Another corvette IRS conversion
 

Well, after some hefty research, on this site as well as others, and a fair amount of cash, I've got my camaro, and my donor corvette. I will be installing the Independent Rear Dana 44 from the Vette into my life-long 84 z28 project. Good thing there is actually some good material out there, I'm sure I will be using it! The new and old parts should be waiting at home by now, so check it out as it gets going!

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Sorry guys, I can't seem to upload images from my phone, ill get them up soon

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Subscribed. I am interested to see your design.

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Here's the car!

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Love the tire stand!.... Er log!

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Sorry it's taken so long. I'll post pictures of where I'm at next week. I've got all the brackets cut out, and had to take a pause for work... (Work in Alaska). Because of my nature, with wanting to do it only once, I bought banski's control rods, toe rods and strut rods. These aren't really necessary but it will give you room for error, not that you want many! Also, in leu on not putting ugly on the car, I spent about 40 hours a work polishing the batman wing, and diff cover. A well spent work week......

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Awesome! I want to do this myself as well. Please, for the sake of all of us. Don't get butt hurt over some comments and ragequit the thread.

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That's going to look sick! Subd.

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Looking forward to the build pics

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So here's the 1st mockup. The wing is at a machine shop getting the bushings pressed in, I tried everything and the poly just laughed at me. Axles will be here soon, but there's no problem using stock for the install. I spent a week researching a brake upgrade, but there's no way to do it at a decent cost if you want to keep your e brake. Replacing the entire stock setup can be done for as little as 200, and they are still better than camaro brakes. One thing I am noticing is how lightweight this setup is. One of the worst places to lose weight on a camaro, but assuming you have gone this far with your car, you will adjust your center of gravity enough with a fuel cell and battery relocation to make up for lost weight in the rear. Adding the control arms, pan hard bar, and torque arm on a stock setup, it's a huge difference! The welder will fire up tomorrow....

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I got the fuel tank in today. Another part I didn't need, but mine hadent had fuel in 20 years, so it's gone. Nast perf makes a tank that straps in, and adds room. So after welding shut my cuts, I'm mounting this tank, and then will weld in pads similar to the last one done. My advice to others would be. So far, this is not a hard project, if you can weld it's yours. Suspension geometry will play a factor and also easy, ill post everything I'm doing. All cuts you make need to be welded closed for strength! You basically just cut off the pre existing spot welds, those need to be replaced! I took them
All down to what frame rails we have, you will want to do as much structural
Rebuilding as possible!

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https://cimg1.ibsrv.net/gimg/www.thi...4f0940b5c8.jpg


Fuel tank straps

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https://cimg6.ibsrv.net/gimg/www.thi...37f2c93276.jpg


And here's my installation mess. Looks bad but only a few brackets and bolts to go now!

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Surprised to see this thread is nearly dead...I went for a datum bar, but as you can see I have no lift, and that equals zero room. Eventually I bumped it enough that it was going to do more harm than good. So I started mocking everything up last night. A test fit to see where things are going to end up has been key. You can't do it enough. I'm wondering now if I will run into issues with the fuel cell. But either way, it will fit. My goal is to have the pads under the frame rails my tonight. A very useful tool has been a laser level, and a plum bob! The more I get into this the easier it is to see that it's not that hard of a project!
https://cimg6.ibsrv.net/gimg/www.thi...2b2766583c.jpg

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I am 1/3 of the way into a C4 IRS into my 91 Firebird. I started 2 years ago and then moved on to other projects. I can't wait to get back into it honestly and threads like this make me want to quit my job and finish it, lol. I just bought another project that will be a daily driver, then it's the truck cab floor, and the LR4 into my 92 Firebird, then I can move onto the 91 again!

I have only been using a plum, small level and a tape measure on the floor. I use large pieces of cardboard under the car and transfer all my points to that. I decided to wait to buy all the fancy suspension pieces until I finish the swap, or cat the car into pieces and get rid of it

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That's what I have been doing with the cardboard too. I'm lucky to have months at a time off work so I can put in a lot of days , if you don't mind scooter, show some pics of where you're at, more reference is always good!

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How much of the doner vet do you have?

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I didn't take many while I was in the process and the car is filled with stuff and underneath is filled too, lol. I ran out of floor space, so parts coming off other projects got placed where I could, including the underside. I haven't really done much except cut out all the sheet metal around the spring pockets by cutting ALL the spotwelds out. I plan on sectioning the rear frame rails and welding in the rear frame from the corvette so I didn't have to figure out any angles or measurements really. I just have to make sure the pinion angle is right and that the wheel is centered front-to-rear and the ride height to suspension travel area is close for ride height. I bought a front end wrecked 94 with a D36 and cut it in half essentially. I figured it was easier that way, plus I would get a little more frame strength in the rear since the rear crossmember is still there. I may have to cut the crossmember a little to get the stock gas tank in though. It is also retains the mounting points for the rear mounted sway bar, and I can go to a coil over setup instead of the leaf with minimal work. Once I get back into it, it should go pretty quick, but the car had a fire, so it will take a lot more than that to get it back on the road. The fire was the only reason I even started in the first place, nothing more to lose than a little money (not out much $$ from parting the 94 C4), some garage space and a little time. My friends keep telling me to cut the car up and move on

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I've been subscribed and watching the whole time. This is my all time dream mod when done in the capacity it would all hold up to extreme road racing. I've been dreaming about it for over 10 years and I watch all the threads on this that come up.

A Dana 44 solid rear axle like the Firehawks had is my backup plan haha! Just need to inherit that trust fund lol.

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I don't have much of the doner vett left, other than hood and a few boxes laying around I deemed not valuable. So you are going a different route than I am scooter. I agree with the backhalf strength. I probably would have done that if I didn't have a full cage. I really beefed up the frame rails though so far. I just got done plating the bottoms of each frame rail with 1/8 inch after welding up all the seams. This will give me something to build off and it's ready to start making brackets!

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I didn't even think of using a laser like that. that is pretty sweet. Don't forget that the diff axle stub is forward of the wheel center line

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I caught that thank god! The laser is key to an easy life. Kind of a spendy tool but I use it somehow once a week in my life. Just squaring things up and I'll start the brackets tomorrow!

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What laser setup are you running? I may pick that up once I get back on it

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It's fun so far! The axles will be a weak point, and when one breaks the camber loss isn't pretty. Atleast you won't get rear steer like earlier versions of the irs, but there's plenty of great axles available aftermarket. I was dreaming about it for a long time too, Infact I think I thought too long about it and that's why I hadn't done it. Grab yourself a few beers and cut out enough the first day that you are obligated to keep going! I'm going to try to take as many pictures as possible and keep up with the details and get it all on here, that way there will be finally some good material for anyone wanting to do it!

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I thought the axles were only really a weak point for drag racers?

Haha, yeah that would commit me lol. There is a reason I'm not married lol.

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Not married either lol, my girlfriend made a comment the other day that the guys on tv build cars faster than I do, so I think I'm single again haha. I talked to several companies and people about those axles, and the general thought is that they aren't strong enough for much more than the stock output of the vette. Probably untrue, but when they break, your wheel will get crammed into the back of your fender so I figure 500 bucks is cheap insurance. Im running 650 hp so I definitly have to.

Re: Another corvette IRS conversion
 

Subscribed!

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https://cimg4.ibsrv.net/gimg/www.thi...8b665eb9d7.jpg


Here we go. Here's the deal. If you want IRS, unless you are much more crafty than I, to maintain any kind of functional geometry and ground clearance, your back seat is gone! If you manage to keep it, it will likely be too dangerous for somebody to ride back there. I went with a similar set up as the iroc from the past. I will make a torque arm though, to gain some leverage on the diff. There will be a forward mount as well. I have 4 bars into another 1/8 inch plate here, plenty rigid to tie the rear bars in after removing so much! I did this BEFORE CUTTING! While the car was on solid level ground!

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Interesting build. I'm watching...

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Well guys I hopped on my ship to Alaska, time to go make some monies.... I won't stall on the project so check back in a month or less for more updates

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What do you do that you're going there? I really want to go to Alaska, to live but I need to find a job there first, lol

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Engineer on a Towboat.... Not exactly the dream but pays the bills... Sorry it's taken longer than expected, home in 10 days and back to work on it!

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Nice work ! zombie thread revival. Its quite possible to retain your rear seat doing this. just need to fab a torque arm setup that simulates the stocker.

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Yes you could do with a torque arm, but the control rods come way into the cab, and if you want correct geometry, you can't get around that.

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Heads up, this isn't dead! Just have been enjoying sunshine in a state where it rains every day! I have made some progress and will get back on it in the beginning of October.

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Why are you guys doing Dana44's. Why not a 68-79 rear end?

I'd think the fabrication would be easier. No aluminum parts. And they are quite stronger.

It's held in by basically a crossmember that is flat. You could reproduce that with some box steel in about an hour.


https://cimg7.ibsrv.net/gimg/www.thi...ef38d13cdd.jpg


The only other attachment is two lower control arms, which again are steel. You could cut the vette arms half way and weld some thirdgen tubular arms to them.




https://cimg3.ibsrv.net/gimg/www.thi...b8cffeb6ba.jpg


Guys have been putting these in other cars for years on other forums. I'd think putting one in a thirdgen would be very straight forward, and quite safe.

-- Joe

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Because aluminum is shiny!! Lol. I'd imagine he got a good deal on the donor car, and I'm sure the less mileage on a newer rear were prolly a factor in the decision. That shiny aluminum does look impressive when people look under the car though.

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That's a valid answer, for show.

I had a C4, and the front suspension is remarkable, but the rear IRS is junk.

between all the attachment points, weak IRS, and expensive gears I just figured it would be easier and better to use the earlier IRS. Also, they make coil over kits for them, fiberglass leafs, etc.

-- Joe

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I thought they were pretty much junk?

Also, for me, I got my Dana 44 setup complete for around $400 or less? It's been a while so I don't remember what I am actually out of pocket anymore. I bought an 86 Vette with a manual transmission, then I bought a 94 front end wreck auto, swapped the rears, sold the 86 for what I paid for it, maybe $100 more and parted out the 94. I still have some parts from the 94 to sell still and I have the entire rear suspension, brakes, DS, and c beam.

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What is wrong with the D44? I know the 36 is very weak.

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They both are. The difference between the 36 and 44 is very minimal. 7.8" vs 8.5" ring hear.

The case still flexes, the pinion tries to walk up the ring gear and it explodes.

The shafts break.

The fast C4 guys run 9" rear ends.

The fast C3 guys run stock rear ends.

Variations of course exist, some diffs built by eaton, others not, different clutches in 68-75, vs 76-79, but generally speaking the C3 diffs are way stronger and can be built up even better.

-- Joe

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7.8 to 8.5 is a subtantial increase. My second gen 10 bolt it will hold up to everything I will ever do to it, but a 3rd gens 7.5/6 break pretty easy, so that can't really be a factor in the strength of the D44 being "junk".

I can understand the aluminum case being the issue though.

And I am thinking your line of though is drag racing? The people doing auto cross and road race, and are going fast, are still using the IRS in the C4 from what I have been reading. I don't think the intent of going to an IRS is for drag racing.

At any rate, I hadn't read up too much on the C3, but I think the general concensus is that people don't think of them as anywhere near as good as a C4 rear for handling and they are a lot heavier.

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For me it wasn't strength it was weight. Also the C4 setups come from the factory with vastly superior brakes and a fiberglass leaf. Granted you can change that out on a C3 setup but it's just added cost. I don't know much about the C3 trailing arm geometry, but I don't have a problem with the late C4 geometry. In my area there are many trememdously successful C4 autocross and road race cars, they work well.

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C4 brakes are a downgrade from the C3. The C3 has 4 piston fixed calipers and thicker rotors.


This is one of the biggest gripes amongst Corvette guys when the C4 first came out.

You've got to remember, the C3 had some pretty wicked engines in the late 60s. By 1984 when the C4 came out, they were slow turds.


I'll give you the weight, the C4 IRS is much lighter than the iron C3 IRS. And for an autocross application you might not need the strength.


I was just curious if anyone had considered the c3 setup.



-- Joe

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A C4 will out handle a C3 every day of the week. My C3 rides like a stage coach.

But, a lot of that is the front end.

Yes, I'm thinking more of a drag racing application. I'm sorry. I hadn't really considered the auto cross aspect.

I don't know if the C4 IRS is superior 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

Re: Another corvette IRS conversion
 

scooter
wouldn't happen to have a ZF trans VSS and speedo gears would ya?