My 2005 Z51 M6 put down 476 rwhp. I am wanting to put 3.90's or 4.10's in the stock diff to increase the fun factor on the street. I dont drag race the vehicle at all, and I dont do any 1st gear street launches. I mainly do second and third gear pulls without banging any gears.

It seems most of the issues are broken cases caused by wheelhop. I dont have any wheel hop right now; however, I have a set of Bilstein Sports that I will be installing when my widebody kit arrives. I will also be removing the runflats and replacing them with Nittos and Z06 12" rims in the rear. With the new rubber and shocks, I doubt I will have any hopping if I dont have a problem currently. Outside of wheelhop, are these 2005 diffs that bad

 

they are the weakest, you can put in a newer year

 

I know I can change it to a newer year or swap to a C5 unit with a conversion brace. However, I dont want to spend money where money isnt needed. I am just seeing if anyone has grenaded one outside of wheel hopping and/or drag racing.

 

I replaced my 07 Z51 A6 diff with one from RPM.

 

Without those two elements it certainly is a lot less likely to break for sure, but it could still happen, with a manual at least. The automatics can live a long time even with some racing/abuse.





That's a different animal than the 2005 rear, the 2006 and up rears were a huge improvement.

 

I've seen some diff's that blow up and they do all seem to have wheel hop. There are some members that are running some serious HP with the 05 diff with no issues so far. The 05 diff does have its issues but I wouldn't waste my time with swapping with a later year C6. If I was going to swap I would put something bulletproof back there.

 

That is what I was thinking. The threads I have seen have either been wheel hop or dumping the clutch. For those that have shattered the diff, was the ring and pinion ruined or just the case? If I grenade the diff, I am curious if the 3.90's would be ruined or if they will still be usuable on the replacement?

 

For the money you'll spend upgrading the '05 diff, pony up the extra and just buy a built 3.90/4.10 later year diff. All that needs to be swapped is the tail housing on the tranny. It's bolt-in, other than that.

If you do it this way, you can still recoup several hundred dollars (or more) out of your stock diff, and that will have paid for a chunk of your new gear. If you upgrade the current diff and it does blow up, well now you're out the amount of money you could have recouped by selling it in working order, and you're out the amount you just spent on the new gears and labor. And better yet, often times the diff exploding will take the lower section of the tranny tail housing with it and/or snap the mainshaft off at the back of the tranny.

It makes zero sense to me whatsoever to skimp so dangerously on a very, very worthwhile upgrade when we're driving around in 50K cars. Have the peace of mind, and build a proper differential for it.

Oh and by the way, I'm on the third diff in my '05. The first two stockers blew up, one of which when it went did what I mentioned above, and snapped the mainshaft off at the back of my brand new, fully built T-56. That one little mishap ended up costing me several grand. All because I hadn't put a proper differential in the car to begin with. I now run a full Z06 trans/housing/differential setup.

I make ~20rwhp less than you, and also pretty much only get on it between 2nd and 4th gears. One of the diffs blew on the 1/2 shift from a 40 roll. It was a couple days after adding 335 nittos and 12" wheels, too.

 

Thanks for the feedback. I will swap the diff. I will do the C5 swap to save some costs.

 

My 05 M6 is very close to your power level with 4.10 gears in the original housing. I drive it the same as you describe, and no problems at 82K miles. I have about 50K miles on the differential.

 

Anyone that wants this mod, I'm de-modding my car and need your core. PM if interested. It can save you thousands over a breakage. If anyone in the Mountian area (Colorado or surrounding) wants to head here we can do the swap at my house and both of us can be hooked up and happy. Mine has 4.10's and both shafts are hardened. Its a severe duty diff and Cartek built it.

 

I'm not sure where you're located, Csnow.... but if it's anywhere within a day's full drive from Spin, that would absolutely be the most cost-effective option for you, and the guy has a sterling reputation.

If I didn't have a new setup I just swapped in I'd be headed to Colorado tomorrow, literally.

 

PM sent

 

I got 301 hard launches out of my 05 rear...but on the 302nd, it cracked in half like they all do and took out my transmission, like it seems they always do (and I had a brace).

If you are going to jump on your car, I'd swap out the rear while it has some value. Sparo2 can help if you don't work a deal with Spin.

Spin I spoke with Double A today, he's not going to swap his, little bit that he drives the car he's hoping for the best.

 

Spin,

Left you a PM with my number. I aint tire kickin.....give me a ring.