9 inch rear end swap

[Steven73SE]

I know this may be blasphemy to some, but I'm planning on swapping a ford 9" into my 73 charger 440 build. Just curious as to whether anyone has ever done this before and how it went. Any tips?

 

[Cranky]

It's not hard but you need to find the right width or be prepared to narrow it. Also, the spring pads will probably have to be moved and rewelded with the right position to obtain proper pinion angle. What's under the car now?

 

[Steven73SE]

Right now there's an 8 1/4 in the car, but around here mopar parts are very hard to find. Ford and Chevy parts are plentiful though

 

[Mocajava]

I did that swap into a 55 Chevy, tubbed rear and narrowed axle myself. Know and source your rims as some manufacturers are limited in their offerings of backset and you may have to adjust your width to what you can get. Custom rims after the fact can get very expensive! I also beefed up the housing with a back brace I welded in place, there are several kits you can buy to do this yourself. After getting full measurements and welding her up(skip welding) I contacted Strange and ordered Auburn plus correct length axles. I added a coil over, 4 link just to make things more solid which went according to plan also. All of these mods were tacked up and test fitted before I did the final welding. Pretty seamless but make sure of which 9" you are starting with, double check all measurements and know/understand which brake set up you are going with. Had even though of going to a 9" for my 69 Coronet, still undecided.

 

[Steven73SE]

My plan was initially to use magnum 500 rims, do you know if these will fit the 9" in the rear? Also what companies make the kits, do they have websites I can check out?

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[PurpleBeeper]

My plan was initially to use magnum 500 rims, do you know if these will fit the 9" in the rear? Also what companies make the kits, do they have websites I can check out?

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Now don't hold me to this, but I think the bolt pattern on B-bodies and Fords are the same except the center of the wheel (where you might have your wheel bearing up front). If I remember right, Ford rims will fit on a Mopar, but Mopar rims are a little tight in that center part going onto a Ford, so you might have to grind out the centers a little bit. Someone with better info., please jump in and correct me.

Cranky is right.... you WILL have to grind off the spring mounts & replace with Mopar ones (cheap) and this will allow you to set you pinion angle at the same time. The big deal is the width of the rear end. Shortening rears/axles gets expensive IMO. Plus, if you can find the "right" one, you might actually gain a little extra wheel/tire clearance for "free" and not have to buy hardened axles. If you're running slicks, then you'd have to buy hardened axles anyway - fyi

 

[Schober Motorsports]

I just got done doing this on my 67 Coronet. I put my wheels I wanted to run under the car, set em up where I wanted them. Got my measurement and called up Moser Engineering and they built me a housing. I believe it was 53 1/2 from axle end to axle end. I didn't want them to put the perches on so I could figure out my pinion angle as well as center the housing. Stuff is not cheap though. If you have any questions or anything I can help with, please ask. I'd love to help. Also with the back brace... Something to think about is where the shocks mount up. Hard to see in the pictures, but I had to notch mine out so my shocks would be able to mount in the stock locations.

 

[Photon440]

Now don't hold me to this, but I think the bolt pattern on B-bodies and Fords are the same except the center of the wheel (where you might have your wheel bearing up front). If I remember right, Ford rims will fit on a Mopar, but Mopar rims are a little tight in that center part going onto a Ford, so you might have to grind out the centers a little bit. Someone with better info., please jump in and correct me.

Cranky is right.... you WILL have to grind off the spring mounts & replace with Mopar ones (cheap) and this will allow you to set you pinion angle at the same time. The big deal is the width of the rear end. Shortening rears/axles gets expensive IMO. Plus, if you can find the "right" one, you might actually gain a little extra wheel/tire clearance for "free" and not have to buy hardened axles. If you're running slicks, then you'd have to buy hardened axles anyway - fyi

It's actually the other way...you can't put a Ford rim on a Mopar because of the smaller center hole. But most aftermarket wheels will fit both.

 

[Steven73SE]

Little extra info on the build, it's not going to be a full out racer, mainly just a moderate street build. The only reason for swapping the ford 9 instead of an 8 3/4 is I can find a complete 9 around the area for next to nothing and then have it rebuilt if needed and swap what parts need to be swapped and fabbed to make it work easier than I can even find an 8 3/4 here. As a matter of fact my brother has a 9 inch sitting out in his shop from an old mustang project he never finished and later sold. So as far as the back braces and all go, I wouldn't think I'd really need them, unless there's something you guys know that I don't, which I'm sure there is a lot. Plus junkyards around here are overflowing with ford and Chevy parts, while finding anything mopar is near impossible. And finding the people that know anything about them is even harder so I really appreciate the help

 

[Steven73SE]

Also any suggestions on a good differential ratio? Like i said its going to be a street car, probably will be driven often. I want to have decent acceleration, while not sacrificing too much on economy(yes I know, big block and economy don't belong in the same thread but I want decent economy if possible). Its a 440, stock bore, stock pistons, 452 heads milled slightly with stock size valves. Right around a 10:1 compression ratio, stock cam for now. 727 automatic long tube headers, 3 inch exhaust. Right now I'm looking between a 3.25 to 3.70 ratio not sure exactly what to use yet.

 

[Speedwagon]

9 inch swap

Also any suggestions on a good differential ratio? Like i said its going to be a street car, probably will be driven often. I want to have decent acceleration, while not sacrificing too much on economy(yes I know, big block and economy don't belong in the same thread but I want decent economy if possible). Its a 440, stock bore, stock pistons, 452 heads milled slightly with stock size valves. Right around a 10:1 compression ratio, stock cam for now. 727 automatic long tube headers, 3 inch exhaust. Right now I'm looking between a 3.25 to 3.70 ratio not sure exactly what to use yet.

3.55 is a great street gear,not too low and still a lot of fun

 

[Photon440]

It also depends on how much street vs. highway driving you like to do. I had a '74 Firebird 400 once with 4 speed and 3.73 gears and I was quite happy with that ratio.

 

[Steven73SE]

There's really a close mix between city and highway driving. But when I hit the highways or interstate around here I rarely run under 80. And that's in my 1 ton dually pickup. That's why I was kinda looking at the higher gear like the 3.50 instead of the 3.70. I haven't seen a 3.55 or a 3.73 for the 9 inch looking at summit. I didn't think those were ford ratios. Would a 3.50 gear perform well in the city from red light to red light in a car with a lot of low end torque?

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And while the thread is still going does anyone know if the magnum 500 rims 15x8 will fit on the 9 inch? Will backspace be an issue?

 

[Photon440]

Considering the standard road runner gear was a 3.23 you should be doing well with a 3.50.

No 3.73 but there is a 3.70 and 3.64.

 

[polywideblock]

sorry for butting in but what about the "mopar 1 1/4 inch drivetrain offset ? do you take this into account ?
ford 9" diffs are more plentiful than Chrysler diffs down here in oz

 

[MOPOWER871]

View attachment 312693

 

[YY1]

Look for a E body 8 3/4.

For some reason they are very plentiful and not in demand.

They are super close to your needed dimensions and may even drop right in.

Going price with non SG center is $100-$200.

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If you absolutely must go with a fomoco swap and are going to grind off and re-weld perches anyway (see above on E body), go get an explorer or ranger 8.8.

Easy to find limited slip, disk brake and 3.5 or 3.7 gear all in one package. Total width can be an issue for other body styles but may be a lot closer for 71-74...might mean no narrowing.

 

[Steven73SE]

As I said before, any dodge/Chrysler parts a very hard to find around here. I can go to a local junkyard and find complete ford 9s by the dozen. And as I said before my brother even has a complete on I could get cheap. So for me it's looking like that's definitely going to be the route I take. Is there any reason to take the 8.8 over the 9?

 

[Mocajava]

As I recall when I went to Strange for my differential and axles, they cut the axles to fit (length) and you can get whatever bolt circle you want made into them. The bracing is not really needed for your application but it looks unique and beefs it up so you CAN get crazy with HP/TQ later on. The 9" is much stronger than the 8.8 and easy to find change out parts for ...ring and pinion change will drastically effect your RPM's. I'm even considering having a complete pumpkin to swap out with a higher gear ratio, one for cruising and one for playing at the track, Fords are pretty easy to swap in that respect. There are several multipliers for gear ration vs RPM's and I used those to pick a gear . If I find where I saved that I will post it to you. I am in the same boat in Alaska, there are not many choices for finding a full Chrysler rear end up here, my Coronet has the 8 3/4 but a one legged 2.73 ratio. I too will have to order and ship an Auburn/ Detroit Locker up here and the shipping costs me as much as the parts!

 

[Steven73SE]

can the leaf spring mounts be cut off of my old 8 1/4 and used on the 9? The 9 I'm getting doesn't have any mounts on it.