Engine/Transmission (1998.5 - 2002) Transfer Case oil/Axles

[CrewCabDiesel]

I am changing out the clutch and I want to change lube in the transfer case while I am there, Can I use the same lube as what I use in the NV4500 to avoid cross contamination if a seal goes ?.

Also Can I use a 75w90 in the axles ? I would like to just have one gear lube used in the truck.

Kyle

 

[CFarlow]

Don't think so CrewCab-- they call for automatic trans fluid for the transfercase. The "oil" in your trqnny might be to thick for it to pump properly in your "case". I'm thinking , better safe , than sorry.



Chcuk

 

[CFarlow]

accually, my name is "Chuck"----sure wish I could type!

 

[LSMITH]

5W-30 synthetic motor oil is the same weight as the ATF that is called for in the T-case. NASA flys without me in confidence, but I would think that motor oil lubes more effectively than ATF. I put Mobil1 5W-30 in my T-case 30k miles ago, it simply does not get more than lukewarm anymore. It used to get pretty warm with ATF, but not hot. Temp reduction tells me friction is reduced, and life extended. Gear oil is too heavy for the T-case. YMMV.



75W-90 is what I use in the axles. I used Mobil1, but any good quality oil should be fine. I noticed nearly 30 degree drop in rear diff temps when I went from dino 75W-90 to synthetics. Unless you tow heavily a lot 75-90 is the best choice, 80W-140 is not needed unless 50% or more of the miles are towing hard and/or heavy IMO. Front axle disconnect operation is much quicker and smoother with the Mobil1 in there too.

 

[Riflesmith]

I am currently running 5W-30 synthetic oil in my transfer case as well. I am seeing lower operating temperatures too. However, I feel a good 75W-90 synthetic gear lube will offer superior protection and longevity. I will be switching to gear lube on my next change.



ATF's viscosity as it relates to motor oil would actually be around a 0W-20. Most ATF's list a viscosity at 100 deg. C of around 7. 5 centistokes. This is a 20 weight oil. 5W-30 oils list a viscosity of around 10 to 11. 5 centistokes.



75W-90 gear lubes are not as thick as many people believe. Their viscosity is actually very similar to a 15W-40 motor oil. Gear lube viscosities are listed under a different SAE grade system than motor oils.



There is an interesting chart explaining the different viscosity grading systems. Here is the link; http://www.bobistheoilguy.com/visc.html

 

[Pit Bull]

Originally posted by LSMITH

5W-30 synthetic motor oil is the same weight as the ATF that is called for in the T-case. NASA flys without me in confidence, but I would think that motor oil lubes more effectively than ATF. I put Mobil1 5W-30 in my T-case 30k miles ago, it simply does not get more than lukewarm anymore. It used to get pretty warm with ATF, but not hot. Temp reduction tells me friction is reduced, and life extended.

.

Do you guys think that DC went with ATF because of cost versus the Mobil 1 synthetic option? Does the ATF have any other wear properties that would make it better versus the synthetic oil?

 

[Texas Diesel]

I would suggest that you use Royal Purple Synchromax, it is rated to directly replace ATF and motor oil in gear boxes and is labelled to be compatable with syncros.



My 241HD used to grind on engagement anytime over 25 MPH then I put the RP stuff in and now it engages smoothly at any speed, plus the synchromax is 100% synthetic.



Disclaimer: I dont sell RP so my opinion is unbiased, the RP simply works great.



Others have had success using Amsoil 5w-30.



Disclaimer: I've never used Amsoil anything.

 

[LSMITH]

Originally posted by Pit Bull

Do you guys think that DC went with ATF because of cost versus the Mobil 1 synthetic option? Does the ATF have any other wear properties that would make it better versus the synthetic oil?

Well, it only needs to last 36K miles to get out of warranty, and the design life of the vehicle is around 100K miles. That is all they intend for the component parts of the vehicle to last. ATF will get it there easily. Let one thing be very clear, if an automaker can save one penny per vehicle without repercussions they WILL do it every time.



IMO ATF is suitable for transfer case use, and it will live a long happy life. I wanted a little better is all.