No, what you're not understanding is that there were 5 running changes of the 2005 differential during that model year alone we've documented in building them. I already stated this in my posts last year, but obviously it was forgotten again...

We've seen the case design change once, the left output shaft design changed once, the right output shaft design changed once, the rear cover sealing design changed once and the clutch pack disc count, including the Belleville pre-load washer change design once- All within the 2005 model year, but there was only two part number changes from it's inception to cover all of these. As I've said before, just because you can't "see" the changes, doesn't mean their not there.

 

No need to keep on being a smartazz to talk here intelligently online, you might learn something....

You are correct. We've built 3 of these 2006 differentials for a WD retailer of ours that sent them here on a pallet directly from the manufacturer in late 2005. Each had a tag affixed to them that decoded to the 2006 model year, even though they had the earlier 2005 transmisison mounting bolt pattern. Internally, these differentials had most of the component designs from the 2005 model year, but had the pinion shaft support design and the divorced right output shaft/gear design of the 2006 model.

The first 3 out of 5 early C6 Corvette's we upgraded the differentials on here in-house early last year also had these weired combinations, as well as, 2 more later on about a month and half later. All of them had very early build dates, all of them had early VIN number breaks for the 2006 year and all of them were publically registered cars- abiet the first 3 cars having dealer/gm tags on them. That's why I made the statement before that we think those cars were pre-production 2006 transition year models.

 

I understand what you say here and have from the beginning. The fact is that some of the 05 and 06 differential castings are not interchangeable. I guess I need to go back and read again because that to me says the differentials are not completely interchangable. I must be wrong. I really dont want to participate in this thread any longer but really, what am I missing? I thought that was the question in the first place? Did I miss where you in fact said," all parts are not completely interchangable?" In the future I have promised myself to stay out of such threads.

 

I have stated in the past as I do now that the 2005 and 2006 model year differential will interchange with themselves and that is an absolute true statement, as the scenarios described above we've seen dictate. If you're one of the lucky C6 Corvette owners out there that has this odd drivetrain combination in your car, you'll appreciate that true statement since it applies to you- especially if you decide to upgrade your car and you want the correct differential to fit your car. If you're the owner of the 2006 Corvette that has the later design differential casting on up car, than they won't be interchangable, since this doesn't apply to you.

This is why I said it "depends", but got ridiculed for that statement also...

I have no idea how many of these odd differential combinations are out there on the roads, as we've only seen a limited few, very early 2006 model cars with 2005 differential designs in them- on top of the 3 tagged "2006" model differentials we built for a customer that had the 2005 bolt pattern. As the months wore on, we saw less-and-less of the odd-ball configurations, so we surmised that GM settled in on the 2006-2007 differential casting design that the pictures folks have posted are of.

As I said before, there is no simple yes/no answer...

 

Sure there is. Some of the 2005 model differential castings are not interchangable with some of the 2006 models and vice versa since some of them have a different bolt pattern. Seems pretty simple to me.

 

That's why I stated it "depends".

If a customer calls here and asks for a "2006" differential, I can't simply say to him, "Some of the 2005 model differential castings are not interchangable with some of the 2006 models and vice versa since some of them have a different bolt pattern- which one do you have"? He would have no clue as to what I was talking about and he would probably get the wrong differential for his car in most instances if an assumption was made. If I asked him, "do you have a 2006 differential" and he simply said "yes", than how would I distinguish what model design he had if he was one of those fellas that had this wierd combination?

That's what I was referring to when I said it's more than just a yes/no question. Had I not made that clear distinction in this thread and someone called here to place an order for a differential using the "yes/no" answer on the model of differential he thought he had, he would be very upset with us if we sent him the wrong component for his car and he would have wanted to know, "why didn't you tell me of the differences in thr first place so this wouldn't have happened"?

It may seem that simple to describe when you're not the one taking orders from folks/dealers/tuners/WD's all over the USA that cover 10 years of C5/C6 Corvette application, but it isn't really. A lot of questions need to be asked to get the customer the correct component they need...the first time.

 

I understand all of that, have from the beginning. I am well aware that you can't ask a customer" do you have a 2006" or "which one do you have" I think the people on this thread were just looking to see if the 2005 and 2006 were interchangable. I was assuming they meant "completely" interchangable. Meaning ALL 2006 and 2005 castings included. The simple part is that some of them have different bolt patterns on the castings and are not interchangable. Thats really splitting hairs. Enough of all that.

I have no doubt your knowledge on C6 differentials exceeds most if not all the people on this forum. Your insight can't do anything but be helpful!! Don't let a spirited debate ( yes thats what I'm going to call it) prohibit you from posting facts you think may be helpful. If I have any questions or consider an upgrade I'll give you a call.

 

Aside from the "you might learn something....", that was well written, mature, informative and calm. I thank you for that.

I will offer it once....a truce to the hostilities and I will stop being an azz. You can accept the deal or throw a rock at the white flag.

I realize that through the shear number of cars that you have modded, you will be in the know about the special cases. From the start however, my only point was that the exceptions dont make true for the norm and in general 2005's and 2006's arent interchangeable.

The thing I feel strongly about is this: If a person has a 2005 with a 2006 bolt pattern diff, he wouldnt need a new one since it is already the stronger model. If a person has a 2006 he wouldnt want a 2005 diff. Internal differences werent discussed 1 1/2 yrs ago since you had shut down in that first thread long before I posted for the first time in it. New question would therefore be, is there a 2006 bolt pattern diff with the center not being reinforced with additional webbing or with weak internals? I'm not asking for myself. I have a C5 rear and very happy to have it. For the guy with the 2006 that would accept a 2005 with the newer bolt pattern he would be best served to make sure he gates one with better internals. Maybe it would be more accurate to say that some are interchangeable but the number of cars produced in those 2 years is staggering and statistically makes them not interchangeable in the norm.

1 1/2 years ago you were so agravated when some guy accused your posts as a 'marketing tactic' and you shut down to the rest of us pissing me off. You do have a short fuse and so do I. It isnt a fault, you should have been a fighter.

As a compliment, you certainly make the best looking rear diffs that one can eat off of.

Knight to queen's bishop 3.......

 

Fair enough.

 

I've never seen a 2005 model year C6 Corvette have a later design larger 2006 bolt pattern differential casting- only the other way around, so I'd think that if someone had either of these two model years of cars with similar 5-bolt pattern differential types, there wouldn't be much more to offer in the way of strength from one model "year" to another. The only other changes we've seen we're internally and they we're minor. Those internal parts are usually replaced with HD aftermarket parts anyway when built for performance use, so it's of no consequence really.

Since 2005, all the differential castings are now produced from a permanent die-casting molding process, compared to the 1997-2004 models being of a sand-cast molding process.

The die-cast castings are cheaper/easier to produce in numbers once the initial tooling cost is absorbed, but the negative is that the casting walls are thinner to reduce weight, which is going in the wrong direction when it comes to performance use.

The earlier sand-cast castings are a bit stronger due to the heat treat/tempering of the aluminum after the casting is complete; therefore, they are ultimately stronger by metallurgical design than their die-cast counterparts.

The 2005 differentials are perceived as weaker because of this die-cast process and the fact that they still used the original, weaker, 5-bolt mounting pattern of the 1997-2004 differential version. Combine that with the fact that the 2005 model had less rear mounting support than any model preceding it and that it had less ribbing present compared to the later 2006 design, etc., it was of no surprise when that design led to the rash of failures that everyone has seen. Not to mention the extreme deflection the cheap, internal aluminum parts go through when put under heavy load.

This is why we're so adament about our customers putting a C6 differential struts on the 2005 cars more than any other model, in an effort to provide *some* kind of extra support back there where it *really* needs it most. Usually by the time we build a HD 2005 differential with internal billet parts, combined with a differential strut, we've effectively removed the bulk of the differential/differential component deflection compared to stock and the thing lives. It is expensive to do though..


The 2006-07 models are manufactured basically the same way, however, GM reconized the inherent weakness problem and added a *LOT* of additional webbing all across the case in an attempt to prevent case deflection/fracture of the thinner die-cast casting, plus they changed the mounting pattern on the transmission to incorperate multiple mounting points to better spread the tensile/stress loads over a greater surface area to try to eliminate the common area of fracture at the transmission/differential juncture.


Since the C6 was first released in 2005, we could tell that GM was struggling with driveline durability for quite a while, (about 1.5 years or so) given all the changes we saw within such a short time frame. Now that we're in 2007, it seems as if they have settled down on all the major changes for the most part and most of the differentials these days are not changing much as the years progress.

 

Hence the entire point that for those that can swap there isnt any benefit. In order to use the bigger stronger case of the 2006, the bolt pattern was different. For the ones that needed it, it wasnt a viable option. I dont see why you said interchangeable then.

Are you able/have you tried to swap out the C6 Z06 rear transmission case to use the Z06 diff and how much is the core for the Z06 diff? Fred beans said the rear part of the trans case is 360 or so. Do you see any benefit to that route? I dont think the 4.10's are available for the 9 inch rear but it is a seriously big unit that I saw out of a car.

 

I stated that those two model years we're interchangable, because based on what we had seen at that time (late/early 2005/2006) they were- irregardless of the differentials being the same basic 5-bolt mounting design or strength similarities. Those two model year of cars had interchangable differentials- if you we're one of the lucky souls who had one of these odd-ball combinations during the transition from one model to another. I'd guess GM was probably using up their parts inventory while they made the transition from the 2005 to 2006 model of car, hence the reason there are a small number of odd-ball combination cars out there on the road. How many there are overall, we don't know.

If one was so inclined, they *could* swap out their regular 27-spline M6 LS2 transmission for the 30-spline C6Z box/differential and that entire combination would be stronger, but then you'd be stuck with only a 3.42 gear ratio to chose from, as their aren't any aftermarket gear sets for the C6Z differential yet.

We've done a cost analysis on gear set manufacturing already and the tooling costs are way out there, compared to the expected returns for us to consider that right now. Besides, our focus is on getting this cast-iron case completed first, before we tackle another huge endeavor like that. Far too cost prohibitive to both at the same time- at least for us.

 

This has now become a good thread with lots of info....thanks Phil & Spin!

 

Maybe let it go, Spin?
DTE is being really cool now.

 

now we are geting some info

 

This thread reminds me of holidays with my family; starts out OK, someone starts yelling, everything turns nasty (...entertaining if you're not involved) and by dessert, everyone is getting along again....

I knew you guys were my second family...

 

Right now I'm hoping (wishful thinking?) that the 08 base cars and Z will share the same tranny and differential. That would provide a much larger customer base and improve the business case for Motive or some other outfit such as yourself to get the gears on the road.

I have been watching this stuff closely because I'm thinking about mounting a centri and my early 05 case is at best shaky in my mind.

 

The after dinner drinks are kicking in.

 

If you had read post 88 and Phil's prior post to me you would have seen that you missed something.

Everyone is talking.

 

That answers the question of why you say they are interchangeable.

Cartek had already posted pictures (2 months earlier than your 2/13/06 thread) of the new mounting pattern for the newer 2006 which later went on to show the new ones would not be interchangeable (for any meaningful strength gains). It was this that I based my opinion which remains unchanged that for those interested in a strength gain in the case the newer 2006 cases (which account for 90% of the cars made that year) do not fit the 2005 model year's 5 bolt pattern.

The odd ball combo's today are the exception and not the norm due to the number of cars that were made.

Your dilema is obviously that if a guy with a transitional car asks you for a diff you cant send him one without knowing what is in the car. This is not what a guy like me was asking for. I had a weak 5 bolt rear and wanted a newer design 2006 with the different mounting pattern. To me are those interchangeable?....no it wont bolt up. 2 very different animals. From that point of view (a guy wanting a stronger diff for a 5 bolt pattern 05 diff they arent interchangeable). It was too broad a generalization to stick to today and would certainly cause more confusion than help. A better sttement today would be that while some 2005-2006 diffs were interchangeable the majority arent due to bolt pattern changes after a certain date when stronger diffs became available.

On the Z06 rear diff issue, the transmission output shaft is different too? I was just PM'ed that.