EDIT TO ADD: I forgot about this thread, and the image links went dead. But I have a YouTube video that covers the same subject.
Rodney Dickman has instructions on how to "split the case" on the Getrag 5-Speed transmission. You can find those instructions here:http://www.rodneydickman.com/n36.html
Unfortunately, there aren't many pictures, just a drawing. So when I split the case on my Getrag to replace a bad seal, I took lots of photos. Now I'll walk you through the procedure, using the photos as visual aids.
First of all, you need to drain the oil from the transmission. Drain the oil BEFORE removing the axles from the transmission. Otherwise, your transmission will puke oil all over the place.
The drain plug is pretty easy to find. It's on the bottom of the transmission, near the rear tranny mount (15mm socket). Looking up from the bottom, you will see this.
The next step would be to remove the axles, detach the transmission from the mounts, and separate it from the engine. I'm going to assume you know how to do this, or can follow the instructions in the service manual.
After getting the transmission out of the car, you're ready to start disassembling it. Unfortunately, it isn't as easy as removing the case bolts and prying the case apart. There's something called the "detent assembly" that will prevent the transmission from coming apart. So that detent assembly needs to be removed.
If you look inside the bellhousing, you'll see a round black piece near the input shaft, that resembles a hockey puck. It's called the "detent cover". You need to pry that out. There are a few different ways to do that. One is to punch a screwdriver through the center, then stick an Allen wrench in the hole and use it to pull the cover off. Another is to wedge a small screwdriver into the seam around the edge of the cover, and pry it out that way. I opted for the second method, since it doesn't leave any holes in the cover.
After you get the cover off, you'll see this. That is the detent assembly. And it needs to come out.
To get it out, you remove the two bolts (10mm socket). That funky looking metal plate (the detent plate) is under tension. When you remove the two bolts, some of that tension will be released. That's normal.
You'll notice that there are 4 little metal balls (held in place by springs) under the detent plate.
Now that the bolts are out, you can pull out the detent plate. However, the plate, balls, and springs are still under some tension. So when you remove the plate, those springs and balls are probably going to go flying. Just FYI.
After removing the detent plate, springs, and balls, you will see that one of the rods in the transmission has a metal bushing. That bushing needs to come out. It's probably pretty tight. But you can pry it out with a pair of small Allen wrenches.
Congratulations, you've removed the detent assembly! Make sure none of the parts have "walked off". I like to put the parts inside the cover. You should have one plate, one bushing, 2 bolts, 4 springs, and 4 little metal balls. If any of these parts come up missing, you're basically screwed. Seriously. So don't lose anything.
And just for kicks, here's what the transmission looks like with the detent assembly removed.
NOW, you are ready to remove the case bolts and pry the case apart. There are 15 bolts around the perimeter of the transmission (13mm socket). They aren't hard to find. But just in case, here are a couple photos showing you where they are.
Just a side note, one of the case bolts will not come out all the way. I'm referring to the bolt directly under the round black protrusion (the shift shaft cover). It will unscrew from the threads, but doesn't have enough room to come completely out. That won't be a problem. The bolt will just "float" in there while you have the transmission apart.
There are 3 places on the transmission case where you can pry it apart. DO NOT try to wedge a screwdriver or pry bar into the seam. That's a great way to damage the mating surfaces on the case halves, which can cause the transmission case to leak oil. However, you can insert wood or plastic shims between the case halves to prevent them from closing back together while you're prying on them.
The photos below show the 3 places where you can pry on the case halves. You can see the metal tabs sticking out.
Eventually, you'll be greeted with this.
Congratulations! You just opened up your Getrag. But eventually, you'll want to put it back together again. Re-assembly is pretty much the reverse order from disassembly. However, there are a few things to note.
First of all, it would be wise to seal the case halves with RTV silicone. If you don't, there's a good possibility that oil could seep out through the seam. Clean the mating surfaces with acetone or lacquer thinner before applying the sealant. BTW, the torque spec on the case bolts is 15 ft-lb.
Second of all, the transmission MUST be in Neutral when you re-assemble the detent assembly. Otherwise, the transmission will lock up internally, and will not function properly. Rodney's instructions cover this, but I'll go over it again.
Those rods that poke out through the holes in the detent plate must be put in a certain arrangement. Sit the detent plate in position, so you can use it to help position the rods. The rod furthest to the left (assuming the transmission is right-side up) needs to be recessed about 1/4" below the surface of the detent plate. The other 3 rods should be flush with the surface of the detent plate.
Installing the springs and the little metal balls can be tricky. I prefer to load the springs into the detent plate, drop the plate in place, and then depress the springs with a small screwdriver so the balls can drop into place. Each ball needs to be centered on its spring.
After you accomplish that, you will need to press down on the detent plate, so you can install the two mounting bolts. I just pry on it with a big screwdriver. The torque spec on those two bolts is 84 inch-lb.
After you finish with that, it's time to re-install the detent cover. Spread some sealant around the outer edge, and push it into place. You should be able to get it most of the way by hand. Some careful tapping with a rubber mallet will finish the job. Also, if you drilled or punched a hole in the cover in order to remove it, you will need to plug that hole.
Now your Getrag is back in one piece. And you can re-install it in the car.
Don't forget to re-install the drain plug. And don't forget to refill the transmission oil... AFTER you plug the axles back in.
[This message has been edited by Blacktree (edited 02-07-2020).]