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Old 08-25-2013, 09:35 AM   #1
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rb25 and n/a 300zx transmission

sup zilvia. so i would like everyones general input and experience on using a n/a 300zx 5 speed transmission on an rb25. general key points of discussion are what needs to be done to the 300zx transmission to make it work and bolt together with the rb25 as a full drivetrain and what clutch options are there (planning on using the n/a 300zx clutch and pressure plate because rumors have said they are the same part as the rb?)

a long morning of google searching has brought me countless threads of mating 300z/rb25 trannies together because someones rb syncro went out, can't seem to find any about using the actualy transmission itself.

thanks guys-tj
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Old 08-25-2013, 10:40 AM   #2
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Use the TT 300ZX transmission. The NA is basically the same as the KA. If you need a tranny on a budget, you'd probably be better off trying to use a KA transmission. only 2 bolts wont line up for the bellhousing to mount up on the RB.
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Old 08-25-2013, 11:54 AM   #3
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for sure the only real reason as to why the n/a tranny would be used is because it came with the motor and things.

I would assume that rules out using the n/a clutch as well?
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Old 08-25-2013, 03:39 PM   #4
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Quote:
Originally Posted by fliprayzin240sx View Post
Use the TT 300ZX transmission. The NA is basically the same as the KA. If you need a tranny on a budget, you'd probably be better off trying to use a KA transmission. only 2 bolts wont line up for the bellhousing to mount up on the RB.


TT and n/a Z32 5 speeds have the same internals. One is not stronger than the other.
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Old 08-25-2013, 04:28 PM   #5
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TT and n/a Z32 5 speeds have the same internals. One is not stronger than the other.
and we are back into discussion.

i would assume the z32 tranny and rb motor have slightly different patterns as a sort of conversion plate was included with everything as well, maybe it was to space the transmission back and sit the shifter in oem place. So what does this mean concerning the clutch? i have a full, and nice, n/a z32 clutch assembly that if was worth anything towards the rb would be nice to use
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Old 08-25-2013, 05:02 PM   #6
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Most people use the bellhousing off a RB25 or RB26 transmission to bolt on the back half of the transmission.

Everything will line up clutch wise, the only problem is shifter location.

If you google hard enough you can find the distance in lengths of the shifter positions.

I haven't see anyone run an adapter plate to bolt on a 300zx trans to a rb25.
Sounds like more of a headache and more expensive than just getting a bellhousing.

This company makes Z32 shifter relocation hardware which might get you closer to the correct position.
http://www.xcessivemanufacturing.com/

All Z32, RB25DET, RB26DETT have the same internals: gears/bearings/synchros/forks.
The difference is in the length of the mainshaft, shifter linkage and 4WD splitter.

Interestingly enough the 90's era pathfinder V6 5spd shares the same transmission but with different ratios.


If you plan on making reasonable HP and you want to work on your car.
I recommend the RB20DET/RB25DE transmission. It's smaller and lighter. Much easier to remove and install compared to the other transmission.

If you want to make 350+HP(wild ass guess on the HP limit or break point) I would go with a RB25DET transmission.
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Old 08-25-2013, 05:57 PM   #7
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Originally Posted by Suit View Post
and we are back into discussion.

i would assume the z32 tranny and rb motor have slightly different patterns as a sort of conversion plate was included with everything as well, maybe it was to space the transmission back and sit the shifter in oem place. So what does this mean concerning the clutch? i have a full, and nice, n/a z32 clutch assembly that if was worth anything towards the rb would be nice to use

I don't know anything about the RB motor. I was just correcting some miss information about the Z32 tranny.
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Old 08-25-2013, 06:17 PM   #8
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Z32 transmissions have been known to be behind some engine setups making serious power and dragged often. However, used they suffer from worn synchros or baulk ring retaining clips that fall off and end up causing the grinding, not the synchros. If you purchase one, I recommend having it gone through.

The NA and TT are identical transmissions minus the speed sensor gears and the bell housing, specially around the starter pad to accommodate the larger flywheel. I have yet to find any information showing they are two completely different transmissions internally.
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Old 08-25-2013, 07:55 PM   #9
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My bad, was thinking RB25 NA and Turbo transmissions..
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Old 08-25-2013, 10:54 PM   #10
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Quote:
Originally Posted by BoredEE View Post
Most people use the bellhousing off a RB25 or RB26 transmission to bolt on the back half of the transmission.

Everything will line up clutch wise, the only problem is shifter location.

If you google hard enough you can find the distance in lengths of the shifter positions.

I haven't see anyone run an adapter plate to bolt on a 300zx trans to a rb25.
Sounds like more of a headache and more expensive than just getting a bellhousing.

This company makes Z32 shifter relocation hardware which might get you closer to the correct position.
http://www.xcessivemanufacturing.com/

All Z32, RB25DET, RB26DETT have the same internals: gears/bearings/synchros/forks.
The difference is in the length of the mainshaft, shifter linkage and 4WD splitter.

Interestingly enough the 90's era pathfinder V6 5spd shares the same transmission but with different ratios.


If you plan on making reasonable HP and you want to work on your car.
I recommend the RB20DET/RB25DE transmission. It's smaller and lighter. Much easier to remove and install compared to the other transmission.

If you want to make 350+HP(wild ass guess on the HP limit or break point) I would go with a RB25DET transmission.
Believe it or not the motor set came with an adapter plate which i also figured was spacing the transmission back to compensate for the shifter and shaft length. how lucky!

Quote:
Originally Posted by Tom N View Post
I don't know anything about the RB motor. I was just correcting some miss information about the Z32 tranny.
thanks for the input anyway man, help is always appreciated!

Quote:
Originally Posted by jr_ss View Post
Z32 transmissions have been known to be behind some engine setups making serious power and dragged often. However, used they suffer from worn synchros or baulk ring retaining clips that fall off and end up causing the grinding, not the synchros. If you purchase one, I recommend having it gone through.

The NA and TT are identical transmissions minus the speed sensor gears and the bell housing, specially around the starter pad to accommodate the larger flywheel. I have yet to find any information showing they are two completely different transmissions internally.
already inspected the transmission its in great conditon so thats great to hear! the car will be a spirited driven dd so it wont be harsh on the tranny, but the motor will put out 450-500whp so it will be fun, got our hands on a pretty sweet hks manifold and a 3076

Quote:
Originally Posted by fliprayzin240sx View Post
My bad, was thinking RB25 NA and Turbo transmissions..
all good man!
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Old 08-26-2013, 11:26 AM   #11
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Do not use a ka24/rb20 transmission if you have the money to setup others. My piddly rb20 broke the stock transmisison and now on my 2nd ka/rb20 hybrid trans.
A z32 NA and TT are the same internally exept a few minor things the biggest being the TT using an inch bigger flywheel/clutch, NA is smaller I also would just stick with the rb25 clutch setup more abundant than a good hp rated NA z32 clutch The rb25 and NA z32 share clutch size and patterns DO NOT USE A Z32 FLYWHEEL it's a different bolt pattern.

Far as z32 trans you will need a rb25 bellhousing or a ka24 adapter plate. DO NOT USE THE ADAPTER UNLESS you either have a flywheel spacer or machine the bellhousing down to accommodate the space of the adapter.
The rb25 bellhousing bolts to the z32 I would also recommend going to excessive manufacturing and getting a shifter assembly made shorter to fit into a s13 chassis.
You'll also need a starter from a RB and a z32 slave cylinder should work ( I have one on my rb20 now)
Far as wiring goes should be fiarly easy with google searching people using the z32 trans on a s13.
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Old 08-26-2013, 11:30 AM   #12
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Quote:
Originally Posted by fliprayzin240sx View Post
Use the TT 300ZX transmission. The NA is basically the same as the KA. If you need a tranny on a budget, you'd probably be better off trying to use a KA transmission. only 2 bolts wont line up for the bellhousing to mount up on the RB.
Lol No on being same as a ka its internally equal to a rb25
Yes to the bolt pattern I almost just used a ka24 trans on my rb20 but the biggest is one bolt can be drilled to work and the other doesn't exist on a RB block.

Biggest problem is the ka24 transmission is 2" longer so sets the shifter further back and needing to shorten driveshaft is a must.
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Old 08-30-2013, 02:34 PM   #13
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Do not use a ka24/rb20 transmission if you have the money to setup others. My piddly rb20 broke the stock transmisison and now on my 2nd ka/rb20 hybrid trans.
A z32 NA and TT are the same internally exept a few minor things the biggest being the TT using an inch bigger flywheel/clutch, NA is smaller I also would just stick with the rb25 clutch setup more abundant than a good hp rated NA z32 clutch The rb25 and NA z32 share clutch size and patterns DO NOT USE A Z32 FLYWHEEL it's a different bolt pattern.

Far as z32 trans you will need a rb25 bellhousing or a ka24 adapter plate. DO NOT USE THE ADAPTER UNLESS you either have a flywheel spacer or machine the bellhousing down to accommodate the space of the adapter.
The rb25 bellhousing bolts to the z32 I would also recommend going to excessive manufacturing and getting a shifter assembly made shorter to fit into a s13 chassis.
You'll also need a starter from a RB and a z32 slave cylinder should work ( I have one on my rb20 now)
Far as wiring goes should be fiarly easy with google searching people using the z32 trans on a s13.
well i already have the z32 so it's good. I am assuming by the looks of everything that it was already set up to fit in an s13 and work with the rb25 because its everything together as a almost complete swap, the shifter also is obviously not stock which leads me to believe it has already received a new assembly. I will post pictures of the plate and the shifter as well as the everything else sometime tonight or tomorrow.

Quote:
Originally Posted by Bmxer300zx View Post
Lol No on being same as a ka its internally equal to a rb25
Yes to the bolt pattern I almost just used a ka24 trans on my rb20 but the biggest is one bolt can be drilled to work and the other doesn't exist on a RB block.

Biggest problem is the ka24 transmission is 2" longer so sets the shifter further back and needing to shorten driveshaft is a must.
well one thing is for sure i am NOT using the ka tranny lol. also came with a drive shaft lengthened for an s13 so once i get a clutch for it everything should bolt right back up together and drop it.


Thanks for all the help guys. I checked the flywheels p-plates and clutches and they are pretty obviously different. I was hoping i could use the z32 clutch but of course as stated by someone previously, its definitely smaller.

so whats everyones opinion on a clutch?
i have been looking at the competition 6 pad and 4 pad clutch kits. the 6 pads are "stage 4" and rated at 250% increase in tq capacity(4xx-5xx ft-lbs?) and the 4 pads are "stage 5" and rated at 300% increase in tq capacity (600+ ft-lbs?)
My question is, is the 4 pad stage 5 really necessary or will the 6 pad stage 4 hold? i cleaned the flywheel and am about to have it re-surfaced, im shooting for 500whp on this motor with a big turbo, so it will probably make only 400-450 ft-lbs of tq at most. I definitely did 436whp on 14lbs on my last rb with a gt35 and would bump it up to 18 every so often, it was a stock clutch assembly and it held up fine so id rather not buy a clutch that will be shitty-er than the oem clutch. what do you guys think?
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