Am I better using 75w-140 over 75w-90

[12ga diesel]

I'm thinking of changing my rear end fluid and front diff this weekend and was just curious what weight everyone was using. Parts store has both 140 and 90, but I know 75w-90 is for more severe service requirements and the 75w-140 is something that meets most requirements of cars/trucks. Is 75w-90 overkill or can I stay with 75w-140?

 

[psyco66]

I run 75w-90 Amsoil and love it. I also put 75w-90 in every vehicle I work on.

 

[btfarm]

Unless you're doing some heavy towing/hauling I'd stick with the 75w90 synthetic front and rear. I ran 75w140 in my '03 2500HD 8.1/A and when winter came I realized it was just too damn thick. I had lots of trouble getting the transfer case to shift cold even when I backed off a couple of times to get some unloading. Long about mid January of '04 I want back to 75w90 and my problems went away. Plus, with today's fuel costs you don't need any more rolling resistance. I've got 75w90 Mobil 1 front and rear.

 

[12ga diesel]

Unless you're doing some heavy towing/hauling I'd stick with the 75w90 synthetic front and rear. I ran 75w140 in my '03 2500HD 8.1/A and when winter came I realized it was just too damn thick. I had lots of trouble getting the transfer case to shift cold even when I backed off a couple of times to get some unloading. Long about mid January of '04 I want back to 75w90 and my problems went away. Plus, with today's fuel costs you don't need any more rolling resistance. I've got 75w90 Mobil 1 front and rear.

Okay, thanks for the info. It does get cold enough here in winter that I would see the 75w-140 getting real thick come winter time. I'll go and pick up the 75w-90 lube this weekend.

 

[Idle_Chatter]

I think you've got your numbers backwards the 75W140 is the heavier (140 vs 90) and for more severe service. It is recommended only for the rear diff and only for heavy towing and continuous use. You shouldn't go heavier than 75W90 in the front and for normal duty and occasional towing 75W90 is fine for the rear. I had several bottles of 75W140 on the shelf and ran a load of it in my rear diff for 30,000 miles or so. I don't tow often or heavy, so it was "overkill" for my truck. I ran it through a full season, including winter in northern Ohio and saw no loss of mileage and had no issues with the heavier lube. I did notice when I drained it that it was still nice and clear and amber, so I think my diff appreciated the extra lubrication.

 

[rtquig]

If you tow a lot, the 75w-140 is what you would use. For towing only once in a while go with the 75w-90.

 

[psyco66]

When I built my Suncoast stage IV trans I changed my front and rear diff to Amsoil 75w-90 and my transfercase to 3 quarts of Amsoil 5w-30 and I put Amsoil trans fluid in my trans and I gaind roughly 1 1/2 mpg. I am still running Chevrol Delo 15/40 in the engine. I do not know what it is worth but I thought I would through it out there.

 

[Arkapigdiesel]

I've got four quarts of Amsoil Severe Gear 75W-140 if anyone wants to buy it.

 

[12ga diesel]

If you tow a lot, the 75w-140 is what you would use. For towing only once in a while go with the 75w-90.

Well for the time being, it looks like we won't be camping, and therefore towing as much as we have in the past several years. With the baby now along with our daughter, we are getting pretty tight in the camper. And that means a very good excuse for looking for a bigger camper come fall. We haven't tried it yet, but I think we will be going camping at least a couple times this summer. So that being said, I think when I change it I'll go with the 75w-90.

 

[Wrecker]

75w-90 Severe Gear is a great choice. Let me know if I can help.

BTW I also love the smell of Diesel, no matter what the time of day!

 

[Ragindiesel]

Guys amsoil also offer the 75-110 for Gm vehicles. This works much better than the 75-140 and won't hinder milage as much.

The 75-110 would be my choice in your truck