Derek Posted August 18, 2020 Share Posted August 18, 2020 Ever since I was a small boy I dreamed of having a 6 speed transmission in my Z car. Ok it was actually in 2014 when I heard that people were retrofitting the CD009 into various different vehicles and thought that would be awesome. At the time I was up to my ears in KN20 development and I put it aside immediately. Fast forward to a few months ago and I decided to finally bite off doing my own system. The Hoke system is a great piece of engineering but it wasn’t what I wanted. JWT offered a conversion plate but you needed to source a used bell housing and like the Hoke adapter required a special flywheel. The solution for me was always going to be a cast bell housing. My goals were to be able to use my existing clutch, pressure plate and flywheel. I contacted Chris at at Godzilla Raceworks too get his input on the feasibility of my approach. I know a lot about castings but my knowledge of what components play nice with other components is seriously lacking. Based on the info Chris provided I decided to move forward. Step one. Jump in with both feet by buying a brand new CD00A from Z1 Motorsports. Step two. Cut the bell housing off of a brand new transmission so there was no turning back. The first thing I needed to determine was can I get 100% spline engagement on the clutch disk. I setup a block, crank and flywheel on the bench. I removed the pilot bearing. I then slid the transmission into the crank until the pilot shaft bottomed out. I pulled it back 6MM and made a reference mark on the bench. Visually the pilot shaft looked like it would play nice with the pilot bearing so I moved on to the next step. Check spline engagement. I bolted an old PP and disk on and slid the transmission back into place. I had over 100% engagement and it looked like some version of the longer release collar would bridge the gap. So now that I was confident the math would work I had to work out how I was going to machine the casting. The big problem for me is my CNC mills are converted Knee mills and they don’t have a lot of Y axis travel. I also don’t like doing uber precision work in a production environment. I decided early on that I was going to leverage the existing front cover to be the “glue” between the transmission and my bell housing. My plan was to sandwich the front cover between the bell housing and transmission. After confirming that I had a decent machining strategy it was time to collect data. I scanned an old 5 speed case I had. This is what I refer to as a dirty scan. It’s only for me to design around. I import the mesh into my solid modeler and it becomes a reference for the features I want to add. All of the critical measurements are done with a touch probe in the mill or conventional calipers and micrometers. First step was to align the mesh with the bell housing holes I acquired with the touch probe. I also pulled the input bearing hole from the case when I got the bolt pattern. I then then positioned the scan and the probe data I made of the CD009 cover centering the input with the input from the case. And then I push a couple of keys and suddenly like magic a bell housing casting model appears. Ok there is a lot more to it than that but you get the gist. Next I had to design the machining fixtures. All of the important stuff is done in the first setup. This ensures the input shaft of the transmission lines up with the pilot bearing in the crank. Pattern time. Without getting into a ton of detail here is the finished tooling just before I shipped it to the foundry. So while I waited for the castings I worked on all of the fixturing. By using the existing front cover I was able to save a ton of precision machining. But the cover has to be positioned properly. I accomplished this by making a fixture that indexed the cover on the input bearing. I then bring all of the bolt face bosses to the same level and then ream 3 of the bolt holes to accept a 10mm hollow dowel. Here is the finished cover with the dowels installed. So I guess I was in a hurry on the machining since I didn’t get any process shots. Here is a shot of the first test after machining the engine flange. This is testing the cover fit. This is before the clutch lever and slave work. And the finished product. I designed the cross member to be as versatile and adjustable as I could. I also decided to share the load between the floor/frame and tunnel. On most of our cars the tunnel is probably one of the most unmolested rust free parts of the car. It uses the crossmember from a 72 and up and an Energy Suspension transmission mount. Both ears are adjustable up and down and the ears are slotted so the cross member is adjustable side to side. You can remove the transmission just by removing the ears. The floor/tunnel bars stay in place. Here is a slightly fuzzy shot from underneath. And the finished product. What’s next? Now that I have a running car I’m finishing off a second bell housing and cross member and sending it out to Chris at Godzilla. He is going to test fit it in a 280Z and check the fit of the cross member as well as the clearance on some headers. Godzilla Raceworks is going to be a dealer for these and he took care of having the drive shaft made. As soon as we verify the fit on his test vehicle I’m going to go into production. I’m not taking pre orders but if you want to be on the list of pioneers you can contact me or Chris at Godzilla. When the bell housings are done you will have the first option to purchase. Pricing: Bell housing. $900.00 Crossmember. $295.00 Labor charge for modifying front cover. $75.00 You must supply either a brand new cover or brand new take off as a core. No used covers will be accepted. So far I’m really liking the gear spread on the 6 speed. I currently have a Subaru 3.9. I’m going to put the stock 3.364 diff back in to see if it brings the revs down at 75mph and see how it effects the first and second gear feel. For me that is the most important thing. Thanks Derek Quote Link to comment Share on other sites More sharing options...
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