So i got this Fiat 124 with a rx8 rotary and now its time for the drivetrain. So the driveshaft Won't be a problem i can get that custom made easily, But the rear end is what I am worried about. How much would it be to get a rear end custom made(typically, keeping in mind its a small car)? 1000?, 2000? , or should I just get beefier axles and gears put in the stock housing? (its pretty grody though) How much would that cost?
Assuming you are going to keep a live axle if you considered changing the guts of the Fiat axle, so: 1) You can not reasonably upgrade said Fiat, the case is too small 2) Custom certainly possible but many $$ 3) look for an early RX7 live axle. Find one from a GSL/SE and you get limited slip too, and the brake calipers are easily compatible with your Fiat. A good one will not be cheap cause they are getting rare, but it will be a lot cheaper than custom, and close to your track width. Easy to weld the Fiat brackets to it.
I suspect that was the wrong 124 :) It would probably be easier to swap the entire rear subframe from an NA or NB Miata if the track width is about right. Or does the old 124 have a live rear?
Custom halfshafts can be done, but aren’t cheap. I’m going to guess $500-1000/set, depending on what the ends look like.
First step is figuring what gearing you want.
Keith Tanner said:First step is figuring what gearing you HAVE.
FYP.
The suggestions are very different depending on what 124 we are talking about - as you alluded to...
For a live axle, I'm sure a live axle from an RX7 would work fine, the original Fiat would have to be examined, but I know an Alfa live axle could also deal with it.
For an independent- there are so many engine swap upgrades for the Miata, the choices are numerous.
He's obviously asking for an old 124.
The new Fiata's rear axle would have no problem dealing with the RX-8's "torque".
Get a 7.5" 4-bolt Fox body rear end and narrow it down. I'm assuming the fiat axle is narrower. Limited slips are available and you can occasionally find an axle with the stock one. Order new axles to length and have them done to whatever bolt circle you need. Moser can do this. IIRC, my Fox 8.8" axle is about 60" face to face.
When I did my MG, I looked around for a live axle about the right width and with the right gear ratio. Turns out there's a specific Blazer that was just right, and this forum helped me figure that out.
I then had Moser make custom axles so I got the 4x100 bolt circle I wanted. Straight axles like this are a whoooole lot cheaper than custom halfshafts with CVs for an independent rear, the cost was quite reasonable.
DeadSkunk (Warren) said:Get a 7.5" 4-bolt Fox body rear end and narrow it down. I'm assuming the fiat axle is narrower. Limited slips are available and you can occasionally find an axle with the stock one. Order new axles to length and have them done to whatever bolt circle you need. Moser can do this. IIRC, my Fox 8.8" axle is about 60" face to face.
Another possible source for a 7.5 would be an old Ranger. They should be both cheaper and narrower than a mustang axle, and also had an optional lsd.
therieldeal said:DeadSkunk (Warren) said:Get a 7.5" 4-bolt Fox body rear end and narrow it down. I'm assuming the fiat axle is narrower. Limited slips are available and you can occasionally find an axle with the stock one. Order new axles to length and have them done to whatever bolt circle you need. Moser can do this. IIRC, my Fox 8.8" axle is about 60" face to face.
Another possible source for a 7.5 would be an old Ranger. They should be both cheaper and narrower than a mustang axle, and also had an optional lsd.
Rangers had the differential offset to the passenger side, while Mustangs had the dif centered. If it's going to be narrowed anyway, that might not matter.
How much torque will this rotary make? In stock trim, you could a yota 8”. Those are cheap and have plenty of options for final drive.
In reply to Keith Tanner :
I believe the S10 axles start at 54" and the Blazer and ZR2 (?) are 58, or so. Plentiful in the junkyard and lots of ratio choices.
In reply to STM317 :
If the offset is right then getting a Ranger housing and a 2nd right side axle would be a cost effective way to build a narrowed rear end. Just depends on what width the Fiat is.
to solve the confusion yes its a 1976 fiat 124, probably should have mentioned that LOL. Also my question was actually how much would it cost to have a custom (solid) rear axle to be made, thank you for some good suggestions But I would like to know the cost of a custom one if anyone knows because I've already and still have to do so much fabrication on this car, this is one thing I'd rather pay for if its not ridiculously expensive.
How custom? The easy answer is to get one that's too wide and narrow it. Are you imagining building your own housing out of plate steel and a couple of tubes?
Keith Tanner said:How custom? The easy answer is to get one that's too wide and narrow it. Are you imagining building your own housing out of plate steel and a couple of tubes?
Going this route, I have... a lot... in the RX-7's rearend. I pretty much stopped counting when it got over $2000. Granted, I could have done it much more cheaply if I was willing to sacrifice weight or performance in the name of saving money, but then I'd just end up doing it twice. (Main excessive expense was the aluminum centersection, which was worth every penny as far as I'm concerned... I got the 9" to only weigh about 40lb more than the Mazda rear, but it is about eleventy zillion times stronger, and gears/diffs are cheap cheap cheap on eBay since it's the NASCAR standard rearend, and bearings/etc are commonly stocked items at Summit)
I had axles made to my spec for, I think, $400, by Dutchman. But then I also needed axle ends, a "dogbone" tool for accurate width cutting (I built the rear to fit the axles, not the other way around), alignment mandrels for the new axle ends, etc. As well as buying the rearend itself. As well as quite a few instances of having to spend more money to make up for having bought a crap example of a 9"... On the other hand, a place called Speedway in California (not Speedway Motors) quoted me $1500 for a "light weight" full floater 9" rearend with aluminum hubs, built to my width spec, complete with brake rotors. All I'd need to do is get a centersection, calipers, and weld on my brackets. Seemed like initially more, but I'd have actually saved money because I'd have only needed to buy it once, and I'd have a better product.
I sold some of my broken RX-7 axles to a gentleman who was narrowing an RX-7 rearend to fit into a Datsun Roadster (!!!) and he sent them to Dutchman to be cut and resplined. His way of doing it was probably much cheaper than mine 
But I was also sick and tired of breaking RX-7 parts and GSL-SE rearends aren't $300-400 anymore. I don't know how the V8 guys get away with these rears.
Here's the easy answer to the question. Moser does custom rears starting at about $970 for a bring-your-own-third-member unit.
I'm not aware of a firm making custom light duty rear ends, although I'd be surprised if there isn't one out there. Every manufacturer I'm aware of uses standard center sections and supplies a custom housing and axle. Moser will custom build you an axle. They start around $1200 and go up to anything you want, but their online site deals in axles that are for high horsepower applications. I didn't see anything in there smaller than an 8 3/4 Chrysler.
In reply to DeadSkunk (Warren) :
Speedway will build you a rearend around Ford 8" centers. http://1speedway.com/index.php?route=product/product&path=79&product_id=59
They also say theh will build around something else to your request.
An aluminum 9" center is lighter though, and has more aftermarket support if you care about that.
In reply to Knurled. :
Diamond axles will build you one based on a Ford 9", Toyota 8"/8.4"/10.5", Nissan h233b, or a GM 14 bolt.
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