Well I found out the following:
5-speed €2900 includes strengthened input shaft and main shaft
The RB20DET 'box is the FS5W71C, similar to the one found in SR-powered S-chassis cars.
The RB25DET 'box is the RS5R30A, similar to the Z32 (300ZX) NA and TT box.
The Skyline applications list for these gearboxes is as follows:
R32 GTS and GTSt - FS5W71C
R33 GTS - FS5W71C
R33 GTSt - RS5R30A
The designed allowable engine torque for the FS5W71C and FS6R92A is approx. 30kgm/294Nm
The designed allowable engine torque for the FS5W71C and FS6R92A is approx. 30kgm/294Nm
| gear | FS5W71C | F4W71B |
| 1st: | 3.321 | 3.529 |
| 2nd: | 1.902 | 2.246 |
| 3rd: | 1.308 | 1.415 |
| 4th: | 1.000 | 1.000 |
| 5th: | 0.759 | - |
| Rev: | 3.362 | 3.364 |
So the only thing I need to figure out is if the bell housings are the same, but most probably not. Well, I might as well get the RB20DET complete with a matching gearbox. Should I blow the gearbox at some point, I always have a spare one. And if that one breaks, I might try the OS Giken gear upgrades (see below).
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| R32 - RB20DET gearbox | 200/240SX FS5W71C |
Here's how the old 4-speed compares in terms of gear-speed (speeds in mph):
But wouldn't this Nismo Silvia 180SX reinforced cross 6-speed transmission be awesome if it'd be made to fit? :)
The designed allowable engine torque for the NISMO Reinforced Transmission is approx. 40kgm/392Nm.
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| FS4W71B vs FS5W71C |
But wouldn't this Nismo Silvia 180SX reinforced cross 6-speed transmission be awesome if it'd be made to fit? :)
The designed allowable engine torque for the NISMO Reinforced Transmission is approx. 40kgm/392Nm.
 | Ratios: 1st: 2.9071 2nd: 1.9888 3rd: 1.5373 4th: 1.2179 5th: 1.0000 6th: 0.8624 |
| Nismo reinforced cross gearbox |
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| FS5W71C vs NISMO Reinforced Cross |
OS Giken FS5W71C upgrades
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| Close-ratio gear sets |
OS Giken close-ratio gear sets offer greatly increased gear strength, along with closer gear ratios to suit racing applications. The retention of normal synchromesh parts and a helical gear design means the gears are still almost as quiet as a standard gear set, so this is an excellent upgrade for street-driven vehicles too.
Close Gear Kit 3-Speed €1500 €1850 incl. main shaft
Close Gear Kit 3-Speed €1500 €1850 incl. main shaft
1st: 2.717 (3.321 OEM)
2nd: 1.722 (1.902 OEM)
3rd: 1.232 (1.308 OEM)
5th gear overhaul €275
5th: 0.833 or 0.759 OEM
5-speed €2900 includes strengthened input shaft and main shaft
Suits applications up to 600hp
1st: 2.596 (3.321 OEM)
2nd: 1.765 (1.902 OEM)
3rd: 1.250 (1.308 OEM)
4th: 1.000 (1.000 OEM)
5th: 0.833 (0.759 OEM)
OEM FS5W71C - ~ € 1,425
Overhaul kits from drivetrain.com
bearing & synchro kit from Cobra-transmission ($140)
RB25DET transmission
The transmission tunnel doesn't need to be stretched out with the rb25 transmission.
Nismo engine and transmission mount set
RB25 tranny - from GT-R Canada
The driveshaft of the RB20 is NOT compatible with the RB25 tranny. The yoke is not wide enough to slide on to the tailshaft of the tranny, so you need an RB25 yoke. You also CANNOT use the RB25 driveshaft, because (a) it is too long, and (b) the hanger bearing on it has no points to be bolted onto the hinges in the middle. So your best bet is to:
(a) put an RB25 yoke onto the RB20 driveshaft; you have to cut off the yoke along with around 2 inches of the pipe towards the front of the RB25 driveshaft. Slide INTO the RB20 driveshaft and then weld to strength and balance it. This ensures that the final product would be strong and won't bend under load.
(b) shorten the RB25 driveshaft, or
(c) get a one-piece driveshaft of the same length as the RB20 driveshaft with the RB25 yoke.
