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No Fear Gears
How To Install Gears In A 10-Bolt
Rearend
By Scott Crouse
All too often the average enthusiast installs
a killer engine into his Chevy only to find that
the car doesn't accelerate like it should. He then
realizes that the factory 2.73 rearend gears are
holding the engine back. Whether your vehicle is
meant for drag racing or top speed cruising, it's
crucial to have the proper rear gear.
The plan here was to upgrade the 10-bolt in
our pal Larry Richard's 175-mph '87 Monte Carlo.
His 7.5-inch 10-bolt carried a 3.73 gear ratio,
but it needed a new posi, bearings, and axles. The
3.73 gear ratio combined with Richard's six-speed
transmission allows the 355ci 500hp engine to make
use of every last bit of horsepower when he's well
into triple-digit speeds. To get the project done,
we contacted Drivetrain Direct in Corona,
California. Drivetrain Direct supplied its
rearend-rebuild kit and a pair of Superior axles.
The kit includes a Superior ring-and-pinion,
Timken bearings, an Eaton posi, and all the
necessary shims and gaskets. The company also lent
us its head mechanic, Martin Barraza, who showed
us how to properly rebuild the rearend.
Remove the rearend cover and
drain the 3 quarts of gear oil. Next, extract
the cross-shaft bolt (A) and cross-shaft (B).
Then, spin the rearend until the ends of the
axles are visible inside the carrier. Locate the
axle C-clips and remove them by pushing the
axles in toward the center to free them. Once
the axles have been removed, you can unbolt the
main caps and remove the carrier. |
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It's always a good idea to
replace the axle bearings located in the ends of
the axletubes. Hundreds of repetitious heat
cycles have a tendency to really seat these
bearings. If they have been in the rearend for a
long time, you are going to need a slide hammer
to remove them. |
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Before we could clean the
housing, we had to remove the pinion. We removed
the 1-1/4-inch hex pinion nut and drove the
pinion assembly out with a brass punch and a
hammer. From left to right you can see the yoke,
seal, outer bearing, crush sleeve, inner
bearing, depth shim, and the pinion gear. Once
everything is out of the way you can remove the
pinion races with a punch and hammer.
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Before attempting to remove
the ring gear from the carrier, be aware that
these bolts feature a left-hand thread. When
re-installing your new ring gear, it is best to
use new bolts and torque them in a
cross-tightening pattern to 75 lb-ft.
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The carrier bearings must be
pressed onto the carrier. This requires the
proper tools to remove and replace them and it's
best left to a professional shop. |
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The holes in the rearend
housing allow gear oil to lubricate the axle
bearings. It's crucial that the rearend cover
gasket is equipped with these openings.
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The next step is to install
the pinion races and pinion. Generally, the
stock pinion depth shim (located between the
pinion bearing and the pinion head) will be the
correct thickness and can be reused with the new
components. When assembling the pinion into
place, include the crush sleeve between the two
pinion bearings. This sleeve must be replaced
every time the pinion nut is torqued. Many
mechanics use an impact gun while others insist
the nut should be torqued by hand. Either way,
the nut should be tightened to produce
24-32-in-lb of torque to turn the pinion gear
with a new bearing. This is without the ring
gear in place. |
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We are now ready to install
the complete carrier into the rearend housing.
Carrier shims are placed between the carrier
bearings and the rearend housing on both sides.
These shims place a pre-load on the carrier and
keep pressure against the bearings. The shim
thickness on both sides also determines the
amount of ring-gear backlash. Backlash is
adjusted by changing the shim thickness side for
side. To decrease backlash, increase the
thickness on the left side while reducing the
thickness an equal amount on the right side. To
increase backlash, do the opposite. Once the
carrier is in place, re-torque the main caps to
65 lb-ft. At this point the carrier should turn
freely inside the rearend housing. |
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With your new carrier
installed, apply the provided marking compound
to five teeth of the ring gear then spin the
carrier (while applying a light load on the
gears) until it makes several
revolutions. |
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According to the pattern
imprinted on the ring gear, a trained
professional can determine whether the right
number of shims have been installed. |
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The key to a proper rearend
setup is to establish the correct pattern. This
comes from following the factory specs. Backlash
is the amount of clearance between the
ring-and-pinion teeth. By placing a dial
indicator on a ring-gear tooth and rocking the
ring gear back and fourth, this rearend showed
an acceptable amount of backlash between 0.005
and 0.009 inch. Pinion depth is determined
according to the thickness of the pinion shim
installed between the pinion gear and the
bearing. A proper pinion depth setting is
noticeable once the marking compound is applied.
Increasing the thickness of the pinion shim
places the pinion gear closer (deeper) to the
ring gear. |
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Once the carrier is properly
placed inside the rearend housing, reinstall the
axles, C-clips, cross-shaft, cross-shaft bolt,
and rearend cover. Because we installed a
posi-traction unit, 3 quarts of limited-slip
gear oil were used instead of the standard
rearend gear oil. |
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Drivetrain Direct
1477 Davril Cir.
Corona, CA 92880
888/584-4327
www.drivetraindirect.com
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