Questions about R33 RB26 AWD transmission (for transmission Swap)

[AOE_Danny]

Starting with my objective:

I'm seriously looking into putting the TRANSMISSION from an R33 Skyline GT-R [RB26DETT AWD] into an S14 240SX with an SR20DET. Yes, I'd be converting the car to an AWD, and yes, I'm talking about putting an RB26 AWD transmission on an SR20DET.----------------I work part-time at a Motorsports shop (a.k.a. a "Speed shop"), and, if we do undertake this project, it would be done by the motorsports shop (with my help). Case in point, I'm NOT looking at doing this alone: there will be knowledgeable hands involved with this project. Nonetheless, I'd like to get as much information beforehand as possible, so we can spot as many "issues" as possible before hand.

Also, yes, I am aware of what a project like this would cost, so please no "It's out of your budget so I won't bother explaining" posts. No, I'm not trying to be mean or start off on a rude note, but my searching these forums would have turned up a bit more information if that hadn't already happened a couple of times in the past.

BTW, I posted this in the "RB" forum because this mainly is questions on the RB26DETT AWD transmission. With that in mind, some of these questions DO partly pertain to the SR20DET. If you're not familiar enough with the SR20 to answer the question, don't worry about it; those parts _ARE_ slightly "out of place" in this forum.

Lastly, if I'm wrong on any note here, please let me know. Information obtained via the internet is always far from "100% accurate" :P. So, if I've been misinformed, please let me know.

Thanks in advance for any help at all that you can give me!

All that being said, on with the post:----------------Is there any difference between the GTS-4 AWD transmission (which would be available mounted to the RB25 engine only, I think) and the GT-R's AWD transmission (which would be available mounted to the RB26 engine only)?

----------------The R33 Skyline GTR used the ATTESA-ETS (or ATTESA-PRO, in the case of the V-Spec models) system to control the pressure of the front differential/transfer case (in the simplest of terms).I believe that this was done via an electronic Pump [Hydraulic, I imagine...?] - the same pump that was used for the HICAS all-wheel steering system, I think. If that's the case though, the pressure to the front differential would then probably have to have been varied by some sort of pressure regulator, rather then the pump. Does anyone know which is the case?

Assuming all of that is correct, that means that all you'd need to do is accurately regulate the pressure to the front transfer case to control the torque split from all to the rear to a 50:50 split. I realize it would be a massive project to attempt to gather all the parts and computers in the ATTESA-ETS system, and then - the worst part - attempt to go through an electrician's nightmare of wiring in an attempt to get it to work. Instead, as long as I knew the correct minimum (100:0 split, I'd imagine) and maximum (50:50) pressures, I could use "my own" system to control the split (i.e. anything from a manual wheel/slider to an electronic traction control system).

With that in mind, does anyone know what the pressure levels ARE? (Or would that be very hard to gauge i.e. if it's hydraulic…?)----------------I know that the AWD transmission has the side/part of the front differential as the side/part of the oil pan. How much "together" are they? Is the whole oil pan part of the front differential? Do parts of the differential (and/or casing) actually stick "into" the area of the oil pan? If you "cut off" the oil pan right where it meets the differential, would this cause a problem with it? (Obviously, a custom pan for the SR20 would be necessary)

----------------Is the starter for an RB26DETT [AWD] different from the RB25? (I believe it is, but I'm trying to make sure). What about the RB20? (I'd assume it's the same as RB25, but just checking)

Is the location of the starter anything unusual? (I.e. May be "in the block" area when put up to an SR20)

----------------I noticed in the sticky thread "RB series replacement part numbers, etc" that a couple people stated that the clutch from a N/A 300ZX was compatible with the RB20 transmission. Some people also said that the clutch from an SR20DET was the same as well; this was not confirmed however.

Does the RB26 AWD transmission use the same clutch and flywheel as the RB25 RWD, or is it different? If it's different, is it (RB26 AWD) compatible with anything else?

I know the RB25 and RB26 transmissions are completely interchangeable (i.e. same bolt pattern. I believe the RB20 transmission fits on the RB25 (correct me if I'm wrong). If so, that would mean that the RB20 is the same bolt pattern as the RB26.

All those similarities make me wonder: is the transmission bolt pattern of the RB26DETT AWD transmission the same as the SR20DET?

----------------Lastly, just an FYI: I know that there is a "bulge" in the transmission near the shift knob, which would probably "stick into" the passenger floorboard slightly on the 240SX; I'm aware of this and we'll take the necessary steps to facilitate it if this is the case.----------------Does anyone have any other information regarding the RB26 AWD transmission that might be helpful to know, or a potential problem we'd run into?

Any other helpful comments in general?

[s13rb25]

why spend all the time and money of awd and then run an sr20? makes no sense to me.

[Slo_240sx]

Thats alot of questions to be asking in 1 thread.

You should have tried to independantly search each question

All RB transmission are interchangable... while out of the car atleast.

The 26 trans however does not use the same clutch as a 20/25 because the 20/25 is a push type clutch while the 26 is a pull type. Good luck with that one.

an RB trans WILL NOT bolt up to a SR. You could try using a an adapterplate, once again good luck.

It would be a million times easier to just get a rb25 or rb26 instead of trying to mate it to the sr20.

If you are going to get a awd trans then get the r32. its less complicated, less wiring. All models run the Attessa system but the r33 and 34 run electronic systems while the r32 is hydraulic and runs off pumps in the truck I believe, and I also believe they the pumps run the hicas also... not sure.

The only way you are going to find specs on the transmission like pressures is to find an engineer who designed it.

Starters are placed in the same place but the 20/25 differ from the 26.

You gonna have to cut your floor board out possibly take out the seat or make one hell of a custom bracket. You are going to have to use gtr front suspension, cut your cross member, cut this and that, than you are gonna have to wire it all up. Mechanically very possibly, electronically... wow.

Not worth the trouble and the hassle to just stick it in with a sr20. when all said and done youre not going to be happy because when I get my rb25 going I'll be able to yank the wheels off the ground and that sr20 won't have enough torque to even move it all with the added drivetrain LET ALONE a rb26dett transmission.

There could be alot of mistakes in here also so please correct me if I am wrong but i think everyone will agree with me.

I think you have one hell of a imagination, but if you attempt it post pic and if it ends up working you just made yourself a million dollars.

-Alex

[BoostFab]

another one....what's good with the awd conversion, anyways? most people disable it for rwd power. i guess just something to waste money and time on and...uh...magazine cover challenges?

[AOE_Danny]

Thanks for the information! He's my replies, mainly in chronological order:--------------"Thats alot of questions to be asking in 1 thread."

Errm, yea, you're right; I probably should have split it up into a few more concise posts --------------"The 26 trans however does not use the same clutch as a 20/25 because the 20/25 is a push type clutch while the 26 is a pull type. Good luck with that one."

Humm... I had thought that only the R34 used the "pull-type" clutch; do ALL of the AWD trannies really use the "pull-type"?

What about the R32's AWD transmission: Is that a "pull-type" as well?

(Also, once again: are the GTS-4 and GT-R trannies different?)--------------"an RB trans WILL NOT bolt up to a SR. You could try using a an adapterplate, once again good luck."

I fully expected to need an adapter plate, but I wanted to make sure; now I know. Thanks!--------------"If you are going to get a awd trans then get the r32. its less complicated, less wiring. All models run the Attessa system but the r33 and 34 run electronic systems while the r32 is hydraulic and runs off pumps in the truck I believe, and I also believe they the pumps run the hicas also... not sure."

Humm... It would seem that the information I had must have been talking about the R32. I had thought that R34 was the "electrical" one and R33 was the "Mechanical" one; Guess I was wrong. Yes, I definitely want the mechanical setup, so let's change it to an R32 transmission, not R33. Thanks for pointing this out! (BTW, the "trunk" pump was what I had in mind, so we're definitely talking about the same setup now)--------------"The only way you are going to find specs on the transmission like pressures is to find an engineer who designed it."

... or by tapping and gauging a line, assuming the pressure isn't TOO high. If possible though, I'd much rather use the R32's stock trunk pump and deal with an electric signal instead if I can. I don't want a massive amount of electric work (i.e. R34), but sometimes some is easier then the alternative.--------------This is a much more trivial matter, but does anyone know what the drivetrain efficiency of the GTR is? I'm guessing somewhere around 20% drivetrain losses between the crank and the wheels; maybe even as bad as 25%. Does anyone know?--------------"You gonna have to cut your floor board out possibly take out the seat or make one hell of a custom bracket. You are going to have to use gtr front suspension, cut your cross member, cut this and that, than you are gonna have to wire it all up."

I intended to use the GTR Suspension, and more or less expected to have to do something custom with the crossmember [and probably transmission mount]. It's nice to have this confirmed though.

Now, in regards to "cutting out your floorboard and possibly the seat", I expect to have to cut the floorboard somewhat there; I can move the seat if I have to as well, as long as it doesn't stick in TOO far...

How far does the transmission really stick out? And does it stick out directly next to the shift knob, or up closer to the front of the car?

Also, on the R32 GTR transmission, how many wires really do run from the transmission?Speed Sensor of course, perhaps some type of crank sensor on the flywheel, and maybe a few diagnostic sensors (i.e. oil temp), but is there anything else significant?--------------Lastly: I got an e-mail that someone else replied to this post, but I don't see their post here ... ? Anyway, it was in regards to the front drive axle/differential being part of the oil pan (they weren't sure though, so it really didn't tell me much). Could anyone confirm/elaborate on this? How much of the oil pan is a "critical part" of the differential? Assuming the oil pan was cut off of the transmission, could a highly-custom oil pan work, or would the differential case, etc. be completely in the way of the oil pan mount bolts?

Also, is the R32 AWD transmission and different in this respect?--------------"why spend all the time and money of awd and then run an sr20? makes no sense to me."

and

"another one....what's good with the awd conversion, anyways? most people disable it for rwd power. i guess just something to waste money and time on."

Since it seems many of you still don't see the purposes of this swap, I'll spend a little time to elaborate on it (if you're not one of these people, you don't have to read the rest of this post). Please, I'm not trying to flame anyone - positive criticism is good, especially in the motorsports industry where few people know all they should about what they're trying to do/talking about doing. Here, I'm explaining my reasons for wanting to do this swap. I have Three main reasons for this swap project:

1. The SR20DET, an Inline 4 engine, costs a FRACTION as much on maintenance/rebuild as the RB25/26, an Inline 6 engine. Don't get me wrong, I'm a very big fan of the skyline engine; but that also means I know how much parts for it cost. I could upgrade my whole bottom end (using the stock crankshaft) for what it would cost you for a good set of upgraded connecting rods; add a good set of upgraded pistons for you, and I could rebuild my head as well for the same price. As they say, "It all comes down to cost and availability". If you then want to get into availability, SR20 parts are infinitely easier to find stateside then Skyline parts. This is the main reason I'm trying to use an SR20 instead of an RB25/26.

2. Just turn the boost up on the stock SR20DET w/ stock turbo (with just a few supporting mods, like fuel pump & injectors, FMIC, etc.) you can make 320-350 Crank HP. In an RWD setup (i.e. 240SX), this is like 300 to 320 to the wheels; that's MORE then enough to break the [stock] tires loose in the first three gears whenever you build boost. What point is that? All that wheelspin would be KILLING your 1/4 mile times. Yes, you'd loose some top-end due to the added drivetrain losses of an AWD, but you'd come out of the hole so much harder and faster it would way more then make up for it. As for big wide drag slicks on an RWD 240, you'd have to spend easily what I'd have in an AWD conversion in transmission/differential/axle rebuild to handle that kind of traction.

3. We're talking about a LIGHT car. Probably a 2700 lb car with AWD (perhaps less if lightweight mods are done), compared to the about 3400 lb Skyline. 700 lb less would have a MASSIVE impact on performance. If it's true what they say that "10% less weight is equivalent to 10% more power", then we're looking at a car that's 20% LIGHTER. Theoretically that means I'd get the same performance if I was cranking 20% less power, i.e. at 400 crank hp it'd perform like a 500 crank hp Skyline. Obviously, that equation is not going to work that perfectly in practice, but it's probably not too terribly far off. Case in point, I don't have to make quite as massive amounts of power to be quick.

I'M NOT saying this to flame anyone; a few years ago I probably would have agreed with you, but now I have to say:Have you ever ridden in a built 2-Liter Inline 4 AWD car?Trust me when I say you can make MORE then enough power for a street car with an I4. You could make 500-600 crank horsepower on the SR20 with PUMP GAS and a relatively mild bottom end rebuild (lots of supporting mods tho); 800-1200 would be attainable with a serious rebuild and race gas (I have no intention of making this a drag-only car; and yet, if I did, it still wouldn't cost what a complete performance rebuild would cost on an RB series engine).

I have personally seen/ridden in a 500 crank HP 2 Liter I4 AWD car [DSM]; with a cheap 3-year-old set of 225 pep-boy tires and stock rims that thing would pull the front tires off the ground as high as a pop bottle off the line. In fact, it even pulled the front tires off the ground on the 1/2 shift [no exaggeration].

Again, an I4 can make PLEANTY enough power AND TORQUE for the quickest street car you'd want to drive - and it does it at a fraction of the cost (albeit at slightly less reliability, yes, but then, repairs cost a fraction as much as well).

(Yes, a DSM probably has a more efficient drivetrain then an RB26, but it shouldn't be a MASSIVE difference).

Now you all know why I'm trying to use an SR20 instead of an RB25/26.--------------Sorry for the long posts, and thanks again for the replies - they have been very helpful!

[NISMO_RB25]

Have you considered looking into using a nissan bluebird drivetrain instead? You get your SR20, but with an AWD transmission that is meant for the that motor. You can buy front clips pretty cheap and it would have everything you need for the front part of your AWD setup. Then you just need to figure out how to mount it and how to setup the rear half of the awd.

I support your quest to do something different, so I am just throwing out some ideas.

Good luck.

[Nameless EJ6]

I read everything, and I personally think it's still a waste of time.

First of all, if you're concerned about the money it takes to rebuild a 4 cylinder vs. 6 cylinder, you're not going to accomplish this.

Secondly, the RB26 box was designed for the RB26. Nothing else. Have you thought about how you're going to drive the front wheels with that transmission? Once you get past the part of adapting it to the SR, which will probably need a custom input shaft, you'll have to fab a front diff setup similar to the RB26's. It's INSIDE the oil sump. A LARGE, long oil sump that weighs about 65 Pounds (estimated guess).

It would be ALOT easier to use an RB engine. I wouldn't even think about trying it with an SR.. that's rediculous.

Unless you're an engineer and have a factory full of machines for fabrication, you're not going to finish it.

If you want to do an AWD vehicle, I'd suggest starting out with one. If you think about this, you're only doing all of this work to drive a car that is still a 240sx, it's not worth it. Get a DSM or a celica all trac or something.

g/l.

[gawdzilla]

the biggest challenge is going to be driving the front wheels. you will somehow need to adapt the 26 oil pan to the sr20.

regarding push/pull type trannies: the early r32 gtr is the only one with a push-type clutch. r32 late, r33, and r34 gtrs are all pull type. The RB25DET RWD transmissions are ALL push, except for the R34 GTS-T which is pull.

if you are trying for an awd 4 cyl, you should sti swap a 2.5rs subaru or build a dsm up. if you're going to try and use the 26 awd transmission, use the rb26 motor too

[Phat_Optimo]

"...cutting out your floorboard and possibly the seat..."

The seats mounts are not in the way. The hole will be fwd of pass the seats mounts. I cut my hole the other day.

"How far does the transmission really stick out? And does it stick out directly next to the shift knob, or up closer to the front of the car?"

It mainly hangs down low but its off to the rt side where it won't fit without cutting a hole. Its just fwd and to the rt of the shift knob.

"Also, on the R32 GTR transmission, how many wires really do run from the transmission?Speed Sensor of course, perhaps some type of crank sensor on the flywheel, and maybe a few diagnostic sensors (i.e. oil temp), but is there anything else significant?"

To get the Electronic Control Torque Split 4wd System to work. your gonna have to install ETS (Electronic Torque Split) computer whis is a seperate computer from the ECU. G sensor. Also have to install the hydraulic unit. Which consists of a resivior, actuator, and lines. Then you would have to install wheel speed sensors for each wheel. Getting the front suspension perfecty lined up would require auto body electronic measuring equipment & auto body laser measuring equipment. The R32 GTR uses a speedo cable its not an electronic vss. Theres only 2 sensors on the trans. Neutral switch and reverse lights.

You should buy a Skyline and put your sr20 in it. Probably would be cheaper.

[hybrids14]

My suggestion would be to try to bolt the entire drivetrain from the RB20 GTS-4 complete into the S14 chassis. First off, the front crossmember is very similar and only mods to the suspension mounting points is required. The rear end is also very similar to the 240sx because it uses the same diff. The fwd part of the awd transmission is actually incorporated into the oil pan of the RB motor, therefore it's a lot more work trying to get the fwd part to work on a SR motor. Therefore I don't recommend doing AWD on the SR motor. The pulsar GTI-R have a completely different configuration for AWD. If you really want AWD on SR that's the way to go, do not use the RB's AWD transmission... it's a lot more work. The reason why I would tell you to pick the gts-4 is because that's the cheapest chassis with AWD. Also, the price for RB20DET is actually cheaper than the SR. If you plan to upgrade later, you can just bolt a RB25DET or better yet the RB26DETT in. Also for your reference, I asked a person on the Australian Skyline forum how he put the GTR's AWD transmission in his S13/RB30/RB26DETT and converted to RWD. It requires some banging and some custom fabrication, but it's not that hard. I'm currently building a S14 with RB26DETT RWD. But I've seen pictures of a RB26DETT S13 with front suspension bolted on. If you need the link, email me. The only reason why that guy's car is not running is because of electrial work and missing pumps and misc items on the awd system. It's a very complicated setup but I'm sure if you have the $$$, time, and knowledge to undergo such a project it can be done. BTW, I plan to run AWD too in the future that's the reason why I picked my BCNR34 RB26DETT motor instead of the 2JZ motor. But for now, I just want a RB26DETT running in my S14. Keep me updated on what you plan to do.... and good luck!!

[themadscientist]

I would forget the RB running gear and use a Pulsar GTi-R engine and trnyy mounted in the rear with the output shaft for the rear diff pointing foward. Mount the original S14 diff up front and graft in GTR hubs up front for the halfshafts to pass through. Off the top of my head I cannot remember the direction of rotation of the engine but you may need to reverse it so the foward gears were still foward which would require reground cams and electric oil and water pumps. Move as much weight foward as possible to get the car balanced; fuel tank battery, radiator etc. Oh yeah or get a Pulsar