Some things really make you question your sanity. I'm finishing up the hybrid rebuild of my T56 (CTSV donor, SSR mainshaft). I had to buy a new fbody extension housing. I went to mock up the shifter install and noticed there are no threads in the housing. I'm assuming the manufacturer missed a step, but I'll admit this is my first T56 so I'm turning to you for a sanity check.

If these do need to be tapped, can someone tell me the thread? 8mm won't fit through the shifter side, so I'm thinking 1/4-28?

 

Does the hole go all the way through ? Never messed with one, but maybe nut and bolt, other than that I'd assume they missed it

 

You had me worried that I wasn't just crazy, but also an idiot. I ran out to double-check...the holes are blind. Thanks for the thought though.

 

They're supposed to be 8mm if memory serves, with the "standard" (not "fine" thread pitch for that size, which I think is 1.25mm. Right close to 5/16". Metric for sure though, DEFINITELY NOT any SAE size.

I'd STRONGLY suggest, rather than tapping the metal directly, install Heli-Coils.

 

That's different... Wonder what happened

 

That's probably why it got tossed in the "for sale as replacement" bin at the factory (aka "now it's somebody else's problem") instead of in a transmission.

 

A lot of times, holes like that are not threaded because it's up to the end user to determine what thread pitch they want to use. Standard, metric, fine or course thread. Generally, you end up using self threading screws/bolts so that they cut the threads the first time you put the bolts in.

 

Tremec doesn't tap the extensions housings.
The OEM shifter bolts for T5 and T56 are tri-lobular thread.
This forms the thread instead of cutting them like a tap.

If you have OEM shifter bolts or dealer, or a junkyard who would have them, that is your best option. Look through the M8x1.25, bolts you have access to, and the triangular formation of the bolt threads will identify what you need.