Ok, we have a lot to discuss here.
1. Do you plan on installing these gears yourself? If so and you have never done them...it is not a simple bolt in affair, and is quite complicated.
2. If youre serious about it, youll need a wide variety of special tools to do the install, and I suggest you get reading now. If you cant answer the questions you asked in your first post by yourself, then you arent even close to being able to install them.
3. Read this:
http://www.pirate4x4.com/tech/billavista/Gear_Setup/
Once youve read that thoroughly, re-evaluate whether or not you think youre going to be able to install them.
4. If you are actually going to go through the process of setting up a new set of gears, then get a YUKON master install kit, and replace all the bearings in the differential. Dont try and half ass it.
The kit will come with new carrier bearings, as well as inner and outer pinion bearings. It comes with 2 crush sleeves, because more than likely you WILL ruin the first one trying to set the preload on the pinion bearings.
5. If it is indeed a used gear set, than focus on trying to get a good pattern on the coast side of the gears. The coast side usually isnt worn as much, and is able to give you a much more readable pattern.
If you have questions feel free to ask, but realize that this is not a trivial task, and setting them up wrong can result in catastrophic failure.
Cheers,
Nate
Actually installing gears is quite simple...
The problem is there is very little margin for error on proper installation and if you do the slightest thing wrong the parts WILL self-destruct, because of how severly they are loaded.
But you'd be suprised how sloppily many of the production rears are actually set up by some lazy ass UAW worker that simply doesn't give a damn.
there is an exhaustive complicated setup proceedure that if followed will give consistant results.
the rub is that for follow that proceedure you need $2500 worth of special tools that nobody except a few dealers bother to buy.
(I personally own those tools but I'm weird...)
For general purposes if you get a replacement gear from FORD the g3ear will be paint marked on the shank with a Big " 0 ". this indicated that no correction is required to the shimming.
IF the pinion gear you remove from the axle is also marked w9ith a zero you can reinstall the original shim, but what I;d recommend you do is measure the original shim and install a new shim the next size thicker...
Why? because in service the original shim got itself crushed down
by .001-.0015", so it's now thinner than when the factory technician
installed it.
then the pinion nut must be tightened carefully to achieve the proper pinion bearing preload (with new bearings this is ~20in/lb, and 20in/lb needs to be measured with a torque wrench, and ththis is the torque that it takes not to get the pinion moving but the torque needed to keep it rotating smoothly
(this is a ticklish measurement to make, but if it's eather too tight or too lose the bearings self-destruct)
Backlash must be CHECKED but on my personal truck after setting aside the original final assembly shims and following the procedure EXACTLY I've wound up reinstalling the original side shims back in the housing through several carrier and gear swaps... (red the proceedure below and then come back this paragraph to understand how perverse this is)
the proceedure you are supposed to follow is by installing a shim of known thickness (a 0.265" thick shim) on the tooth side of the carrier then fit the thickest shim that will fit on the "Back side" of the ring gear with a "sword-in-the-stone" fit.
Measure the backlash (ideal ring gear backlash is 0.013",
but anything between 0.008 and 0.018 is "acceptable"
Now after you have swapped shims (actually cast iron select fit spacers)
to achieve the correct backlash you REMOVE both shims and replace each one with a shim that is 0.005-0.006" THICKER, this is to achieve proper carrier bearing preload
if you don't do this the carrier will literally slam side to side as you get on and off the gas and this can wreak havoc inside your rear ddoing anything up to physically breaking the axle housing!
And now review the paragraph above where I said on my own 8.8" axle
I'm using the original factory shims in their original locations....
and this is with three different gear sets and four different carriers my
axle is currently wearing the shims that were installed in Dearborn sometime late in 1995.
So just how critical is it all? very, but the precision of the factory parts usually obviates most of the effort in making SURE it is right.
And even though on my own all the measureing and checking leaves me exactly where I started, I'll still check it all again, next time, because there
are such diasterous consequences if something isn't exactly right.
I really don't want to have my axle fail on some desert washboard road 20miles from the nearest cellphone coverage and 40miles from the nearest road with pavement....
OR fail somewhere in the middle of any of the five states that seperate my place in Pennsylvania from my brother's in Wyoming...
So even though I know EXACTLY what I'm doing and know that in all likelyhood that I could take it all apart and put it back together with parts picked randomly off the floor of my shop and that it'd likely work for 10k-15k miles without any serious issues I still check everything because "likely" isn't nearly good enough when you are 1000 miles from home or family rescue.
Generally speaking I just don't feel that lucky...
If you do, go for it... but make sure you don't call me if it all goes wrong unless you want your free "I told ya so"
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