Axle bolt Sizes?

OK, a search didn't yield anything concrete, so will ask a question. Did find some info from Bill Mussara (I think that was right) on an old thread from Chuck and Ryan that indicated his bolts were the same inboard and outboard. I have G50 transmission, went to install the half-shafts last night and the bolts there were supplied (still shrink wrapped in the box from driveshaftshop with not to torque to 57 foot pounds) didn't want to turn into either the flange on the G50 or the flange at the wheel. I believe the bolts are 10mm (.396 on the micrometer or so). When I looked at the threads on the bolts and the threads on the wheel end, it made me think that the bolts were standard pitch and the wheel end was fine pitch. Looked at the bolts and the threads on the G50 and it made me think the bolts were fine thread and the G50 was standard pitch. Found at least one reference chart that indicated that 10mm bolts come in three configurations (Standard, fine and extra fine, which I think was 1.00, 1.25 and 1.5). Hmm, that would explain what I think I am seeing visually.

I am heading to a bolt store today to get a bolt of each pitch to test the theory, but figured I would ask that question to see if anyone has run into this and can maybe confirm the bolt pitch at either end.
Update. G50 bolts are the 1.00 pitch (standard). Easily threaded in. The bolts on the RCR side are apparently not any of the pitches, none of the bolts will thread in. Sent a question in to RCR, will have to wait and see if I get a response.

Not sure if picture will be clear enough once uploaded but have the bolt lightly resting in the hole if you zoom in you can see thread pitch looks different




Could they have mistakenly shipped SAE bolts instead of metric? If the heads are stamped "10.7' or something similar they are metric for sure.

Chris Kouba

Hey Mitch,

I might be late to the party but just went through this with Vaughn. The outboard (hub-side) bolts should be M10 x 1.5 IIRC. Give that a try.



RCR GT 40 Gulf Livery 347 Eight Stack injection
I just torqued all of mine today. I know they are 10 mm but did not check the pitch. The charts online (Porsche) said they are 10 mm x 1.5

Terry Oxandale

Skinny Man
I hope I'm not being stupid here, but I'm using aftermarket Microstubs (31 spline) on my project, which use 3/8" NF for the outboard 930 flanges. The difference is barely discernible by eye, and confusing being I've got to stock to very similar bolts to install my half-shafts. I don't know where RCR sources their outboard stubs, but thought I'd throw this out to consider.
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Ok. My situation is good now. Sent the stub axles back to RCR and got new ones (with bolts that turn into them). Fran said they are 10mm by 1.25. The Porsche end is 10mm by 1.5 as Dwight said. So now I have the right bolts for both ends and the right threads for the bolts to turn into. Maybe tomorrow the axles get installed. Yeah.