Finally got the ring gear and new bearings put on this "trac-lock" carrier for the rear axle. Just wondering what type of fluid to put in there? Also, can you mix the two fluids? I was thinking 2 quarts 80-90w and 1.5 quarts 85-140w. Someone was saying fill it up with 85-140w and run it for a week or two then drain and put 80-90w. Don't really want to do this cause the lim-slip additive is like $12 a tube.

 

Also, I was told to put some oil on the new bearings before I put the races on them and install the carrier. The thing I was wanting to know is, should I put oil on the outside of the races and underneath the bearing caps? I don't think the races move underneath the bearing caps, but I just want to make sure. Thanks in advance

 

I'm not 100% sure on all your questions.

The only answer I have for you is that you should soak the clutches in the friction modifier over night before installing them into the carrier.

You should press the bearings on with out oil.

As for installing them in the rear end, I don't think oil is necessary, you could lube them up with some oil though to make sure there is oil in the bearings while you set the backlash, which you'll have to do because you have replaced the bearings.

I'd run 80-90 in it with a tube of friction modifier.
I've never heard of run and change after a week, but I would change it out after some miles are put on the truck. The friction modifier for the clutches is kinda an add to taste thing too. More you put in, the more slip you get. But if its popping while you turn, you dont have enough in there.

Before you re-assemble the rear end, make sure you pop out the VSS and clean that as well. when you add your fluid, just pull the VSS and add it though that top hole there, and its easy as pie then. =)

So, make sure you clean the area first so you dont knock dirt in there. or have the sensor break off inside like I had happen to me.

 

80-90 is too light for the rear end in my opinion. 80-90 for the front end, and 85-140 for the rear end in mine.

 

A good quality 75-140 synthetic. I run it in both pumpkins.

 

This is not hard. No need to press the bearings on they will slide on. Just add the 85w-140 after you put it together. The fluid will submerge the set in the case.
Ford calls for 85w-140. Don't used the lighter stuff at all. No need to pre-lube the set will be submerged in the case so you will be ready to go once you fill it up.

I used Royal Purple fluid. It is a bit more $ but already has the additive in it. So may be cheaper in the long run.

 

Wow guys that's pretty weird. I finally got around to calling the dealership and the guy there told me 80w-90. He said the newer Sterlings use 70w-145, but ours don't. The guy from the transmission shop that did the work also told me 80w-90. It seems kinda like a pick your poison thing. Unless you do a lot of towing then I could see the heavy oil.

 

The old spec was 80w-90. New spec 75w-140 synthetic. All sterling rear diffs regardless of year of manufacture.

 

Well, this is what I used: 2qts Valvoline 80w-90, 1qt Lucas 80w-90, 1 qt Lucas Heavy Oil Stabalizer, and the 4oz lim-slip additive. I've got to admit, that Lucas stabilizer was thick. I wish they would put the weight on the label.

Ford said they had the 75w-140 for $18 a qt. The truck isn't my daily driver and I don't tow, so I'm hoping the lighter oil will work.

 

You will probably be just fine. Especially with your use.

 

The ford service manual calls for 80w90 for standard service and the heavy one for extreme service. I always follow the extrems service guide. It' gets used to the extreme! I have always greased the bearings when I rebuilt a differential. Just use some good lithium based chassis grease and be done with it. No worries about lube the first few miles then. It won't hurt a thing. If you read the manual it tells you to do this. Especially for the outer axle bearings. Those things could run dry for several hundred miles before enough oil gets out there to do any good.
FWIW, I used royal purple on this oil change too. My clutches are still too tight. It's never been apart on this axle either. The darn thing is worse than my other truck with the detroit locker in it for driving on all the sandy roads around here. It will not slip. I can't even make it slip with a 6 foot long snap on ratchet on the hub with one wheel jacked up. I'm about to tear into this thing and redo the clutch packs. It's killing my rear tires.

 

In work we run only 80 - 90 wt in all our trucks. Dumps, tractors, our F250 pickups,

 

I didn't think mine would. I was reafing on a rear lug though and that sucker snapps the clutches hard. bout broke my wrist when it let go. surprised the hell out of me.


IMO. go with the 75-140 synthetic.
its kinda a new standard to upgrade too.

Remember, products are diff now with different bases and additives. The 80-90 was the standard at the times of our trucks, while still useable, they using the snytheitcs for a reason.

I'd still stay away from the lucas with the aeration problems they have with their additives.


What about Additives?

 

Running the synthetic 75-140 in the rear differential. What is the recommended change interval with synthetic?