240SX Gearbox
240SX Gearbox
Can any of you tell me the designation of the gearbox found in the various models of 240SX found in the U.S. I have a Datsun 280Z and some things I've read suggest to me that 240SX transmissions are at least related to mine (I have an FS5W71B), except that the more modern models have a larger diameter countershaft and otherwise can handle more torque. I'm sure I'd have other problems with getting one to match up even if they were similar, like bellhousing or input shaft differences...but this would be a start. Thanks.
Re: 240SX Gearbox
CU Zcar wrote:Can any of you tell me the designation of the gearbox found in the various models of 240SX found in the U.S. I have a Datsun 280Z and some things I've read suggest to me that 240SX transmissions are at least related to mine (I have an FS5W71B), except that the more modern models have a larger diameter countershaft and otherwise can handle more torque. I'm sure I'd have other problems with getting one to match up even if they were similar, like bellhousing or input shaft differences...but this would be a start. Thanks.
We've had both the Z car and the 240SX gearbox in our EP 240SX. The Z car gearbox (5-sp) is quite a bit different, but you can make it work. If this is for a Z car (L motor) and you want to use the 240SX gearbox, you will have to remove the front case/bellhousing and replace it with the Z car front case. This is a direct bolt on with the exception of one of the shifter shafts. We did this the other way (Z car box behind a 240SX KA24D) and had to bush the one shaft. So, you would have to enlarge the Z car case slightly to fit this shaft (I don't remember which of the three shafts, but it's only one). This will rotate the 240SX gearbox to fit the L series mount pattern.
If this is too much, call Eddie Radatz at 770-926-6609 and he can make you either one. Keep in mind the 240SX gears are better (except 5th) but the box isn't as strong as the Z car box.
No, that makes perfect sense. I was supposing I could put the front half of my case on the other transmission. I was hoping that the 240SX boxes were stronger, but if you raced them and say that's not so then I'll have to take your word for it...I may return to the search for a 280ZX Turbo box, which I suspect has the larger countershaft I am looking for which supposedly makes it stronger. I also may have a chat with your gearbox builder friend, thanks for the contact info.In case your wondering, a lot of my "suspicions" I mention come from http://members.ozemail.com.au/...r.htm . I thought the 280ZX Turbo, and 240SX, transmission may be stronger due to the following statement:"The main difference with early 5C turbo boxes is the use of heavier section countershaft (38mm diam) and gears. This means they change slower but can handle heaps more grunt. The earlier boxes (240K, 260Z etc) up to about 85 usually had a 29mm diameter countershaft. All boxes from 87 on seem to have the larger countershaft."But for one, that's an Australian webpage, perhaps theirs are different, and maybe the 71C family of transmissions is also different. I'll have to look into it, but thanks for the start guys!
[edit] Oh yeah, what about input shafts? Are they the same length/diameter/same splines, or would I retain my Zcar input shaft to go with the front half of my case? Or would I use the 240SX shaft and have to mix-and-match a clutch, like with a 240SX disc and a Zcar pressure plate...
[edit] Oh yeah, what about input shafts? Are they the same length/diameter/same splines, or would I retain my Zcar input shaft to go with the front half of my case? Or would I use the 240SX shaft and have to mix-and-match a clutch, like with a 240SX disc and a Zcar pressure plate...
Now, we don't put a million turbo horsepower through the gearbox (maybe 240 with comparable torque), but the countershaft isn't the source of the 240SX/early 300ZX gearbox problems. The synchros and shifting mechanism don't seem to be as good. The guys at the shop are always rebuilding the 300ZX and 240SX gearboxes, but the Z car gearboxes last much longer. Shifting is more positive as well, though it's still sloppy.
If you're making a lot of hp, the Borg Warner Z car box is pretty strong, but heavy. I know Eddie has at least one of those to sell. I'd say if you're making less than 250 hp, a Z car box is the best compromise. The close ratio ZX non-turbo is pretty good except for 5th, but 5ths are interchangable. If you're making more, I'd go for aftermarket or the Borg Warner box. If you like the splits of the 240SX gearbox and aren't making a ton of hp, it can work.
If you're making a lot of hp, the Borg Warner Z car box is pretty strong, but heavy. I know Eddie has at least one of those to sell. I'd say if you're making less than 250 hp, a Z car box is the best compromise. The close ratio ZX non-turbo is pretty good except for 5th, but 5ths are interchangable. If you're making more, I'd go for aftermarket or the Borg Warner box. If you like the splits of the 240SX gearbox and aren't making a ton of hp, it can work.
Oh, I see. I'm not making nearly that kind of power, I'm sure it's nowhere near 200hp or ft-lbs yet. I'm kind of looking to the future when I go turbo though 
but anyways, I rebuilt my second FS5W71B with a cheap bearing kit. The reason it was worn in the first place was that the countershaft bearing that sits in the adaptor plate in the center of the transmission was severely worn (the balls were falling out, to give you some idea). It recently began acting up again after about 6 months of abuse :icesangel and I suspect the same bearing. Maybe this time I'll just rebuild it with proper Nissan OEM parts, but if I could find a not-more-expensive alternative that would be stronger anyway I'd jump on it. Perhaps if it turns out that the larger countershaft would help my problem, there would be some way of using the good parts out of the Z mechanism with the 240SX parts... :thinker Or, I could just stop doing clutch kicks to initiate drifts.
but anyways, I rebuilt my second FS5W71B with a cheap bearing kit. The reason it was worn in the first place was that the countershaft bearing that sits in the adaptor plate in the center of the transmission was severely worn (the balls were falling out, to give you some idea). It recently began acting up again after about 6 months of abuse :icesangel and I suspect the same bearing. Maybe this time I'll just rebuild it with proper Nissan OEM parts, but if I could find a not-more-expensive alternative that would be stronger anyway I'd jump on it. Perhaps if it turns out that the larger countershaft would help my problem, there would be some way of using the good parts out of the Z mechanism with the 240SX parts... :thinker Or, I could just stop doing clutch kicks to initiate drifts.I hate it when my balls fall out.
If you're having center bulkhead bearing problems, you've got a bigger problem than simple abuse. Those things on a Z box are pretty stout. Check the install to make sure it's square to the shaft and not too loose. I'm not a gearbox guy, but I've seen the non-turbo Nissan gearbox put up with 310hp at 9000 rpm in GT2 cars on big slicks (a Nissan Comp direct drive box uses stock center bulkhead geometry). Those guys are likely to break hubs or mash a synch ring or bend a shift fork, but not have bearing problems.
Maybe it's time for a new gearbox instead of a rebuild. The 280ZX 81-83 non-turbo makes a nice upgrade, except 5th.
If you're having center bulkhead bearing problems, you've got a bigger problem than simple abuse. Those things on a Z box are pretty stout. Check the install to make sure it's square to the shaft and not too loose. I'm not a gearbox guy, but I've seen the non-turbo Nissan gearbox put up with 310hp at 9000 rpm in GT2 cars on big slicks (a Nissan Comp direct drive box uses stock center bulkhead geometry). Those guys are likely to break hubs or mash a synch ring or bend a shift fork, but not have bearing problems.
Maybe it's time for a new gearbox instead of a rebuild. The 280ZX 81-83 non-turbo makes a nice upgrade, except 5th.