G31 Transmission Removal

Here are some instructions on how to remove the G31 transmission. Although the instructions in the Haynes and factory manuals cover the subject, there are some "gotchas" that are not addressed in the manuals. Furthermore, the factory manuals sort of combine procedures from a couple/three different transmission models into one narrative and it was confusing.

Special thanks goes out to the membership of www.924.org, their assistance with this project was helpful and greatly appreciated.

To remove the transmission you'll need:

• 8mm, 10mm hex (Allen type) sockets
• 8mm, 12-pt star (tri-square) socket
• 15mm, 16mm, 17mm sockets and wrenchs
• 18mm open-end wrench
• assorted socket extensions
• u-joint socket
• ratchet handle
• Floor or transmission jack
• Blocking and bracing materials to keep the transmission on the jack

Transmission Removal:

• Out of force of habit and for safety sake, disconnect the battery's negative cable. The only electrical component you will be messing with is the backup light switch.
  
  
• Put the car in 5th gear and disconnect the gear shifter from the left-hand linkage rod. You need to disconnect the rod because when moving the transmission to the rear after unbolting it, the disconnected coupling has to move farther back than would be allowed if still connected to the shift lever.
  • I recommend disconnecting both rods, and inspecting/replacing the anchors of the right-hand rod while everything is apart anyway. To replace either the right-hand rod's anchors, or the bushings on the left-hand rod, the transmission has to be removed, so you'll want to do this while you have the transmission out this time around.
  
  
• Chock the front tires, jack up the rear of the car and put jack stands under the torsion bar carriers. You are going to be spending a lot of time on your back under the car, so make damn sure it is securely on the stands.
  
  
• Disconnect the exhaust pipe at the last joint and remove the pipe and final muffler. For US cars the joint is at the Cat converter. I had to cut off the nuts/bolts (15/17mm?). Don't lose the sealing ring that goes between the two pipe sections.
  
  
• Unbolt (15mm, 16mm, 17mm, 18mm?) and remove the aluminum cross-member support/reinforcement located just in front of the torque rod tube.
  
  
• Find and remove the rubber plugs on the bottom of the central tube that give you access to the drive shaft coupling pinch bolts. There are two round covers on the tube about an inch in diameter, and one oblong cover (inaccessible) under the front transmission housing.
  
  
• Hold one tire stationary and roll the other until the pinch bolt (8mm hex) is accessible through one of the holes. Completely remove the bolt. There is a groove in the drive shaft that the bolt goes in, and unless the bolt is removed, the coupling cannot slide off the shaft in order to remove the transmission when time comes.
  
  
• Disconnect the CV joints and remove them along with the short axle shafts (use the proper 12- point 8mm star socket or you risk stripping the bolts).
  • You can get by, by disconnecting the CV's from just the transmission and tying them horizontal, but they just get in the way. I recommend you go ahead and completely remove them. While they are out, you can clean, inspect and re-pack them with grease anyway.
  
  

• Remove the 17mm nut from the underside of the rubber transmission mounts.
  
  
• Loosen the 17mm bolt from the sides of the rubber transmission mounts.
  
  
• Remove the two lower transmission-to-central tube mounting bolts. The bolt heads are on the front side of the flange, and are 10mm hex bolts (Allen type) that fasten into 18mm nuts on the rear side of the mounting flange. It is a tight fit and you'll need to use an open-end wrench to get to the nuts while you loosen the bolts
  
  
• Position your jack under the transmission and secure it to your jack with a sturdy bungee strap or two. The center of balance for the assembly is just about at the differential/ central case joint. I used a floor jack with a piece of ½" plywood, about 12"x18" bolted to it's saddle. You will need to brace the transmission so it doesn't roll off when you remove the bolts and slide it back, and to keep it level, put a block of 2x4 under the "neck" of the transmission.
  • The assembly weighs about 100 lbs, so be careful. I used an old pair of jeans rolled up under it and on either side to provide padding, and the rolled portions on the sides kept it from tipping over. A loosely filled sandbag or similar setup will probably work well too. It's important to keep the assembly level as you raise and lower it so it will slide off the drive shaft.
  
  
• Gently take up the weight of the transmission just enough to get everything nice and steady, then raise the transmission just enough to unscrew the remaining two bolts in the rubber mounts, then remove the rubber mounts. There is a brake line above the transmission, so be careful, raising it too much can damage the line.
  
  
• Lower the transmission until it rests on the tube that houses the rear suspension torque rods. Push the transmission to the right to get access to the shift rod coupling.
  
  
• Remove the conical bolt (13mm head) that holds the shift rod coupling to the transmission shift shaft. It must come all the way out, as the "point" on the bolt goes into the shaft pretty far.
  
  
• Disconnect the shift shaft coupling from the transmission. I had to use a long brass drift and hammer to separate the two. The coupling is aluminum so don't beat on it too hard all at once.
  
  
• Remove the top left transmission-to-central tube mounting bolt using the 10mm hex socket and an extension. You probably will need a U-joint at the end of the extension, or a "wobble socket" if you are lucky enough to have the right size. I had to use the 10mm hex bit, a 3/8"- ½" adapter, then a U-joint, two 6" extensions, a ½"-¾" adapter and a ¾" drive impact wrench to break free the upper two bolts. It is tight quarters up there and it is pretty hard to get leverage.
  
  
• Push the transmission to the left in order to get access to the upper-right-hand mounting bolt, and remove it.
  
  
• Once the upper bolts are out, remove the lower bolts loosened earlier. The transmission won't drop immediately, as there are two "locating rings" that surround the upper right and lower left mounting holes. When you go to pull back the transmission from the central tube, things will shift as those locating lugs disengage.
  
  
• Double check to ensure the transmission is still firmly secured to the jack.
  
  
• Raise the transmission (again be careful of that brake line up above) so the bottom of the mounting flange will clear the torque rod tube.
  
  
• Gently work the transmission back by rolling, rocking, wiggling it free and back. Once it is over the torque rod tube and the drive shaft coupling has separated, begin to lower it as you roll the whole thing out.

Here's an article on how to replace the synchronizer bands.
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