SteveDoten

Replacing the mainshaft in a C5 T56.

1. What's the best/strongest available part?

2. OEM C6Z 30 spline mainshaft and EDM the pinion gear?

3. Of course the 30 spline mainshaft/2006 up tail housing could be used with the C6Z06/ZR1 diff and C6 cradle/LCA's/Pfadt mounts, this setup has been proven since 2009 (Bret Bradbury has a great writeup in C5 F/I)

What's the weaker link, OEM T56 27 spline mainshaft or the OEM pinion carrier support?

I have replaced trans where both have broken and I've also seen cases where ONLY the mainshaft has snapped(aft end), leaving the diff in serviceable condition after a complete teardown and trip to the parts washer

Thanks

ZZOOM06

Steve,
When my mainshaft broke back in 2006, I replaced it with a 9310 27 spline hardened shaft I got from G-Force and haven't had a problem with it since and I have 100 more rwhp now. HTH

Jimbo

LoneStarFRC

Option #2 sounds good to me.

Ask Rick; see what he thinks?

Georgies

How.many splins is the stock input shaft? (The one that goes into clutch)

Thanks

mykream

GM is 26 spline.

mykream

I would say either route is a good way to go, but if you do not do other modifications such as a trans brace and/or the pfadt mount to prevent side to side play, then you could end up breaking whatever you put in it, or the trans/diff cases regardless.

I replaced my broken mainshaft once, did not add anything else bracing wise, and broke the mainshaft as well as the intermediate case 2 weeks later on a 1-2 shift.

I have seen 30 spline c6z shafts break in c5's as easily as a 27 spline.

When it comes down to it, this is really stupid old school ****. Driving that much force with a roughly 1" diameter shaft is ridiculous. I have never been quite fond of the setup but it is what it is.