Live axle rear - restore or replace?
 

Hey All,

I recently picked up a home built v8 Miata. It's a 97 donor with a Ford 302 connected to a C4 driving a Ford live axle. The rear suspension is a ladder bar suspension using the stock chassis coil-over hard points.

Here are some pics showing the driver side rear axle and driveline:
https://cimg8.ibsrv.net/gimg/www.v8m...587f8e5e23.jpg
As you can see there is good amount of corrosion, the car had been stored near the ocean for the last 10 years, and it shows. And the springs are broken, shocks blown and brakes leaking. A lot to fix.

I think these are my options:

1) Pull it all, blast it, paint it and reinstall it.
2) Buy a new diff and install with the existing ladder bar suspension.3) Convert it back to an independent rear suspension.Regardless, I'll be installing new springs, shocks and brakes. If I keep the live axle, I'll upgrade to discs, and if I get an IRS, I'll upgrade to bigger discs.

My inclination is to keep it as close to it's current state as possible. it is a cool old school build.

But I also really enjoy HPDE track days. So the IRS seems really attractive (along with a manual tranny).

Any thoughts or comments on my options?

Ladder bars have two connections to the rear axle, and only one connection to the frame in front of the axle. They are made for weight transfer in a drag car. They bind in the corners and on uneven pavement.

A 4 link, on the other hand, has two connections on the axle, and two connections on the frame. They can also bind, but only on severe articulation.

If you're planning on street driving and autocross, IRS is the best way to go, IMO.

If you are going to be re-doing everything anyway, go with IRS, will fit your needs much better than your current setup.

Unless there is something the pictures are not showing I would personally be inclined to keep the rear end in present configuration and simply remove the assembly and clean everything up.
You can use some flapper wheels to clean up what is there real cheap then hit it with rattle can rust neutralizing paint.
Once that is done and you drive the car a bit you can then evaluate if you want to spend real $ to switch things around.

You didn't mention the HP level of the engine presently in the car but I would guess it is higher than would be recommended for a stock Miata differential.
If that is the case you would need to do further evaluation to determine how strong the differential and axles and driveshaft needs to be.
If you do go the route of switching things back to IRS you might as well upgrade to the 8.8" differential and axles that can take the abuse you will probably be dishing out.
It all comes down to money and time.

Thanks BGordon, yeah that's a much more reasonable path. I don't know why I didn't think of wire wheeling it. I had in my mind either I just slather it in paint now, or I blast it and spray it nice.

That's exactly what I'll do.

Plus I really want to take advantage of these last bits of summer and that sounds faster than the rest! :-)

I'll start a build thread to document it.

If I swapped to the original Mazda rear, I would definitely upgrade to a Ford 7.5 or 8.8.

Thanks everyone, I appreciate all the comments. :-D

Booger welds on the shock mounts and binding shocks due to an inappropriate mounting location. I would shitcan the entire rear suspension and start over with a ford 8.8 based IRS.They are all over e-bay for $600-800.
https://cimg2.ibsrv.net/gimg/www.v8m...23b6cbb898.jpg

You can also pick up the original rear suspension cross member for about $120.00
https://cimg4.ibsrv.net/gimg/www.v8m...832c5239ce.jpg