The goal for this project is to provide an adapter plate to mate a VQ35DE 6 speed transmission (CD) to an L-Series block. Our Z32 transmission adapters have worked well, but the hardest part for many folks is finding a machine shop capable of modifying the bellhousing at a reasonable cost. A key feature for this design was to come up with a solution that required little to no machining and can be done in the home garage.
I have owned a 350z track edition and now run a VQ35DE in my 240z, both of which used the CD transmission. The transmissions are wonderful to drive, they are very smooth and the shifting feel is direct. The later revision transmissions, CD009, have robust syncros and are capable of handling as much power as most L-Series builds can produce!
It is a close ratio transmission which gives a short first gear, great for low end acceleration in N/A when matched with a short rear, I run a 3.7 in my car. Turbo guys may want to opt for a 3.36 or 3.54 to help load the engine down low. All CD transmissions are interchangeable and can be had used for a reasonable price, especially earlier revisions, new transmissions are also available for under 1700 dollars.
- 1st 3.794
- 2nd 2.324
- 3rd 1.624
- 4th 1.271
- 5th 1.000
- 6th 0.794
To kick off the project the 6spd bellhousing and block were delivered to a local machine shop with accurate measuring equipment. A CMM was used to capture the engine block mounting dimensions along with the crank centerline. The same was done with the transmission bellhousing except a vertical milling center was used for location which allowed us the reach to measure the input shaft bearing surface.
Profiles for the bellhousing and engine block were transferred by hand and scanned into the computer for digitization. The accurate bolt and alignment feature measurements along with the perimeter profiles provided the building block for the adapter plate design.
The first piece of the puzzle is to adapt the mounting patterns between the engine and transmission. Patterns were clocked in relation to one another to orient the transmission properly and maintaince critical alignment features. A plate was designed from 3/8" steel which covers the entire perimeter of the bellhousing. This design makes for a stiff, thin plate, with minimal offset aiding in the no-machine design. The thin plate provides a challenge for thread engagment of the transmission mounting bolts, to overcome this FHCS where choosen as studs which will be permantient welded to the plate.
With the adpater plate design complete a few prototypes were made. The plate starts out as a laser cut blank which is then finish machined in a CNC mill. THe final product turned out great with the engine and transmission aligning as intended.
The next challange was to properly align the L-Series clutch with the 6spd transmission input shaft and clutch hydraulics. The stock L-Series and 6Spd share the same input spline count. However the 350z's dual mass flywheel and clutch assembly is much taller then the L-Series which places the input shaft splines further awap from the engine. The adapter alos moves the transmission mount further. These differences require the relocation of the L-Series clutch which can either be accomplished through a flwheel spacer, or an altogether new custom flywheel.
The spacer route was initially explored as I percieved it as a cheaper option that also allows for the use of any L-Series flywheel, as many people will have already upgraded this as part of their engine builds. Spacing the flywheel out not only requires a spacer which must be precisly machined but also requires custom flywheel bolts and stator relocation. Starter relocation was explored both by modifying a tilton stator and buy incorperating the offset into the aapter plate. Neither proved viable especially is machning of the bellhousing was to be elminated.
Ultimately it was decided a custom flywheel was the best route and would provide the most value for the kit. A stock flywheel and 3D printed spacers were used to ensure the new spacing was correct. The new flywheel maintained the same start ring gear location and center button dimensions. This allows for the L-Series starter to remain in the same location and for OE flywheel bolts to be used.
As you can imagine the L-Series stater location does not line up with the reliefs on the 6spd bellhousing. Using a gear reduction starter from a 280zxt the issues is nearly eliminated. Not only is the starter nice due to the gear reduction but is also does not have a bearing or nose cone outboard of the spur gear making it very compact. This allows for only a small amount of material removed which can be done using a carbine bur on a die grinder, a 3D printed jig takes the guess work out of the location and size.
While we are working towards a complete bolt in solution I though it would be good to offer some 'DIY' kits for folks that were interesting in being an early adopter installing a kit in parallel with my vehicle developement. Included is everything needed to bolt the transmission to the engine, its up to the installer to fabricate a transmission mount and either modify the console for a rearward shifter location or fabrication an alternative linkage! I am working on shifter design now and will be doing the first vehicle install during July.