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Corvette IRS Pics (LONG!!)


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I know this is probably too long a post so I promise I will make a quick and dirty page documenting the install. But, here are some shots. I have deceided to narrow the entire unit 3".

 

This is a front view showing the links in their "normal" position. How about the size of those halfshafts? They will need to be narrowed. That arm below the halfshafts is for camber adjustment. It will also needed to be narrowed but will be replaced by a custom-made unit with heim joints, $110/pr.

irs-front.jpg

 

This a rear view again showing the camber adj arm. Above that you see the tranverse, monoleaf, composite spring. It will also need to narrowed but will be replaced by a custom-made spring to my specs with an trick setup to adjust ride height and spring rate on either side, $450. Above the spring you see the toe-in/out adj rods. The will also be narrowed (cut and rethreaded).

irs-rear.jpg

 

This shows the IRS jacked up in position. The axles are not connected so everything is hanging low. The aluminum driveshaft is on the floor.

trial-fit1.jpg

 

Here is a view looking through the hole that was the spare tire well. Note that the triangulated mount bar is up against the horizantal frame rail. It also servers as the diff cover. Here you get a closer look at the toe adj rods and the leaf spring.

trial-fit2.jpg

 

Here is a drivers side wheelwell view. The end of triangulated mount bar ends up just below the well for the strut, so the hangar will be welded there. The shocks end up just below the frame rail next to where the brake line bracket is. The link is hanging low in this pic but it must be swung up so the bottom inside of the inner wheel fenderwell needs to be trimmed and a mount point welded up for it.

trial-fit3.jpg

 

Brakes need to be cleaned up but they are 11.5". I have the hangars mocked up and will get that to the machine shop tomorrow.

 

STAY TUNED

 

[ August 26, 2001: Message edited by: Scottie-GNZ ]

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Guest Anonymous

I was wondering that as well, its a fabulous solution, but when I asked for a quote on that year vette it was 1200.00 complete hub to hub. I guess its all relative, a swapped in rearend is going to be expensive anyway you slice it... icon_sad.gif

 

Regards,

 

Lone

 

PS: Thanks for sharing the pictures, you're the man... icon_smile.gif

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Thanks. Those kind words served up some inspiration when I went into the garage and looked at the "MESS" on the floor icon_biggrin.gif. I have started to take the IRS apart.

 

On the surface it seems like a very expensive swap, BUT, keep in mind that my goal is to not exceed $500 OUT OF POCKET (OOP). Keep the OOP in mind as I detail the expected cost. Because I had what I believe was a successful Z-car IRS setup, I was able to sell it and a 3:36 R-200 for a reasonable price. At least I think the buyer believes it is reasonable icon_rolleyes.gif. That sale will go a long way to achieving the goal.

 

Before I go into the actual cost, lets consider the problem and the alternatives. I had to have at least a 3:36 or taller to run the expected 125mph trapspeed in 3rd. I also wanted to have the confidence to launch the car harder with more HP and stickier tires to get the 60' down to 1.50. Although a LSD to replace the welded rear was not a must-have, it was nice. Ross has a NISMO 3.36 R&P for $300 (good buy) that would have cost me about $35 to ship, $400 for a LSD if I could find one and $200 to have the R&P swapped to the LSD and setup with new bearings. Out Of Pocket - ~$1000 and I would still have the stock CVs and 280Z stub axles. The other alternative was a solid rear. Selling my IRS would help but the cost of a 9" with the links, coilovers, etc or a 8.8 with stronger axles, links, coilovers, etc is way more than $500 OOP.

 

The cost of a C4 IRS varies wildly from 4-figures like mentioned to as low as $500 as in this eBay sale: http://cgi.ebay.com/ebaymotors/aw-cgi/eBayISAPI.dll?ViewItem&item=594583296

 

I will not say how much I sold my IRS for unless the buyer wants to. I paid "less than" $500 for the C4 IRS with the driveshaft and aluminum torque arm from a close friend. I have decided to narrow the entire unit 3". The listed rear track is 60.4" and the measured width from the outside edges of the tires is 70". The wheels are 16x8.5" with a 32mm offset, so there is ~3" from the inside mount point of the wheel to the outside edge. Add ~.5" for tire pooch for a total of ~3.5" on each side out from the hub. That makes the hub-to-hub measurement ~63". Hope that made some sense icon_rolleyes.gif. I have 15x8 Weld Wheels but have to go to a 16" because of the big brakes. The 16x8 Weld has a 5.5" BS and with a .5" pooch yields a total of 3" on each side. My Z IRS tire-to-tire was 66" so I need to get the C4 IRS hub-to-hub down to 60", therefore it has to narrowed 3". With me so far? icon_biggrin.gif I also have my eye out for any late Z28 16x8s which have anywhere from 45-55mm offset and are cheap.

 

So, on to the cost. If you are building a Z with bigger flares than mine, you do not have to narrow it. I just got a price from the machine shop for making the hangers for the tri-bar and it is $70/pr. With a little sheetmetal trimming, those get welded to the frame rail at the bottom of the strut tower. The halfshafts have to narrowed. I have not priced this yet but basically the u-joint yoke has to be cut off, 1.5" taken out of the tube and rewelded. With new Spicer joints I am estimating $150. The leaf spring has to be narrowed. A Vette shop in Tampa makes custom springs to any length or spring rate for $275 with poly bushings. For $450 you get the spring plus ride height and spring rate adjustability on either side. The lower camber adj bar must be narrowed. Instead of cutting and rewelding cast aluminum, they sell a steel replacement with adj ends, $110/pr. The toe adj rods must be narrowed and I estimate $50 to cut 1.5" off the end and rethread. The lower inside of the inner fenderwell must be cut and a mounting box welded in to mount the suspension links. I need to fab up a way to tie down the front of diff. Will use the combo of a stock Z diff x-member and the big aluminum torque arm that came with the rear. If not, I make it from scratch with 3/8" flat or box. Probably cost me $50. When I am done, $50 to have the rear-end aligned. Have not addressed the driveshaft yet. All welding will be done by my daughter's boyfriend icon_biggrin.gif.

 

Add that all up + what I paid for the IRS and subtract what I got for the Z IRS and R-200 and that is my OOP. So, what do I actually get? Taller ratio that I need with a LSD, 100lbs lighter, 11.5" brakes, infinitely adjustable rear suspension, and if I elect to polish it up..... Take a look at the top pic and notice the right side of the diff and a spot on the halfshaft icon_biggrin.gificon_biggrin.gif That took 30-secs with a Scotch-Brite.

 

Before you conclude it is too expensive, make sure it is what you need then price out fully the alternatives.

 

Yeah, I know, I am writing the web-page in a post icon_biggrin.gif.

 

[ August 27, 2001: Message edited by: Scottie-GNZ ]

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Scottie, yeah the buyer thinks he got a fair price. Some might think I paid too much, but most others (me included) would probably agree that a proven, complete, no need to hit all the local junkyards for six months straight, rearend package (driveline to disc's) was worth the price.

 

What was the price, well lets just say that unless Scottie paid $499.99 (which is under his stated $500) and his quotes for the needed work hold true, the chances of staying under the projected $500 out of pocket expense looks good.

 

Even with the UPS shipping cost ($200) the deal still seems pretty darn sweet to me. I now know my rear suspension is good to the low 11's (w good tires) so now I can focus on the engine and tranny.

 

How many of us have or have had cars with way more engine than the suspension can handle? Big-old smokeee burn-off's were cool in High School icon_cool.gif but now it's all about 60 foot times icon_biggrin.gif

 

Let me know when you got all the bugs worked out of this swap and in a couple of years maybe I'll need an even better rearend setup then what you just sent.

 

The Vette IRS swap looks great, keep us all posted on the progress.

Was I crazy to walk by and leave a complete Vette Limited Slip 3rd member (no half shafts or other suspension parts) at the scrap yard. Not a junk yard but scrap yard where they sell things based upon weight and material. They sell dirty aluminum for $.50 a lbs so what does a 3rd member weight 50-60lbs ($25-$30)

 

Scottie any thoughts on making a Vette 3rd member fit in the Z car and getting half shafts made.

 

At what point do NHRA rules prohibit IRS's? Is there a requirement for safty loops on the halfshafts?

 

Thanks again and keep us posted on the IRS swap process

 

[ August 27, 2001: Message edited by: Peternell ]

 

[ August 27, 2001: Message edited by: Peternell ]

 

[ August 27, 2001: Message edited by: Peternell ]

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Larry, unless you are just hung up on saving 25-30lbs, there is IMO, no advantage (except a LSD) to trying to swap a Corvette DANA36 3rd member into a Z. The custom halfshaft and stub axles would make the cost too high. The R-200 and the DANA36 are both 200mm and so I do not believe there is any gain there. The R-200 is plenty strong and you would be better off finding someone to make up a thicker CV or finding an OEM that can be adapted.

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Couple of things... Denny's can narow those shafts if you'd like,when I spoke t them about my driveshaft I also asked about that and they claimn to do it all the time. They can do SOME CV shafts too BTW.

 

Polishing - don't do it In the Florida air it'll just get nasty again unless you clearcoat it - BUX! I'd just have it powdercoated black and be done with it. I've polished lot's of aluminum and I've seen how the Florida air eats it up too - electrolosys (sp?!) is also VERY bad down there so watch that where iron and aluminum meet. My Father's pool latch was eaten up BAD down there and it had been anodized!

 

I cannot wait to see hwo this comes out Scottie. will you be doing the front brakes too in order to balance things out? any and all measurements you can document would be great. I don't anticipate doing this myself and am more apt to go R230 but I do have a friend who's offered to set me up should it become "necessary" down the road icon_smile.gif

 

Lastly, somewhere I've to pics from Carlisle of a complete 'Vette suspension out of a C5 held together by wire ties and the backbone piece. I'll try to dig that one up - it was wild! That stuff is fosale all over the place. People must be whacking the new 'Vettes at least as fast as they did the older ones (sigh). Goo luck Scotty, this is going to be awesome and can't wait to hear about that 10second time slip!

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irs-apart.jpg

 

Hope I remember how to put this puppy back together icon_biggrin.gificon_biggrin.gif.

 

Now that it is apart, the narrowing processing begins. This weekend I plan to hang the diff and as you can see I already have the hangers made. One is on the floor behind the driveshaft and the other is on the tri-bar on lower right of the pic, pretty much exactly how it will be mounted. The horizantal part gets welded to the frame rail just below the strut tower (A little sheetmetal trimming is needed) and the eyelet of the tri-bar comes up between the vertical pieces. Trial fit, drill the hole, round off bottom edges, weld, paint, voila.

 

Weighed the individual components and it is not as light as I first thought. It is only 80lbs lighter than the OEM not 100lbs icon_rolleyes.gif

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