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Old 11-15-2010, 11:52 AM   #1
69427
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Default D36 batwing on iron differential case?

Just curious if anyone has played with this combination. I currently have the late C3 batwing on my '69, and it allowed a removal of 15# of weight off the car. The D36 batwing looks to be about 10# lighter than the C3 batwing. It appears that a 1 inch spacer would be required to provide clearance for the ring gear, and the bolt pattern adaptation looks to be reasonably straightforward. Outer mounts would need to be welded in, but I had to do that with the C3 batwing, so that's not a new experience.

Any issues I'm missing in my quest to pull weight out of the car?

thanks,
Mike
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Old 11-15-2010, 06:14 PM   #2
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Of course, a 1" spacer is going to eat up some of that ~10#, so you're not going to end up saving all that much weight for the trouble if the D36 can be adapted. Also, the real issue I can see, if I've got this right, is the D36 being a good bit less desirable for HD service than the D44 batwing (which weights ~7# more), you could very possibly pass the point of diminshing returns, weight vs strength wise. My $.02, free of charge since I'm certainly no guru on batwings.

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Old 12-02-2010, 05:57 PM   #3
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Mike, I'm surprised no one else has chimed in, and curious if you've gained any more info on this. Also, would you happen to know of any complete D44 C3 installs (w/C4 rear suspension)?
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Old 12-02-2010, 06:15 PM   #4
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There is a guy in the purdue car club that has done the C4 swap. My not have been the correct way to do it, but he did it. Here is a link to the build up.
http://web.ics.purdue.edu/~papa/foru...ad.php?t=10903
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Old 12-02-2010, 10:20 PM   #5
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Originally Posted by TheSkunkWorks View Post
Mike, I'm surprised no one else has chimed in, and curious if you've gained any more info on this. Also, would you happen to know of any complete D44 C3 installs (w/C4 rear suspension)?
I admit this is an odd combination of parts.

I've got an initial pattern made for the adapter, and I'll be hogging out an aluminum sample sometime over the winter. My setup is more compatible with the C4 batwing, obviously, as I currently have bracket adapters to mount the toe rods and the C4 rear spring to the C3 batwing I'm using. The C4 batwing would let me eliminate those brackets (offsetting the adapter weight). I like using the C4 springs as there are several rates available and swap meet prices for them are reasonable.
I don't have any firsthand knowledge of a C3 D44 used with a C4 suspension. I did consider using a D44 at the start of the suspension change, but I had several of the iron rear ends on the shelf with different ratios, so it seemed to make more development sense to use parts that I can swap around easily. I'll confess that I don't know how much aftermarket ratio selection there is for the D44.
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Old 12-02-2010, 11:51 PM   #6
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This Post has real good timeing as I'm working a deal on buying a C4 D44 for my C3 as we speek. However I wasn't planing on doing the Suspension just the Rear it self. Dose anybody know if the C4-C3 (1980-82) Frame Bolt distance is the same? I realise that the forward Mounting is completly diffrent. Dose the C4 batwing Hold the C4 Spring in the right place to line up with the C3 Trailing Arms?
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Old 12-03-2010, 10:32 AM   #7
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Originally Posted by Gale Banks 80' View Post
This Post has real good timeing as I'm working a deal on buying a C4 D44 for my C3 as we speek. However I wasn't planing on doing the Suspension just the Rear it self. Dose anybody know if the C4-C3 (1980-82) Frame Bolt distance is the same? I realise that the forward Mounting is completly diffrent. Dose the C4 batwing Hold the C4 Spring in the right place to line up with the C3 Trailing Arms?
Are you referring to the outer batwing bracket holes? If so, IIRC, there's about an inch or two width difference. I have a couple spare batwings in storage and last month I set a C3 batwing on a C4 batwing (gasket flange to gasket flange) to compare the differences in width and angle. That was a month ago, but I'd bet a beer that the bolt-in possibilities are nil.

Regarding the spring alignment question, you might be okay. I went the opposite direction and the spring lined up fine. There are spring length or mounting issues to consider, though.

Give some thought to any floorpan clearance issues with a C4 D44.
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Old 12-03-2010, 02:18 PM   #8
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E-mail Bee Jay He did the aluminum bat wing during his on going lightening up the 79 program

He did a nice write up here!

http://forums.corvetteforum.com/c3-t...g-install.html

Last edited by gkull; 12-03-2010 at 02:21 PM.
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Old 12-03-2010, 02:52 PM   #9
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E-mail Bee Jay He did the aluminum bat wing during his on going lightening up the 79 program

He did a nice write up here!

http://forums.corvetteforum.com/c3-t...g-install.html
Apples and oranges. BeeJay installed a C3 batwing (which I also did a few years ago). This thread, and Gale Banks '80's post, is about C4 batwing issues.
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Old 12-05-2010, 02:01 AM   #10
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Originally Posted by 69427 View Post
Are you referring to the outer batwing bracket holes? If so, IIRC, there's about an inch or two width difference. I have a couple spare batwings in storage and last month I set a C3 batwing on a C4 batwing (gasket flange to gasket flange) to compare the differences in width and angle. That was a month ago, but I'd bet a beer that the bolt-in possibilities are nil.

Regarding the spring alignment question, you might be okay. I went the opposite direction and the spring lined up fine. There are spring length or mounting issues to consider, though.

Give some thought to any floorpan clearance issues with a C4 D44.
Yes the outer Batwing Holes is what I'm refering to. My 80' looks to be about 38 3/8" and I understand that a C4 is about 36 1/2". So Shorter is a whole lot better than Longer. As involved as this all is going to be I also am planing on moving the Rear Up an 1" as per the Gulstrand Mod. I'm set up to Fabricate so that not an Issue. As far as the Forward Mount I have no intentions of Mounting the the Rear to a Ladder and Attaching it to the Trans C4 style I'd just make a braket to mount it to the C3 frame this how the Paul Newman Creations dose it. If this dosn't work I also have a Viper D44 wich I think will bolt to a C4 Batwing and it has a couple of Ears on the sides wich should be Ok to mount to the Frame. The Viper Batwing is way Shorter than the Vetts and it has no provision for the Spring as the are Coil Sprung. As far as the Spring goes I'd probably be ordering one from VB&P and I could get any Lenght I want.
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Old 12-05-2010, 10:01 AM   #11
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Quote:
Originally Posted by Gale Banks 80' View Post
Yes the outer Batwing Holes is what I'm refering to. My 80' looks to be about 38 3/8" and I understand that a C4 is about 36 1/2". So Shorter is a whole lot better than Longer. As involved as this all is going to be I also am planing on moving the Rear Up an 1" as per the Gulstrand Mod. I'm set up to Fabricate so that not an Issue. As far as the Forward Mount I have no intentions of Mounting the the Rear to a Ladder and Attaching it to the Trans C4 style I'd just make a braket to mount it to the C3 frame this how the Paul Newman Creations dose it. If this dosn't work I also have a Viper D44 wich I think will bolt to a C4 Batwing and it has a couple of Ears on the sides wich should be Ok to mount to the Frame. The Viper Batwing is way Shorter than the Vetts and it has no provision for the Spring as the are Coil Sprung. As far as the Spring goes I'd probably be ordering one from VB&P and I could get any Lenght I want.
I think this will be an interesting swap. As I mentioned earlier, please do some serious measurements of your tunnel area. The D44 is a large chunk of aluminum.

Keep us updated!
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Old 09-30-2011, 03:42 PM   #12
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Mike, just wondering if you've any update on this, as I'm looking at options while my rear suspension is out.

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Old 09-30-2011, 04:16 PM   #13
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How can you tell what year this is from?

Click the image to open in full size.
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Old 09-30-2011, 05:41 PM   #14
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How can you tell what year this is from?

Click the image to open in full size.
If the spring is original, it's off an 81 or 82. If the spring isn't, it could be off an 80 as well. I'm not sure about earlier cars, but the 80-82 had aluminium differentials as well as the batwing mount.
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Old 10-01-2011, 03:11 PM   #15
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Originally Posted by TheSkunkWorks View Post
Mike, just wondering if you've any update on this, as I'm looking at options while my rear suspension is out.

Man, you've got a good memory! I forgot all about this thread.

Things got delayed a bit due to my recent move from Florida to the midwest, so all I've got is a minor update. I've got a (wooden) spacer made up that is drilled for the C3 cover pattern, and I just need to make some simple measurements off of my spare D36 housing to get the cover vertical position defined. This isn't a big deal with the stock C3 suspension that doesn't use toe rods, but I want to duplicate the factory toe rod assembly position for my car. Right now it looks like the C4 cover can be drilled to allow at least 4 through-bolts or studs into the C3 bolt pattern. The rest may have to be (4) bolts attaching the spacer to the housing, and (3) bolts attaching the cover to the spacer (somewhat like wheel adapters). I'll know a little bit more when I get the cover placement finalized.
The C4 batwing is about an inch narrower than the C3 batwing so there shouldn't be any additional packaging issues. On my car I had to narrow the C3 batwing about 3 inches to clear the C4 suspension, so I will have to do a somewhat similar narrowing of the C4 batwing. An additional hassle for my application, but the narrowing will help offset the minimal weight addition of the spacer.
I'm catching up on garage stuff, so I should have a better update in the near future.

Thanks for your interest.
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Old 10-01-2011, 08:29 PM   #16
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Quote:
Originally Posted by damoroso View Post
If the spring is original, it's off an 81 or 82. If the spring isn't, it could be off an 80 as well. I'm not sure about earlier cars, but the 80-82 had aluminium differentials as well as the batwing mount.
.

thank you,....... I bought it years ago intending to lighten up my 68`s rear end...the spring is original so by your comment its a 80-82 as I had no clue....It was removed from a unknown Vette and I was afraid to sell it as I was not sure of the year
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Old 10-01-2011, 08:45 PM   #17
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Much appreciate the update.

I'm studying up on options for future upgrades while raising my diff, installing spherical TA bushings and going back thru everything else, and you came to mind. I'm going to wait on doing a batwing until I can also step up to either C4 or Guldstrand 5-bar link rear suspension, but it's never too early to start planning ahead, no?

FWIW, one idea I've run across you might consider is evolving your adapter/spacer into a mid-plate.

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Old 10-01-2011, 11:14 PM   #18
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Originally Posted by TheSkunkWorks View Post
Much appreciate the update.

I'm studying up on options for future upgrades while raising my diff, installing spherical TA bushings and going back thru everything else, and you came to mind. I'm going to wait on doing a batwing until I can also step up to either C4 or Guldstrand 5-bar link rear suspension, but it's never too early to start planning ahead, no?

FWIW, one idea I've run across you might consider is evolving your adapter/spacer into a mid-plate.
Not sure I'm following you on what a mid plate is.
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Old 10-01-2011, 11:14 PM
 
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