All,

This is a bit of an odd question but I'm hoping some of the differential gurus on this site can help me positively identify a rear end. Long story short, I got a killer deal on what was supposed to be a C6 Z06 rear end minus the cooler right before I left for a long deployment, but a year later I looked at it with a fellow forum member and we weren't quite positive that's what it was. Now that I am back from more military travel I have time to really look at this thing and figure out what I've got.

It looks and feels like a C6Z rear end, but a few things are throwing me off a bit. I know that the serial number on a C6Z rear is 24238614, but this one has 24238615 (1 number off) on it which I can't cross-reference to anything. It is also missing the "Z-3.42" tag that the C6Z rear's usually have on the casing.

I did take it apart and counted what I believe to be the splines (see first attach pic to verify that I counted the right thing), and I counted 30 grooves which checks out. I also counted the teeth in the gearset and found 41 primary and 12 smaller, which divided makes 3.42.

Below are some pictures, I took a ton of them so if any other view would be helpful definitely let me know...

-Tommy

 

First, I am by no means an expert. Based on a few observations, my bet is that it is a Z06 diff. Here is why. The pinion appears to be cut to drive the oil pump and there are cooler lines on the side cover. If it is not a Z06 diff, than it is a European Z51, but a European Z51 would not have 30 splines.

 

It is from a Z06.

 

Z06. The spline count is the giveaway.

 

Does the c6 Grand Sport use a Z06 rear? I know it uses the 6060 except with the Z51 gearing.

 

There's been some debate over this, I think that the consensus was that MT Grand Sports use the same differential case, but the Z06 has beefier internals.

 

and you wouldn't call the dealer or GM?

 

It's a 06-08 Z06 differential. The case/bigger ring gear/pinion gear made for pump drive gives it away but the drain plug is pre 2009 (09 has different drain plug).

 

Thanks Rick.

Do the Grand Sports come with the z06 rear end?

 

You can get a standard diff with a cooler on it because I have one. The Z51s shipped to Europe had coolers with base diff.

 

Yes, it's the same big diff that Z06 uses but GM has a different part #. All parts interchange between GS and Z06 diffs.

Yes, we use the export drivers side cover for owners wanting other than 3.42 on the Z06/GS diff. We use a base diff, install gear of their choice and have the pinion gear cut for pump drive/30 spline and it's a bolt in. Not a strong as Z06/GS diff but you do have choice of gear ratios.

The diff on the original post is a Z06. If you look at the spacing of the ribs on top and lack of cooling fins on the bottom is another way to tell them apart.

 

^^^ Thanks for the great advice Rick.

I figured GM would use the Z06 diff in the Grand Sport since both use the 30 spline mainshaft. It would be silly for GM to cut the smaller pinion gear for 30 splines when they've got the bigger ones sitting there.

It is odd that they use a different part number. That costs them a lot of money.

By the way Timd38 and others, I have a diff & tranny temperature gauge in my car, with a factory tranny cooler and no diff cooler. I also have 4.10 gears. On the highway, my tranny stays around 230 similar to my oil them (I have a factory oil cooler), but my diff will get up to 270. On the track it will get close to 300 after 20 minutes or so and that's when I get off track.

So GM did everyone a solid installing a diff cooler, they are needed on the track or at extended high speeds which is, I'm sure, why they installed them on European spec cars.

 

The base diff holds about 1.8qts. The big diffs hold 2.8 qts. With the diff HX and higher capacity, the Z06/GS diff doesn't get as hot as the base diffs.

On a side note, road raced cars MUST use a trans/diff cooler or heat exchanger. We have seen overheated differentials that got so hot the pressed in side carrier races just fall out.

 

Thanks for the help everyone - I am planning on selling the rear and my biggest concern was passing it off as something that it is not. The original seller did say that it was from a 2008 Z06 so the analysis was spot on!

-Tommy