Re: IRS conversion...coming soon
So since this was brought up, I've been looking into it more and more. Now I will state right out that I am very unfamiliar with the corvette IRS, so if there is something I'm not seeing, don't hold it against me. It does seem like a completely feasible swap, but definitely not for a part time/weekend wrench-er.
From what I've found so far, the C4 IRS, while not a direct bolt in, requires the least amount of fabrication (although still more than what many are willing to tackle by themselves) to install. Another option that I've found that a lot of mini truckers use the 80's Mazda RX-7 IRS. All the ones I've found using this set up have been air bag trucks. Personally I'm not a fan of air suspension, so I didn't do too much digging to find more info. Yet another option was the Lincoln mark VII. I haven't dug too much into this yet, but it is similar to the T-bird rear, except it uses an aluminum center section instead of the cast iron, which drastically reduces the weight. This is what was used on the original Grappler truck (stock frame) and if you look at the pics, the rear tires stuck way out (at least 2+ inches per side). I would imagine you could narrow the rear, but I'm guessing this would adversely affect the handling characteristics.
Back to the C4 stuff - The range for these rears seems to cover 1984 to 1996, with a change in the E-brake assemblies from 87 to 88. I can't find anything too specific, but it looks like the 84 - 87 rears had the parking brake in the rotor, and the 88 - 96 rears had it in the caliper.
The two options I've found for the rear were a Dana 36 and a Dana 44, and it looks as though these were common through out the C4 production line. I believe these were both 10 bolt rears, but again this might be incorrect.
It looks like the Dana 36 was available in the slushbox corvettes, and the common gearing was 2:79 to 3:07. I haven't found anything to denote if these were LSD rears, but regardless, the gearing would need to be changed.
The Dana 44 was the option for the manual C4's and the gearing ranged from 2:79 to 3:43 (3:42?). I would imagine the 3:43 is close enough to the 3:42 that it could work without any changes. These rears are apparently harder to come by than the Dana 36's, but there is more aftermarket support - at least according to a few corvette forums I dug through.
Of all the swaps I saw, 99% of them ditched the rear monoleaf in favor of a set of coilovers. I would imagine you are going to have to shorten the rear half shafts in order to get this to sit correctly, but just like the T-bird/Lincoln rear, I would imagine this will mess with road feel.
Now, I know we have a resident corvette expert on the board *cough* DaveP *cough* so if he wants to correct any of my info I would appreciate it.
Finally, if you did decide to go this route, there are plenty of rears available on Ebay, for between $500 and $800. These look to be the Dana 36's, and the few Dana 44's I came across were in the neighborhood of $1500. These were for complete rears, so add in whatever cost for additional fabrication to make it work.
Hope this helps a bit :tup:
