Modified Stock Transmission Mount for RB25 5 speed

[Jboogsthethug]

I recently picked up my RB25, and after looking at the crazy high prices for transmission/engine mounts and reading some of the reviews I figured it wouldn't hurt to give it a go myself. If it works out, great, if not then I'll buck up and pay the money for the pre-fabbed ones. Anyways, I decided to start with the transmission mount as it seemed easier and It would hold my engine in place beter for  the motor mounts.

 

First things first, I took the old transmission mount off of the 4 speed transmission, and it bolts up perfectly to the 5speed RB tranny. I was pleasantly surprised! That meant I could at least use the original mount to an extent.

 

Then, I put the engine in place to get measurements. I pushed it almost as far back as I could towards the firewall. I noticed that the mckinney mounts seemed to bolt the engines straight down, but it seemed like you'd have to modify the trans tunnel in order to have the shifter go through. I wanted my shifter to be in more of a stock location, and it wouldn't pop through until I pushed it farther back. Then, I crawled under and got some measurements. These probably aren't;t universal and probably won't work for everyone, but what I got was this:

 

The original mounting area allowed the transmission mount to be 14 inches long. The new area I was mounting was 10". The original mounting holes were 12.25 inches apart in the middle of the holes, with the other hole being directly center. It was also farther back in the tunnel by 5".

 

I figured the easiest way to do this would be to make some sort of jig, so I put together a crude assembly with just some shelf wood and some nails. I measured the above measurements, cut the ends off of the tranny mount 2" in each side, allowing it to fit in the new location.

 

 

Then, I took some 1"x 2" bar I had lying around and just eyeballed it basically, holding it above and marking it with a pencil, then cutting it along the lines and shaving it as needed.

 

 

I then tacked it in place, got under and double checked it and everything fit really well. Probably nto perfect, but it seems like it is pretty much perfect.

 

I then pulled it back out and welded it all together. My welds are supreme, I know. 

 

I also cut a corner out of the passenger side tranny mount thing that I need to go in and weld up. The Speedo sensor, as many already know, doesn't fit in that area without that being modified.

 

Also, a little plug for grinding masks. I bought this a few years back after cutting my lip off with this very grinder. I wised up and decided I wanted protection across my whole face. Yesterday, there mustve been some sort of manufacturing error with the disc I was using and it exploded while in use. The biggest chunk hit me right in the face, but thanks to this bad boy I'm all good.

 

 

I'm curious everyone's thoughts! do you think this will old, assuming my professional quality welds penetrated well? Of does it need to be more centered across?

 

 

[winstonusmc]

I decided to make all of mine from scratch. Be careful if the pinion angle. Mine was way off using the factory rear mount with R32 mounts. I found the stock 240z has a weird high pinion angle, or at least mine did, something like 3 degrees up. So I had to make my trans mount lower. 

[Jboogsthethug]

15 hours ago, winstonusmc said:

I decided to make all of mine from scratch. Be careful if the pinion angle. Mine was way off using the factory rear mount with R32 mounts. I found the stock 240z has a weird high pinion angle, or at least mine did, something like 3 degrees up. So I had to make my trans mount lower. 

 

interesting, I'll have to keep that in mind. I got my RB from a 240sx so that's what mounts it has, not sure exactly how it will work. how far back did you push your engine? I've realized that with me pushing mine back it also has made it so I'll have to make my engine mounts where they angle forward from the engine to the stock mount location. I would imagine it would hold alright if given the correct support. Did you have any problems like that?

[winstonusmc]

My engine mounts are also custom fabricated to sit the engine about as far back as McKinney mounts. I have compared them side by side. My drivers side mount is a modified R32 mount to clear the head drain. The passenger side mount is fabricated though, it's centered above the mount on the crossmember.

[BeastioBoi]

Some good work ya got there!

[Jboogsthethug]

On 7/19/2018 at 9:27 PM, winstonusmc said:

My engine mounts are also custom fabricated to sit the engine about as far back as McKinney mounts. I have compared them side by side. My drivers side mount is a modified R32 mount to clear the head drain. The passenger side mount is fabricated though, it's centered above the mount on the crossmember.

 

Did you have to cut the shifter opening to open it up more or did your shifter line up? I've realized I'll need to push m engine a bit farther forward but it also means I need to widen the hole so I'm hesitant to do that.

 

[winstonusmc]

I am running the 71C transmission and my shifter is in the middle of the hole. With the R32 mounts, the shifter was in the front of the hole, which is really why I wanted to move the engine back. That and I wanted power steering, the electric fans were too close to the pullies. 

[ZT-R]

The problem i had with mine is it seemed like it was to much leverage and was kinda flexible, not the bracket just the leverage on the mounting positing. I ended up welding on attachment points inline with the mounting bolts in the transmission. 

[Jboogsthethug]

On 7/28/2018 at 2:05 PM, winstonusmc said:

I am running the 71C transmission and my shifter is in the middle of the hole. With the R32 mounts, the shifter was in the front of the hole, which is really why I wanted to move the engine back. That and I wanted power steering, the electric fans were too close to the pullies. 

 

hmm interesting, I'm pretty sure I have the same transmission (I have been searching for days on identifiers and if there are even any other transmissions that the RB25 came with other than 1 model of 5 speed and one 6 speed model for the RB26?) and I can't get it through the hole without moving it pretty far back. I cut out the part of the trans tunnel mounts that hits the speedo sensor and I think I'm too far back. did you install yours into a 240z or a 280z? mine is a 240, if yours is a 280 it might make more sense as to why the hole isn't lining up with the shifter as well as it sounds like yours is.

 

On 8/11/2018 at 6:00 AM, ZT-R said:

The problem i had with mine is it seemed like it was to much leverage and was kinda flexible, not the bracket just the leverage on the mounting positing. I ended up welding on attachment points inline with the mounting bolts in the transmission. 

Great to see you chime in here ZT-R, I've followed your thread for a while now. If I remember correctly, you bought it with the RB26 already installed, right? If so, do you know if they bought mounts or built them? I'm worried about the leverage as well, I fear my placement is too far back. Do you have any pics of what you did? Also, how are you liking that sequential trans? that is a beautiful gearbox!

 

[ZT-R]

The engine was literally laying in the bay. The mounts are some of mckinneys first ones, which require a boat load of shims but I guess they are ok. I went though a few different mounts mckinney sent me and a 2 of there downpipes way back in the day, I never could get them to fit. I guess they used the rb20 trans or something, mine was the beefy gtst r34 one. Loving the sequential, it was like it was made for this chassis, if i didn't cut off my original trans mounts it would have been perfect fit, i did use one of them though.  You could take that trans mount and then weld a rear bolt bracket to the chassis for added reward support, but it wouldn't be just a bolt up thing, also gotta leave clearance for the exhaust, but mines 4" probably a bit overkill.

 

[Jboogsthethug]

On 8/12/2018 at 12:41 PM, ZT-R said:

The engine was literally laying in the bay. The mounts are some of mckinneys first ones, which require a boat load of shims but I guess they are ok. I went though a few different mounts mckinney sent me and a 2 of there downpipes way back in the day, I never could get them to fit. I guess they used the rb20 trans or something, mine was the beefy gtst r34 one. Loving the sequential, it was like it was made for this chassis, if i didn't cut off my original trans mounts it would have been perfect fit, i did use one of them though.  You could take that trans mount and then weld a rear bolt bracket to the chassis for added reward support, but it wouldn't be just a bolt up thing, also gotta leave clearance for the exhaust, but mines 4" probably a bit overkill.

 

 

yeah I've heard the Mckinney mounts need a lot of shimming, dumb considering the price! do you have any pics of the welded setup?

And I am drooling over the sequential, that thing is so sick. I've wanted one since coming across this 240z :

 one day I'll be cool like you guys

[ZT-R]

Paul's car is sick, his new aero package I'm told works really well, pretty slick one off carbon fiber from topstage. I doubt I do ill see. The only things I have picture of is how I modified the oem mounting tab to clear the speedo sensor, that's in the build thread.

 

[Jboogsthethug]

13 hours ago, ZT-R said:

Paul's car is sick, his new aero package I'm told works really well, pretty slick one off carbon fiber from topstage. I doubt I do ill see. The only things I have picture of is how I modified the oem mounting tab to clear the speedo sensor, that's in the build thread.

 

Yes sir I agree, that thing is super slick. It seems like it holds him down pretty well, the footage of his acceleration is pretty mind-boggling ha. and no worries if not. I've got plenty to learn until I become a master builder, this will just be more practice ha

 

 

[Jboogsthethug]

On 7/28/2018 at 2:05 PM, winstonusmc said:

I am running the 71C transmission and my shifter is in the middle of the hole. With the R32 mounts, the shifter was in the front of the hole, which is really why I wanted to move the engine back. That and I wanted power steering, the electric fans were too close to the pullies. 

 

ok so I thought I had the same transmission but I'm confused. Here are some pics of the fitment, I've got about an inch between the firewall and my engine, if that. And you can see my transmission shifter (not centered in the pic) is barely able to fit in the shifter hole without modification. Does this seem right to everyone else with their fitment?

 

[winstonusmc]

My trans is from an R33 RB25DE (FS5W71C). I know what it came out of because I pulled it from that car myself. It has a "71c" and a Kangaroo cast into the bellhousing. It is a similar trans to the 240sx but it's about an inch shorter. It's the smaller trans, not the big version that's in the RB25DET (FS5R30A). 

 

I can't tell from your pic if the shifter is towards the firewall or not. 

[ZT-R]

I think my gtst one was almost centered maybe a touch to the front. engine placement looks about right. Its been awhile and many beers ago.

 

[Jboogsthethug]

10 hours ago, winstonusmc said:

My trans is from an R33 RB25DE (FS5W71C). I know what it came out of because I pulled it from that car myself. It has a "71c" and a Kangaroo cast into the bellhousing. It is a similar trans to the 240sx but it's about an inch shorter. It's the smaller trans, not the big version that's in the RB25DET (FS5R30A). 

 

I can't tell from your pic if the shifter is towards the firewall or not. 

ok interesting> I bought my motor/trans from a company here that pulled it out of a 240sx to swap in a 2jz, so they don't really know anything about it and they also don't have the contact info for the PO so I'm kind of stuck trying to figure it out ha. No kangaroo though, not that I've seen anyway. It is indeed toward the firewall, sorry the block of wood has a strap around it that is holding the trans in place as I build motor mounts. In the end, it fits and I do still have some room to push it even farther back if needed so that's the important part. Trying to identify the motor or trans has proven to be difficult though, as a lot of the tell-tale parts on the motor have been swapped for aftermarket parts and there doesn't seem to be much on the tranny.

 

2 hours ago, ZT-R said:

I think my gtst one was almost centered maybe a touch to the front. engine placement looks about right. Its been awhile and many beers ago.

 

Haha I guess as long as the boot fits! thanks for the input, I'm probably going to scoot it back slightly more as I measured it and have about 2 inches between the firewall and engine, I'll put that back an inch and then have the shifter mounted slightly more centered in the hole.

[jthom5147]

A quick way to tell: look at the shifter housing. If it is parallel to the tail shaft then it’s a 71c (commonly known as rb20 trans, but found on RB25DE). If the shifter housing slopes back toward the ground then it’s an RB25DET trans. Side by side the difference in size is obvious, in photos alone not so much.

 

you could swap your RB bell housing onto a 240sx 5 speed from a KA car and it’ll move the shifter back.

[Jboogsthethug]

On 9/24/2018 at 4:59 PM, jthom5147 said:

A quick way to tell: look at the shifter housing. If it is parallel to the tail shaft then it’s a 71c (commonly known as rb20 trans, but found on RB25DE). If the shifter housing slopes back toward the ground then it’s an RB25DET trans. Side by side the difference in size is obvious, in photos alone not so much.

 

you could swap your RB bell housing onto a 240sx 5 speed from a KA car and it’ll move the shifter back.

Interesting! I figured out a big part of my problem was just leveling out the engine/tranny. After I got it more level it goes farther back thankfully! I believe I have the RB25DET, I need to pull out the pics or the tranny but from memory that matches up with the pics. Very helpful info!