Jump to content

5-speed swap: Tight vertical clearance for transmission?


Recommended Posts

I have a 75 automatic transmission spec'd 02.


I have ample room laterally for the slave cylinder, but if I try to jack the transmission up to be the same height as the old mounts, I hit the top of the tunnel.

There is about 65-70 mm between the transmission mount and the frame rails when Bimmers.com/02 guide states it should be 80mm (height of original mount tabs).


So before I take a hammer to it and start swinging, am I doing something wrong? Im not the most adept googler but I have looked up and down for this issue and havent seen anything conclusive.  If anything, the auto trans tunnel should be doing me favors.


Other issue, did anyone have to hammer a flat surface for the transmission mounts?  Mine want to sit on a rounded section that would have them pigeon toe a bit.


Just want to ask questions before I start beating the tar out of the poor girl.




Edited by jaredmac11
Link to comment
Share on other sites

When I paid a shop to do my 5 speed swap a decade ago, they simply welded in new mounts at the same height as the originals but further back in the tunnel. The trans was too high and ended up being super loud as it was rubbing on the roof of the tunnel. It's now shimmed down so everything is aligned. It took 2 giubos to get it right.


So the lesson here is that the trans might need to sit a little lower than you think. 

Link to comment
Share on other sites



Are you going to use the original brackets?

Are you measuring from the bottom of the brackets?

Is the reverse light switch on the top of the 245 hitting the tunnel in some way?

Are you using the straightedge correctly?


I planned well ahead to have the specified 80-mm distance from (a) a steel straightedge spanning the frame rails to (b) the shelf or level part of the new transmission bracket on which the round black rubber transmission support bushing sits.  Throughout the entire install process the distance always measured ~80 mm.  Never really a problem.


Photos to help with the comments below...

Pre-Install (guibo bolts just place-holders):  

#1  The Bluntech mount showing the flat surface in (b) above.  Ignore the faint and incorrect PASS and DRIV markings.

#2  The mount installed pretty much on the same level with the original brackets in the background.


#3  Same comment in 2. above. 


As I am sure you've experienced, the steel straightedge would have spanned the entire width of photo #3.  I found the magic distance varied rather greatly (+/- 7-8 mm or so) as I maneuvered the straightedge between the rails and depended on where I placed it (fore or aft).  Maybe your distance varies b/c of where you placed the straightedge fore or aft or you did not have it exactly 90 degrees to the rails.  Check it out.


When you get everything to fit in place nice and functionally correct in your last prelim fitting, measure the distance from the center of the drain plug to some arbitrary point on either floor pan, e.g., 10 inches to the L of the plug.  Mark that spot with a paint pen.  Then when you do the final install, you'll know exactly where to place the transmission into its correct center line, rather than starting over and again adjusting that damn guibo and its bolts. 









  • Like 5
Link to comment
Share on other sites

Never just use any measurement from the internet to install the transmission mounts. Always install the drive shaft and the diff and line it all up correctly first. Then put the transmission mounts in where the transmission ends up after aligning the drive shaft.


When the transmission is installed, the back of the transmission will end up jammed against the upper part of the tunnel and jammed all the way to the left in the tunnel.

  • Like 2
Link to comment
Share on other sites

10 hours ago, 2002#3 said:



Are you going to use the original brackets?

Are you measuring from the bottom of the brackets?

Is the reverse light switch on the top of the 245 hitting the tunnel in some way?

Are you using the straightedge correctly?


Great info in your post, thank you. To answer your questions.. 


I am not using the original brackets, I have the replacement 5 speed mount tabs. 

Reverse light switch is OK. It seems to be hitting a bolt towards the back of the transmission. 

I am using a straight edge but in the least scientific way. Just slapping her into the bottom of the original tabs and trying to get a sense of level. 


I have a jack under my trans and I cannot get the transmission close to 80mm so I need to reaproach. I'm going to have a friend help check the tilt of the motor as something is very off. 


Pictures to come later, I've already dropped down the trans to take a look. The tunnel is worn in a specific spot where I tried to hoist her to the right position. 


Literally dropped her off the jack as well and stuck my selector shaft so that's a whole other problem to address. 



In regards to proper angles for the DS and engine , is that in the manual? 

Link to comment
Share on other sites

I think what's getting missed here is that Jared's car has an auto floor pan.


I've never tried installing a 5 speed into one of those.


As to the driveshaft, you're shooting for 'as straight as possible'

which with a manual car, is 'jammed up so far it touches, then lowered

just enough so the buzzing doesn't drive you nuts.




  • Like 2
  • Thanks 1
Link to comment
Share on other sites

Just to follow back up in case someone finds this thread through a search..

For me, this whole issue was caused by the engine not seating properly due to an askew motor mount.  the passenger motor mount was impeded by a drain plug (previous owner had aspirations of running a turbo), as discussed in this thread


Once I got this corrected, the transmission hovers JUST under the tunnel, which is great.  On to getting it all mounted, which seems to be no small task.

  • Like 3
Link to comment
Share on other sites

  • 1 month later...

Looking to glean some more insight.. 

Not sure if a new post is better or not. 


I have my shortened drive shaft and Im checking tolerances for the Guibo alignment. 


I sent the diff back a bit to give some space between shaft and Guibo. 


80mm up from the rails and the propeller flange really warps the Guibo. If I go up to 90mm were really happy and I can keep a shim between the propeller and Guibo and it will stay there as I rotate. 


If I go down from 90, The gap shrinks and grows as the shaft rotates. 


The problem with the height is the shift platform is binding with the tunnel, especially at the bolts that attach the platform to the transmission. 


Is there anything I can do here? 

I wonder if I'm missing anything obvious? 

Link to comment
Share on other sites

  • 3 weeks later...

What a pain, but I think Im set for now.

I picked up the 02again alignment tool to help out a bit and Im going to check angles before I make anything final.


I shimmed down the CSB which allowed me to move the trans down about the same height.  Im at 85mm.  90mm would have the shift platform be at the very top of the trans tunnel and cause a bind.  85mm isnt much better but its some wiggle room.

80mm is the height you hear mentioned in most guidance.


I set the mounts at 80mm and shimmed up the transmission with washers, just in case theres something going on with how I got the drivetrain in, I can sit my trans at this height.  I feel this is the optimum height.


Also, the front DS is about 5.2 degrees and the back is about 5.8 degrees (these degree finder tools are less than consistent so Im not going up to bat for the accuracy of these)


Some take-aways...

  • The automatic tunnel is different from the 4 speed.  I was under a buddies car around the same time and his tunnel is mostly straight where-as the auto tunnel bends in places like a bottle neck. 
  • The front of the tunnel of the auto is much wider at the front. There is no need to hammer out the tunnel for the slave cylinder, so thats a plus. 
  • I have to contend with a seam RIGHT around the back of the transmission/where the platform bolts on.  This makes it more difficult to make any room for the platform via hammering. 
  • I had to chop down a 4 speed motor mount on the driver side so that the speedo cable wouldnt bind/rub.
  • The tunnel narrows right where the trans mounts go.  This means that the mounts are pigeon toed a bit and its just a nuissance getting the trans crossmember to be sized and fit in.


Now lets hope this is a good 5-speed 😕




  • Like 2
Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.


  • Upcoming Events

  • Create New...