Gear Change 75w110 or 75W140

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Smith5361

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Have a heavily modified 97 GM K2500 that runs 40" tires and 5.38 gears, and a Detroit locker. Truck pulls occasional trailer but nothing too heavy. Its more of a play toy and cruiser.

The front has a 79 Ford Dana 60, runnig. 5.38 gears, and a ARB locker

Just pukled and drained some Lucas 75w140 and am curious if I should replace with 75w110 or 140. Definitely going with Amsoil either way.
Thanks
 
Originally Posted by gathermewool
"pukled"?

Pulled, yes its a typo from a phone keyboard but I think you figured that on out.
Originally Posted by rubberchicken
Originally Posted by gathermewool
"pukled"?


" GM " ?

Whether a GMC Sierra or Chevy Silverado the models boil down to C/K 1500, 2500, and 3500. They share almost every part imaginable other than some badging and the Grille and parking light assemblies. Chevy and GMC are both GM.
 
Originally Posted by zeng
5.38 gears ????
Definitely a 140.

Thanks for the suggestion

Yea its geared pretty low due to tire size. With the 5.38 the final ratio is still not as low of a ratio as the factory 4.10 and tire combo.
 
Go with the 140. My Amsoil rep told me that they actually recommend the 75w-140 in most applications, even when a 75W-90 is called for. With as beefy a setup you have, I wouldn't hesitate to run the 140.
 
I'd just go to Autozone and get Mobil 1's 140 ... it's PAO and that's why it costs more than the 90 ...
(I'd bet that's where Amsoil gets the base stock anyway) ...
 
Since on topic what benefits does 75w140 have over 75w90?

Supertech 75w90 looks like the best bang for the buck at $5.86/qt

100% synthetic / API GL-5 and MT-1, MACK GO-J, SAE J2360 and MIL-PRF-2105E
 
Originally Posted by Smith5361
Definitely going with Amsoil either way.


If you're an Amsoil fanboy and feel better using it, go ahead, but M1 or the Walmart synthetic will give the same protection at a fraction of the cost.
 
Originally Posted by 14Accent
Go with the 140. My Amsoil rep told me that they actually recommend the 75w-140 in most applications, even when a 75W-90 is called for. With as beefy a setup you have, I wouldn't hesitate to run the 140.


Beefy isn't the word I'd use-- more power going in, and more "load magnification" of the tall tires means this twiggy set up is fragile AF! I'd go for the best oil I could find, and amsoil 140's a strong contender.
 
Originally Posted by 14Accent
Go with the 140. My Amsoil rep told me that they actually recommend the 75w-140 in most applications, even when a 75W-90 is called for. With as beefy a setup you have, I wouldn't hesitate to run the 140.



+1
 
Originally Posted by eljefino
Originally Posted by 14Accent
Go with the 140. My Amsoil rep told me that they actually recommend the 75w-140 in most applications, even when a 75W-90 is called for. With as beefy a setup you have, I wouldn't hesitate to run the 140.


Beefy isn't the word I'd use-- more power going in, and more "load magnification" of the tall tires means this twiggy set up is fragile AF! I'd go for the best oil I could find, and amsoil 140's a strong contender.


Twiggy and fragile lol
 
140 for sure. I doubt you're too concerned with MPGs. If you're going to be fooling around with water/mud I'd go with the much cheaper 85w-140 conventional stuff so you can change it more often.
 
Agree with the 140 also.

Originally Posted by krismoriah72
Since on topic what benefits does 75w140 have over 75w90?



When the differential is working hard the fluid heats up. At higher temperatures, oil thins. The 90 therefore will thin out too much in some circumstances, resulting in more rapid wear.
 
Originally Posted by hatt
140 for sure. I doubt you're too concerned with MPGs. If you're going to be fooling around with water/mud I'd go with the much cheaper 85w-140 conventional stuff so you can change it more often.


Thanks for the suggestions. Luckily I wont be in too much water and if I end up in it i have breathers located pretty high up with check valve to keep it from coming int. If i didnt i woukd be thinking just the same as yourself
 
Esters being the best in heat points to Redline or Motul, no scamsoil for me anymore!! my driver + rare hauling 2011 frontier with the nissan-dana 44 specs factory 75-140 said to be semi-syn. my preowned 2011 SV likely had all OE fluids i changed to Redline, + when looking on the dana-spicer site i see 75-90 real synthetic + literature i got with the dana-spicer finned alum cover aka OE Titan stated the same. using my basic truck mildly with daily driving use i looked for mpg's + the full replacement with redline fluids including the 75-90 in the rear netted 3 mpg 16 to19 is a nice jump IMO. as stated your not interested in mpg's but redline's gear lubes are far better than any scamsoil product IMO or as noted use mobil I + save a buck
 
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