We mounted the shifter to the transmission in the furthest forward position, which is the setting for the FD RX-7. Now our CD009 is ready to be installed.
The CD009 configured for the FD RX-7 with the Fisch Racing Tech bellhousing, Tilton HRB, and Serialnine CD999 shifter weighed in at 134lbs. This is exactly 40lbs heavier than the 94lb stock FD RX-7 transmission.
This weight increase is perfectly centralized in the middle of the car, which is ideal if weight must be added to a car. We saved 9.2lbs from the aluminum Ford 8.8” diff and mounting bracket, gained back 15.78lbs from the beefy Driveshaft Shop “Direct-Fit” Axles, totaling in a 6.58lb weight penalty to the rear of the car.
Now we added 40lbs to the center of the car for a 46.58lb overall weight increase to our FD RX-7, which now has a drivetrain that can handle over 1,000whp and 750lb-ft of torque. We saved 42lbs from the Antigravity Lithium Ion Battery in Part 6, so we now have a total weight increase of just 4.58lbs
GEAR RATIOS:
In Part-15, we chose a 4.30 to 1 final drive ratio due to our engine’s 9,000rpm+ redline and with the anticipation of swapping to a Tremec T56 Magnum Transmission in the future. Now that we went with the CD009, we had to revisit our choice on the final drive ratio.Analyzing the gear ratios, final drive ratios and their corresponding top speeds with an 8,000rpm redline:
Stock FD RX7 – 4.1 Final Drive, Gears: 3.483, 2.015, 1.391, 1.000, 0.793
mph: 42, 72, 104, 145, 202
Stock FD RX7 – 4.3 Final Drive, Gears: 3.483, 2.015, 1.391, 1.000, 0.793
mph: 40, 69, 100, 139, 193
T56 Close – 4.3 Final Drive, Gears: 2.66, 1.78, 1.30, 1.00, 0.80, 0.62
mph: 52, 78, 107, 139, 173, 220
CD009 – 4.3 Final Drive, Gears: 3.794, 2.324, 1.624, 1.271, 1.000, 0.794.
mph: 37, 60, 85, 109, 139, 174
CD009 – 3.55 Final Drive, Gears: 3.794, 2.324, 1.624, 1.271, 1.000, 0.794.
mph: 44, 72, 103, 132, 168, 211
9,000rpm Redline:
CD009 – 3.55 Final Drive, Gears: 3.794, 2.324, 1.624, 1.271, 1.000, 0.794.
mph: 50, 81, 116, 149, 189, 238
When selecting gear and final drive ratios, it’s important to determine what the most important goals are, how much power, and the tractive grip the car will have. Optimizing the gearing for 1/8th mile, ¼ mile, ½ mile, standing-mile competitions, road racing, freeway cruising rpm, etc…might all have different optimal transmission and final drive ratios.
We intend to be over 600whp in competition trim on road courses, so a longer 2nd and 3rd gears will help put down power better than an overly short gear. After analyzing the cornering speeds of the tracks that we will be running on, the 4.30 final drive ratio was going to be too short for our redline and power goals. For comparison, 4th gear would top out at 109mph, which isn’t much more than the FD’s stock 3rd gear. This might be pretty ideal for cars in the 400-500whp range, but we decided on pulling the differential and removing the 4.30 final drive in favor for the original 3.55 that originally came with the Ford 8.8” differential. Now we just have to deburr and WPC treat that gear again before installing it.
The Fisch Racing Tech ROTARY to CD009/CD00A Adapter System was very easy and straightforward to install, and combined with the Serialnine CD999 shifter, we have a high-rpm capable 6-speed manual transmission ready to bolt into our FD and handle all the power we can throw at it.
Stay tuned where we mate the transmission to the engine and install the drivetrain into the FD.
7 comments
All of the CD009 conversions, I’m a little bothered that the replacement bellhousing bolts to the relatively small bolts intended for that cover. Obviously it works, I can’t think of a better way that’s not a lot more work and cost, it’s done a lot, it’s not actually a problem, but it just bothers me a little.
Nice to see the thoroughness of the upgrades – some of the other transmission options would mean the stock final drive ratios would be less than optimal, but that problem’s taken care of too.
There are (11) M8 Bolts that hold on the front cover, and (now) attach the Fisch Racing Bellhousing adapter. These bolts are also close to the very outer diameter of the transmission. Fisch has numerous 1,000hp drag and drift cars that use this adapter design on various RX-7s, Supras, IS300s, LS engines and K-series engines. Based on the success of their extensive testing and customer base, there should be no reservations of this tried and true design.
I know that any other solution would be a much larger casting, with a lot more post-casting machining and a lot more work to install. I know the design Fisch Racing came up with works and is well executed. I just wish there were a way to do it that fed torque loads into the case how it was originally designed; I’m really annoyed that design trends have gone away from separate bellhousings.
I suppose you could weld the bellhousing to the case if you really wanted to make it permanent.
If I were in charge of things, someone would make a front casing for the CD009/etc that had a T56/Magnum bolt face.
I’m not though.
Your builds are always thorough and exciting. I can’t wait for the next installment!
I’ve never had the privilege to drive any of the mentioned transmissions above. Are any of them smooth like S2k or Miata 6spd? I have a 05 STi 6spd in my 00 2.5 RS and while its wonderful, I still find it awkward to shift super fast. Its not a skill issue on my part (at least in my opinion), because I was still able to do some 90s style drag shifts in a low mileage FK8 CTR.