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A C4 will out handle a C3 every day of the week. My C3 rides like a stage coach.
ior to the C3 in regards to cornering or autocross, I just think dimensionally it would be easier to graft into a thirdgen (since I've seen it grafted into a bunch of other car lines), and i think the center section is much stronger for guys with epic power .
-- joe
Interesting to know your opinion. I've never been in one and not seen many in any racing event except at E-Town at the fast drags. Early 70's, blew a radiator hose spun around a few times and put the nose into the wall.
It does look like an easy donor, but the design doesn't look too much different from the C4 from the pictures you poseted. What holds the knuckle from moving laterally? is there a lower control arm I don't see in the pictures?
Also you're really on about the brakes. I think my friend said back in the 70's and early 80's the hot thing was to put those calipers from the Vettes on the Camaros and Novas.
Interesting to know your opinion. I've never been in one and not seen many in any racing event except at E-Town at the fast drags. Early 70's, blew a radiator hose spun around a few times and put the nose into the wall.
It does look like an easy donor, but the design doesn't look too much different from the C4 from the pictures you poseted. What holds the knuckle from moving laterally? is there a lower control arm I don't see in the pictures?
Yes, sorry. So the diff attaches to the crossmember. That bolts to the frame on either side.
Then you've got leaf springs connecting to the lower control arm. The lower control arm then mounts to the frame just like a thirdgen.
i chose the c4 rear for several reasons. Halfshaft strength wasn't an issue as I was replacing them anyway.... The very little unsprung weight was appealing. As far as shiny, yeah it looks great, because I spent about 50 hours polishing the diff wing alone. There is a difference in width too I believe, the c4 is almost exactly the width of a stock third gen.... I had also previously built a cage and it turned out to be perfect mounting points for the c4 setup, so that was already out of the way.... Something that leaned me toward the c4 axle also was the changes that were made from the c3 to prevent nasty rear steer in the event of parts failure.... Which I was sure will be a possiblity because this car is built to be my toy. Also you guys nailed it with getting a good deal.... I managed to snag one without a title, sitting in a garage with 22,000 miles that was beat up from being vandalized for 1500. Not saying the c3 is inferior, buy the stars aligned and I got a c4
I was just at the Corvette show/swap in carsile PA this past weekend. There were hundreds of complete IRS assembles for sale for pretty cheap. The IRS C3 looks like a more viable option as long as you can fab the Upper support and tie it into the rear subframe strong enough.
I like that idea actually... But too much hassle for a car like mine that sees a few hundred miles every 5 years lol. But for ***** and giggles i wouldn't mind giving it a try lol.
Do NOT use the C3 setup, it's not a good option at all. It has severe toe control issues wearing stub shafts resulting in even more camber and toe control issues. For a somewhat acceptable operating sytem the suspension needs to be rather stuff and the halfshafts near horizontal (just below) at ride height so that any movement does not alter the lateral halfshaft component too much (angular effect on vector components), this is what changes the toe and gives a toe OUT result from anything other than horizontal, in other words rear control issues. This makes diff placement critical, on the c3s to lower the car and get an acceptable geometry the solution is to cut the crossmember and raise the diff to correct the halfshaft angle.
As for the trailing arm mounts, they ened to be wide and you msut be able to shim them for toe setting, or use the guldstrand jack bolt setup.
Do NOT use the C3 setup, it's not a good option at all. It has severe toe control issues wearing stub shafts resulting in even more camber and toe control issues.
Is this why my '75 seems to have in/out play ? I can grab the wheel and pull it in and out quite a bit. Figured it was a bad bearing.. ?
Yes, especially the iron units have this issue, worn stub shafts (wear against cross pin), they will wear down to where you can pull the whole half shaft out.
There are no conincal side load bearings in these units.
If it wears down to where the c clip falls out you have a real problem.
Yes, especially the iron units have this issue, worn stub shafts (wear against cross pin), they will wear down to where you can pull the whole half shaft out.
There are no conincal side load bearings in these units.
If it wears down to where the c clip falls out you have a real problem.
So Obviously new yokes will "fix" a broken diff, but whats the permanent "fix" so the problem doesn't happen?
I've been wondering what was wrong with the diff in my '75. My '79 diff is perfect. Thank you. At least now I know it's a cheaper fix.
The solution is hardened yokes but best is to fabricate a 6 link and take out the snaps then slightly preload tge stubs out. Geometry has to be spot on. I have cad drawings for a diy sheet metal multilink setup that van be set up with coil overs. It's also great for retrofit. The iron diffs can be built to be pretty stout.
The solution is hardened yokes but best is to fabricate a 6 link and take out the snaps then slightly preload tge stubs out. Geometry has to be spot on. I have cad drawings for a diy sheet metal multilink setup that van be set up with coil overs. It's also great for retrofit. The iron diffs can be built to be pretty stout.
Interesting.
I've always been under the impression that the C3 iron diffs are way stronger than the Dana44 in the C4's.
As you can see it's finally hung! With the help of centerline gauges, which are pretty much a must I've found, I went a different route with mounting the wing than I have seen, but I like this way as it will be much stronger. I removed the diff again and am assembling it to put it back in and start working on mounting the control rods. Prepare to take this thing in and out about 50 times! When you measure to get it lined up, remember the rear frame rails are off center.
Assembled the rear and got it all lined out. I used koni shocks for a third gen. I recommend using the vett shocks because they sit slightly inward due to a longer mount shaft, although I was able to get mine to work, the vett shocks will give much more room. After I installed the rear and made sure it fir well, I was able to add support to my new section of frame rails and then cut the forward part out so there was clearance to the shock. I am using a motor mount modified for the torque arm mount. I just got started with that so there aren't pics yet. Here ya go!
More bracing=absolutely. I have gone overkill already compared to others, but I've learned the hard way 1000 times not to do your gussets until you are 100% sure it's where you want it and working correctly! I haven't done the control rods yet because stupid me ditched the mounts with the parts car. Had to order new ones off eBay the other day. All I have done is some cutting. The issue there is that they pretty much have to extend into the car. They can not be shortened, or the angle chanced away from how it would be on a stock vett, or you will get binding and bad geometry pretty much everywhere. Because I have a cage, that will be the main support for the control rods. Unfortunately I had to ship out to Alaska for two weeks yesterday, but I'm back on it when I get home. 99% of the main issues worked out and it's basically welding from here. Easy!
where did you get those nice sl;eeves with clamps on the end? Tires are the wrong way around but it's probably just for a pic right? The more I see these swaps the more I want to do it on one of mine. I have a couple of C4 D44s and a bunch of rear susp. parts...hmmmm
Haha I was wondering when someone would catch that. Yeah I just threw them on to get things lined up and take a pic. The sleeves are made by banski motorsports. In my opinion they are a must because you may need the adjustability, they create a margin for error ( not that you want one )You will be into any swap for the price of bushings anyway. Oh and they look cool! However I won't lie I think I spent around 800 for the four you see in the pic and the four control rods. I'm good at fabrication, but this is way easier than I thought it would be. If I was working consistently I probably could have gotten this far in 4 or 5 days, that counts the time of sitting on a bucket wondering what I'm doing.
Tom Banski makes a nice product. I've got his stuff on my IRS setup as well. I have everything except the toe links which are factory adjustable so I kept them. I've run them on the street and track for quite a while. I did my swap 5 years ago at this point. They are still tight as a drum.
More bracing=absolutely. I have gone overkill already compared to others, but I've learned the hard way 1000 times not to do your gussets until you are 100% sure it's where you want it and working correctly! I haven't done the control rods yet because stupid me ditched the mounts with the parts car. Had to order new ones off eBay the other day. All I have done is some cutting. The issue there is that they pretty much have to extend into the car. They can not be shortened, or the angle chanced away from how it would be on a stock vett, or you will get binding and bad geometry pretty much everywhere. Because I have a cage, that will be the main support for the control rods. Unfortunately I had to ship out to Alaska for two weeks yesterday, but I'm back on it when I get home. 99% of the main issues worked out and it's basically welding from here. Easy!
The solution is hardened yokes but best is to fabricate a 6 link and take out the snaps then slightly preload tge stubs out. Geometry has to be spot on. I have cad drawings for a diy sheet metal multilink setup that van be set up with coil overs. It's also great for retrofit. The iron diffs can be built to be pretty stout.
Your snap rings are off, they are floating down in the diff somewhere and the stubs are shot. Time to fix that.
There should be onloy a hair of play on those.
If you have access to laser or water cutting and can properly weld (preferrably tig but mig will work just fine) I have some cutting patterns for a real nice C4 style IRS with upper links (so leave the c clips/snap tings off) that allow for custom camber adjustment, leaf spring and coil over option. Uses factory diff and huibs.
This is unrelated, but I took about 5 inches out of the trunk to make some room. You can't even tell, and there's so much more space under the car! Now I have a good place for the fuel pump
Here was after I cut the forward part of the wheel wells out. Everything had to go, there was no way to save any of the stock metal
I used 3/16 steel for the back panel and made a torque box as well, I cut clear to the rear part of the stock lower control arm mount to maintain correct geometry.
This is the finished product of the mount. There will be support from the roll cage hoop in the car as soon as I put on the control rods. I used the stock rods to fin my distance, and will use the stock bracket with the banski rods. You can hardly tell from the pic of what I did!
Here it is! It's time to rip it all back out and start building support!
Looks good! Got any inside pics of how u supported the tq boxes? Thought about taking out the rear trunk area as well. Ton of room if it's dept is reduced.
Looks good! Got any inside pics of how u supported the tq boxes? Thought about taking out the rear trunk area as well. Ton of room if it's dept is reduced.
I'll get you some when I get off my two week stint at work here. Sorry progress has been slow, there's many hours of welding in this project! Yeah I cut about 5 inches out of the trunk, up to the gas tank straps anyway. It's great because really the trunk seems just as big as it always has been, but you gain so much room under the car.
Any chance for an inside picture of the trailing arm area? I stopped a little after i cut some of the wheel well out, just wondering how much further I will have to go
Any chance for an inside picture of the trailing arm area? I stopped a little after i cut some of the wheel well out, just wondering how much further I will have to go
Two weeks until I can take more pics, sorry. I'll let you learn from my mistakes! I'm pretty confident in how I have it though. I will say as far as cutting, on the first side, I cut 3 times because I hadn't gone far enough toward the center of the car. It ended up, that you go about 1/2 inch from the frame rail. That leaves the entire bucket for the rear seat intact, but not by much. If you go less, the arms aren't straight, any more, and you will have to butcher a lot of the seat bucket. I just ordered my t56 magnum, which other than a driveline is the final chapter of the car! I've been working on this for 7 years, so once it's on the road, I'll let everyone know of the mistakes I may have made!
Two weeks until I can take more pics, sorry. I'll let you learn from my mistakes! I'm pretty confident in how I have it though. I will say as far as cutting, on the first side, I cut 3 times because I hadn't gone far enough toward the center of the car. It ended up, that you go about 1/2 inch from the frame rail. That leaves the entire bucket for the rear seat intact, but not by much. If you go less, the arms aren't straight, any more, and you will have to butcher a lot of the seat bucket. I just ordered my t56 magnum, which other than a driveline is the final chapter of the car! I've been working on this for 7 years, so once it's on the road, I'll let everyone know of the mistakes I may have made!
OK, cool. No rush. I have like 3 others projects I am working on too, lol
What are you doing about the nose of the center section? How are you going to support that?
Other projects? Come on, there's not time for other things! Diff carrier..... Hmmm. I've got several ideas, just have to wait and see what I come up with. I've been thinking about using something like a motor mount. I don't want a solid connection. I haven't put too much thought into it because I've been racking my brain with everything else. I'm sure a 6 pack will lead me the way.
08-26-2015, 01:13 PM
