04/05 Gto Irs

[Daz]

Has anyone done a 04/05 GTO IRS on their Camaro ? I see them all the time on craigslist and was just wondering.

[JKnight]

That particular IRS unit is not known for it's strength so I believe a lot of people avoid it for that reason. Most figure that if they're going to fab in an IRS unit, they might as well at least use a strong one.

[Daz]

Thanks for the info ! I was going to use a C4 IRS but cannot find a someone to make a kit for me or one for under $1000.

[BMR Tech]

The GTO IRS is a nice compact unit and you can get them ridiculously cheap but gear selection and posi options are limited and somewhat expensive. As for strength, they are not really too bad since the GTO came stock with a 400 horse LS2 and the car weighs 3750 lbs. We took our project car into the 10's with a stock IRS and our HD 300M CV shafts/stub axles. After a while we tore up the posi unit and went to an aftermarket differential. Keep in mind that our race weight was just shy of 4000 lbs. and we were drag racing it hard. If you put one in a 3400 lb. Camaro with a typical 450 horse motor, it would probably survive for a while. We sell a lot of the 300M stub axles and CV shafts for these cars and I believe there is a company offering a 8.8 Ford differential upgrade for them now that bolts in place of the stock diff. For the low prices I have seen on Ebay for these assemblies and the compact nature of the design it just might be a viable retrofit option. You could put it in there stock and upgrade down the road when it becomes necessary!

[Daz]

I really appreciate the info ! I've seen whole units for $250-$400. My 67' will probably weigh somewhere around 3400-3600 or so and it won't be driven much. It will be more like a weekend fun to drive, occasional track day/drag car. I'll be stuffing a LQ9 w/ LS2 rods, Victor Jr Mani, 750 Holley, .600+ Cam, L92's and a t56 in it. So I'm looking at around 450-475 to the wheel and I heard those rear ends can handle up to 500whp. I just need to find someone to fab it in and then I'll be set.

I found a guy that can make a S/C T-Bird rearend/IRS fit in it but I'd like to stay with the GM as much as possible but if it come to it I'll thow a 8.8 on it !

Any info I get is deeply appreciated so you guys keep it coming, Thanks !

[BMR Tech]

I really appreciate the info ! I've seen whole units for $250-$400. My 67' will probably weigh somewhere around 3400-3600 or so and it won't be driven much. It will be more like a weekend fun to drive, occasional track day/drag car. I'll be stuffing a LQ9 w/ LS2 rods, Victor Jr Mani, 750 Holley, .600+ Cam, L92's and a t56 in it. So I'm looking at around 450-475 to the wheel and I heard those rear ends can handle up to 500whp. I just need to find someone to fab it in and then I'll be set.

I found a guy that can make a S/C T-Bird rearend/IRS fit in it but I'd like to stay with the GM as much as possible but if it come to it I'll thow a 8.8 on it !

Any info I get is deeply appreciated so you guys keep it coming, Thanks !

The rear will handle that power easily with a few mods, there are tons of GTO's running around with 450-475 to the wheels. The nice thing about the IRS from a fabricators point of view is that it only has 3 mounts, two front bushings and one on the diff cover, so physically mounting it is a breeze. What I am unsure of is just how much floorpan surgery will be required and if it will physically fit between the frame rails. If it fits within the frame rails and doesn't require frame rail modifications you could simply relieve the floorpan where it was necessary, fabricate cradle mounts off your existing frame rails, make upper shock and spring mounts (or even better, coil-overs), and have an IRS in your car!

The other good thing about these IRS rears is that they work. They really weight transfer well. We have seen 60 ft. times down in the 1.40's with just our polyurethane cradle mounting bushings and Drag Bags. If you want to see real world usage, check out our Project GTO (http://www.bmrfabrication.com/GTObuildup.htm). Some of the stuff is outdated now (this was back in 2005) but a lot of what we learned about the rear could be helpful in making your decision to go for it or pass. I have wanted to do this conversion for a while now, would love to see somebody actually do it!

[Daz]

Thanks for the info ! Man I wish you guys were here in Cali cause I would let you guys handle it. I'm really liking this better then the C4 IRS. This way seems a lot easier and updated. Anymore info you have on this is deeply appreciated.

[wgearhead67]

DAZ (or anyone else), did u do this swap? I came across a great deal on a GTO IRS, and was thinking of swapping it into my 67 Camaro. My concern is track width. I think the GTO is wider and narrowing would be tough. So really interested to know if anyone else was successful with this swap. Thanks!

[Daz]

DAZ (or anyone else), did u do this swap? I came across a great deal on a GTO IRS, and was thinking of swapping it into my 67 Camaro. My concern is track width. I think the GTO is wider and narrowing would be tough. So really interested to know if anyone else was successful with this swap. Thanks!

Sorry man, I ended up selling my camaro ! It was just too much work for me, especailly on a budget(need some major welding) ! I now have a '74 Datsun 260z. Parts are much easier to find, and are cheaper, and I can find them in the junkyards. I've built a turbo 4.8 for it and I still need a t56.

[wgearhead67]

Thanks for posting a reply Daz. Sorry to hear the Camaro is gone, but I certainly understand the cost limitations - constant struggle. Similarly, I am going to forego the IRS idea for now and focus money and time on other parts of the car. Your new project sounds like fun too. Too bad we aren't closer in location as I have a T56 I bought for my Camaro that I don't need any longer.

[Daz]

How much did you want for it ? Where are you located ? Is it a LS1 or Lt1 t56 ?

[wgearhead67]

I'm in Michigan, so I would think shipping to SoCal would be pretty pricey. It's an LS1 T56 out of a Camaro. There's no bellhousing. I'd like to get $1200 for it. I bought it when I was collecting parts to build a LM7/T56 combo for my Camaro. But then I found a complete LS1/T56 set-up pulled from a Camaro for a good price, so I grabbed it to save a little money and a lot of time overall.

[Daz]

Ok, I'll keep you in mind ! My wife's uncle is truck driver so I was thinking if he had a run through there he could just pick it for me. We'll see what happens. I'm not in a hurry for it right now, I have plenty of other stuff to sort out on this car !

[wgearhead67]

Sounds good. I haven't listed it or any of the other parts anywhere yet. So when you're ready, check back with me and see if I still have it. Good luck with the project!