[pbonsalb]

I happen to have a GS6-53 from an E90 335i in my turbo E36 M3 on my lift right now and put calipers on the shaft and measured about 0.6 inches or 15 mm. The 135/335/535 version of the GS6-53 is the same trans as on E90M3 but with different bellhousing bolt pattern for the I6 and and 105mm rather than 110mm bolt pattern on the output flange to the driveshaft.

It was tight getting up in there with the caliper and my caliper is a cheap one, but based on what I measured, I not spend $30 on a tool designed to screw into the middle part of a seal with a 0.5” ID.

I did change the seal on this trans last year before installing it and it was no big deal to pop it out with a small screw driver. I had the trans off the car at the time. It would be tougher to do in my little E36 but the E90 has a bigger tunnel. However, there are console mounts on either side. Worst case, you might have to pull the driveshaft, which means pulling the midpipe.

Since this trans was in use in a variety of cars for over 10 years, I am sure someone has done it and posted about it. I’d google. Not so many E9xM3 DIYers.