Adapter plate and coupler complete

I finally got some time from my uncle to machine the parts and it took longer than we anticipated. Engineering as you go and a lot of measuring twice before you cut really added to the time but I think we'll end up with a reliable setup.

I loaded up the truck with everything I could think I needed and headed to my Uncle's house.


First was to create the coupler. The coupler needed to be 3.125" OD with a 1.125" ID with a .25" key. Here is a picture of the raw metal before we began to work with it.



A shot of the metal slowly getting turned down to the diameter we need.


It's starting to take shape. You can see the end is a little less than 2" wide and about .200" deep if I recall. We did this so the coupler could sit flush against the motor bearing and wouldn't be able to work its way in.


Here we are cutting the coupler slightly longer than we want it. This was the only step of the lathing process that had enough friction to require a lubricant.


Now we are slowly shaving off the end to bring it down to the exact length we need.

After the basic coupler was shaped out we broached out the key way using a 40 ton press. This was so cool to watch I forgot to take pictures.

Next we needed to drill and tap the holes. We used the flywheel as the template and a drill bit that was the same size as the hole to make an initial mark before moving down to the correct bit. To use the existing bolts you'll need an 11mm drill bit and a 12mm - 1mm pitch tap. This is not at all easy to find. My Uncle had to order it from a supplier he uses. You won't find this at Napa or Ace as it's a very uncommon pitch for that diameter.


Here is a picture of the final coupler installed on the motor. A couple things I didn't capture on film was the recessed washer and bolt which screws in from the front. We had to recess these to give clearance for the transmission input shaft. We also are using a beveled hex bolt and we beveled the washer on the lathe to match and recess the bolt further. A quick coat of paint to help with rust and we are done. Notice the black garbage bag duct tapped around the motor. This is quick and cheap to do and will prevent anything getting in the motor during the build.


Here is the simple yet invaluable alignment tool. Basically the adapter plate has an existing 4" ID and the coupler is 3.125" OD. So we machine this tool to slide over the coupler and then the adapter plate slides over that allowing us to perfectly align the plate with the center of the transmission.


Here is the shot making sure the alignment tool works. It's a tight fit, just like we want. The outer darker metal ring is the steel alignment tool.


There were quite a few steps again here that I couldn't take pictures of. We needed more hands than we had.

The first thing you'll do is use any alignment pins on the transmission and mark those across first. Simply slide your plate onto the alignment tool and find a good position that will make sure no part of the transmission is sticking out past the edges. Then using a rubber mallet give the plate a whack over the pins to mark out their location.

In order to start marking your holes you'll need a couple of things. First is a good set of transfer punches. This can be placed in different sized holes and mark the center where we'll need to drill. There were four holes on the tranny that were threaded and we couldn't use a transfer punch. We bought extra bolts and cut the heads off and turned a perfectly centered point in the lathe. We could then use our mallet again to mark these locations and drill them all out.

After we had all of our holes drilled out we butted the transmision to the adapter plate and secured it with a few bolts and marked the outline which you can barely see as a scratch in the metal.

Now comes the cutting. In our case the most precision cutting tool we had was a plasma cutter.

It's not a perfect cut but only took about two minutes. I later took a grinder to the sides to clean it up a little bit but it doesn't need to be perfect as this edge is only cosmetic.

So next we realized the flywheel didn't have enough clearance and was rubbing on the plate. We then had to bevel the inside ring of the plate and recess the four motor bolts. I believe we put those in about .150".

Here we finally have the transmission mounted to the motor! The clutch and flywheel at this point were not actually attached to the coupler. My uncle and cousin held the assembly in place while I snapped a quick picture.

The next step will be to tear this back down and reassemble it with proper torques specs, locking compound, etc and then finally give it the 12v test!

I also had about 80k miles on this setup so I'm going to spend the money and replace the pilot and throw out bearings while I'm here. I'm thinking of just replacing the clutch too as it does show some decent wear.