85 Vette rearend in a 68 Question???

[juveteach]

Hello All,

I have been working on a project at my school with my students for a while now.(Autoshop Teacher) I was wondering if anyone on here has ever tackled a vette IRS rearend into a 68 camaro?
My question is this...If the "BATWING" is ridgidly mounted to the frame and the pinion mount is ridgidly(I like that word) mounted to the frame, "HOW MUCH MOVEMENT" i.e. deflection in corners or acceleration other than shocks and tires should one expect? I want to know this because during a "BENCH RACING SEGMENT" in class I got to thinking about my "BATWING" mounts.
Should I or Should I not put in a gusset?
All that for my little question...sorry tend to ramble.

I have provided some pictures for ya'll to look at and send me your thoughts.
In these pictures you can see where we have cleaned off the paint to install 1"x1" squares to act as our gussets. Is this a necessary improvement? I am really tired of thinking about it and I'm going to leave it to you.

[oestek]

Do it.

[aosborn]

That is a great shop project! I have done many of these installs and a couple of things come to mind. The double shear plates you have on the ends of the third member appear to be 1/8" plate. I typically build them out of 3/16" and "wrap" them around the corner of the frame or sub-frame so at least some of the bracket is in shear. I can't tell in the photos if yours are like that, or just welded to the bottom of the frame. If the mounting plates don't hang far below the frame, gussets probably won't be necessary. Secondly, I always use some kind of bushing to mount the pinion to the frame. An easy way to do it is to install a 3/4" urethane bushing that hangs from the frame off a crossmember, and then build a double shear bracket for the pinion that will allow you to connect to the bushing. There will be movement there in the factory rubber bushings on the end of the third member, and you should allow for movement at the pinion. If you design the bracket properly, you will be able to adjust the pinion angle also if necessary.

When it is at ride height, make sure the toe adjusters don't hit the frame in bump travel. If this is a concern, you can C notch the frame for clearance. If you need more room than that, e-mail me and I will give you some specifics on how to solve that problem.

Are you going to use the composite transverse leaf spring?

Andy

[juveteach]

"The double shear plates you have on the ends of the third member appear to be 1/8" plate. I typically build them out of 3/16" and "wrap" them around the corner of the frame or sub-frame so at least some of the bracket is in shear. I can't tell in the photos if yours are like that, or just welded to the bottom of the frame. If the mounting plates don't hang far below the frame, gussets probably won't be necessary."

I assume that you are talking about the mounts for the "BATWING" the outter most mounts. (SEE new pictures) Is this Wrapping and shear what you are speaking of? What do you think abou the gussets now after the pictures?



I also like the idea of a rubber mount to the pinion but we are very tight on driveshaft clearance. Any ideas? I guess I can cut the tunnel out and make it taller, and "C" notch the crossmember.

[perry mitchell]

Nice project. Wish I had that much fun when I was in school. I did this same installation using an 88 Vette IRS in our ZR/28 Camaro a few years back. I agree that you should have used 3/16'' material for the batwing mounts but if you adequately reinforce the sides, you should be alright. I believe Chevrolet used 1/8'' material but it was stamped out which provided reinforcement around the edge. I believe if you swap out the factory rubber from the ends of the batwing for a harder graphite bushing, the need for any bushings at the pinion will not be necessary. It worked for me. Our car sat as low as possible without modifying the driveshaft tunnel, No need to go lower. It appears you are going to use coil over shocks as indicated by the square tube representing the shock. NICE JOB!

[juveteach]

Hey Perry,
Nice car!! Was it worth all the work? Did it handle and perform well? We are using the automatic rearend(small one)which one did you use? We are planning on a semi-stock LS1 engine and 6 speed trans. Will this thing handle more power than that engine is capable of giving in case we add more to it? This is a school so its seriously LOW BUCK indeed. This is my car and everything comes from my teachers salary. I'm just wondering if it was worth the expense. Did you car handle well, as my kids say will it do a NASTY burn out? We are trying to do this for 15K. Think it can happen? Already around 8k so far. Any feed back or more install pics would be great.
Thanks.

[aosborn]

[/quote] I assume that you are talking about the mounts for the "BATWING" the outer most mounts. (SEE new pictures) Is this Wrapping and shear what you are speaking of? What do you think about the gussets now after the pictures? [/quote]

Those photos show the batwing mount much clearer. The design looks fine, it should hold up ok. Next time I would still go with thicker material.

I would try to put some flex into the pinion mount though. If you have flex on the ends of the housing, and none at the pinion you stand the chance of cracking the housing over time. If clearance on top is an issue, how about making a bolt-on mount that hangs off the side of the housing? That way you could install a bushing off a crossmember down to the bracket on the side. You should have room to do that. It is a little hard to describe, but you have got this far, you should be able to come up with something.

Andy

What about the composite spring?

Attached are some photos of a 55 Chev chassis I did years ago. It might give you some ideas.

[Samckitt]

Nice project. Wish I had that much fun when I was in school. I did this same installation using an 88 Vette IRS in our ZR/28 Camaro a few years back. I agree that you should have used 3/16'' material for the batwing mounts but if you adequately reinforce the sides, you should be alright. I believe Chevrolet used 1/8'' material but it was stamped out which provided reinforcement around the edge. I believe if you swap out the factory rubber from the ends of the batwing for a harder graphite bushing, the need for any bushings at the pinion will not be necessary. It worked for me. Our car sat as low as possible without modifying the driveshaft tunnel, No need to go lower. It appears you are going to use coil over shocks as indicated by the square tube representing the shock. NICE JOB!

Nice motor!

[juveteach]

Hey Andy,
Thanks for the input. No I have plans to run a set of coilovers instead of the composite spring. Have you hade good luck with the composite spring. My friend who builds cars for nascar says a good set of coilovers will do just fine, so that is the way I was going. What do ya'll think?

Thanks for looking!!

[zbugger]

Send a PM to MrQuick. That or I can call him and let him know you want info on this. We did it a couple years ago.

[aosborn]

Hey Andy,
Thanks for the input. No I have plans to run a set of coilovers instead of the composite spring. Have you hade good luck with the composite spring. My friend who builds cars for nascar says a good set of coilovers will do just fine, so that is the way I was going. What do ya'll think?

Thanks for looking!!

Coilovers will work just fine. Not many (if any) folks run the composite springs in part because it can be difficult to track down the proper rate, difficulity of ride height adjustment on the front end, and cost. I have had great success with composites, they are very responsive especially over small road bumps at speed, weigh next to nothing and virtually never sag. They also have the added feature of transfering load while cornering, sort of like a small anti-roll bar.

Andy