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I'm getting ready to order the parts from Ray to rebuild a stock 93 manual transmission. Are there any internal upgraded OEM parts from later model year transmissions that can be swapped into my 93 trans? I know the 5 speed that came in some RX8 cars are supposed to have some better parts in them but are those upgraded parts interchangeable with the FD box?
I think the 5th gear “crunch” was pretty common in the 93’s. It was attributed to drivers missing 3rd and hitting 5th instead. It was supposedly strengthened in later models, and a shift-select spindle was given a stiffer spring to make it harder for drivers to miss 3rd gear.
Not internal to the transmission but the shift fork was said to similarly have been strengthened, in models subsequent to the 93’s.
Thanks. I am aware of them. I have already contacted them and am having them put together a quote for me. BUT that is not what I want to know. I'm most curious about seeing if our old FD box can be internally upgraded to the newest spec that was used in the RX8. Even if I don't end up going down this route, I think it'd still be beneficial to the forums to know about the potential of any OEM parts interchangeability for upgrade or parts availability purposes.
I think the 5th gear “crunch” was pretty common in the 93’s. It was attributed to drivers missing 3rd and hitting 5th instead. It was supposedly strengthened in later models, and a shift-select spindle was given a stiffer spring to make it harder for drivers to miss 3rd gear.
Not internal to the transmission but the shift fork was said to similarly have been strengthened, in models subsequent to the 93’s.
My trans does have the 5th gear problem which is the main reason for going through the transmission. It also has over 100k miles on it so I feel a rebuild is in order simply to match the zero miles engine and clutch that it's getting attached to. I knew about the shift fork and plan on getting the stronger one. This is the first I have heard of the stiffer shift select spring.
The later boxes had the new and improved 1st/2nd hub and syncro assembly, not quite sure if that amounted to the same dual cone syncro the rx8 5 speeds had on 1~2?
Gearboxes here used to be $500, asking prices are a bit nuts now though, if a late box is still available for cheap over there, might be easier to grab one of those and avoid hundreds in bearings and syncros and the need to make/buy special tools......with the bonus of the shorter 5th.
I have the shorter 5th, wish I had the longer one. Unless you're doing 140mph+ there's no benefit to the shorter 5th, you just end up with worse gas milage.
I've been waiting for OS Giken to make new gear sets, it's been 2 years so far and it they keep pushing back the ship dates. Just went from the end of August, to December. Nobody else makes better ratios with a helical gear set, pretty sure Liberty's only make straight cut gears.
i still chew up 5th gear synchros with the late model transmissions and the mainshaft upgrade from liberty.. the Main shaft helps with the flex of the shaft in the middle, ie 3rd misalignment
Liberty makes helical gears also, or at least that what Paul from liberty had told me.
I switched to the US 5th gear on my latest iteration with the 4.77 Final gear and i am very pleased having the taller 5th gear as opposed to the jdm 5th.
The later boxes had the new and improved 1st/2nd hub and syncro assembly, not quite sure if that amounted to the same dual cone syncro the rx8 5 speeds had on 1~2?
Gearboxes here used to be $500, asking prices are a bit nuts now though, if a late box is still available for cheap over there, might be easier to grab one of those and avoid hundreds in bearings and syncros and the need to make/buy special tools......with the bonus of the shorter 5th.
I believe the updated 1st/2nd hub/synchro you are referring too happened mid year 1994? Please anybody correct me if I am wrong. I'm assuming if you ordered the1995 parts you'd get the updated parts for sure. That said, I do not think these updated FD parts are the same synchro setup used in the RX8 transmission. Hopefully someone can confirm this?
I have the shorter 5th, wish I had the longer one. Unless you're doing 140mph+ there's no benefit to the shorter 5th, you just end up with worse gas milage.
I've been waiting for OS Giken to make new gear sets, it's been 2 years so far and it they keep pushing back the ship dates. Just went from the end of August, to December. Nobody else makes better ratios with a helical gear set, pretty sure Liberty's only make straight cut gears.
I used to want the shorter 5th gear but now that I am older and on my second FD I totally can't see giving up the tall gear. It cruises so nice at interstate/highway speeds and the fuel economy is more than welcome to me since the FD has a too small fuel tank (in my opinion) as is.
Thanks for bringing up the OS Giken topic. I had no idea they were working on developing any new FD stuff
Thanks. I am aware of them. I have already contacted them and am having them put together a quote for me. BUT that is not what I want to know. I'm most curious about seeing if our old FD box can be internally upgraded to the newest spec that was used in the RX8. Even if I don't end up going down this route, I think it'd still be beneficial to the forums to know about the potential of any OEM parts interchangeability for upgrade or parts availability purposes.
yeah, you can swap out the FD3 center section with the RX8 5 spd. Which is going to be a lot cheaper than trying to buy and swap internals. You can also switch to a push clutch setup with the RX8 bellhousing and slave. The rear housing, shift tower, and shift rods are different on the FD3 and make up for it putting the shifter about 3” further back than the RX8 trans. Because the Renesis engine is further back in the chassis than the FD REW by that amount.
You get triple cone 1st-3rd on the RX8 trans, but the gears are narrower to account for it. I don’t know that 5th is any better. A friend with an RX8-REW conversion with the RX8 5-spd had to get 5th rebuilt due to the synchros grinding.
OSG isn’t developing anything, that’s why people are waiting 2+ years with no end in sight. I thought it was more like 3 or 4 years myself with some people waiting since 2019 or so …
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I believe the updated 1st/2nd hub/synchro you are referring too happened mid year 1994? Please anybody correct me if I am wrong. I'm assuming if you ordered the1995 parts you'd get the updated parts for sure. That said, I do not think these updated FD parts are the same synchro setup used in the RX8 transmission. Hopefully someone can confirm this?
the 1993 used a R523-17-260 hub set, and the early 95's get R523-17-260A, and the late 95's get R523-17-260B. all of the replacement parts are the R523-17-260B
the 99+ got an R525-17-260. the synchro's are the same
the Rx8 uses an R527-17-260B hub set, different synchros (R507-17-26Y), different gears. etc
i still chew up 5th gear synchros with the late model transmissions and the mainshaft upgrade from liberty.. the Main shaft helps with the flex of the shaft in the middle, ie 3rd misalignment
Liberty makes helical gears also, or at least that what Paul from liberty had told me.
Thanks for clarifying that! I'm just going off of what I recall from a conversation with Paul a few years ago. I had Liberty do EVERYTHING (including adding an oil bar) they offer other than face plating on my trans. I haven't been able to finish my build yet though, so I can't speak from personal experience
the 1993 used a R523-17-260 hub set, and the early 95's get R523-17-260A, and the late 95's get R523-17-260B. all of the replacement parts are the R523-17-260B
the 99+ got an R525-17-260. the synchro's are the same
the Rx8 uses an R527-17-260B hub set, different synchros (R507-17-26Y), different gears. etc
Biggest upgrade you can do to the stock FD transmission if you keep the H pattern is put a Banzai bushed transmission brace in the car.
FD 5th synchro isnt weak.
It just cant handle being smashed into at 40 or 50mph and 6-8000 engine rpm when you went for 3rd and hit 5th gear because the power plant frame plus liquid filled motor and diff mounts allowed the entire transmission to twist altering the spacial relationship of the H pattern.
Too much rpm differential between engine and 5th gear. You are trying to slow the rotating engine mass from 6-8,000rpm to 1,500 to 2,500rpm with just the synchro clutch in an instant.
Hell, your fighting engine torque as well if you havent disabled the throttle dashpot (throttle still open).
Worse yet, people will often drive an FD with blown out engine or diff bushings or a cracked power plant frame and and the H pattern is moving around like mad.
RX-8 and miatas have less of an issue with 2nd to 5th mis-shift since the engines have less torque, so the H pattern moves less with load.
The top heavy miata piston engines actually have the issue of the H pattern moving around under cornering loads as the engine flops over.
^ Didn’t connect the dots with his question and the brace until your post, but totally agree. I installed Banzai’s transmission brace over the winter and close to finishing a driving season with it. I’d give it two thumbs up.
I have Noltec engine mounts and Mazdaspeed differential mounts but the shifter still moved around noticeably under load. It always bugged me. Banzai’s brace cured it. Easy to install and VERY minimal nvh…and I’m old fart and pretty sensitive to that.
OSG isn’t developing anything, that’s why people are waiting 2+ years with no end in sight. I thought it was more like 3 or 4 years myself with some people waiting since 2019 or so …
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It's definitely been a long time, I've been waiting for 2 years it's never been in stock, 4 years wouldn't surprise me. I email OS Giken USA, sales@osgikenusa.com, about 6 months ago, and they said they were still planning on making gear sets they just didn't have a production date assigned for those parts yet. If you guys are serious about wanting a gear set, 3 or 5, please email them and ask. Perhaps we can get the gears turning again if enough of us reach out..
08-30-23, 11:47 AM
