The Official 356Talk Forum

Ron LaDow wrote:Suggested (honest) subject line so the rest of us don't waste time trying to suss out the facts:
"I'm trying to fit an aftermarket shift knob to a T6. Can anyone help"
Thank you and, no, I have no idea why the knob you bought somewhere or other doesn't fit a 356. Why not ask the seller?

Ron, I sold the knob to Scott. It came off my T6 coupe where it fit fine - I've fit four different shift knobs on the T6 without issue. I don't know what knob Scott's S90 had before he tried to fit this one and why this one won't fit. A simple swap to move the shift knob from a T6 C Coupe to a T6B S90 Coupe didn't seem like a big deal. I believed there would be no differences and Sebastian confirmed that. Scott and I could have tried it directly when all parties were present, but we didn't. I am willing to meet up with Scott and take a look myself, we just haven't done that since the original transaction. I have not seen his shift lever without a knob on it so I don't know what the problem may be.
The original subject line was not as you suggest because "I (am not) trying to fit an aftermarket shift knob to a T6." Scott is and I started the post to try to help resolve the issue. I wanted to understand if there are differences in the diameter and threading interface between a knob and a lever in two different makers (and models) of cars.

I believe the threads should be the rather unusual diameter of 15mm * 1.5mm pitch.

gregorycampbell wrote:I believe the threads should be the rather unusual diameter of 15mm * 1.5mm pitch.

Greg, are you related to Tony Campbell perhaps? Used to race 356s back in the day in Canada. 2nd owner of my car.

Sebastian Gaeta wrote:Scott,

The next step is to get a factory knob and see if it works. It is now back to only one possibility--either your shift lever is non-factory/modified or Mark's is.

I've had a dimpled original, a VW, the AMCO and an Emory outlaw knob on my shift lever at different times. They all fit. Maybe there is an insert from the knob that came with the S90 that is still on the lever after the knob was removed. I'll have to see it for myself and check it with a caliper and thread gage. I've also offered to buy the AMCO knob back if it won't fit.

The latest on this saga is that original knobs fit both shift levers and the Amco knob fits my shift lever but not Scott's. I didn't have one but I bought the correct tap and ran it through the Amco knob for Scott. Other than a few bits of chrome near the trim ring, very little slag came out so the knob threading is clean. His car is currently at a local Porsche shop for some minor fix-up and I suggested to Scott to see if they have a M15x1.5 die to run onto the shift lever. That seems to be the only piece of the puzzle that hasn't been checked.

Too weird! I am very curious to find out what it ends up being.

The Amco knob does thread onto the shift lever but it only goes on about one turn. I eyeballed the threading on the lever and it may be that those threads are not quite as forgiving as on my lever. By that I mean, it looks like the threads could be a bit shallow because the outside tips of each thread are not sharp but somewhat flatted, like the original die was not deep enough, leaving the threaded diameter a tad oversized, even though the original knob fits. It is very odd.

Sebastian Gaeta wrote:Those have set screws. Is the screw backed out all the way or still screwed in? If screwed in it will appear to be “too small”.

Edit: Amco shift knobs may have more than one set screw so check for multiples.

Not the one in the picture. Many AMCO knobs came with a jam nut that screws on before the knob. This knob is one of them.

Regards

Jim

Jim Breazeale wrote: Many AMCO knobs came with a jam nut that screws on before the knob. This knob is one of them.

Regards, Jim

Agreed, thanks Jim. The jam nut is missing at this point.