Ben wrote:
I’ve been trying to find information on fitting the various transmissions into the chassis/body. I’ve done a bunch of searching and found lots of speculation but minimal photos/documentation. Michael, are you willing to post some info on that?
Transmissions:
For the SR20-series engines, there are three main choices, and then two other alternatives.
Standard SR20DE/T 5-speed transmission FS5W71C:
Offered in two versions, RWD SR20DE/T transmission (FS5W71C) has the same gearing set, the only difference is the SR20DE transmission has a .85 OD, and the DET has a .75 OD 5th gear. The 5-speed transmission fits the tunnel with almost no modifications other than removing the reinforcement rib on early 1600s, and reversing the shifter hole on the later 2000 model cars. The X-member needs a modification for the mount, where we do something like this, and set the transmission height using a 2x4 on end to get the driveshaft angle correct. The 1600-series driveshaft needs to be shortened, but and the dust shield removed from the yoke, but otherwise will slide into the end of the transmission-- thank you Nissan!
The FS5W1C transmission is used in a lot of 90s RWD Nissan products, including KA24E/DE engines, VG30E engines, etc. Changing out the bell housing to an SR20 version allows you plenty of replacement choices (with different gear ratios) if you have an issue with your gearbox.
This transmission is robust, reliable, rebuild able (with domestically sourced parts from Nissan USA), fits the car well, and will suit 98% of roadster owners.
S15 6-Speed Transmission FS6R92A
The 6-speed found in the S15 Silvia (with SR20DET engines) is one of my favorite modifications to do for a roadster. It is a close ratio box adding an additional gear between 1-5th gears, so you can always be in the right gear. It really brings the SR20-series engine alive, and when mated with a SR20DE, makes the car super fun to drive. The 6-gear is a .76 OD just like the other DET gearboxes.
The 6-speed is physically a larger transmission, so we often will modify the transmission tunnel, and the front legs of the X-frame will also need to be rebuilt to accommodate the larger 6-speed case. See photos below of some of the mods we have done in the past. The driveshaft has a different yoke, but after a lot of research, we found that it is the same as a KA24DE automatic (from a 240SX) so use that yoke when you have the driveshaft built.
There is an alternate version of the 6-speed (aka the Nismo version) which has reinforced internals and a .86 OD instead of the .76 OD found in the standard version.
The 6-speed gets a bad reputation from drift bros who abuse the hell out of them, but again, for most roadster owners, this is a great gearbox IF you are willing to do the extra work to get it to fit into your car. Negatives for this gear box are parts have to be ordered directly from Japan, and a surprising amount of them are now NLA. Finding a good gearbox that has not been destroyed by drift bros can also be difficult. Still, if you find a good one, it is a sweet swap for a roadster!
SR20DE/T Automatic Transmission
We have also modified roadsters to use the automatic transmission often found paired with SR20DE/T engines. This modification needs similar modifications to the 6-speed-- with the passenger side of the transmission tunnel needing to be modified to clear the shifter linkage. We have modified Datsun 280ZX automatic gear shifters to work with this swap, and then added a button for the electronic OD. The driveshaft yoke is unique to the automatics, but using a 240SX automatic (with KA24DE engine) will get you what you need.
X-Frame Mods:
Transmission tunnel modification:
Automatic shifter:
Other choices:
Z32 300ZX 5-speed RS5R30A
Many drifters have complained about the "weak" 5-speed transmission on 300hp+ drift cars, and have opted to to swap to a modified Z32 300ZX 5-speed transmission. These gear boxes are shorter in length than the 5-speed, have a remote shifter, reward facing starter, and are HEAVY, but they are bullet-proof. In my opinion, total over kill for the car.
This transmission does NOT bolt to the SR20-series engines and will require modifications such as a kit like this:
https://frsport.com/products/xcessive-n ... nissan-s13
Z33 6-speed Transmission CD09
The CD09 6-speed transmission found in 350/370Zs are probably one of the strongest RWD gearboxes that can be used with a SR20DE/T (with an adapter or bell housing swap). These will require MAJOR surgery to the X-frame, transmission tunnel, etc. but they have been done into the roadster chassis-- really suitable for 400hp+ applications with a LOT of tire.
