confused by fluid recommendations for diff change

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jeepmullet

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Oct 4, 2005
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2001 Dodge ram 2500 4x4 Cummins. Dana 60 up front and Dana 80 limited slip in the back. 6 speed manual NV5600 transmission. 3.54 gears. 262k on the clock

Fluids:
Engine: Amsoil premium diesel changed every 7-10k
Gearbox: Redline 5w-30
Power steering: Royal purple synthetic PSF
Front differential: Amsoil Severe Duty 75w-110 changed 30k ago (has mag-hytec extended cover)
Rear differential: Amsoil Severe Duty 75w-140 changed 30k ago (has mag-hytec extended cover)

Truck has meaty 35" tires with the 3.54 gears and I tow
Fluid needs changed ASAP. Ive been launching boats in flooded areas and both diffs show signs of contamination. I have not had one single axle problem since I got the truck 250k miles ago, but it spends a lot of time on the boat ramp and off road. If it makes any difference the truck is heavily modified from stock.

Anybody like anything better than the amsoil gear oil?
 
I'd use the 75w140 front and back. Stick with ANY name brand synthetic. Amsoil, Redline, RoyalPurple..... are all good. Local autopart stores might have Mobil1, Castrol, Pennzoil, Valvoline, and dealerships have OE 75w140. ANY new GL5 75w140 is better than water logged gear oil.

Amsoil MTF, Redline MTL, Synmax MTL, or Driven STF for the manual. I am no fan of motor oil in a manual. Local autopart stores have Valvoline/Pennzoil synchromesh, along with GM/Mopar dealerships. BG shops can install Syncroshift II.
Ravenol STF, Pentosin MTF2, Ravenol MTF, and Torco MTF are a little thinner and might be better for colder northern climates.


Amsoil PSF is good too.
 
Given that you submerge it often, and per your statement, see signs of "contamination", then I'd recommend frequent OCIs. And you might consider a couple UOAs just to understand the nature of the contamination and a reasonable OCI duration.

That in mind, there is ZERO logic to using any syn whatsoever. It's just money whizzed down the drain.

There are PLENTY of good quality dino lubes that protect very well, and will do so for less money, given your likely need to OCI frequently.

Check out the PRI current product listing:
http://p-r-i.org/other-programs/automotive-qpl/lubricant/
click on the current QPL listing ...


You'll see that there are lots lubes that meet that SAE-J2360 spec, and many are dino lubes! Across a broad range of vis choices. You can get excellent protection AND low cost; you just need to alter your thought process here.
 
Last edited:
Originally Posted By: jeepmullet


.......................Anybody like anything better than the amsoil gear oil?



No, sir.

Though if you are going to "dunk it" frequently I would likely change it more often than 30k miles.
 
Originally Posted By: dkryan
Originally Posted By: jeepmullet


.......................Anybody like anything better than the amsoil gear oil?



No, sir.

Though if you are going to "dunk it" frequently I would likely change it more often than 30k miles.


That is definitely on me and a poor decision to not check the fluid more frequently. I have also never checked the vent tube I'm guessing its been compromised somehow. The truck mostly sat for 18 months while I was out of state working 25-30 days a month and it got neglected as a result of having a company truck while I was in town.

Originally Posted By: CT8
75w-140 !!!


Thank you for the reply, that seems to be the consensus and I will continue to use it.

Originally Posted By: DoubleWasp
Chrysler downgraded the spec for different in all heavy duty vehicles, likely in the interest of fuel economy. Stick with what you have.

Did not know that thank you.



Originally Posted By: Greasymechtech
I'd use the 75w140 front and back. Stick with ANY name brand synthetic. Amsoil, Redline, RoyalPurple..... are all good. Local autopart stores might have Mobil1, Castrol, Pennzoil, Valvoline, and dealerships have OE 75w140. ANY new GL5 75w140 is better than water logged gear oil.

Amsoil MTF, Redline MTL, Synmax MTL, or Driven STF for the manual. I am no fan of motor oil in a manual. Local autopart stores have Valvoline/Pennzoil synchromesh, along with GM/Mopar dealerships. BG shops can install Syncroshift II.
Ravenol STF, Pentosin MTF2, Ravenol MTF, and Torco MTF are a little thinner and might be better for colder northern climates.


Amsoil PSF is good too.



I'm an idiot, I did not mean 5w-30 its the redline manual transmission fluid. The local speed shop had it in stock.

Originally Posted By: dnewton3
Given that you submerge it often, and per your statement, see signs of "contamination", then I'd recommend frequent OCIs. And you might consider a couple UOAs just to understand the nature of the contamination and a reasonable OCI duration.

That in mind, there is ZERO logic to using any syn whatsoever. It's just money whizzed down the drain.

There are PLENTY of good quality dino lubes that protect very well, and will do so for less money, given your likely need to OCI frequently.

Check out the PRI current product listing:
http://p-r-i.org/other-programs/automotive-qpl/lubricant/
click on the current QPL listing ...


You'll see that there are lots lubes that meet that SAE-J2360 spec, and many are dino lubes! Across a broad range of vis choices. You can get excellent protection AND low cost; you just need to alter your thought process here.


Thank you for directing me to that site, I had no idea it existed. A lot of info to digest.
 
Most diffs really don't care about what grade you use, as long as it's in an acceptable range. The debate of 75w-90, 80w-90, 85w-140, 75w-110, etc is moot IMO. They are all reasonable grades found in diffs. Whereas the common logic that "thicker is better" still prevails, the real data shows that there's very little difference in wear, to a point where you probably cannot delineate the difference.

If you're happy with buying that product, go for it. But you're spending a LOT of money on a product that you probably should be changing frequently upon your usage descriptions. Therefore there are lots of less costly dino lubes that still perform VERY WELL; see the PRI link I posted.

You don't "need" a syn, but by gosh if that's how you sleep well at night, do it.
 
You should NOT be getting water in the diff from launching boats. Its just not that great of water pressure. I would replace the seals first if I were you.
 
Originally Posted By: dnewton3
You don't "need" a syn, but by gosh if that's how you sleep well at night, do it.


Good point.

Locally I can buy Shell Spirax 80w-90 and 85w-140 for about $5 a quart. For those of you scared of store brands, there you go. Plus I cant think of any other 140 weight that cheap? Supertech synthetic is pushing $12.
21.gif


OP I vote conventional diff oil at 30k. I'd personally go up to a 140 just because of the larger tires. (constant "load")
 
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