drain and refill rear axle

[jtate]

well im thinking about draining and putting in new gear oil in the rear axle, cause this truck has 233,000 miles on it and i know the po has never changed it or refilled it. i went last knight and picked up 4 bottles of valvoline 80w-90 and the guy asked if i need the additive that goes in the rearend. i answered i dont know because i thought the additive was for limited slip, and i dont know if its limited or posi. how can i tell if its either one and if i need the additive?

 

[MUDKICKR]

fords name for the limited slip is "traction loc" chevys name is "posi trac" they are all clutch type limited slips, which will require a friction modifier, aka rear axle additive. if you would raise the rear axle off the ground and turn one tire and the other turns the same way, it has a type of limited slip or locker. if it turns the opposite direction then its just a reg. diff.

 

[Diesel JD]

Ooh, tough call, if the axle is original the code in the doorjamb should tell you. If you don't know that info is here a couple places on what the axle codes were. The problem is not all trucks have the original axles. Mine came from the factory with 3.55s according to the door code, when I got it it had 4.10s and then I swapped a 3.55 open axle in, so in slightly more than 200K miles its had at least 3 different rear ends or R&P. I think there is some way to jack up an axle and then tell if it's L/S or not. Someone wiser will have to post it. I also wonder if there's a problem with having the limited slip additive in a non L/S gear set?

 

[Shadetreemechanic]

I don't know what year you are dealing with, but in the early 90's a "c" starting off the axle code indicated limited slip.

 

[jtate]

fords name for the limited slip is "traction loc" chevys name is "posi trac" they are all clutch type limited slips, which will require a friction modifier, aka rear axle additive. if you would raise the rear axle off the ground and turn one tire and the other turns the same way, it has a type of limited slip or locker. if it turns the opposite direction then its just a reg. diff.

mudkickr thanks for the info, just two days ago i jacked up the back of the truck with both tires off the ground and if you turn one tire the other turns in the same direction that you turn it. i also tried leaving one tire on the ground while turning the other and its almost impossible. i looked on the sticker on the door jamb and the axle code reads d-5, what does that mean?

 

[tractorman86]

not sure about the code but it is definately some kind of a trac-loc

 

[jtate]

i just found the diff code in the tech articles and a d5 is a ford, l/s, 7400lbs, 3.55.

 

[jtate]

one other question i have is after i drain all the fluid out the axle and am ready to fill it back up, how much of the additive do i put in? the tube i bought is 7oz, do i put it all in and topoff with oil the rest?

 

[fastass350]

Correct, add the whole tube, but add it while you add your fluid, or mix it with one bottle of fluid rather than pouring it straight in. I prefer to buy the friction modifier from Ford, it's only about 5 bucks for a little bottle. Also I let the sealant on the rear cover set up as long as I possibly can before I add any fluid to it, to help avoid it leaking.

Chris

 

[Fozz]

When you open it up, wipe out the inside of the differential housing, there may be some metal filings, and check the gear teeth. Napa has a cork gasket you can use for the cover. And yes as stated, put in all of the friction modifier then top off with gear lube to the bottom of the filler plug threads (make sure the truck is level). I think Ford recommends changing every 100k miles.

 

[OLDBULL8]

http://www.guzzle7pt3.com/rdiff.php

You might want to look at that. They recommend 75W-140 and 4 oz. friction. Should be about the same as your rear end, no the one on the truck.

 

[jtate]

well i called ford to see what gear oil they recomended to put in the differencial and how much additive to use. they rec synthetic 75w-140 and 4oz of additive, but at $18.73 a quart plus the cost of additive making a oil change of $80.00. i dont think so, so i bought 4 bottles of lucus 85w-140 and the additive. i dont think a little heavier oil is going to hurt anything and summer is just around the cornor so it will make up for the heat lol. what do yall think?

 

[Truck#3]

I use synthetic especially if you get cold winters beacause I seen differentials go out because people warm up their engines and think its all good and just take off full speed when the oil in their diff. is so thick you can grab it with your hands and make a ball out of it.

 

[jtate]

I use synthetic especially if you get cold winters beacause I seen differentials go out because people warm up their engines and think its all good and just take off full speed when the oil in their diff. is so thick you can grab it with your hands and make a ball out of it.

i dont think it gets that cold here in louisiana. you might have maybe 5 or 6 days out of the whole winter months, that you might see the temps in the low thirties. not to mention in the summer 102*, so i dont think 85w-140 is going to hurt anything.

 

[tractorman86]

i just put lucas 80-90 in mine and it says not to use ls addative