Which gear oil?

[Wheaties]

Thar' she blows!!!! ... . an EXPERT! :-laf :-laf :-laf



(just couldn't resist)

 

[BigDaddy]

Matt,



Actually I thought you and Fred were doing pretty well on your own



I was just waiting to get my two cents in



Joe

 

[Wheaties]

Right! Proving once again that two people that don't know what they are talking about know less than one person who doesn't know what he is talking about.



... see if you ever help me install gauges again!!



What we were saying before, where are the real experts now? Where are the folks that could tell us some real information about our oil?



Hungry For Knowlege

 

[HEYBOSS]

BigDaddy, I sincerely appreciate your expertise here.



I always respect and look up to your posts, I know that you always do a lot of research before you jump into anything, I try to do the same and that's what TDR is about and it's great, we can all improve our knowledge and always learn something from someone.





Fred... ... ... ... ... Not so Super Drone.

 

[HEYBOSS]

Originally posted by Wheaties

Right! Proving once again that two people that don't know what they are talking about know less than one person who doesn't know what he is talking about.



... see if you ever help me install gauges again!!



What we were saying before, where are the real experts now? Where are the folks that could tell us some real information about our oil?



Hungry For Knowlege

Here we go again with all the political bull s**t



Just tell him; It's like the blind leading the blind



See how simple?:-{}

 

[RustyJC]

Re: Matt

Originally posted by HEYBOSS

RustyJC_ I read your post too fast and didn't notice you noting that the Royal Purple has the modifier in it

From my previous quote:



We tow a 13,500 lb GVWR 5ver and use Royal Purple 85W-140 which has the LSD friction modifier already formulated into it. It worked great for us right out of the bottle - no supplemental Mopar friction modifier required.



Yes, the Royal Purple is full synthetic with the friction modifier formulated into it. At least, that's what the bottle says!



Rusty

 

[thepitts]

Mopar gear lube

The Mopar gear lube will require friction modifier, 2 bottles. Just had mine changed due to leaking cover.

 

[RustyJC]

Originally posted by HEYBOSS

You could have a problem with leaky seals due to overfill. I believe they recommend 1/4" below the fill hole.

I cured the problem with a siphon hose! The only reason I brought it up was, in case anyone is filling the Dana 80 rear axle with a stock cover, I'd slow down and check the level before putting the last bit of the 3rd quart bottle in!



Rusty

 

[Wheaties]

Okay, I'll fess up! I have huge respect for both BigDaddy and HeyBoss. I am a big fan of both of them. They are both great guys that would do anything they could to help you out.



Back to the subject at hand: I believe my question is how much friction modifier are you getting with a full synthetic and is it the right amount for your limited slip? Dave Fritz' web page says the 2wd rear end calls for 8oz and the 4x4 rear calls for 10oz. Does this mean the synthetic with friction will need another 2oz or 2oz should be taken out?



Matt

 

[Don M]

75/140 or 85/140 is the better choice IMO.

It is just tougher to shear a thicker lube from between the gear faces under harsh conditions like higher HP bombed trucks or towing. As the gears rotate and mesh together the thinner oils are slung off and squeezed out easier and the lubrication of the moving parts begin to rely on barrier lubrication and additives more than the oil itself.

Guys with standard transmissions that bang gears and shock load the axle harder can add to the shearing effect of the thinner oils as well.

Rear axles are not like engines that wear during start-up. Generally, guys dont get the truck running and instantly accellerate to 100 miles per hour. Further, a 75/90 lube has the same viscosity of a 30 weight engine oil. Too thin IMO and this is why the manufacturer asks us to use the thicker lubes for towing.

Any brand of quality lube like Royal Purple, Redline, LE, etc wil do the trick and not harm warranty coverage.



Don~

 

[HEYBOSS]

Matt,



You're bring up a good point. Now the if the 2wd rear end takes less gear oil then the 4wd, then it tends to justify that the more synthetic gear lube you use the more modifier will have due to the larger quantity in the oil used? Maybe, maybe not.



Just thinking here.



Fred.

 

[HEYBOSS]

Re: Mopar gear lube

Originally posted by thepitts

The Mopar gear lube will require friction modifier, 2 bottles. Just had mine changed due to leaking cover.

Are you using the regular Mopar or their 75w140 synthetic?





Don M, thanks for your input,



Fred.

 

[Wheaties]

I read the label on a bottle of RedLine 75W90NS at the parts store today. I believe it said it was good for use in a weak limited slip differential. That is, it has little or no friction modifier. RedLine also makes a 75W90 with the friction modifier, and the bottle said you can add modifier to the 'NS' lube, or blend the 'NS' and non-NS to get the right amount of modifier.



Matt

 

[HEYBOSS]

Situation resolved and I have drawn my conclusions

I decided to go with the Royal Purple, reason being it has the modifier in it, I got it local and at a very reasonable price $7. 99 qt.

I just picked up some. My decision was also based from the TDR input and from some very creditable and respectable people I know.



At the end I guess all gear oils mentioned here are good and all comes down to personal preference.



I want to thank you all, this has been educational to me and I guess, others.





Fred.

 

[Cooker]

Originally posted by Don M

Further, a 75/90 lube has the same viscosity of a 30 weight engine oil. Don~

I find this very hard to believe. Viscosity is viscosity, right? 75 or 90 doesn't sound like 30 to me. I'm not trying to start anything, but I don't see how that is a true statement.

 

[Don M]

The Society of Automotive Engineers (SAE) grades gear lubes and crankcase oils differently.

A 75/90 has a viscosity range of 4. 5 centistokes (cst) at 75 through about 22 cst at 90 respectivly. This is measured at 100 degrees C. The range of nearly all 75/90 gear lubes is the same as the range of all 30 weight engine oils. These thinner oils rely on the barrier lubricants and EP additives faster and more often than the thicker oils in the 145 range

 

[Cooker]

As I clicked to read your reply, I recalled an article I read sometime back about this very issue. I answered my own questions before I read your response. Thanks for the reply. I guess I shouldn't ask questions so late at night anymore

 

[Don M]

Ryan,



here is a chart to peek at on viscosity.



https://www.turbodieselregister.com/user_gallery/displayimage.php?&photoid=1210&width=0



Don~

 

[Dave MacArthur]

I have a question about the friction modifier. I know this is a little off topic but I think it will get the attention of those who may know the answer. Is there any reason why I shouldn't use any (zero), or very little friction modifier? What I mean is, if I like my LS to pull hard on both sides and don't mind a little chirping, would I be doing any harm? All the instructions I have seen say to add the modifier until you like the drivability. Not that there is any set amount (just a suggested amount to start with).



Thanks,



Dave.

 

[BV]

Royal Purple

Just picked up some Royal Purple to change out the front diff, tcase and rear diff when time/weather allow



I see mention of 3 quarts to fill the rear (Dana 80) but the book shows capacity of 10. 125 pints (including the friction modifer) which equates to just over 5 quarts. So what is the correct amount or are they both correct because 3 is for 2x4 and 5 for 4x4?



Also for anyone interested: Jegs Hi Pro has Royal Purple for $6. 99 a quart for gear lube or atf and has a $7. 99 handling fee but free shipping.



I ended up at our local Baxters Auto and asked if they could do better than list and they gave me the discount when I mentioned Jegs pricing. It doesn't hurt to ask unless your affraid of the word no