2nd Gen Non-Engine/Transmission Differential fluid change

[ILIANBG]

Hello everyone! I am going to change the fluid in the differential. I have about 55000 miles, but more than 2 years, I think almost 4.
I have the Mag-Hytec cover. The last time I did it I bought the fluid from the dealer. It was expensive, almost $130, just the fluid. I got the modifier from Geno's, they have the OEM I believe.
What kind of fluid is recommended? I am either empty or with moderate load in the bed: 80/20%. A lot of city driving, about 20% freeway driving.
It is the D80 axle and I remember I needed a friction modifier.
I welcome any suggestions, the truck has to last me for a long time
Ilian

 

[Ram4Sam]

I have had Royal Purple in mine since I cant remember when.....It comes with friction modifier, never had any issues.

Sam

 

[BIGNASTY]

DELO® SYNTHETIC GEAR LUBRICANT
SAE 75W-90

Don't need the modifier in mine, I have pulled heavy in both heat of Calif deserts and the cold of MT, I like it for two reasons. One it is a company that I have stock in and two I get it for free. JMO

 

[DavidC]

Royal Purple here also

Dave

 

[Bob4x4]

75/140 synthetic is recommended for HD's use in the 80

 

[dresslered]

LE-607
Product Code Name SAE ISO 100°C 40°C VI Flash Point Pour Point Timken OK Load
607 ALMASOL® Vari-Purpose Gear Lubricant 90 220 21.0 236 95 210°C -24°C 65lbs (29.5 kg)

 

[SDalgleish]

Amsoil 75W-90 Severe Gear here and never had an issue in any of my Turbo Diesels. If you tow heavy try 75W-140.

Scott

 

[jeepit]

Amsoil same as Scott.

 

[BDaugherty]

Ive been buying Super S brand synthetic gear lube from my local napa. I buy 5 gallon bucket and it comes in 75w90 and 75w140. I have not had any problems with chatter, but the friction modifier is available in a small tube at most parts stores.

 

[fest3er]

I'm an Amsoil dealer, but I'll only speak to the viscosity.

Never mind that Dodge calls for 75W90; that's the same as required for vehicles with engines producing a *lot* less torque 40 years ago. Behind a Cummins, the minimum viscosity used should be 75W110 for a normally unladen P/U. If the P/U is normally laden (2k-4k in the bed) or towing that much or more, 75W140 should be used.

 

[JCyrbok]

Amsoil 75W-90 Severe Gear here and never had an issue in any of my Turbo Diesels. If you tow heavy try 75W-140.

Scott

same for me too.

J-

 

[ILIANBG]

So, I wanted to see some info on the LE 607. I don't think it's made any longer. I found LE 9920 , a 75W-140 synthetic. It is something not found in the regular auto parts store. I think Mobil 1, Redline or Royal Purple will be available around me.
I just want to be sure that if I use 75W-140, and I'm not heavily loaded, it will be ok. Now usually I have heavy loads in truck bed about 20% of my driving. The other times, it'll be empty. Or is 75W-90 synthetic better for my use. I do not want to cause damage. And if the 75W-140 is all-around better and safer choice, why is not everyone using it.
About 75W-110- I can't find it locally.
Also, is friction modifier needed for the synthetic lubes?
I am just trying to educate myself as much as possible, and to use the best product I can find. That's why I really welcome and appreciate any of your experience.

Bob4x4, nice to hear from you too.
Ilian

 

[DavidC]

Did not require friction modifier with Royal Purple and I use 85-140 year round empty or pulling 5th wheel

Dave

 

[DFark]

Does amsoil still require the limited slip additive?

I'm an Amsoil dealer, but I'll only speak to the viscosity.

Never mind that Dodge calls for 75W90; that's the same as required for vehicles with engines producing a *lot* less torque 40 years ago. Behind a Cummins, the minimum viscosity used should be 75W110 for a normally unladen P/U. If the P/U is normally laden (2k-4k in the bed) or towing that much or more, 75W140 should be used.

 

[fest3er]

Does amsoil still require the limited slip additive?

Best I can say is, "Maybe." Middle of last year I changed my diff lube using, I think, the newer Severe Gear 75W110 and haven't needed any modifier; I don't detect any chattering any more. Before, with the other Amsoil lube (80W90, I think) I used, it'd been chattering (grumbling) a little in recent years. The Amsoil lube before that didn't chatter either. But, IIRC, the clutches might've chattered a little for a while after the previous changes until the lube made its way into the clutch packs.

But then, I've got 280k miles and 16 years on the truck. And my clutches might've been on the loose side to start. I believe the standard advice is to add friction modifier only if you need it.

75W140 should be OK even if the truck isn't worked hard. The lube is effectively 75 weight viscosity when cold, but works up to 140 when hot. I do not know as fact, but I suspect the lube would be similar to 110 when warm or very warm. It's intended to, and designed to, maintain consistent viscosity throughout the expected operating temperature range; it's part of the art and science of manufacturing lubricants. 140 is needed when you tow heavy; you're pushing a lot more work through the gears and that extra work raises the temperature, potentially beyond the ability of the lube to maintain viscosity. (In turbo terms, higher temps could move the lube out of its 'map'.) Viscosity is almost everything; but in a differential behind a Cummins, better extreme pressure additives are needed to prevent metal-to-metal contact during short periods when the lube isn't spread around well enough.

 

[jdross440]

I used Redline 75W90 Synthetic in my 2000. I got mine from Jegs and the modifier from the Dodge dealer.

 

[jdross440]

I have Redline 75W90 Synthetic in the 2000. I bought it from Jegs. It's about $17 a quart. I am using Mobil 1 Synthetic Gear Lubricant LS in the 2007 from Advance Auto, $11 a quart.

 

[GAmes]

My D80 is the only major original part on my truck. About 60% miles are towing, sometimes as much as 16,000 pounds but usually about 10,000. I use 75W140 Royal Purple and change it every 50k. No additives needed for the L/S.

 

[JMcCoy]

The reason they recommend lighter fluids is mostly for fuel effiency. I have run Mobil 1 since my first gear lube chance. Mostly because I'm lazy and I can go down the street and buy it. It's also pretty cheap. I do have to use friction modifier, but I did not. I never had to years ago. I don't know if I used a different viscosity or Mobil 1 changed the formula. All I know is that I do now.

 

[jeepit]

I did not add any modifier when I did my change over to Amsoil.