D60 and D80 with Trac-Lok.

I can't seem to find a clear answer to a clear question through my searches.... What type (make and weight) of differential fluid is everyone using?

For front and back OEM says 80/90 is this general consensus with everyone?

Also what specific limited slip additive should I be using?

I was leaning towards non-synthetic Lucas 80/90 (which I use in all of my other vehicles) because changing out 2 gallons of diff fluid is a fairly expensive endeavor.

Thanks.

 

I use synthetic Royal Purple 75w140 because I tow heavy.
If you don't tow any good 90w +/- dino oil is fine.

 

The truck is a daily driver for me, dont plan on doing anything other than occasional towing... I also change out diff fluids in my vehicles every 15-20k so the fluid should always be pretty fresh in there.

 

You dont need to change diff fluid that often cadillac man. Occational towing, you should be fine at 50-75k intervals. The owners manual says you dont even need to change it just make sure it is at the right level. Add one bottle of the dodge friction modifier when you do change it. Its around $8 a bottle.

 

Redline 75-140 front and back

 

Thanks for the input. Do you happen to know the part number for that friction modifier?

 

Don't just routinely add friction modifier.
Too much and you'll lose your LS, it will just slip.
Many gear oils already contain modifier, adding more can be too much.
There is no set amount to use, it all depends on the type of gear oil and the amount of wear on each individual differential.
It may be you don't need any. Start out doing some figure 8s in a parking lot.
If the rear hops and makes noise add a quarter bottle of modifier at a time till the noise stops.

 

Oh this is news to me... I thought the modifier allowed the clutch packs to grip, but from what your telling me the modifier REDUCES the friction in the packs to an acceptable level...?

 

That is correct. Without enough of it, you'll get noise and vibration going around corners.

Don't get the cheap stuff from a parts house. Get good stuff. I got mine from the Ford ***********. It is just a re-labeled bottle of Dana Spicer additive.
Also, if you plan to use synthetic lube, make sure you get the additive that is compatible.

 

In your part of the country, and not towing heavy, I would use 75w-90 or 80w-90.
And IMHO, you can do a lot better than Lucas.
I recommend a synthetic also. Flows and protects better, on cold mornings, in the winter.
As stated, most higher quality synthetics have the FM already added.

RJ

 

Friction modifier is often called whale oil by the old timers.
Not sure if it first was made from sperm whale oil but under a microscope the additive looks like sperm.
How it works is the "head" of the additive "digs" into the clutch face and the "tail" acts as a lube allowing the clutch to slip until there is enough force on the clutch to pull the sperm out of the clutch causing it to grip.
So if you add too much additive there is more sperm that has to be ripped out, LS clutches just slip, result is one wheel drive.

 

Im sure I could do a lot better than lucas as well.... however that is the intention of this topic, to find out what is better. Suggestions?

I change my fluids based on their current contamination level, not on their current structural integrity. I find that fluid is contaminated far before it breaks down and also that contaminated fluid is worse than broken down fluid.

For instance in my Cadillacs I run a high grade full synthetic through the engine but I STILL do an oil/filter change every 3-4k. I am not wealthy by any means but an extra dollar here and there keeps my classic machines running like new.

So even if I dont need to change out my diff fluids at small intervals I probably will anyway... what would be considered a high grade dino? Should I really be using a synthetic?

 

If I lived where you do, I'd use a Synthetic. A gearlube that will still flow well below zero is worth it, IMO.
From the testings I've done...Lucas is a small step up from national brands.
A full step up would be Royal Purple, Amsoil, Schaeffers... just to name three. Also, LE (Lubrication Engineers), which is especially well known for the quality of their gear lubes.
Sorry, these are all synthetics. You asked about mineral oil based gear Lubes.... Check Schaeffers and maybe LE.
http://www.schaefferoil.com/
http://www.le-inc.com/

Bill - Very nice, easy to understand description of how a FM works.
I've been in the oil/lubrication business for 15 yrs and never heard it done better.

RJ

 

I really appreciate the input guys! And yes, Bill thank you for that interesting description... I completely understand what you said and it makes perfect sense.


RJ, it looks like I might settle down over a couple gallons of Amsoil 75W-90 Long Life Synthetic Gear Lube, seems to be the modestly priced as well.

 

Read up on Delo gear oil here> http://www.chevronlubricants.com/wor...+lubricant.asp

This is what I use in the farm equipment gear boxes.
Could be hype but it works for me.
Here's some more hype that sounds true http://investor.chevron.com/phoenix....948&highlight=
Says that it is approved by Eaton and Meritor for 750,0000-mile extended service in their heavy duty axles.