Gm 7.5/7.625 gear install


This in an internet guide put together to assist persons who wish to install a gear set into their s-10/car but arent sure they can do it. This was my first install and although it will test your patience , its fairly straight forward. The tools you will need are: Oil drain pan , A heavy Impact gun , inchlb wrench, synthetic oil(2 quarts),A pinion depth tool (jegs, \$100), a Mega Install kit(Jegs, $139) , Jack , wheel chocks , Jackstands/tire ramps , Drum puller, calculator,shop press.

The first thing your going to do is verify you have the correct gearset. Count the number of teeth on the ring gear and divide that number by the number of teeth on the pinion. After you verify the ratio is correct note the carrier series. 3.08 down is #2 series and 3.23 up is #3 carrier. All motive gears are #3 series! The rear end code can be found in the glove box in s-10's. Mine read code GU6 which is a 3.42 ratio. That means my carrier is a #3 series. Get it? Good. Next verify the serieal# on pinion and ring gear are the same , gear sets are lapped in at the factory together and will never work with another gear(s). Next write down the factory depth written on the face of the pinion. You will use this number to set up your gears. Now go ahead and clean the gear in solvent thinner and wrap in a clean towel and set aside.

Begin by setting the vechicle on jackstands(I prefer wheel ramps on the frame*no death baby*). Remove four drive shaft bolts push forward and set to floor. Take off the rear cover and drain the old oil. Impact off the wheels and pull the brake drums off . Frozen drums are no fun at all. None of the local parts store jackfucks knew what a drum puller was so I bought a large gear puller and it barely worked. A few beers kept me from suicidal rage :). Next loosen the cross pin bolt or on the zexel loosen the retainer plack bolt and remove. Kick the axles towards the center of the housing and the c-clips will fall out. Remove axles. Impact off bearing capsand remove.*! Note remember which side is which they are specific*!

Remove carrier. This is the only way to do it , use a bottle jack and a hammer. Place the bottle jack under the handle and the claw into the carrier with head on face of housing. Jack away.:)

Once carrier is out remove ring gear*!Bolts are reverse thread*!Install new ring gear and ring gear bolts. Torque to spec in a criss cross pattern.
Now measure the existing pinion to get a reference number and to get a feel for the tool. This is done by setting up the dial gauge with a 3" extension and calibrating it with a 3" tube. Once calibrated , place the red anodized bar /gauge on the passenger side carrier bearing surface. What you want to measure is the distance between the face of the pinion gear to the centerline of the carrier housing. My OEM speced out at 2.28( :) Motive was 2.28 as well what a nice coincidence). On the gauge it actually read .72 but since I had a 3" extension I subtracted .72 from 3.
Remove old pinion. This is done by impacting off the old nut. Thread the nut back on and hammer towards the rear of the vechicle. The nut will keep you from hacking the threads. Next remove old pinion seal and bearing. This is acompilished using a hammer and a socket and a screwdriver. Pop out the old seal with hammer and screw driver , and hammer out the bearing. Replace with new seal and bearing. Next run to NAPA or car quest and have a counter worker press off the old pinion bearing( the point for this is to get the oem shim).

Install the original pinion shim on the new pinion gear and press on new pinion bearing(I got my press from habor freight tool for \$99)
Install new crush sleeve on pinion gear and place the gear back into the housing. Install the yoke and a new pinion nut and Impact the pinion nut. Using the depth guage check the pinion depth and impact as nessasary to obtain correct checking distance. Once you arrive at the correct value , Impact off the pinion nut hand thread it on a few turns, and mack the nut with a brass hammer , hitting towards the rear of vehicle. A few medium-light taps will do it. Using a inch lb wrench set the bearing preload to 25 inch lbs. Note the pinion will spin with out retaing its motion. I made a retainer out of steel and drilled two holes in it and bolted it to the yoke by hand each time I needed it.See the picture below , breaker bar pipe attached to the piece I made.

Now check the checking distance again Look in the picture below.

If its too deep you have to remove the pinion and install a new crush sleeve. To close and you have to impact it some more.
I previously put on new carrier brearing about 6 months ago so I wont go into that. Place the carrier/ring gear assembly back into the housing and add the carrier shims so that the shims resemble the factory thickness. The factory shims will be to thick.Tap in new shims with a hammer so it is snug tight and the carrier wont fall out. Check your backlash with dial indicator mounted to the housing surface. Backlash settings are stamped into the side of the ring gear.

Using marking compound verify the tooth contact pattern. This is done by painting a few teeth and rotating the gear. You want the contact pattern to be in the middle between the heel and toe of the gear with the coast side slightly higher than the drive side(towards heel/outside).

Reinstall axles with c-clips. For you zexel torsen users you might need to machine down the center c-clip retainer piece to get it back in, what ever you do dont hammer it in or its never coming out and your toast. I machined mine 100% flat on a table grinder/stone quenching it with water as needed.

Fill with oil. Reassmble and break in gears by driving about 15 miles to car wash. At car wash rinse down rear to cool it off and drive 20 miles back. Let sit for 4-5 hours or overnight , enjoy! :)



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