01 7.3l, auto trans, almost 200k miles. My rear end is leaking and it appears to be from the pinion seal is. The entire bottom of the pumpkin is wet, but you can see where the drive shaft has spun fluid all over the underside of the truck. How common of a problem is this, and what all is involved in the repair?

 

Depending on if the pinion bearing has gone out or pinion is loose, it could be as simple as changing the seal. Have someone familiar with differentials do it as the pinion bearing pre-load has to be set up correctly or you'll have another, possibly worse failure down the road.

 

I have a feeling this is something that most people would just throw back together with no care for torque or anything else. I am thinking the only way for it to be done right is for me to learn how and do it myself.

 

With 200k miles, it might be a good time to take it to a good differentials shop and have new pinion bearing, pinion seal, and carrier bearings put in. I would think that would cost $400-500 max with labor, probably less.

Also, another think you can check first is the rear axle vent tube. If it is plugged, temperature changes can cause axle lube to burp out the seal, sometimes in large volume. The vent is a hose from the top of the differential up to the frame, take it down from the frame, visually inspect the end (bugs can build nests/eggs in them) and try blowing air into it (with your mouth, not compressed air). You should be able to blow a bit of air in as it compresses in the differential.

 

Thats the problem, I know differential work is specialized and I dont know anyone that does that kind of work and dont trust paying someone just because they say they know what they are doing.

 

Ask around for recommendations. Ask one of the more experienced people at your local NAPA, or other parts house (not one of the idiot computer jockeys). If all else fails, find the place with the best price and good warranty on their work. Definitely check the vent first though.

 

Checked the vent, all is well with it... No clogs... From what I have been reading it looks like something I could do myself, but I have no clue what is meant by "rotational torque"

 

Rotational torque is the amount of torque it takes to rotate the pinion. This has to be measured with a good in-lb torque wrench, the dial type, not clicker. Here are the basic steps:

1 - Disconnect driveline,remove rear brake calipers (e-brake released), drain differential.
2 - Measure pinion bearing preload (rotational torque), this will include the carrier bearing preload and force required to rotate axles.
3 - Remove pinion nut with large breaker bar and cheater. DO NOT use an impact driver as you will chip the pinion/carrier teeth, only use impact if the carrier is removed. You will need to hold the yolk from turning, wedge a bar through one of the bolt holes or bolt on something to immobilize it.
4 - Remove old seal. This can be difficult and requires a good seal puller. I didn't have a good seal puller, so I punched a small hole in it and used a screw-in slide hammer.
5 - Install new seal, lightly oil sealing surface.
6 - Reinstall pinion nut with red loctite (clean threads on pinion and nut well).
7 - Tighten with breaker bar again until pinion bearing preload is 1-5 in-lbs higher than original measurement (I'd get it closer to 5 in-lbs higher). Again, hold yolk solid while tightening and release when checking preload.
8 - Refill differential with proper fluid, reinstall driveline (loctite again), reinstall brake calipers and rear wheels.

Good luck!

 

So basically you just rotate the axle around with the tq wrench on the pinion nut and watch how much torque it takes to turn it over? I dont get how that works when you are putting it on, regardless of how tight the nut is the tq wrench is going to require the same amount of torque to turn the axle over, right? From what I gather you arent measureing how many in-lbs of tourque are on the nut but rather how many in-lbs it takes to turn the axle over, thus how does that relate to how tight the nut is? Does the axle bind up more the tighter then nut is?

I know the parts stores carry the seal, but from what I have been reading I will need a new crush sleeve and nut, How vital is it that I Repalce these, and are they dealer only?

 

As you tighten the nut, it increases the preload on the bearing and it makes the pinion harder to turn. That is the important spec, not the torque on how tight the nut is, it takes several hundred ft-lbs of torque to crush the crush sleeve. The crush sleeve you can reuse because your goal is to crush it a little more to increase the preload 1-5 in-lbs. If you don't understand what I'm saying then I would strongly advise you take it to a shop that knows differentials. Pinion bearing preload is VERY important.

 

I understand what you are saying now... I know its hard to tell on forums how much skill or knowledge someone has, but I am usually very good with mechanical things, this is just new to me. Should I go ahead and replace the bearings as long as I am in there, or leave well enough alone? From the diagrams I am looking at, if I did replace the crush sleve (collapsible spacer as ford calls it) Id have to pull the bearing anyway. Should I go ahead and get a new nut from FORD, or will the original one be ok?

 

If you're going to do it yourself, I would just do the seal since the pinion race drives into the housing and if the depth is off slightly it will throw off your gear mesh and cause problems. The pinion race is also pressed on the pinion and you need a good bearing puller to remove it. If you have it done, then get the pinion and carrier bearings replaced with new Timken brand bearings. They nut they say to replace because it has a mechanical lock (thread burrs), but any shop you took it to would just apply red loctite and reuse the old. There is no problem with reusing the nut and using loctite, just be sure the threads don't have oil on them when reassembling, clean them off with brake cleaner.

 

One of the sites I was reading on said something about normally the seal wont fail on its one with out some other problem causeing it (ie bearings bad, vent clogged, etc.) is there any truth to this, or did 200k miles just take its toll on the seal?

 

Its the high miles, I'm a little suprised it made it to 200k. One worry with replacing the seal is there is probably a groove worn in the yolk and a new seal won't be able to seal completely. When the yolk is off, clean it up the best you can with some fine sandpaper to get rid of or minimize the wear groove.

 

.....And the story continues.... I was alerted to the leak earlier today because something just didnt feel right with the rear end. Got out, saw the fluid leak and realized the problem. I was a few miles from where I was going so I went ahead and babied it there. I am pretty sure the fluid is too low for it to be safe for me to drive it the 30 miles home. I was going to put some fluid in to get me home so I could change the seal..... As I got under the truck I was reminded of the stripped out fill plug courtesy of "American Lubefast". A few times ago when I was in there they stripped it out, but didnt have any plugs to fit it so told me to remind them the next time I was in and they would get the old one out and replace it.

So now I am sitting here with a truck with no fluid in the rear end and no tools to pull the plug so I can put fluid in. I plan on having it towed to the lube place in the morning and demanding that they 1) replace the plug, 2) replace the seal, 3) Pay the tow bill.

It wouldnt be possible to put fluid in the vent tube to fill the rear end would it?