Bottom line: How tight of a fit should the transmission input shaft be into the pilot bearing? Mine will NOT seat with normal transmission-installation force. I measured the pilot bearing ID at 14.95mm and the transmission input shaft OD at 15.10mm.
More detail: I have spent all day today trying to install the 5-spd transmission into my 2001 M Roadster (not an M3 I know, but an S54, so here I am posting for help). It slides in, but just will not go the last 1/2" or so. Classic symptoms of clutch misalignment. So I spent all day tweaking the clutch position using the plastic alignment tool, since there is a tiny amount of play when installing it. Nothing had any effect. I am relatively confident the clutch is/was properly aligned with the pilot bearing.
I replaced the pilot bearing while the transmission was out, so figured there had to be something wrong with it. I pulled the pilot bearing and tried to put it onto the transmission input shaft, and it would not go on at all. I measured both the pilot bearing and the transmission input shaft, and sure enough, a 15.10mm shaft will not fit into a 14.95mm hole.
I've always been warned not to use the transmission mounting bolts to force the last bit of motion, but is that what is required here? Either that or I just have a defective pilot bearing. It is a BMW OEM part (p/n 11211720310 purchased from ECS Tuning).
Any help would be greatly appreciated. Other than ordering a new pilot bearing and seeing what happens, I'm not sure where to go from here.
In the interests of anyone googling or stumbling onto this, the problem was a slightly "mushroomed" input shaft on the transmission. I sought out and visited McB Autosport (in Bridgeville PA) who had an old input shaft for me to compare to. No way to know for sure if it happened during the transmission's recent trip to the transmission shop or much earlier (car has 220k miles). The solution was about an hour with emery cloth and then fine-grit sandpaper on the shoulder of the input shaft. Worked like a charm.
Pretty sure I had that issue and It all pulled together when I put the bolts In.
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I just installed a ZF 5 speed on an S54 for a swap project. I used a new OE BMW pilot bearing from ECS. My pilot bearing slid onto the input shaft just fine, but it was tough to get everything to slide together nicely when I went to put the trans onto the engine. I got it started on the clutch splines and then used the bolts to gently pull everything together.
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