Hey everyone, as most of you know the rear differential in the 2005 c6 is a serious weak link. As I started modding my car I got more and more concerned with exploding it and destroying the transmission output shaft which would cost a lot more money and headache. So I decided to take the stock unit out and replace it.

At first I had decided on going with a c5 z06 diff so I bought one and had intentions of installing it. However after some more reading and research I wasn't quite convinced that the c5z diff was the best route. I didn't want to ever have to feel the stress of being on the line and worrying about something breaking ever again. So I decided to go a different route.

I found a local that had a diff out of an 07 a6 for pretty cheap so I bought it up with a quickness (this was before people started selling the m6 diffs on here for so cheap).. Since it was out of an auto I had to have it machined for the speed sensor. I went looking for a vendor that could help me with my project. After speaking with almost all of them I decided to go with ZIP. There customer service was awesome and they were extremely knowledgable.
The two people that helped me were : JT and the company vice president Justin Abott. That's right the vice president. Even with the smallest of problems and thoughts about what was going on either of them would take time to answer all of my questions. I never felt rushed or like they were bothered with my interrogating haha.

Anyway, after deciding on what route to go I sent them the differential I bought and they proceeded to build it.

They also set me up with the correct tailshaft housing and all the hardware needed for the install. As some of you may know the mounting points for the 05 is different than the newer 06 and up mounting points (to the transmission).

Here is the old vs new.


And here is the new diff




I just got all these parts in this evening so I plan to start working on it tomorrow evening I only got a chance to pull the tailshaft housing today. I'll keep this thread updated on how the install goes.

After all is said and done Breaking the rear diff should be the last of my worries.

 

Oh I went with 3.73 gears btw. I have a set of 4.10's if anyone is interested.

 

Good deal. Always like to hear a story of a vendor treating someone well.

 

Keep us posted.

 

I have to say i was VERY impressed with JT and ZIP last year
top notch customer service
They mentioned last year about them possibly coming out with a drop in rear that was beefie, not sure if they had, or maybe i mis-understood them????

 

 

That's the way to do it; use the 2006up style 8 bolt diff and install the the new tailshaft housing from a 2006 T56 trans

This allows you to retain the 27 spline mainshaft that is in ALL 2005-2012 base manual transmissions

For those with some T56 skill, you can replace the mainshaft in your T56 with a 30 spline unit(complete trans teardown) and use the 2008 C6Z06 diff (Z06 diff runs about $2500 new from GM)along with the tailshaft adapter seen above

Nice work bud.

 

Thanks.. Sorry for the lack of updates I didn't think too many people were interested. Anyway the install went smoothly and I am very happy to be able to get on the gas and not have a care in the world. I still have to change the clutch master cylinder as the new slave didn't solve the pedal sticking to the floor under high rpm shifts. Ill probably take care of that this week and get some 1/4 mile videos and times.

 

 

Hat's off to you for doing this yourself.

Was it tough to swap the rear trans cover? Can you describe what's involved?

BTW if you haven't taken out your clutch pedal spring...do that. I have fixed countless pedal stuck to the floor issues at the drag strip by removing the spring. Flush your clutch fluid too using the Ranger method.

 

Thanks.. Yea my pedal spring is removed and still no luck, I'm just going to change the master cylinder and see if that fixes it.. I flushed all the fluid out when I put in the new slave cylinder. It's really wearing on my nerves.

Changing the rear trans cover was really not hard at all, just take out all the bolts and give it a tap with a rubber mallet or anything else that's handy. Careful though as in my haste I didn't put anything under it and got trans fluid got all over my driveway. There are some bearings and a gear that needs to be changed over to the new one but it's not difficult, just put them in the same way they came out. The most difficult thing was the bearing race for the output shaft (see the rollers on the output shaft). There is a retainer clip and the race is pressed in the old housing. I used a propain tortch to heat the case around the race and a weird looking bent needle thing with a screwdriver handle to tap it out from behind. I used a hammer and a piece of wood to tap it in the new one. It's not pressed in with very much force so it's not very difficult. Then just slide it on the transmission and make sure everything is lined up it should go right on with a few light taps. The gasket is reusable but I used some gasket maker around the new housing just to be safe. Done.

 

Just for a reference I found some pics. Here is old vs new vs c5z

Old (2005 diff)



C5Z



06+ c6 non z06



Just so anyone that is trying to decide which route to go can see them side by side.

 

What did you do with the c5z diff?

 

Sold it on here. You need one?

 

I actually have a spare, was just asking.

Thanks for the thread.