'91 AWD 82,000. My rear pinion seal is leaking and needs to be replaced
before we go on short vacation in 2 weeks. The Haynes? manual makes
it sound easy but doesn't mention the need for a crush washer. I searched
the forum and found a post that made the operation sound really scary
with possiblity of ruining the rear end if not done properly (which meant
partial disassembly of the rear end). I do not have a 200+ ft.lb. torque
wrench but probably can come up wth everything else I need. My abilities
are moderate compared to many here but usually can do most repairs myself.
Is this something I should leave to Ford or try myself. The two phraises
that come to mind when repairing the aerostar are "No Pain No Gain" and
"Blood Sacrifice" because I usually leave a piece of me in the van somewhere.
Have it replaced. Not a serious issue at the shop, and not too expensive, either. If it goes too long, you end up replacing the whole axle, which gets up toward $750, if they can find one in a wrecking yard. Not to mention sitting on the side of the road a long way from home with kids in the car and the drive shaft on the highway.
94 XLT Long 251 K, and back in the workshop
92 XL Short 141 K still driving while I work on the other one
You can probably manage this yourself. You don't need a 200 fl/lb torque wrench, in fact, you need a small inch/lb wrench to determine the pinion bearing pre-load. You will have to fabricate a simple drilled bar to hold the pinion flange during removal/installation and you will need the longest 1/2 breaker bar you can find -24 inches works fine. In a nutshell, remove the companion flange, pry out the old seal, replace with new and retorque the pinion nut SLOWLY, SLOWLY, SLOWLY until you reach the specified pinion bearing pre-load. You tighten then test the turning resistance with the inch/lb torque wrench. CAUTION! Don't go by the bench test values - those are for a dissembled unit - i.e. no axles/wheels/etc included. There is a separate value for the on-the-vehicle test. I don't have my manuals with me as I write this, but I seem to recall the on-the-vehicle number was somewhere around 25-30 in/lbs of torque as compared to 10-15 in/lb for the bench test. It is easy to overshoot the mark when you are grunting away with that big breaker bar. It will seem like forever to get to 20 in/lb then the next pull sends it way over the mark.
There is a lot of hoop-te-do made about that crush washer when in fact, most shops just reuse the old one. When I rebuilt mine, I measured the new crush washer against the old and found something like 0.003 difference - so they really do not "crush" down as the name implies. It is merely a heavy duty spacer between the the pinion nut and bearing. Neither of the local Ford dealer parts counter even had one in stock. They were a special order item which seems rather odd for this common repair procedure. (Draw your own conclusions on this.)
When you get home could you verify those torque numbers and also that
they are in in/lbs. I'm almost sure my manual said like 200 ft./lbs which
I thought was a bit excessive. The repair sounds like even I should be
able to handle it. If your numbers are correct I'll just buy a torque
wrench I should get one anyway. I thought about an impact wrench to
get that big ol' nut off, but I'm a little queasy about subjecting the gears
and bearings to that kind of abuse even with a big bar holding things.
With the van on jackstands and the rear wheels and driveshaft removed, you use the inch pound wrench to measure the turning resistance of the pre-load on the pinion bearing and indirectly, the entire rear differential assembly. Before removing the present pinion nut, use the inch/lb wrench to turn the pinion nut (and rear differential) through several turns to see what the present bearing pre-load value is. According to the Spicer-Dana rebuild chart I have, it should be in the range of 15-35 in/lb with the old seal intact. A new seal adds 3 in/lb to the total torque to rotate, so afterwards, you need to be within 18-38 in/lb. This same chart also indicates the torque range required to achieve these settings can vary from 140 to 500 ft./lbs. You can see, with this huge range it will still be a slow process to get to the desired pre-load. For these reasons, an actual big ft./lb. torque wrench is not necessary, just the long breaker bar and frequent, careful measurements along the way. Most in/lb wrenches use 1/4" drive and the pinion nut socket will be 1/2" so you will need probably two step down adapters to make this work.
One last tip, have a drain pan under the differential when you remove the yoke. I hope this all makes sense. Now, get under there and go for it!
Last edited by aerocolorado; 07-02-2005 at 01:15 PM.
Measure the bearing pre-load with the old seal in place, use this value +3 lbs to set the pre-load with the new seal in.
I would definitely remove the diff. cover, drain the hypoid oil, check for any metal debris, examine the ring and pinion for abnormal wear, then put in new synthetic 70w-90 hypoid oil. Only takes 2 quarts so cost not a factor.
Also check both driveline U joints for any looseness or signs of overheating, a failing U joint or out of balance driveline can cause front diff. seal failure
Last edited by 96_4wdr; 07-02-2005 at 03:55 PM.
When I bought my 85 mustang in jan of 85 ( same rear axle as aerostar), the pinion seal was dripping when I got it home.
I just replaced it and didn't bother with a new "crush" washer.
230,000 miles later, it still isn't leaking.
nope, I didn't take it back for waranty repair.
Ohhhhhh.......Now I get it. I was confused about where the
in/lbs. related to the huge number of ft./lbs. I was going to
have Ford do it but I think the extra money saved by doing
it myself has a better place. Except for the nut busting (?)
torque required it sounds very doable. Thanks a million
everybody (esp. Aerocolorado) for good info!
My pinion seal is leaking as well, so I'll have to do this soon.
I just want to be sure of one thing: Is it correct that the only thing that needs to be removed to get to the seal is compnion flange? The pinion itself does not have to come out, right? If that's the case, there should be no need to open the rear cover, or to setup the gears afterward?
In theory, you are supposed to measure the force required to turn the pinion with the wheels removed before removing the pinion nut. Then, after you've replaced the seal, you have to tighten the nut to the point where the preload force on the pinion is the same. I tried many times using an inch-pound torque wrench to get an initial reading, but I jsut could not get a consistent reading. So what I did was to scratch a mark on the end of the pinion shaft and a matching mark on the nut before removing it. Then when I assembled it after replacing the seal, I torqued the nut to the marks line up again. It's been almost 5 years since I did that, and the pinion seal is still sealing.
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