IRS for my '39 Chevy - Vette, T-Bird, ???

[48builder]

OK. I'm not even close to finished on my '48, but I'm already thinking about rounding up parts for when I re-do my '39. I want to cut the top off it, make it a ragtop and upgrade the engine and suspension. My parts yard guy has a mid 80's Vette, and also has a T-Bird SuperCoupe. I also saw the recent Street Rod builder where the guy used a Nissan 300ZX turbo IRS rear.

What are pros and cons of this install? Cost to me would be about the same. I'm more concernec with ride, handling, ease of installation, etc.

Thanks,

Walt

[1FATGMC]

OK. I'm not even close to finished on my '48, but I'm already thinking about rounding up parts for when I re-do my '39. I want to cut the top off it, make it a ragtop and upgrade the engine and suspension. My parts yard guy has a mid 80's Vette, and also has a T-Bird SuperCoupe. I also saw the recent Street Rod builder where the guy used a Nissan 300ZX turbo IRS rear.

What are pros and cons of this install? Cost to me would be about the same. I'm more concernec with ride, handling, ease of installation, etc.

Thanks,

Walt

Are you just talking about the back or the front and rear suspension?

c ya, Sum

[Charlie Chops 1940]

I think the T-bird IRS is quite wide, don't know on the Nissan. The C3 Vette rear may be closer to where you want to be, but a C2 (65 to 82) may be better yet. Kits are available for them but I don't know who currently has them.

Charlie

[1FATGMC]

Now this is my view and probably pretty narrow minded, but if the rear isn't out where you can see it I would forget an IRS.  I meet a guy once at a car show in S. Dakota and he had the nicest 38 Sedan Delivery (called 38 Special with the gun on a mural) I've ever seen.  He had a Jag rear on the car and said he hated it and he would never do another IRS again.  I've followed his advice, except of course now I'm using one on my lakester  :oops:.

Unless your Jeff Gordon I don't think you will ever notice the difference in how the car handles in the curves vs. a good live axle setup.  I can't imagine wanting to go around curves much faster than I do now, so I don't need one.  If I had to do my truck again, and I still might do this, I would run a NASCAR type rear with the trailing arms off of a truck or you can even buy these now.  It is simple and effective, no spring wrap, easy height adjustment, lots of spring choices and can handle really well.

Like I said this is my opinon and it is your car, so you need to do what you want.

c ya, Sum

[Phil1934]

All the Datsun Z guys are hunting the 300ZXT rear ends, which are the only posi rears Datsun/Nissan ever offered, and only for 2 years, so are scarce.  All these have a trailing arm and strut setup so are difficult to adapt.  There was a Datsun 510 R180 swap kit offered 30 years ago with custom hub carriers to eliminate all that, but they are long gone.  I'm doing a 260Z now with an R200 chunk and 300ZXT CV axles, Not a posi, though.  Something as simple as the hub bearings are over $200.  The high HP hitters are now going to Infinfiti rears, which are even larger, R230, and have viscous posis.  I did a Jag under another car and it slowed progress tremendously.  I'd have to agree, just put a solid rear under it.

[1FATGMC]

I'm doing a 260Z now with an R200 chunk and 300ZXT CV axles, Not a posi, though.  Something as simple as the hub bearings are over $200.

I have an R200 center (at least that is what I think it is) that I'm using for the rearend for my lakester.

First read the following quotes from a friend of mine:

"Phantom Grip" is wat is was.
I will look for some of the links on the ZXT Halfshaft conversion. As long as you have
240 outer stub axles, the ZXT Parts will bolt on with minor mods.

The Z32 Axles use a true CV joint style joint on them, the "Tripod" uses ballbearings on a
triple yoke, riding inside a companion piece with three recesses milled into it. I will be able
to scan the Factory Service manal photos tomorrow morning and it will make more sense.

But yeah, the 280ZXT axles are close to the same legnth as the 240 units. There is some
lattitude in compression to make up for the differences. On a 240, the tripod styles are
close to fully compressed on the right side I believe, but even with full suspension travel,
they won't bind.

Some people make machined adapters for using the Z32 axles in the 240, but IMHO it's
overkill for what most people run. The U-Joints should easily handle 300HP, and if the
axles are close to straight, there should be less than a 2% difference in absorbed
power---so on your engine even maxed out, it's less than 20HP, which with your aero
should not make that much difference. You can keep the tripods in mind should you need
them, or if you can feel vibrations. Some angles with the U-Joints give a vibration, but
when they are straight, like you will be using, you should be fine.

Here are some shots of the R200 Pumpkin. I don't know why I didn't mention it before.
The R200 has smooth sides where the axles enter the diffy, and the R180 has a five bolt
flange on each side where the axles go into the differential.
You can see the R200 from the later ZX has disc brakes. They will pretty easily retrofit to
the earlier axles using calipers fom a maxima and a commercially supplied bracket. That
applies if you are interested in discs instead of the drums of the early Z. I prefer the discs
becasue of the consistent feel. To set up the brake drums on the early Z's for minimum
drag, you will have to use another master cylinder with a lot of volume to get brake
contact without pumping the brakes once or twice. It's not a big deal, but I guess I'm a
"Drag Freak" when it comes to brakes.

I thought I would throw that in as maybe it means more to you than me.  I have the normal half shafts now with the ball bearings and nylon bushings in them.  I would like to shorten one side about 1 1/4 inches and thought I could do it by maching the outboard end of the 1/2 shaft 1 1/4 inches shorter so that it would slide into the other half further.  It is so hard my lathe cutting tools won't touch it, so I think that is out.  Tony, where the above information came from, suggested that I might want to look into the Z32 half shafts.  I don't think I need them, except, if they would be easier to shorten then they might become more attractive.  

Are you saying I might have to spend a bunch of money to find them?

Are you familiar enough with them to know if they would be easy to shorten and inch or so?

On the bearings I replaced the tapered roller bearings on the carrier for only about $28 each from this place --  http://www.awbearings.com/awbearings/ .  They sent them right out.  I'll want to replace the outer hub bearings with new ones also, but haven't checked the pricing on them yet.  You might want to check these guys out.  

Also if you are looking to find a bearing this site has really good information and is where I was able to find a ball bearing replacements for the tapered roller bearings -- http://www.mrcbearingservices.com/ .

Well thanks for any information you migh be able to give me,

Sum

Lakester Construction In
Progress

[Phil1934]

Most racers are blowing the U joints, first, then twisting off outer flange or blowing carrier.  The Datsun U joints seem to be better quality than replacements.  I had to send the outer axles to RossC at Modern Motorsport (check http://forums.hybridz.org/) for info and have adapters welded to them to accept the 300ZXT axle bolt pattern.  $227.  He is now making billet outers, too.  I picked up the axles for $100 for the pair and swapped the CV's end for end to shorten them 3/8" as they are a little longer than the 280ZXT axles.  The Phantom Grip doesn't work.  It just applies preload to the spiders.  Discussion of all this can be found in a search of the hybridz site.

[WZ JUNK]

OK. I'm not even close to finished on my '48, but I'm already thinking about rounding up parts for when I re-do my '39. I want to cut the top off it, make it a ragtop and upgrade the engine and suspension. My parts yard guy has a mid 80's Vette, and also has a T-Bird SuperCoupe. I also saw the recent Street Rod builder where the guy used a Nissan 300ZX turbo IRS rear.

What are pros and cons of this install? Cost to me would be about the same. I'm more concernec with ride, handling, ease of installation, etc.

Thanks,

Walt

I saw that Chevys or the 40's is offering a front and rear crossmember to use Corvette suspension parts.   It was more expensive than a mustang II  front crossmember but not that much more.  I think it would be less expensive in the long run as you would have the better Corvette brakes and steering.  It is designed to use coil over shocks.

[btrc]

I've got a T-bird IRS in my '37 Ford.  I had to narrow it about 6" to fit right.  I built new shorter control arms to do it, along with having new shorter axles machined and bringing the suspension pivots in as far as I could.  Of course you also have to build a subframe to mount it all to.

It does handle good though.  Probably as good or better then anything else I got. (MX6 Mazda & 427 Cobra)

Even though it came out good I don't think I would go through the effort and expense again.

Bob

[48builder]

Sounds like the consensus is to go with a straight axle. I may do that. Just thought that if I can score the IRS for about $400, when a new kit for a straight axle is $500 +, that I would be better off.

The '39 has a setup that Fatman sold me and I hate it. Conssits of the old stock springs, a Butch's Rod shop mounting kit. It rides horrible.

[1FATGMC]

The '39 has a setup that Fatman sold me and I hate it. Conssits of the old stock springs, a Butch's Rod shop mounting kit. It rides horrible.

It seems to me that a lot of these rear springs they sell are too narrow, and too short.  I've ridden in a couple cars with them and to me they don't ride very well and are more like a truck.  I guess that they use them because they are easy to mount or something.

When I built my truck I bought a '73 Camero and used everything from it including the rear springs.  I used the Camero rear spring front mounts and made new rear ones.  I only had a day or so into this and I really liked the way it rode and handled.  I also installed air shocks in the rear to compensate for different loads (mostly trailer tongue weights).

A few years ago the 25 year old Camero springs broke a leaf or two.  I then ordered new ones from J.C.W..  I ordered the Camero heavy duty ones.  They are stiffer than the old ones and I don't need to air up the shocks much at all, but they still ride very well and are not "truck like" in ride.

If I build another ride I would use them in a heartbeat.  It is easy to get them at a good price.  Since They are Camero there are different options for the bushings and springs and when I went to Cal-Tracs in the back they bolted right up, again since it is Camero stuff.

c ya, Sum

[enjenjo]

I have been using Posie's rear springs, they bolt into the stock hangers, lower the car three inches, come with modern shackles, has the center bolt relocated, and ride great. Price is right too.