How To: Mating an RB25 and Z32 Trans

[Booztd 3]

Guys

 

First off, I would like to preface this with a warning. THIS IS NOT FOR THE AVERAGE MECHANIC. Hell I wouldnt even recommend this for the skilled mechanic. I consulted my older brother who owns a speed shop in springfield IL named FC Customs (http://www.fccustoms.com) to help with the work.

 

Over the last two nights we broke down the Z32 Tranny, as well as the RB25 RWD Tranny. We then mated them together following Charlie C's suggestion that the input shaft needed to be swapped to compensate for bell housing lenght.

 

I will also re-preface this write-up by warning you almost every picture contains the 'shocker' LOL. We were feeling goofy during the process, so why not spice up the pics a little bit?

 

Here we have the Z32 Trans

 

 

You will begin by pulling the outter detent ball out of the trans. On the upper side close to where my bro's index finger is pointed in the picture above. Remove the 17mm bolt on the left hand side and remove the spring and then remove the ball. Keep these in a safe place.

 

Now you'll remove the front cover like so

 

 

Front Cover removed

 

 

Now you'll need a few different sets of snap-ring pliars. There is one small snap-ring and washer and a large snap-ring once you get the front cover off

 

 

Snap Rings

 

 

 

Now We'll work on the shifter rod. Begin by pulling the 10mm bolts out and pull the cover off. You'll see this

 

 

There are two dowel pins you need to remove in order to get the shifter rod out.

 

Now we'll remove the bell housing by removing the casing bolts in the middle of the trans. You'll need a hammer to separate the two pieces.

 

 

A close-up of the gear-set

 

 

Our next part is a highly debated topic regarding Z32 and RB trannies. The 4th gear synchros DONT grind, its actually the insert springs. You can see in the next few pics how the teeth have been ground and dulled down

 

 

 

 

Now you'll remove the forks from the gear-set

 

 

 

After you've removed the shifter rod and the pieces inside the trans, you can now remove the tail section casing

 

 

 

 

 

Here is another component that causes the grinding

 

 

Notice the teeth are worn down

 

[Booztd 3]

Now this is where things get hairy. You're going to need the bomb-diggity puller set in order to get everything off the right way. We accomplished this witha $2500 Set from Snap-On

 

 

Gears starting to come off

 

 

Using the pinch puller for the lower bearing

 

 

 

We had to craft this next setup out of threaded rod and one of the pullers. It worked at least!

 

 

After removing the other gear above with the pullers, the remaining gears should come off with some prying/tapping of a hammer. Now the directions call for pressing the shafts out of the center-section. We did this using a press. Since the shafts are still bound together by the gears, you must press the shafts out one bit at a time, and then switch to the other shaft and press it out a bit. This makes is so the shafts dont bind.

 

 

This is how we felt at the end of night 1

 

 

Moving on to day two, we have an RB25 RWD Trans

 

 

I'm not going to go through the dissasembly process, because its quite identical to the process of removing the front/rear casings.

 

Here we have the Z32 Input/Output Shaft on the top, and the RB25 Input/Output Shaft on the bottom

 

 

Here are some comparison pictures of the bell housings

 

 

 

My stuff was pretty dirty and my bro's shop just had gotten a new parts washer in. This thing RULES. I give you ......"The Cuda"

 

 

Parts going in

 

 

Here's how the bell housing turned out

 

 

Center Section

 

 

 

Here the RB25 trans gearset.

 

[Booztd 3]

Since I wont be needing alot of extra parts, we opted to cut the countershaft out with a plasma cutter, and avoid a crap-ton of parts removal.

 

 

 

 

 

Now since the input shaft isnt bound by the counter shaft, it slides right out

 

 

The mess we made

 

 

Now we're finally on to the reassembly process. We heated the parts on that usually get pressed on. We just put them in the parts washer for a few minutes and they went on pretty easy with a hammer. We used alot of the insert springs and such from the RB25 trans since they were in alot better shape than my Z32 trans. It basically ended up taking all the good parts from both and combining them.

 

 

Everything into place, forks are back on

 

 

 

Snap-Rings going back on

 

 

Front Cover sealed up

 

 

My brother on the right and tony (stallone) on the left. These guys were a huge help and I couldnt have done it withouth them

 

 

The completed RB25/Z32 Trans

 

 

[Booztd 3]

Now onto some notes:

 

When I first read what needed to be done to the RB25 and Z32 trans it made a lot of sense, having to use a different input shaft to compensate for bell housing length, but the way I understood it was that the RB25 bell housing was longer, thus making the input shaft longer as well. If you read through this how-to, you’l definitely see that the bell housing is actually shorter. So in theory if we just switched the bell housings, the input shaft would be too long on the transmission, but this really isn’t the case. We measured the input shaft length, and theres only 1/8” different between input shafts. It is more than likely this 1/8” would be negligible when installing the transmission, considering the input shaft does not even fully seat on the pilot bushing. Even if you did run into that issue, you should be able to cut off the excess 1/8” from the Z32 input shaft.

 

Here is also a picture of the puller kit we used

 

 

Some pics of the shop and the cars

 

Panoz GTS on the dyno and STS C5

 

 

My bro's mid 10-sec stock block/stock head/stock cam 05 mustang

 

 

 

Their Ford GT

 

 

Blower & AFR Head setup going on an escalade

 

 

 

Arial View

 

 

 

 

Peace!

[Stealth-Z]

Excellent write up. Many have talked about doing the bell housing swap and some have done it. But no one documented how and what was involved.

 

I have often wondered if the bell housing off the GTR AWD trans could be used?

[Doug71zt]

So - What you are saying is that you reduced one RB25 tranny to rubble for no reason? You could have used the RB25 tranny as-is like most people do, or used the front case from your AWD RB26 tranny for the Z32 transmission.

 

?

 

Doug

[Stealth-Z]

So - What you are saying is that you reduced one RB25 tranny to rubble for no reason? You could have used the RB25 tranny as-is like most people do, or used the front case from your AWD RB26 tranny for the Z32 transmission.

 

?

 

Doug

 

In his defence, he purchased a blown RB25 trans elsewhere. It was already rubble.

[RB26powered74zcar]

Good going Booztd 3, thanks for the great write up with excellent pics!!

[hotimport]

Nice write up...can we maybe get a sticky on this???

[Booztd 3]

So - What you are saying is that you reduced one RB25 tranny to rubble for no reason? You could have used the RB25 tranny as-is like most people do, or used the front case from your AWD RB26 tranny for the Z32 transmission.

 

?

 

Doug

 

Not hardly, the switch is needed to retain the stock mounts/shifter/driveshaft on the Z32. I would have had to fab up a whole new cross member for the tranny and fab the crap out of the shifter area if I wanted to use the rb25 trans 'as-is' So since I had to open both of them up to do that swap, I took advantage of the situation and cobbled all of the good parts from both trannies and now my tranny will be 'like-new'

 

Remember this is going into a 300ZX, not an old school Z like you guys have....

[RB26powered74zcar]

Remember this is going into a 300ZX, not an old school Z like you guys have....

 

This is the part most didn't remember you were up to....

[Booztd 3]

This is the part most didn't remember you were up to....

 

 

*evil laugh ensues*

 

Current parts table growing....

 

[alexideways]

I almost ran for my welding goggles when I looked at the pic were you're cutting the shaft. LOL. Great writeup by the way, very nice pics and tell your bro. that his shop is very nice, everything is so tidy and well equipped.

 

1 question though, why do they lift the dyno so high?

[Booztd 3]

tell your bro. that his shop is very nice, everything is so tidy and well equipped.

 

1 question though, why do they lift the dyno so high?

 

I will pass the word...

 

The tidiness runs in the family. Every project I undertake I get out a fresh set of zip-lock baggies, a sharpie, and take lots of pics. All bolts and corresponding parts go in the labeled baggies, and they are set out inthe order they were removed (makes reassembly much easier!) All tools get cleaned put away at the end of the night, the floor gets swept, the countertop dusted, etc. Just makes for a good return to the garage when you know you can find all your tools. A big pet peeve of mine is coming out to the shop after a 2-3 day break and going where the hell are all my tools!!!!

 

Regarding the dyno, the dyno itsself isnt that high, they just use a 4 post lift to get the car to the dyno height, its better the way they do it in case they need to store an extra car there over night, they can actually park one car under the lift....

 

Here's a picture of my car on the dyno

 

[synthtk]

Very nice writeup, and very cool shop.

[rb26zed]

I have often wondered if the bell housing off the GTR AWD trans could be used?

 

Yes it can, and excellent write up Boostd3.

[stony]

Stickified

[Careless]

i think i have the best luck in the world, cause i was coming here to ask this question, and now there's a goddamn sticky thread!

 

HAHAHAHA

 

HybridZ is teh bombz0r

[Careless]

*evil laugh ensues*

 

 

hey boozed

 

so let's put this into perspective for a sec, for my own sake.

 

If i get an RB25 with an auto transmission (900 dollars vs 2500 with 5speed), and I buy a 1996 JDM 300zx TT 5 speed transmission...

 

... I should just swap the bellhousing with a 5speed RB25 one that I get from elsewhere, and the 1/8inch would be negligible in the fitment of the transmission?

 

what else would need to be changed regarding the transmission itself. I know i'll have to get a custom driveshaft since it's going in a Z anyways, and I know i'll have to switch the ECU to another unit, as well as wiring, but all things considered... to get this into a regular 240z, or to atleast mate this 5 speed to an RB25 where stock mount location is neither required nor desired... what are we looking at in terms of work.

 

2500 snap-on kit is a little out of my budget

 

EDIT: I also counted 31 pictures that didn't contain shockers... which is an indication of just how many pictures were taken throughout this process, which is very well appreciated by us, I'm sure.

 

but you must retake them, and disassemble the transmission to get that shocker back on those 31 pics.. I'm just so sorry.

[Booztd 3]

hey boozed

 

... I should just swap the bellhousing with a 5speed RB25 one that I get from elsewhere, and the 1/8inch would be negligible in the fitment of the transmission?

 

This is exactly what I would do. We did some measurements and I do not believe that even an extra 1/8" of input shaft going into the pilot bushing will have any ill effects. The input shaft in stock form does not even sit entirely all the way in the pilot bushing to begin with.

 

The bell housing swap could be done in 30 mins with minimal tools (no snap on set required!.) All you need to do is pull the front cap off, remove the two snap-rings, and unbolt the bell housing from the main case and pull it off. Reverse procedure on the install, and you're good to go.