, Torque biasing, Helical gear, Cone, and Auburn will all have there own unique characteristics in regard to street / race application and temperatures. Some manufactures will call out what specific type of lubricant should be used and what application the rear can be used for.
Cheep or expensive brands of parts and fluids will factor in this equation as will the age of the parts and lubricants.
Using Synthetic lubricants, Mineral gear lubricants, and or additives (friction modifiers) will also affect the outcome.
SAE Viscosity Grade will come into play, Choosing the correct type and grade lubricant is paramount in controlling both temperature and wear characteristics of any type of gears / bearings / surfaces.
Most mineral based gear oils will preform well up to around 250°.
Most Synthetic gear oils work well in the 200°-300° range.
Gear sets / bearings tend to last longer (wear) with mineral based lubricants as compared to Synthetic gear oils. Two completely different fluids designed to do two totally different jobs.
This is mostly due to additives used in there formula that may not be in synthetic type lubricants. Again choosing the correct lubricant goes a long way.
There not all the same.
Hope this somewhat helps.
Happy Mopar:
Arron

if ever there was a reason for a mike drop smiley...

Eaton conducted tests on oil/component durability during the late 1980s early 1990s

Their intent was to maximize seal and gear life and to allow the maximum OCI possible for their Heavy Truck gearboxes and diffs when using 75w-90 and SAE50 gear oils

They found;
a) components should not be operated at consistent temperatures above 250F
b) Intermittent operations to 300F do not harm the components or oils (synthetics)

Synthetic gear oils (75w-90 and SAE50) reduce operating temps by from 10-20C

Hello all,

The following is a more complete excerpt of the aforementioned testing.
Eaton conducted tests on oil/component durability during the late 1980s early 1990s
Their intent was to maximise seal and gear life and to allow the maximum OCI possible for their Heavy Truck gearboxes and diffs when using 75w-90 and SAE50 gear oils
They found;
a) components should not be operated at consistent temperatures above 250F
b) Intermittent operations to 300F do not harm the components or oils (synthetics)
c) Oils with a sulphur/phosphorus additive package activate rapidly above 230F.
d) A poor additive package in a synthetic lubricant may not be as good as a good (thermally stable) additive package in a mineral oil.

For a more complete analysis of oils / gear testing you can read the following.
https://www.lastgreatroadtrip.com/wp-content/uploads/2010/11/gear-oil-comparison.pdf
I suggest you read all of it but Pages 19 and 20 kinda sum it up.
BTW It was commissioned by AMSOIL.

Hope this helps.
Happy Mopar
Arron

Rearends run almost hot enough to burn your hand.

LOL..... only babies get there temp taken in the rear end....

thanks all !!

oley340 said:

I have a 8.75 rear end with 430 gears, auburn carrier and Strange axles. It seems to be getting very hot Does anybody know the proper running temp of this set up. Thanks

Click to expand...

I had a Dana 60 in an old Power Wagon I built. With 4.88's, Detroit Locker & 38" tall tires. On one trip down to Pismo Beach (about 4 hours at 70 mph) with less than a year old mineral gear oil; the rear end was so hot, I couldn't even get my hand to within a foot & a half of it because of the radiant heat coming off the rear cover.

A few weeks later, I swapped in some high quality synthetic before the (identical conditions) trip down, and I could put my hand right on the diff cover. It was amazing to me. I've run them ever since with the exception of the True Trac I got from Dr Diff. That traction device specifies non=synthetic gear oil.

A lot of people get hung up on low gears and rear temp. 99% do not have a temp probe.

Think about this though... A 3/4 or 1 ton truck with 4.11 gears will haul a load down the interstate all day long at 75+ in overdrive and no one bats an eye. Those trucks go 300+ thousand miles with a stock rear.