Copyright 2005 - BillaVista Offroad Tech
(click any pic to enlarge)
when it came time for me to install my new 14-bolt ARB Air Locker, I was
horrified to find that my gears were in atrocious condition. So much for
maintenance...gulp! I guess 27 years of hard use - the last 7 or so under
brutal conditions in the rear of my rock buggy take their toll on a set
If your gears look
anything like this - then you are in desperate need of a new set.
The bearings weren't a whole lot better. Here you can see severe pitting
and galling of the carrier bearing race. Note: This is an extreme example
- you need new bearings well before they get to this stage. Basically,
if you see any signs of wear, corrosion, pitting, scoring, or over-heating
they should be replaced. My rule - "If in doubt, throw 'em out"
If you're installing
new gears and/or a locker - it's probably a good idea to replace the bearings
regardless of condition - just for preventative maintenance. That way
you don't end up with garbage that looks like this in your rig!
a die-hard Dana/Spicer fan, this time, especially since I was working
on a non-Dana/Spicer axle, I thought I'd try a set of Yukon gears and
a Yukon Master Install kit from Randy's Ring & Pinion.
is the part number from the box, for Yukon 4.11 14-bolt gears.
When I spoke to Mac
from Randy's to order the gears, I learned that the 14-bolt Yukon gears
are manufactured exclusively for Yukon by an American gear manufacturing
company based in Chicago Illinois, called US Gear.
They also manufacture
gears for quite a few big-name OEM companies such as Meritor (Rockwell),
General Motors, Chrysler, Ford and even Dana.
With that much experience,
combined with the fact that the gears are manufactured to Yukon's explicit
specifications quality assurance standards, the Yukon brand gears are
a top-quality, professional level product.
arrived in short order and well packaged.
The ring gear is stamped
with a production number, the gear-set tooth count, and a "made in
Pinion is similarly marked and also has the tooth count stamped - 45 ring
gear teeth and 11 teeth on the pinion.
ring gear and pinion are also marked with a matching set number.
My only disappointment
was the fact that the pinion was not marked with a pinion depth code number.
This is a number that indicates the difference between the nominal pinion
depth and the correct pinion depth for this set of gears. It can be used,
along with the code from the old gears and a record of the old pinion
shim stack, to create a very accurate starting point for pinion shims
when setting up the gears.
It's not critical,
and you can set up the gears perfectly well without it - but it does give
a convenient starting point and can save some time.
Before I installed the gears
I thought it might be fun and interesting to take some comparison pics of the
4.11 14-bolt gears beside a set of 4.10 Spicer Dana 60 gears (in this case a
reverse-rotation set from a Ford front axle).
gears on the left, Dana 60 on the right.
Yukon GM 14-bolt 4.11
ring-gear on the left. Spicer Dana 60 4.10 ring-gear on the right. The Dana
60 ring gear is 9.75" diameter and the 14-bolt is 10.5".
14-bolt pinion on
the left, Dana 60 pinion on the right. The 14-bolt pinion splines are
1.750" 30 spline and the Dana 60 pinion splines are 1.276" 29
Note also the journal
on the head of the 14-bolt pinion; for the 14-bolt's straddle bearing
(aka the pinion support bearing or third pinion bearing.)
11 teeth on the 14-bolt
pinion (left) and 10 teeth on the Dana 60 pinion (right).
14-bolt on the left,
Dana 60 on the right.
A great shot of why
the ring gear is sometimes called the "crown gear".
Also - have you ever
wondered why gear-lube used in axles is called "hypoid gear oil"?
It's because ring and pinion gears are technically hypoid gears. The definition
of a hypoid gears is: gears shaped like a cone, having spiral teeth, and
that have offset axes (i.e. a line through the centre of the pinion will
not intersect with a line through the centre of the ring-gear). This picture
shows quite clearly how the ring gear is shaped like the bottom chopped
off a cone.
my install I also ordered the Yukon "Master Install Kit". At
left is the part number for the '88 and down 14-bolt. Note that it says
" Except '84-'85 with small pilot bearing" This is because in
'85 and some '84s the 14-bolts use a straddle bearing (on the head of
the pinion) that has smaller rollers than the other design. The part numbers
for the straddle bearings are:
'73-'84 & '86-'99:
'85 (and some late
'88-'99 14-bolts will
take a different kit as well because, in this so-called "second design"
14-bolt, the rear pinion bearings are different from those used in the
Bottom line - when
you order a 14-bolt install kit be sure to quote the year of your axle
(for help determining this see the 14-bolt
to the sound of the name - there appears to be no complete industry standard
as to what comprises a master install kit. And with the 14-bolt
there are a few little gotchas that make things even more interesting.
The Yukon kit comes
well packaged, sealed in plastic, in a box.
from top left the kit includes:
Two crush sleeves
(a nice touch, should you overdo it and crush one too much the first
The kit included only five pinion
bearing retainer shims in the following dimensions (rounded to the nearest thousandth
of an inch, as measured by me using a 0-1" inside micrometer):
This seemed a strange number and
combination of shims, and I know that they are available from GM from 0.006
to 0.024 in increments of 0.001, so I was a little concerned about how setup
would go. However, my old gears used a single shim of 0.013 and I set up the
new gears fine using the single 0.015 shim from the kit. I don't know if I just
got lucky or if Yukon knows what the most often required shims are - but if
you use the Yukon kit you may have to purchase some additional shims of the
thinner dimensions to get the exact right combination for pinion depth.
You may notice from the
above list that a couple of items are missing - especially if you are more used
to Dana axles. The Yukon kit does not include pinion nut, pinion washer, or
ring gear bolts. Interestingly, neither do any of the other kits that I researched.
The reason given to me by a number of suppliers distresses me a little - many
say that the pinion nut and ring gear bolts on the 14-bolt are re-usable. I
completely and utterly disagree with this. First, every manual I have, from
factory GM to US Military, quite clearly states that pinion nut and ring gear
bolts must be replaced after service. Second, it is clearly accepted practise
to replace these parts in other axles during differential service, and I see
no reason why the 14-bolt should be any different. Third, a little knowledge
of fastener theory (you can read about this in my Nuts
& Bolts article) along with consideration of the tremendous loads they
endure and critical functions they perform, leads me to conclude that ring gear
bolts and pinion nuts should always be replaced and never re-used. Finally,
in the case of the pinion nut, it is a deformed-thread style locking nut made
of a relatively soft material, and a quick glance at the threads in the picture
below of a new nut compared to a used nut should convince you.
Being as I live on the other
side of the continent from Randy's, when the kit arrived without pinion nut,
pinion washer, or ring gear bolts I thought I would just source them locally.
When I tried, I found out some more interesting facts. I tried all the usual
suspects - auto parts stores, heavy-truck parts suppliers, and even the dealership.
What I found was that nobody stocked, or even held a listing for these parts
except the dealership - they seem rare as hen's teeth for some reason? I also
discovered that many places will refer to ring gear bolts as "crown bolts";
presumably because some, particularly the British, refer to the ring gear as
a "crown gear" because of its shape. Predictably, the dealership wanted
an outrageous amount for the parts - something in the neighbourhood of seven
dollars for each ring gear bolt and nearly forty for the pinion nut!
Thankfully, Randy's, having
such a huge inventory, had the parts in stock and at a much more reasonable
price. A quick call to Mac and the parts were on their way.
left is the new pinion nut from Randy's, and beside it is the original
nut. Both are "deformed thread" style locking nuts, and you
can see plenty of wear in the threads on the old unit.
Randy's didn't have
a listing for the pinion nut washer, but their replacement nut does have
a flange, clearly visible in the photo at left. Since this flange is still
smaller in diameter than the washer, I re-used my original washer as it
was still in reasonably good condition.
Once again, given
that the 14-bolt is a crush-sleeve design (meaning that pinion bearing
pre-load is set by cranking down on this nut with 350+ ft/lbs of torque),
it baffles me that anyone would suggest re-using it.
The part number from
Randy's is: GM 15994582
14-bolt ring gear bolts held a couple more surprises!
The picture at left
illustrates the original bolt on the bottom and the new bolt on the top.
Note that the original bolt used a split lock washer (not installed in
this picture), and the replacement from Randy's is flanged and does not.
That's why the bolts appear to be different lengths in this picture.
can see in this picture that the bolts are exactly the same length when
they are compared with the original having the lock washer in place.
Personally, I don't
like split lock washers and prefer to avoid them if at all possible (see
my Nuts & Bolts article
for reasons why); and my opinion wasn't altered any when I found four
or five cracked in half upon disassembling my original carrier and ring
gear. As such, I was pleased to discover that the replacements from Randy's
don't use them. Instead, I used a little high-strength thread-locking
compound when installing the bolts into the ring gear.
The final thing you
need to know about ordering 14-bolt ring gear bolts is that they come
in two different lengths, depending on the gear ratio. Bolts for the 4.11
and down carrier are 1.8" long and bolts for the 4.56 and up carrier
are 2.1" long. Note that neither length is the same as any standard
Obviously, since a
different part is required for each, and with such a small difference,
the exact length of thread engagement of the bolt into the ring gear is
The part number for
the 1.8" long bolts is: GM 331422
The Yukon 14-bolt gears
and install kit from Randy's Ring & Pinion arrived promptly and well packaged.
Everything needed was included except pinion nut and ring gear bolts, but these
were available separately at reasonable cost. All the bearings were Timken made
in USA except one carrier bearing race which was Timken made in France. I find
that the yellow gear-marking compound included works quite well, but I avoid
using the included no-name thread-locker in favour of Locktite brand. The gears
are a quality, made in USA product with industry standard markings for ratio
and matched-set numbers, but with no indication of pinion depth code number.
The gears themselves set up quickly and easily with no problems, and have been
smooth and quiet in operation. In the future I won't hesitate to use Yukon gears
again, but I will always confirm the complete contents of any master install