This article was taken from thirdgen.org
By Tom Casey (email@example.com)
* Assorted sockets and open/boxed end wrenches in the following sizes:
Assortment of flat blade screw drivers
Large adjustable wrench
2 lb. sledgehammer (hand held)
2 quarts of ATF
The tail-housing is sealed to the transmission using an o-ring seal. It may be necessary to replace this o-ring if it is damaged.
*Note: I say assorted, because at some places you may be only able to use a wrench or a socket. So for simplicity, I use the term wrench interchangeably with ratchet/socket combo.
Warning: Never work under your car without properly supporting it on jack stands.
Drop the driveshaft using the 7/16" wrench to remove the rear u-joint straps.
Remove the speedometer cable from the transmission (it may be necessary to use channel locks).
Using the 10mm wrench remove the bolt securing the driven speedometer gear assembly (this is where the cable was attached).
Remove the driven speedometer gear assembly. Due to the o-ring seal on the assembly, it may be
necessary to pry the assembly out or use a pair of vise grips to grab it (be careful not to damage the plastic housing as you may need to reuse it with the new gear). **Caution: Removing the driven gear assembly will allow the fluid in the transmission tail-shaft to drain out, the amount will depend on how long the car has been sitting without running. If you had just driven the car the transmission fluid will be very hot!!
Unbolt the (2) 15mm bolts connecting the catalytic converter to the transmission.
Unbolt the torque arm by removing the 13mm bolt holding the (2) clamshells together around the TA bushing. Support the torque arm with the floor jack so it won't rotate downward.
Jack the torque arm up about an inch to allow clearance with the transmission.
Unbolt the transmission tail housing by removing the (4) 15mm bolts. The tail housing should slide right off. (Be careful there still may be some fluid left inside the housing)
Rotate the transmission output shaft until the clip securing the drive gear is facing you.
**Note: There is probably a proper tool for doing the following steps, but I didn't have it. I used this method with no damage to the gear or transmission.
Adjust the adjustable wrench to loosely fit around the output shaft.
Using the adjustable wrench like a lever against the transmission cross-member, push the drive gear towards the rear of the car, while depressing the clip retaining the gear with a screwdriver. (It may be necessary to dynamically lever the gear off)
Once the gear has cleared the clip, use the hammer on the wrench to force the gear off the tail-shaft.
Re-assembly is the reverse of the above directions. Make sure the drive gear and driven gear line up after the re-assembly. Also make sure the drive gear is properly secured with the clip.
Check transmission fluid and add necessary amount before driving.
ATGO is not responsible for any damage done to your vehicle by following the above instructions.