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Discussion Starter · #1 ·
Ive been told the trans of the 2005 C6 is weak and Im considering replacing it with a 2006 C6 tranny with 4.10 gears. It's not cheap but is it worth it? Any advice would be greatly appreciated.

The other option is to leave well enough alone until it breaks and then replace it.
 

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The tranny is fine. It’s the differential case that is a POS. Just like GM to build 50 additional horsepower into their car, then save $3 by reducing the thickness of the differential case. They realized their screw up right before the intro of the 2005 C6’s and attempted to ‘fix’ the issue with their hated ‘torque management’ software re-flash. This program basically reduced the power made by the engine in manual tranny cars by altering the fuel and spark mapping in the ECU. It was bullshit.

After manual tranny cars began grenading their differentials, GM fixed the problem by installing Z06 cases in all cars beginning in 2006.

That doesn’t help us 2005 owners.

The main culprit is wheel hop. As the pinion gear attempts to turn the ring gear, it also attempts to push it towards the side of the car. This force, when accompanied by severe wheel hop, is more that the thin cases can take and they fail with catastrophic results. Sometimes the failure will also take the tranny output shaft with it.

A company called DTE makes a brace that will prevent tranny breakage, should the differential fail, however, it does nothing to help reinforce the differential.

There are a few fixes:
1. The C5 differential is very durable and can be swapped using a custom mount. This is by far the least expensive fix, however, I know of no company actually making a ‘kit’ to accomplish this. Those that have made this swap did so in their garage, fabricating their own parts.
2. A C6 Z06 differential is a bolt in, however, the rear tranny case must also be swapped using the Z06 part to make it all bolt in.
3. Don’t be fooled my some high perf shops selling their strengthened differentials. It does not matter how strong the internals are, when the cases are what are failing.

All this being said, my 2005, 6mn car has 550 rwhp and I have never had a differential failure. If you don’t beat the outright crap out of your car (like ‘some’ people are prone to do!) the differential can survive.

Personally, I’d love to see some enterprising young lawyer sue the crap out of GM and make them retrofit all 2005 cars with the upgraded differential. It’s bull-pelosi that I paid big bucks for a new 2005 car and fear to burn a little rubber every once in a while for fear of causing a $7000 repair bill.

Good luck.
 

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Discussion Starter · #3 ·
Thanks. That is also what I have heard. I've seen the results of one shattered diff on a 2005. Im planning on installing 4.10 gears and thought it'd prob make sense to swap the diff at the same time. The shop Im using made the same recommendations: using a C5 diff or the C6 ZO6 diff. ZO6 option is significantly more expensive, so Im undecided. I may just leave it be for a while and see how things go. I really dont beat the crap out of it too much.
 
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