Yesterday I hit a curb hard as I tried to avoid an accident.
My rear tire hit the curb, the rim and the strut broke and so did the housing of the differential too (at the axle end). Since I have an automatic my rear end gear ratio is 3.15.

Now I have seen some full rear suspensions for sale on eBay and I was wondering whether I could buy any full suspension, like 3.31, for the 2011 5.0 for my car and let a mechanic just swap the gears of that suspension with my current 3.15 and put it back together.

How difficult would that be?

Any advice would be appreciated as I want to see if it's worth fixing it myself or just file an insurance claim and see my premium go through the roof :-( .

 

IMO, I would scrap everything from your old rear end and just swap in a complete assembly with a new 3.15 ring and pinion if your dead set on it, otherwise, see if you can get the computer flashed with the new gear ratio. Ford may be able to do it, or you might have to get a tuning device to do it -either of which is probably cheaper than getting your old gears swapped over correctly.

My reasoning is that if you hit the rear end hard enough to damage the axle and housing then there is no telling what sort of side load you might have put on the ring and pinion.

Then there is the whole deal with setting that ring and pinion up and making sure the backlash is correct. Done right, its a beautiful thing, done wrong and its annoying as hell.

 

There are half a dozen or so complete rear axle assemblies on ebay.

Look around some and you can probably find the correct 3.15 ratio if you don't want to change.

 

Thanks for the elaborate explanation bob.
I'll certainly take your recommendation into consideration.
I just want it done right.

I searched and could not find a proper 3.15.
Can't believe how scarce they are. Most I found were 3.73.
I guess the manual transmissions are by far more popular.
I'll keep looking.

Thanks for the quick replies guys.
If anybody has done a similar swap before I'm all 'ears'.


Based on all the above It looks as if my only options for proper restoration are:

1. Get 3.15 rear suspension (difficult to find out there)
2. Get another fitting full suspension (any gear ratio) and tune accordingly.

 

Check with MPS salvage in Georgia, they are a big time Mustang salvage yard. They have a few axles on ebay but they don't always advertise everything they have or they may be able to come up with one for you.

 

3.55 gears, $1550
http://www.fordracingpartsdirect.com...-4001-a355.htm

 

Thanks will check them out !

That looks awesome...too bad it's not 3.15.
But I may consider buying it and just apply a good tune to go with my automatic transmission. Thanks !

 

You might be pleasantly surprised by having a 3.55, acceleration would be quite nice, though the cruising revs on the highway might be too much.

 

I you do go with a used 3.31 axle, make sure it's 2011+ because the earlier ones were "open" (not limited slip) and you'll smoke one tire all day.

 

If you are willing to piece something together a bit you can get a Torsen. http://www.summitracing.com/parts/FMS-M-4204-F20/

 

The gears and diff are likely fine from your damaged rear axle assembly, worst case scenario, you could have a knowledgeable mechanic transfer the diff parts into a V6 axle assembly to save a few bucks.

The best option would be to get your insurance company involved, they will question why you waited to report the loss. If you want to keep them out, I would buy a new axle assembly, shocks, and control arms.

That's only on rear axle assembly's from pre-2011 V6 models, all rear axles from GT's have limited slip diffs.

 

What about the 3.73 ?
I just bought one !

I found a 3.73 and it's a 2011.
Thanks !

Looks like a quality piece !

I bought a used... complete 3.73 rear end, including brakes, shocks, axles, differential... only 5K miles for a very good price.. I found an experienced mechanic who's willing to swap the 3.73 I just bought with the 3.15 I have in there (it wasn't damaged).


Now I've been reading good things about the 3.55 and the 3.73.
So right now I'm contemplating just going with the 3.73 and apply a tune. This way there wont be any need to open open up the 3.73 differential to swap gears.

In case I go this route, would the SCT X3 programmer be a good tuning device to apply the necessary tune for my auto transmission to shift properly and my instruments to measure accurately as I go from 3.15 to 3.73 ?

On the website the main features of the SCT X3 are listed as:
I was thinking that I can use this tuner now for this and also for future tunes as I apply minor performance upgrades with time.

Does this sound like a good plan to my fellow Mustang enthusiast?

 

That's the ticket, the 3.73's will be a blast, unless you bought a 5.0 for gas mileage. Your rpm's at 75mph will increase by 400 rpm's, or from 2000 to 2400 rpm's. FYI - with a 6MT the engine runs about 2250 rpms @ 75 mph, but unless you commute on the highway a bunch, I wouldn't worry about it.

The SCT Tuner will be what you need to readjust the speedometer, but research where you order it from and the tunes they offer with the SCT Tuner.

 

Don't fear the gear!!!!

 

Definitely not!!!!