What are the differences in TT production 10mm vs 12mm?

My understanding is that 2001+ C5s had the 12mm torque tube which is visually identified as having the large snap ring at the rear to retain the drive shaft and that the 1997 to 2000 C5s had the 10mm design with 11 bolts at the back of the tube to retain the driveshaft.

Pretty simple I thought.

But here I am feeling bad because I followed that understanding when buying a replacement/upgrade intended for my late 1999 Coupe which I then sold having not had the chance to install it prior to the car being wrecked. The buyer is a good guy a few towns over who is building a drift car and he finally got around to installing it today along with intended fresh bearings etc only to find that what I believed to be a 12mm TT which is how I sold it to him. I believe I had ran an ad on the forum here as well.

It seems like a caveat emptor scenario. And it is one which would have struck me square on in the same as it has the ultimate owner. I just want to be sure there isn't some gap in understanding that I missed on the part when I picked it.

 

Somewhere here on the forum is the 97-02 parts manual you could d/l to see what years had what parts are in the torque tube

 

Following...

 

The parts manual lists 12564457 as the prop shaft assembly for 97-99 MM6 equipped vehicles AnD for 2000 and up MM6 aNd M12 equipped vehicles. Obviously, the parts manual has a bit of an error. Additionally, the parts manual does NoT list a part number for either 10mm or 12mm couplers. Just a NS (not-serviceable) notation, and lists 12454456 as the assembly for all automatics, 1997 and up.

 

It seems that the 97-09 auto trans cars used the same bolts for the couplers as the the 97-00 manual car's used (10mm)
01-04 Trans. code MM6; Trans. code T56/M12; USE w/ 88894027 M12X52 CPLG BOLTS; 6 speed Manual trans.

 

See post #11

https://www.corvetteforum.com/forums...que-tubes.html

 

Moved to C5 Tech.

 

Thanks, @Johnny Hardcore, for a solid answer. What I had would definitely qualify as a 12mm visually externally then. One hundred percent. 2000 year production for a 2001 car. Snap ring butt. No eleven bolts. But once it was taken apart the owner says it has 10mm guts. Very plausible someone may have swapped it out, not for performance reasons clearly. This still strikes me as strange.

 

That is somewhat strange, for sure. But based on parts availability during the transition from the legacy run of the 10mm to the newer 12mm it is possible GM shared parts on some of them. Wouldn't be the first time something like that occurred.

Also to your point, it's possible the previous owner did a rebuild just to get the car in working order and not for strength improvement.

It's a bit of a mystery.

 

An odd one, yes. In my mind I wonder about using the larger tube and bearings and would the prior shaft work with it? Or are the driveshafts themselves the same OD? A level of detail not worth digging into I suppose.

But I bought it in good faith from NextGen Parts in Mass. And sold likewise in good faith. No way to know someone did the REVERSE of everyone else and downgraded a 12mm tube. I feel better for knowing it wasn't an eff up on my part at least. Just one of those things.

 

Per the write up from Goose (whom is a very knowledgeable forum member) the driveshaft OD went from 55mm to 63mm. Which calipers or a ribbon tape would be able to confirm. But that's only of the buyer still has it out.

 

My 2000 MN6 Z51 came with snap ring and 10mm.

 

Weird!

OK, so it looks as though we're identifying / confirming that 00 cars may have seen some crossover. Ok, now we know.