RB20 vs 25 Trans - Zilvia.net Forums | Nissan 240SX (Silvia) and Z (Fairlady) Car Forum

whosawmike · 10-24-2017, 07:43 AM

Hey everyone.

I am trying to source an RB25DET NEO.

While looking online I am seeing a few that appear to have RB20 transmissions mounted to them. I want to make sure that I am not mistaken, but photobuckets recent suckery has made it difficult for me to find a definitive answer. It is my understanding that aside from the difference in girth (which is hard to see in some pics), another way to tell is by the bell housing. It is my understanding that a 25s bellhousing does not have the "ridges" along the top.

So if I am correct, this engine has a 25 trany.
25 with 25 trany

Then does this engine not an BR20 trany?
25 with 20 trany?

Thank you for the help guys. I'm just trying to do my build right.

whosawmike · 10-24-2017, 11:38 AM

Alright, I think I have a partial solution.

I forgot that the NEOs have a pull type clutch. I believe that the RB25 NEO is the only version of the 25 that uses one of those.

With that, I think the first link in post 1 is a NEO with a standard 25 trans swap (push slave is visible). I think the second is still the RB20 trans, as its a little slim looking from what I see.

This one looks like it has the pull type slave cylinder. So I think this is a NEO with a NEO transmission.
NEO with a NEO Trans?

But I might be wrong. Please chime in if you have the knowledge!

Sforteen · 11-20-2017, 09:33 AM

Your on the right track, the 25 with 25 tranny link is a R33 Rb25 trans

The Neo is pull type, and the last link in this thread is a Neo trans, you can also spot the neo trans from the ribs on top of the bell housing as well as the pull style.

gaz_moose · 11-22-2017, 01:07 PM

look at the back of the box at the shifter top plate. the 20 is the same as an SR/CA/every small casing box. they also have the same slave cylinder with a mounting bolt top and bottom.
the R33 RB25 shifter top plate slopes down at the back, same as the R32/R33 4wd GTR box as that's what it. also has a slave cylinder with two mounting bolts at the bottom (none at the top).

the Rb25 neo box has the pull type cylinder but the box has the two bosses in front of the 'fork hole' but I cant remember if you can just fit a 'normal fork' and release bearing carrier, then just tap a thread for the slave. it will be the same as converting an early r32 GTR pull type clutch if that broadens your google search. if its not much more money I would opt for the rb25 neo box as it will be less fucked and have better syncros.

whosawmike · 11-22-2017, 02:17 PM

Wow. Thanks for all of that info moose! While it is a little too late to help me, as I already bought my rig, this is sure to help someone else in the future. That is quite a bit more than I was able to find anywhere. Especially about the shifter plates.

I ended up buying one with a neo trans. Both for the reasons you stated and for the fact that it is the only one that I was confident identifying at the time.

I have seen some write ups about converting it to push type. Maybe one day...

My engine came yesterday, so I’m pretty excited to get it in.

10-24-2017, 07:43 AM	#1
whosawmike Leaky Injector Join Date: Nov 2015 Location: Illinois Posts: 52 Trader Rating: (0) Feedback Score: 0 reviews	RB20 vs 25 Trans Hey everyone. I am trying to source an RB25DET NEO. While looking online I am seeing a few that appear to have RB20 transmissions mounted to them. I want to make sure that I am not mistaken, but photobuckets recent suckery has made it difficult for me to find a definitive answer. It is my understanding that aside from the difference in girth (which is hard to see in some pics), another way to tell is by the bell housing. It is my understanding that a 25s bellhousing does not have the "ridges" along the top. So if I am correct, this engine has a 25 trany. 25 with 25 trany Then does this engine not an BR20 trany? 25 with 20 trany? Thank you for the help guys. I'm just trying to do my build right.

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10-24-2017, 11:38 AM	#2
whosawmike Leaky Injector Join Date: Nov 2015 Location: Illinois Posts: 52 Trader Rating: (0) Feedback Score: 0 reviews	Alright, I think I have a partial solution. I forgot that the NEOs have a pull type clutch. I believe that the RB25 NEO is the only version of the 25 that uses one of those. With that, I think the first link in post 1 is a NEO with a standard 25 trans swap (push slave is visible). I think the second is still the RB20 trans, as its a little slim looking from what I see. This one looks like it has the pull type slave cylinder. So I think this is a NEO with a NEO transmission. NEO with a NEO Trans? But I might be wrong. Please chime in if you have the knowledge!

11-20-2017, 09:33 AM	#3
Sforteen Zilvia Junkie Join Date: Nov 2010 Location: USA Posts: 333 Trader Rating: (0) Feedback Score: 0 reviews	Your on the right track, the 25 with 25 tranny link is a R33 Rb25 trans The Neo is pull type, and the last link in this thread is a Neo trans, you can also spot the neo trans from the ribs on top of the bell housing as well as the pull style.

11-22-2017, 01:07 PM	#4
gaz_moose Zilvia Member Join Date: Mar 2008 Location: engerland Posts: 242 Trader Rating: (0) Feedback Score: 0 reviews	look at the back of the box at the shifter top plate. the 20 is the same as an SR/CA/every small casing box. they also have the same slave cylinder with a mounting bolt top and bottom. the R33 RB25 shifter top plate slopes down at the back, same as the R32/R33 4wd GTR box as that's what it. also has a slave cylinder with two mounting bolts at the bottom (none at the top). the Rb25 neo box has the pull type cylinder but the box has the two bosses in front of the 'fork hole' but I cant remember if you can just fit a 'normal fork' and release bearing carrier, then just tap a thread for the slave. it will be the same as converting an early r32 GTR pull type clutch if that broadens your google search. if its not much more money I would opt for the rb25 neo box as it will be less fucked and have better syncros.

11-22-2017, 02:17 PM	#5
whosawmike Leaky Injector Join Date: Nov 2015 Location: Illinois Posts: 52 Trader Rating: (0) Feedback Score: 0 reviews	Wow. Thanks for all of that info moose! While it is a little too late to help me, as I already bought my rig, this is sure to help someone else in the future. That is quite a bit more than I was able to find anywhere. Especially about the shifter plates. I ended up buying one with a neo trans. Both for the reasons you stated and for the fact that it is the only one that I was confident identifying at the time. I have seen some write ups about converting it to push type. Maybe one day... My engine came yesterday, so I’m pretty excited to get it in.