RB25DET transmissions (owners plz post)

[Nameless EJ6]

For those that own RB25DET gearboxes, can you please tell me how they are? Does yours shift smoothly? Is it notchy? Does yours grind often? Do you have an aftermarket shifter and how does it perform? How do you treat it etc..?

Just looking for some general conversation on the RB25DET transmission. Thanks.

[NISMO_RB25]

I have stock shifter on the RB25DET.

Honestly I think it is a little notchy, but that is probably because my other car is the RX-7 TII which is very smooth.

It really reminds me of the way the KA's transmission felt, but if you attached it to a less trucky feeling motor.

It seems to handle the revs nicely, and I have to admit to some high RPM clutch dumps followed by at Redline shifts while testing my vlsd. wheel spin into third

All in all, I think it performs well but just not as smooth as the mazda transmission on my TII.

You are mating it to the RB26 right?

[Nameless EJ6]

Ya I'll be using it on the 26. I'm a transmission freak and I get uber upset when gears crunch because of molested synchros. So, I'm seriously hoping mine turns out to be a nice one, and in the meantime hoping to hear about them from owners here.

From what I've gathered on skyline forums the majority of them are a bit notchy, yet no one has serious problems with them.

[Imissmyturbo]

I have one with 95K kilometers on it. It somtimes grinds second gear but it's not bad and it's only when the transmission is cold. The stock shifter is very long and feels tall in the S13 chasie. I don't care for the gearing much for my 4th gear tops out at around 110 so if I am doing a highway pull and it's close I am always the frist to have to back off. I have 4:11 gears in the back.

[Jezz_s13]

Sorry for the Semi Hijack but do you know what kind of power the RB25 box can handle?I guess if you are sticking it onto a 26 then it must be pretty strong yeah?

[gprodigy85]

i haven't driven mine yet but it does feel sorta notchy i guess thats how youd say it, just not extremely smooth...

as far as the gearing, put a j30 vlsd with a 3.96 ratio and some 17" wheels with a good profile tire and you should be able to hit some higher speeds in each gear...

[Porschephile]

They have the same internals as a Z32 gearbox. They can handle ~600hp. It really depends on how you shift. There are always OS Giken upgraded gear sets with different ratios and a strengthened input shaft available for $2-2.3k if you know where to look. They are still helical gears (not straight cut), however I think they are shot peened or something similar to make them handle a little more power. Hehe, one of the 1st gear options is something like 5.500! Imagine taking 1st gear to ~60mph!

As far as the shifter, I got a Tomei sts, which is the same as the C's and pretty much every other one. Unfortunately my transmission didn't come with the bushings though, so I haven't been able to check how it shifts. What's really odd is that I thought I had all of the bushings with my Tomei shifter, yet I installed it on my brother's CA s13 and it was definitely missing something. It was way too loose and would slip out of the arm in the transmission. Anyone want to sell their gtst transmission bushings?

I really wish the b&m 240sx shifters would work. I've been thinking about buying one, and then having a top plate machined that has the right bolt pattern to it. I remember someone on here tried a b&m shifter and found it wouldn't work due to the bolt holes in the top cover being misaligned. Was this the only problem?

[b-s14]

hey nameless, didnt you get your motor from venus-auto and they mated the rb25 transmission to the rb26 for you.. ?

[Nameless EJ6]

B-s14, yes they sent me it, but they didn't put it on there for me in order to keep a smaller pallet.

I've heard they will take up to 700HP if shifted right. Once you start griinding (or getting grinds) is when you start having problems. I've never heard of anyone bust a gear in one except in the RB20 box.

[jrou111]

Been lurking here for a while, decided to post.

I'm looking to do the same thing, done my homework, and decided that my best bet is gonna be RB26DETT with Mckinney mounts and an RB25 Trans. I have two questions..

1. Just for comparison, how much did you pay Venus for what you have (26 +25)? I have a friend that imports, but I want to make sure he is not ripping me off.. Best deal, you know.

2.Which Clutch are you going to use? Do you still use one for a z32 N/a, or one for a GT-R?

If you want to not post that info here, you can e-mail me at [email protected] or AIM me at: jrou111

Thanks,

[Porschephile]

You can get z32 n/a clutches for about 500lb/ft torque max. I'd only start with one if you planned on living with bolt ons for awhile. If you planned on more than that, like upgraded twins, I'd just go with a twin plate.

[jrou111]

So you match the clutch to the transmission, not the engine?

Actually, I'll probably go for an exedy single or double.

Thanks,

[Nameless EJ6]

Been lurking here for a while, decided to post.

I'm looking to do the same thing, done my homework, and decided that my best bet is gonna be RB26DETT with Mckinney mounts and an RB25 Trans. I have two questions..

1. Just for comparison, how much did you pay Venus for what you have (26 +25)? I have a friend that imports, but I want to make sure he is not ripping me off.. Best deal, you know.

2.Which Clutch are you going to use? Do you still use one for a z32 N/a, or one for a GT-R?

If you want to not post that info here, you can e-mail me at [email protected] or AIM me at: jrou111

Thanks,

II'll email you the info about the price I got from venus. I don't really want to share that info...

I'm not sure what clutch I'll be using yet. I haven't done alot of research on it. A few months back I was considering an ACT clutch for the 300xz.. before I make my decision I'll be doing more thorough look into other clutches available. I definetely want something that will hold atleast 500ft pounds, as my goal on this engine is to hit 500 whp minimum..

[BoostFab]

if we can mate the 2jzgte 6-speed transmission to the rb motor would be awsome, it can handle 1k hp no problem

[Nameless EJ6]

ya that would be nice. I may choose to do the T56 conversion with Mckinneys adapter setup later on down the road.

[Jala47]

Just taking a guess here but do people switch out the RB26DETT transmission's for RB25's because the 25's are 5 spd?

[jrou111]

No, most do it because the 26 trans is awd, and requires alot of custom fabbing at the time to work properly.

The 25 trans is 5 spd, and rwd.

Peace,

[Porschephile]

If anyone knows they are going to be making 500rwhp+, then they might as well go with a twin plate clutch since most single plates would be barely sufficient. I do remember seeing one of the RPS single plates (I believe it was an RPS one) rated at 520 lb/ft. That should be more than enough for most people not doing anything too serious.