Project FD RX7 Restomod: Part 18 – Choosing a Transmission Upgrade

Fisch Racing Tech ROTARY to CD009/CD00A Adapter System RX-7We upgraded our FD RX-7’s transmission with the durable, 1,000whp+ and high-rpm capable CD009/CD00A transmission from the Nissan 350Z.  To make this a seamless installation, we are using the Fisch Racing Tech CD009 Adapter system and the SERIALNINE CD999 shifter assembly.

Now that our differential and axles are upgraded to handle as much power as we can throw at it, the last weak link in our FD3S RX7’s drivetrain is the transmission.  To solve this problem, there are three main transmission upgrade paths to choose from.  We will go over them all and explain our reasoning why the Nissan CD009 6-speed manual, Fisch Racing Tech ROTARY to CD009/CD00A Adapter System, and SERIEALNINE CD999 shifter assembly is the best fit for our usage and goal.

FD RX-7 stock transmission 3rd gear tornThe stock FD’s 5-speed transmission is known to destroy 3rd gear around 400-425lb-ft of torque or 500whp+.  The gearbox’s case starts to flex and causes the gears to separate and fail at these power levels and even at lower power from hard launches.

Output shafts often shear at 350whp on ET Street drag tires, and tailshafts have been known to break at 450whp.  The key to making stock transmissions live is to keep the torque below 310lb-ft.  Needless to say, our power goals are going to be well clear of this issue and upgrading the transmission is our only solution for reliably handling the power that we are going to make.

We learned in Part 14 that upgrading to a Ford Explorer 8.8” diff is a no-brainer because the cost is relatively low and similar to adding an aftermarket clutch-type LSD and bracing the stock cast-iron “FD” differential.  However, the same cannot be said about upgrading the transmission, which is a far more expensive endeavor. Unfortunately, to make a FD RX-7 reliable at over 500whp, you will need to spend at a minimum $7-12K on the drivetrain.


There are three main options when it comes up upgrading the transmission of an FD RX-7 to handle over 500whp, Manual transmissions, Sequential race transmissions, and Dual Clutch Transmissions (DCT).

1. 6-Speed Manual Transmission – Tremec T-56 “MAGNUM”

Tremec T56 Magnum FWhen it comes to 6-speed manual transmission upgrades, the Tremec T56 Magnum is by far the most popular transmission upgrade for big power builds, 3-rotor swaps, LS engine swaps, and it is one of my personal favorite transmissions.  It is typically the go-to solution due to its immense power-handling capabilities, reliability, aftermarket support, and ease of rebuilds which can be done by many shops.  The swap will run roughly $10K for a brand new T56 Magnum, which weighs 150-160lbs.  This makes it one of the heaviest options, weighing in at 55-65lbs more than stock.

As of 2007, when most people refer to a brand-new aftermarket “T56”, they are actually talking about the Tremec “Magnum”.  The Magnum is the aftermarket solution for the OEM “TR-6060” which replaced the BorgWarner-designed “T56” that was originally developed for the Dodge Viper in 1992.  The TR-6060 and Magnum are rated up-to 700lb-ft of torque, features triple synchromesh on 1 & 2nd gears, and double synchromesh on all other gears & reverse.

There are two main gear ratios to choose from: 2.97, 2.10, 1.46, 1.00, 0.74, 0.5 (WIDE) and 2.66, 1.78, 1.30, 1.00, 0.80, 0.62 (CLOSE).  However, there are some options that can mix and match the overdriven 5th and 6th gears with the opposite 1-4 ratios.

The “T56/TR-6060/Magnum” is a great solution for the majority of builds out there.  However, there are some negatives.  The price of new transmissions is increasing, and it is only rated to 7,800rpm.  Since our FD RX-7 will see a redline well north of 9,000rpm, we decided to look into a different option.

2. Sequential (Dog-Ring) Transmissions

OS Giken Sequential TransmissionSequential race transmissions are the most expensive options for the FD RX-7, typically in the $15-25K range.  From manufacturers like Quaife, OS Giken, HGT, Samsonas, they are typically available in 6 and 7-speed configurations, they shift very quickly, are the lightest transmission option for the car, and some can handle upwards of 750lb-ft of torque.

However, straight cut gears and dog ring engagement can make these transmissions a bit jerky, noisy, and tiring to drive.  “Racecars for the street” are not always the best for a daily-driven street car.  For a dedicated race car, this is by far the best option.  At 85lbs without a bellhousing, this transmission will end up weighing close to stock.


  1. 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.

    1. 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.

      1. 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.

          1. 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.

  2. 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.

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