Differential gears and gear oil

Status
Not open for further replies.
2000Trooper

2000Trooper

Joined
May 5, 2013
Messages
134
Location
Maryland
About a year ago I redid the gears in my truck from the factory 3.91 to 4.88. From information I found from companies like east coast gear supply and a couple of other axle focus companies I decided to break in the gears with lucas 80w140 conventional gear oil. They claimed during break in these oils will be nice and thick and stick to the ring and pinion and help pull the heat away from the metal. I know synthtics distribute the heat better whereas dinos localize heat more, but it was coming from a reputable source and I went with it anyways.

After 500 miles I changed the oils and used the same stuff. Now that it's cold I'm getting pretty [censored] mpg and when it drops in the 30s I can tell the gear oil is causing a lot of drag until I travel a couple of miles for the gear oil to warm up.

I'm tempted to switch to Mobil 1 75w90, but there is a lot of hear say about lower gears needing thicker oil due to the extra revolutions causing more heat. Is this a myth or fact?
 
I'm not sure if you're referring to Lucas 85W140, which has a KV @40*C of about 400 cSt.
You could opt for other 85W140 of KV @40*C ranging from 250-300 cSt to mitigate the drag and mpg loss, I suppose.
 
Last edited:
East Coast Gear rebuilt the 3.73 g-80 in my truck. They were very adamant about not using synthetic. They put in lucas 75-140 They recommended lucas. When i hit 500 miles i changed to Valvoline 75-140. I hav heard that a lot of gear companies recommend dino gear oil. Since i tow, i'm staying with the heavier gear oil. Just not lucas.
 
Originally Posted by novadude
Originally Posted by spasm3
Here is the link to east coast gear. They did excellent work on my truck.

https://eastcoastgearsupply.com/files/PDF Files/ecgs-gear-oil-recommendation1.pdf


Does anyone believe this explanation? I'm no expert, but I see some things in there that set off the BS meter (synthetics less viscosity-stable than dino, etc).


That thing reads like the author already had a conclusion in mind and then set about coming up with a document that could back up that conclusion.

And is "cling ratio" a thing? I don't remember ever hearing it before, but that could just be me...
 
Originally Posted by The_Nuke
Originally Posted by novadude
Originally Posted by spasm3
Here is the link to east coast gear. They did excellent work on my truck.

https://eastcoastgearsupply.com/files/PDF Files/ecgs-gear-oil-recommendation1.pdf


Does anyone believe this explanation? I'm no expert, but I see some things in there that set off the BS meter (synthetics less viscosity-stable than dino, etc).


That thing reads like the author already had a conclusion in mind and then set about coming up with a document that could back up that conclusion.

And is "cling ratio" a thing? I don't remember ever hearing it before, but that could just be me...



Yes I don't know that I buy this either. I did use dino in case I had a leak so they would warranty it. I am tempted to change again since break in and towing, to amsoil severe gear.
 
Last edited:
Originally Posted by The_Nuke
Originally Posted by novadude
Originally Posted by spasm3
Here is the link to east coast gear. They did excellent work on my truck.

https://eastcoastgearsupply.com/files/PDF Files/ecgs-gear-oil-recommendation1.pdf


Does anyone believe this explanation? I'm no expert, but I see some things in there that set off the BS meter (synthetics less viscosity-stable than conventional, etc).


That thing reads like the author already had a conclusion in mind and then set about coming up with a document that could back up that conclusion.

And is "cling ratio" a thing? I don't remember ever hearing it before, but that could just be me...


Lots of misinformation in that article.

Quote
Synthetics thin out quickly once hot and lose their cling ratio to the metal object, when the oil is stuck to the gear it provides a cooling factor for the metal. We also believe that conventional oil has better pressure properties, i.e. it provides a better cushion then synthetic for two reasons. First, it does not thin out as much and two it clings to the gear.


1) All diffy gear oils contain tackifiers and thickeners that promote cling, whether mineral or synthetic,

2) I doubt EP additives and so-called "cushioning" have anything in common, whatever "cushioning" means, as they don't define it (are they referring to shock loads due to mechanical impulses generated by popping the clutch?),

3) VII's in both mineral oils and synthetic gear oils reduce thinning at high temperatures.

4) cooling is done by heat conduction (contact) and by convection due to fluid movement.

While these guys may be really good at shimming diffy components for proper loading, they lack knowledge about lubricants in general.
 
Last edited:
https://www.lastgreatroadtrip.com/wp-content/uploads/2010/11/gear-oil-comparison.pdf

This is something I had found a while back, it's 11 years old and I'm sure formulations have changed since but I did find the information in it interesting nontheless.

But to get back to the original post, I guess I'll give M1 75w90 a try and see how it does. I might check operating temps using an IR meter on the diff housing. I'll definitely check the fluid after 10k to see if there is any excessive wear.
 
My owners manual specifies a Synthetic diff fluid, I don't think the OEM would spec a fluid that didn't perform, especially looking at it from a warranty aspect. When I had the diff bluprited and a trutrac added my builder specificaly stated to use a quality conventional oil during a very specific break in procedure and then advised to change the conventional oil to a high quality synthetic. I put Redline 75w140 and the diff works extremely well and is very quiet, but then again the GTO diff is known for its issues.
 
Originally Posted by 2000Trooper
About a year ago I redid the gears in my truck from the factory 3.91 to 4.88. From information I found from companies like east coast gear supply and a couple of other axle focus companies I decided to break in the gears with lucas 80w140 conventional gear oil. They claimed during break in these oils will be nice and thick and stick to the ring and pinion and help pull the heat away from the metal. I know synthtics distribute the heat better whereas dinos localize heat more, but it was coming from a reputable source and I went with it anyways.

After 500 miles I changed the oils and used the same stuff. Now that it's cold I'm getting pretty [censored] mpg and when it drops in the 30s I can tell the gear oil is causing a lot of drag until I travel a couple of miles for the gear oil to warm up.

I'm tempted to switch to Mobil 1 75w90, but there is a lot of hear say about lower gears needing thicker oil due to the extra revolutions causing more heat. Is this a myth or fact?



If I read the article correctly he also stated that when it gets cold to use Lucas 80-90 conventional gear oil if you would like and use the 85-140 when warmer again. I have used synthetics in my dualy crew cab and regular gear oil and to be honest just don't see any difference it has 190,000 and have changed it over the years many times and after break in oil was changed it always looks pretty good when changing. I really would never change a lubricant in an effort to boost mileage my main goal is have no failures on the road. Right now it has Lucas 80-90 conventional gear oil and looks great when checked every oil change.
 
Status
Not open for further replies.

Similar threads

S
  • Locked
Confused Open differential gear oil
Replies
4
Views
7K
oldhp
G
ECGS Gear Oil Recommendation
Replies
9
Views
5K
UNC151
M
  • Locked
manual gear box oil?
Replies
18
Views
6K
Zaedock
J
  • Locked
LSD gear oil in non LSD differential?
Replies
4
Views
13K
Jimmy9190
UNC151
  • Locked
Dana Spicer Advantek Gears After REM Isotropic Finishing
Replies
5
Views
861
ctechbob
Back
Top Bottom