Rear end ? please help I am confused!

[utah300rum]

I looked up the Vin# and Cert# on my F-350 now I have some stupid questions.

My axle code was a 41 which according to the sheet is= 3.73 non-limited slip F-350.

I was trying to find out what type of oil to use in the rear end as I plan on changing it in the near future. I have read many posts about different weights and how much friction modifier to add and I am confused a little.

Now I am even more confused not being a mechanic what is the different between limited slip and non limited slip?

Also does this mean I dont need the friction modifier?

One reason I ask is my truck SUCKS in the snow. My last pick up had an after market posi rear end, so maybe I am spoiled.

Here is an example the other day I had my truck parked next to the wife's Suburban in the drive way. It rained then snowed so it was very slick. My wife backed her Suburban with highway style tires out in 2wd.

My BIG BAD FORD TRUCK would not even move. Not even budge just spin one tire. SO i turn it into 4wd still would not move. Then I remembered some saying that unless you lock in the hubs there is no 4wd in reverse. SO I lock in the hubs and still have to rock back and forth to get the truck out of my relatively flat drive way

ALL THE TIME MY WIFE SITS IN HER 2WD VEHICLE WATCHING AND LAUGHING AT MY BIG BAD PIECE OF S__T TRUCK

[DryHeatDude03]

The axle code 41 is for an open diff 3.73, This would mean you do not need friction modifier. I know some guys even run posi rear ends without friction modifier when running royal purple synthetic or similar. An easy explanation about an open diff. is that the applied power goes to the tire with the least resistance, ie the one that has the least traction,(one wheel peel), Which is why your truck sits and spins on the snow. I'm definately no expert on differentials, so someone may step in here. And I also am not sure what weight lube you require, but that story about your wife laughing at you,,really made me chuckle though,,,thanks for the laugh,

[utah300rum]

HELLO?

anybody?

[planeoldguy]

Welcome to guzzle's Rear Differential Maintenance Web Page

[99bigred]

was the 4x4 working? and a posi was probably helping your old truck but these trucks are also very heavy which doesnt help

[Diesel Freak]

Your truck need to be moving a bit forward in order for it to lock into 4wheel drive.
Heavy or not.............ICE is ICE.............everything spins!!