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I'm building a new frame for my C2 starting out with a 82' frame upgraging to the C4 D44. Looks like the location is the same. Wheelbase measures the same an with some minor adjustments the batwing fits in the existing frame mounts although bolt centers are off. Looking for help locating the control arms on the frame. Pictures always helpfull. Would also love to do front frame clip to upgrade front suspension the C4 or 5.
From: I tend to be leery of any guy who doesn't own a chainsaw or a handgun.
Originally Posted by 66silver
I'm building a new frame for my C2 starting out with a 82' frame upgraging to the C4 D44. Looks like the location is the same. Wheelbase measures the same an with some minor adjustments the batwing fits in the existing frame mounts although bolt centers are off. Looking for help locating the control arms on the frame. Pictures always helpfull. Would also love to do front frame clip to upgrade front suspension the C4 or 5.
The suspension for the C4 (and probably C5) is a different track width than a C2/C3. You have to ask yourself whether you want to use C2/C3 or C4/C5 wheels on your car. That determines where you mount the suspension, along with several other attending items. Think through carefully what you want before you do any cutting.
I wanted to use C3 wheels, not C4/C5 on my car, so I had to narrow the suspension. It was a lot of work, but externally the car looks stock.
body mounts and last 18-20 inches of the frame are different.
I was aware that I would need to clip the rear section of the frame or use mine as a pattern to fab new section as the bumpers mount is completely different. I also believe there will be some modifications to the front section. But since the goal is C4,5 front suspension all that could change to. My thought was to not cut up my original frame even though it needs rust repair. Bought rust free 82' frame for $350.00
The suspension for the C4 (and probably C5) is a different track width than a C2/C3. You have to ask yourself whether you want to use C2/C3 or C4/C5 wheels on your car. That determines where you mount the suspension, along with several other attending items. Think through carefully what you want before you do any cutting.
I wanted to use C3 wheels, not C4/C5 on my car, so I had to narrow the suspension. It was a lot of work, but externally the car looks stock.
Great pictures. Did you narrow front and rear suspensions? Looks like you had a lot of fab work in the front.
Was looking for pictures of the trailing arms mounting postion. With no load on the suspension its hard to tell where to locate the arms I may band the rear down to get a location.
The suspension for the C4 (and probably C5) is a different track width than a C2/C3. You have to ask yourself whether you want to use C2/C3 or C4/C5 wheels on your car. That determines where you mount the suspension, along with several other attending items. Think through carefully what you want before you do any cutting.
I wanted to use C3 wheels, not C4/C5 on my car, so I had to narrow the suspension. It was a lot of work, but externally the car looks stock.
do you have any photos of how you mounted the dog bones to the frame. Trying to put a c4 irs in my 76 right now. Tried messaging you but the forum won't let me
do you have any photos of how you mounted the dog bones to the frame. Trying to put a c4 irs in my 76 right now. Tried messaging you but the forum won't let me
That user 66silver hasn't been active on the forum since March 2012. Take your question to the C2 section starting a new thread or searching there!!! User 69427 is around very often and if he sees the thread will likley respond.
It says 69427 was active on July 14th. Thats only 2 days ago. I just can't seem to message him. It won't let me.
Your install will likely be difficult if you can't sort Jan 14 from July 14. You haven't been around long enough to have access to PM function. @69427 has been tagged by me and he'll be notified that someone is looking for attention.
Your install will likely be difficult if you can't sort Jan 14 from July 14. You haven't been around long enough to have access to PM function. @69427 has been tagged by me and he'll be notified that someone is looking for attention.
From: I tend to be leery of any guy who doesn't own a chainsaw or a handgun.
Originally Posted by WVZR-1
Your install will likely be difficult if you can't sort Jan 14 from July 14. You haven't been around long enough to have access to PM function. @69427 has been tagged by me and he'll be notified that someone is looking for attention.
I've been tied up in the garage, but I got your tag.
From: I tend to be leery of any guy who doesn't own a chainsaw or a handgun.
Originally Posted by Simplicity9
do you have any photos of how you mounted the dog bones to the frame. Trying to put a c4 irs in my 76 right now. Tried messaging you but the forum won't let me
I would have to look to see if I have any of those old pictures stored somewhere. Storing them on photobucket ended up not being helpful. I'll search through some dust covered files this evening.
I would have to look to see if I have any of those old pictures stored somewhere. Storing them on photobucket ended up not being helpful. I'll search through some dust covered files this evening.
Yeah basically just trying to see where your diff is mounted (forward and backward). All the photos, like you said, from 10 years ago no longer exist on photo bucket or other sites like that.
From: I tend to be leery of any guy who doesn't own a chainsaw or a handgun.
Originally Posted by Simplicity9
Yeah basically just trying to see where your diff is mounted (forward and backward). All the photos, like you said, from 10 years ago no longer exist on photo bucket or other sites like that.
These are the only two pictures I've found so far. As I mentioned in a previous post, I wanted to keep using stock C3 wheels, so I narrowed the C4 suspension width by 1.5" on each side. That then determined where I put the plates that take the acceleration and deceleration forces from the suspension dog bones. I still used the dogbone brackets because I wanted the option to remove and modify the brackets if I wanted to change something about the rear geometry/anti-squat.
I kept the stock C3 differential because they're strong, inexpensive, don't require underbody butchery, and I had several spares of different ratios onthe shelf. Also, I initially used a (narrowed) late C3 batwing as it is lighter than the steel crossmember and cast iron differential cover setup. A few years later I modified a C4 D36 batwing to fit my C3 differential, taking another 5# off the car.
I have 3.5" OD aluminum halfshafts in the final assembly. The original C4 halfshafts are IIRC about .093" wall thickness. The driveshaft company I contacted also had .134" tubing available, so I went that route. I don't drag race, so these shafts have been durable enough for a lot of track miles and the occasional autocross.
There's more details, but these are the highlights.
Last edited by 69427; Jan 17, 2026 at 08:43 PM.
Reason: Added content.
These are the only two pictures I've found so far. As I mentioned in a previous post, I wanted to keep using stock C3 wheels, so I narrowed the C4 suspension width by 1.5" on each side. That then determined where I put the plates that take the acceleration and deceleration forces from the suspension dog bones. I still used the dogbone brackets because I wanted the option to remove and modify the brackets if I wanted to change something about the rear geometry/anti-squat.
I kept the stock C3 differential because they're strong, inexpensive, don't require underbody butchery, and I had several spares of different ratios onthe shelf. Also, I initially used a (narrowed) late C3 batwing as it is lighter than the steel crossmember and cast iron differential cover setup. A few years later I modified a C4 D36 batwing to fit my C3 differential, taking another 5# off the car.
I have 3.5" OD aluminum halfshafts in the final assembly. The original C4 halfshafts are IIRC about .093" wall thickness. The driveshaft company I contacted also had .134" tubing available, so I went that route. I don't drag race, so these shafts have been durable enough for a lot of track miles and the occasional autocross.
There's more details, but these are the highlights.
so it looks like since you have the stock diff then its obviously in the stock location. Do you know where your Instant center for your dogbones was relatively. Im keeping stock c4 width, and a stock c4 diff. I have a older c3 diff laying around but didnt realize you could use the iron diff with the c4 suspension.
Also was curious at ride height how much space there is between top of knuckle and bottom of frame.
From: I tend to be leery of any guy who doesn't own a chainsaw or a handgun.
Originally Posted by Simplicity9
so it looks like since you have the stock diff then its obviously in the stock location. Do you know where your Instant center for your dogbones was relatively. Im keeping stock c4 width, and a stock c4 diff. I have a older c3 diff laying around but didnt realize you could use the iron diff with the c4 suspension.
Also was curious at ride height how much space there is between top of knuckle and bottom of frame.
Thanks for the pictures aswell!
Well, the easy question first. There's not a lot of room between the frame and the knuckle, the actual amount dependent on your chosen ride height. I ended up lowering my ride height over the years, and I've got perhaps a couple inches. Knowing what I know now, I would have cut and raised the lower surface of the frame area above the knuckle to gain another inch of space.
Regarding the instant center, I just copied the dogbone angles of my '84 to use as a starting point. The C3 and C4 wheelbases are within two percent of each other, and my engine is lighter than an iron small block, so I figured the '84 geometry was acceptable as a starting point. I can remove the stock front brackets in case I wanted/needed to make a geometry change. One item I've wanted to play with if I had excess spare time is using the long wishbones on all four locations instead of two long and two short. It does seem that C4s have excessive wheelbase change in the rear due to the stock dogbone configuration.
Using the C3 differential with the C4 batwing required a lot of aluminum cutting, welding, and drilling, but worth it to me to have a strong differential but with lighter vehicle weight. And I'll admit, I like the look of aluminum on a Corvette.
Well, the easy question first. There's not a lot of room between the frame and the knuckle, the actual amount dependent on your chosen ride height. I ended up lowering my ride height over the years, and I've got perhaps a couple inches. Knowing what I know now, I would have cut and raised the lower surface of the frame area above the knuckle to gain another inch of space.
Regarding the instant center, I just copied the dogbone angles of my '84 to use as a starting point. The C3 and C4 wheelbases are within two percent of each other, and my engine is lighter than an iron small block, so I figured the '84 geometry was acceptable as a starting point. I can remove the stock front brackets in case I wanted/needed to make a geometry change. One item I've wanted to play with if I had excess spare time is using the long wishbones on all four locations instead of two long and two short. It does seem that C4s have excessive wheelbase change in the rear due to the stock dogbone configuration.
Using the C3 differential with the C4 batwing required a lot of aluminum cutting, welding, and drilling, but worth it to me to have a strong differential but with lighter vehicle weight. And I'll admit, I like the look of aluminum on a Corvette.
hmm, never thought of doing that to the frame but i might as of now i think i have like 2-3 inches of room at my desired ride height. (I think frame is around 6 inches from ground)
Onto the rear diff, I dont mind doing all the cutting and aluminum welding ad thats no problem for me. I might do it if I blow up my aluminum diff. Just not sure how hard I can beat on it. Not planning on launching the car much but burnouts and very spirited driving yes.
For instant center time not sure what to do yet. Going to have 3 different settings to mount the dogbones but just need to figure out where I should have it stock. Was thinking the bottom arm being parallel to ground and then top arm down at a slight angle. Best for road racing and autocross i think. (Still learning alot about suspension)
C4 D44 swap into c3 frame
