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gjc5500

RB25DET S1 Tranny options

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gjc5500    10

so I have been digging around on various site for about a week and have yet to find a concrete answer. the 280z 2+2 im helping a buddy build is getting a rb25 and ditching the SBC thats already in it. 

 

the rb we are picking up is coming with an auto trans so we need a manual to mate with the engine. i was looking at the z31 trans, but i have been getting conflicting reports on whether it will mate and align properly with the engine. i saw the pinned thread about doing it, but the pictures are all broken so it was really hard for me to follow what he was doing exactly. 

 

would the 350z trans w/ an adapter plate be a good option if i cannot use a 300z trans?

 

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Geno750    0
Posted (edited)

The 350Z trans is a solid option since you can just run any RB clutch kit. The only annoying part about the swap is milling the bell housing .5" to accommodate the adapter plate.

Edited by Geno750

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PNW280Z    0

I just went through this, you can get a cd009(a) or jk4## transmission for around $900. The whole adapter kit from collins is about $900.  If you don't have access to a CNC machine you will have to pay to have the bell housing milled, we will call it $250 for this, other small parts we will say $200.  That's $2,250 for a z33/z34 trans.

 

I just bought a brand new gts-t 5 speed (no miles) from RHDJapan for $1,950 (including shipping and processing fees). 

 

The aussie guys say that the 5 speed is pretty stout, and there is a strong resell market for the five speed (at least in the US). I eventually chose the 5 speed because I know it will just work with my RB.  I don't have to worry about something wrong with the milling or the correct clutch/hardware.  

 

I hope this helps.  If you have any questions about using RHDJapan I am more than willing to help answer.

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Geno750    0

Where are you seeing $900? The plate is $350. By my math, plate and using your figures for the machining and other parts you're looking at $1350. The clutch/flywheel systems are the same between two so that's essentially a fixed cost.

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PNW280Z    0

350 for the plate.

Most of the jk/cd009 models on ebay have the concentric slave so you are either buying the adapter 175$ or swapping to external slave (https://www.z1motorsports.com/z1-products/z1-motorsports/z1-clutch-concentric-slave-cylinder-csc-elimination-kit-p-7340.html) $430.  Additionally the stock slave is pretty garbage but I wont include that cost in this.

The shifter shortening is $110

 

350 plate

175 concentric adapter

110 shortening

635 Parts for basic swap

 

250 Machining (A way low estimate btw)

200 Other small parts

900  Used Transmission

1,985 

 

These are low estimates so that price is on the low end. Realistically if I was doing it I would either get a stronger internal slave or convert to external.  Additionally, I have heard of people having trouble getting it lined up correctly as the plate has no guide pins and going through T/O bearings like crazy. 

 

Full disclosure if I ever get bored with the five speed I would do this swap, for me the thought of having a transmission with a known history (no history) and knowing that it would just work was worth it.  

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jthom5147    1

There are several options:

-- CD00X adapter. Per my previous conversations with McKinney Motorsports, there have been quality issues with some of these. YMMV.

-- RB25DET trans. I bought one for $800 on ebay. $200 shipping. no issues.

-- RB25DET / RB26 bell housing (for AWD trans or RWD 5MT) with Z32 or 87-89 Z31T 5MT. Needs shifter mods. The shifter mods are available through McKinney and other vendors. The bell housing can be purchased independently through RawBrokerage.

-- RB25DE / RB20DET 5MT. Not as strong. Essentially same trans as KA24 (and early Z31 5MT). 

-- RB25DE / RB20DET bellhousing with KA24 trans. Trans is ~2 inches longer so it sits farther back in the trans tunnel.

 

The VG bell housings won't mate to the RB block, but the 300ZX transmissions will mate to the companion RB bell housing as mentioned above.

 

I have an RB25DE trans available for sale if you're interested. Located in SoCal.

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gjc5500    10

There are several options:

-- CD00X adapter. Per my previous conversations with McKinney Motorsports, there have been quality issues with some of these. YMMV.

-- RB25DET trans. I bought one for $800 on ebay. $200 shipping. no issues.

-- RB25DET / RB26 bell housing (for AWD trans or RWD 5MT) with Z32 or 87-89 Z31T 5MT. Needs shifter mods. The shifter mods are available through McKinney and other vendors. The bell housing can be purchased independently through RawBrokerage.

-- RB25DE / RB20DET 5MT. Not as strong. Essentially same trans as KA24 (and early Z31 5MT). 

-- RB25DE / RB20DET bellhousing with KA24 trans. Trans is ~2 inches longer so it sits farther back in the trans tunnel.

 

The VG bell housings won't mate to the RB block, but the 300ZX transmissions will mate to the companion RB bell housing as mentioned above.

 

I have an RB25DE trans available for sale if you're interested. Located in SoCal.

 

 Sorry for taking a long time to reply. thanks for all the great information. just out of curiosity on the rb bellhosing to ka trans, would the bell housing form the stock AWD rb25 trans work for that?

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jthom5147    1

No, the AWD trans is the same as the DET 5MT RWD trans with a different tail shaft and a transfer case

 

...Which is why you can use an AWD bell housing with a Z32 5MT gears and tail shaft with shifter mods.

 

There are some parts conserved though but mostly just ancillary stuff: the shifter is the same between the non z32 transmissions, the clutch fork and TOB (need to confirm TOB fitment with clutch but the collar fits right) are the same, and I've read that the 350z slave is a direct fit to rb25det 5mt, but I have yet to confirm.

 

Bear in mind that buying an AWD block complicates the swap as the oil pan has to be resolved and requires a custom rear sump made. The AWD block has a wider oil pan flange and different pickup from RWD. Pat1 who modified my RWD pan makes a rear sump AWD compatible pan, and to my knowledge he is the only one that does.

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