Jump to content
Sign in to follow this  
garvice

300zx Transmission behind a RB26 in a 260z

Recommended Posts

Hi guys,

 

I am putting a RB26 in my 260z with a 300zx transmission (RB26 bellhousing, 300zx transmission). I found very few photos of custom transmission mounts so wanted to share what I had done in the minor chance it might help someone else in the future. I included lots of photos as they tell the story far better then words. I have sat my engine completely vertical to allow more exhaust space, this is why my transmission is on an angle.

 

As most are away, the 300zx transmission is longer then the existing L series 5 speed and and the mount is further back.

My original transmission mount was the later style with two ears off either side of the tunnel and a crossmember between.

 

I started by cutting the ears off (spot welded on). This is the passenger side, don't have a photo of the drivers side.

260z_300zx_TM_1.jpg

 

I then folded some 2mm sheet to make the drivers side mount parallel to the existing mount (essentially taking the thought of extending the existing mount base). The existing mount is 2mm and is spot welded to the transmission tunnel (which is much thinner) so I felt this was an appropriate thickness. To get the mount to marry up to the tunnel I used a profile gauge (quick google search will bring up what it is). Worked a treat and got the profile spot on first time.

260z_300zx_TM_2.jpg

 

I plug welded it to the existing mount and then seam welded around the edges. I hope I never have to remove this as it will be a complete pain to remove.

260z_300zx_TM_3.jpg

260z_300zx_TM_4.jpg

 

The drivers side was a bit more difficult as the tunnel actually narrows rear of the existing mount rather then getting wider like the passengers side. So I just plated the tunnel with some 2mm sheet (it is not parallel to the existing mount like the passengers side is). To weld this on, I plug welded through the tunnel from the inside, then again seam welded around the mount.

260z_300zx_TM_5.jpg

260z_300zx_TM_9.jpg

260z_300zx_TM_10.jpg

 

The next couple of photos are of the existing crossmember and two different isolation mounts. The first is the L series isolation mount and the second is the GM mount (that I bought for the diff). I had to move the fixing hole in the existing crossmember over to allow for where the transmission sits in the tunnel. This created an issue with the crossmember hitting the transmission bolts. In the end I decided to go with the GM mount as it felt like it had a better construction. The white pipe is 90mm water pipe to simulate an exhaust and the blue tape is in line with the chassis rails.

260z_300zx_TM_7.jpg

260z_300zx_TM_8.jpg

 

I wasn't overly happy with how the crossmember sat on the GM mount in relation to the new tunnel mounts (sat a bit low at the mounting points).

260z_300zx_TM_11.jpg

 

So after a bit of deliberation I decided to make my own crossmember (also didn't want to have to burn out the isolation mount, burning rubber stinks). The original is a 2mm pressed mount (a top hat construction with a small bridge over the bottom), so I built mine out of 2mm sheet. The 2mm sheet is rather easy to bend over some pipe. Here is how I made it. Cut a 40mm strip of 2mm sheet, bent to the shape of the mount I wanted. Laid the shape on a sheet and drew a line offset 20mm from the top sheet. Bent a 60mm strip to match this line. Held them together with magnets to offset them 20mm and transfered the shape onto some 2mm sheet. Cutout the shape in two pieces and then had my four sides. Used some 30mm pipe for the isolation mounts. Ok here are the pictures that really explain it.

260z_300zx_TM_12.jpg

260z_300zx_TM_13.jpg

Reinforced the bolt hole section with more 2mm sheet

260z_300zx_TM_14.jpg

260z_300zx_TM_15.jpg

260z_300zx_TM_16.jpg

Measure twice cut once people, I drilled some holes in the bottom sheet and then realised I had drilled too far over, had to weld the hole back up.

260z_300zx_TM_17.jpg

260z_300zx_TM_18.jpg

Had to turn down the isolation mounts as my pipe is a bit smaller then the existing crossmember.

260z_300zx_TM_19.jpg

 

The new crossmember although larger is considerably lighter then the original (not quite as wide).

260z_300zx_TM_20.jpg

260z_300zx_TM_21.jpg

260z_300zx_TM_22.jpg

 

Cardboard templates for the mounting ears

260z_300zx_TM_23.jpg

Made the ears out of 4mm sheet (existing ears where a folded piece of 2mm sheet and then a second piece of 2mm sheet to reinforce), notched and seam welded from both sides.

260z_300zx_TM_24.jpg

260z_300zx_TM_25.jpg

260z_300zx_TM_26.jpg

260z_300zx_TM_27.jpg

260z_300zx_TM_28.jpg

260z_300zx_TM_29.jpg

260z_300zx_TM_30.jpg

260z_300zx_TM_31.jpg

 

Finished crossmember and mount

260z_300zx_TM_32.jpg

260z_300zx_TM_33.jpg

260z_300zx_TM_34.jpg

Share this post


Link to post
Share on other sites

Nice work, looks very "stock" looking.

 

Does the gearbox line up with the existing gearshift hole when you use the 300zx one that has that remote gearshift position?

 

What are you doing in regards to the tailshaft?

Share this post


Link to post
Share on other sites

No it sits too far back. However I have cut out the rod that goes between the two uni joints and welded the uni joint yokes together. I also have a shifter mount that 240hoke built for the gearboxes. This places the shifter at the back of the original hole. Will try and find some photos.

 

Also, just a not to people, this would be much easier with an early 260 or a 240 as the original mount is very different.

 

EDIT: Will need a custom driveshaft.

Share this post


Link to post
Share on other sites

Sure did.

Going to add an oil drain at the back of the head to make up for any oil drain issues I might have created.

Only photo I could find, will get some better ones later.

IMG_5868.jpg

 

Here are some ones I just took.

IMG_7536.jpg

IMG_7534.jpg

IMG_7533.jpg

Share this post


Link to post
Share on other sites

I would've thought you'd need more clearance on the inlet side than exhaust? Ever tried to work on a GTR. :o

You must be planning a large high mount with a disco potato ;)

 

Looks awesome.

Share this post


Link to post
Share on other sites

Inlet side has heaps of room, will also have remote oil filter mount so wont be too bad to work on.

Wont be a disco potato, far too small. I sold my GT30/40R so anything new has to be bigger.

Share this post


Link to post
Share on other sites

You read my mind Peter with the 3540.

Was thinking of aiming for the 400hp mark to start with.

Share this post


Link to post
Share on other sites

Good work garvice.

 

I was faced with the same problem if I was to use the Getrag 6 speed in my conversion. The 5 speed ZF fits exactly in the same position as the original crossmember and is a nicer shifting box so that made the decision for me.

Share this post


Link to post
Share on other sites

The 5 speed ZF fits exactly in the same position as the original crossmember and is a nicer shifting box so that made the decision for me.

I also thought the fact the 6 speed is almost a non serviceable item would have been in the 5 cog favour too. Back on topic.....great work on the new mount setup. I too would have thought the engine would lean more to the exhaust side like a factory RB install.

Share this post


Link to post
Share on other sites
make shore to use a good manifold like 6boost  with external wast gate for good boost control and 3in exh will make that hp no problem

I was thinking of a GAS manifold (Garvice Auto Shop  ;D)

 

I was faced with the same problem if I was to use the Getrag 6 speed in my conversion. The 5 speed ZF fits exactly in the same position as the original crossmember and is a nicer shifting box so that made the decision for me.

I know what it is like to put off jobs, I bought this gearbox about 2 years ago to put behind my L28. Even had an adapter and had machined up the bellhousing. Just didn't get around to building the transmission mount until now.

 

Back on topic.....great work on the new mount setup. I too would have thought the engine would lean more to the exhaust side like a factory RB install.

Thanks. I thought about leaning it like normal, but then thought, no, it will look much better standing up. Also gives me more room to work around the turbo (the gtr I pulled it out of was far to cramped around the turbos, would hate to work on one). But mainly it just looks cool.

 

the only reason i run rb on the angle is so you dont upset the sump pick up .but im sure you will mod the sump to fix the problem

Yeah another job to do. I have an rd28 sump to modify or a r200 sump to modify. Or might even make my own. (Already given into the fact that this is a long term project, hopefully I have it done before my 7month old gets his license.

Share this post


Link to post
Share on other sites
Very nice work, the Z32 box is a good choice too. You have heaps of turbo room in that bay, I am soooo jealous

That is because I don't have a wide V engine in my engine bay. ;D

Share this post


Link to post
Share on other sites
No it sits too far back. However I have cut out the rod that goes between the two uni joints and welded the uni joint yokes together. I also have a shifter mount that 240hoke built for the gearboxes. This places the shifter at the back of the original hole. Will try and find some photos.

 

I got the transmission out again today to clean up the mount and get the flex plate back in. So I took the opportunity to finally get the photos of the modified shifter uni-joint and mount.

 

2011-04-27165900.jpg

 

2011-04-27165910.jpg

Share this post


Link to post
Share on other sites

Photos showing where the gear stick now comes through with the shortened shifter linkage.

 

Gas_Forum_Build0026.jpg

 

Gas_Forum_Build0029.jpg

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
Sign in to follow this  

×