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2/05/2018 3:59 PM  #1


New Rear Axle or Rebuild Old one?

1966 Mustang Coupe, 1988 5.0 HO Swap, T5z, EFI w/ MAF

I'm looking at my rear end (chuckle).  

Should I rebuild it or but a complete new one.  It's currently a Ford 8" stock rear. 
Based on a quick internet search, looks like I can buy a complete (Option A) 9" rear for $2500-$3500 + Shipping (Option B) Pull a Ford Explorer rear and go down that rabbit hole or (Option C) Rebuild what I have with some upgraded components.

I need to do a drum to disc conversion and rebuild the differential.  So If I bought a complete rear I could "save" money on not having to but the brake kit and rebuild the rear but I doubt that nets me more than $600-700 bucks.  I'd probably have to find a donor 9", order all the parts individually and rebuild it all.  I'm not opposed to that by any means.  However, from past experience I wonder if after a month of sundays, 10 bloody knuckles. half a dozen new tools, and cursing like a sailor, I won't end up wondering if the money I saved is worth it.  In my book, anything less than $500 isn't worth replacing w/ new.

Anyone go through this and speak from experience?

Last edited by TremendousWand (2/05/2018 4:06 PM)

 

2/05/2018 4:35 PM  #2


Re: New Rear Axle or Rebuild Old one?

There's another thread out there somewhere in which I state this butt (TS&T)  I'll say it again.

I bought, narrowed, straightened, and rebuild (except new gears) a '96 Explorer 8.8, limited slip, 3.55:1, disc brake rear axle for our 66.  All new brgs, clutches, seals, rotors, calipers, pad, e-brake hardware and shoes.   $750 includes the price of the boneyard rearend.  No whines, vibrations or other ugly problems.  Me very happy and I learned new stuff.

BB


"you get what you pay for, good work isn't cheap, and there are NO free lunches...PERIOD!"
 

2/05/2018 5:17 PM  #3


Re: New Rear Axle or Rebuild Old one?

TremendousWand wrote:

1966 Mustang Coupe, 1988 5.0 HO Swap, T5z, EFI w/ MAF

I'm looking at my rear end (chuckle).  

Should I rebuild it or but a complete new one.  It's currently a Ford 8" stock rear. 
Based on a quick internet search, looks like I can buy a complete (Option A) 9" rear for $2500-$3500 + Shipping (Option B) Pull a Ford Explorer rear and go down that rabbit hole or (Option C) Rebuild what I have with some upgraded components.

I need to do a drum to disc conversion and rebuild the differential.  So If I bought a complete rear I could "save" money on not having to but the brake kit and rebuild the rear but I doubt that nets me more than $600-700 bucks.  I'd probably have to find a donor 9", order all the parts individually and rebuild it all.  I'm not opposed to that by any means.  However, from past experience I wonder if after a month of sundays, 10 bloody knuckles. half a dozen new tools, and cursing like a sailor, I won't end up wondering if the money I saved is worth it.  In my book, anything less than $500 isn't worth replacing w/ new.

Anyone go through this and speak from experience?

​Your 8" is good to 400HP and that HO is nowhere near that.  You don't need a 9".  Rebuild the pumpkin with whatever ratio suits you and install a rear disk kit from a reputable source like MS.  Going with the 8.8 sounds good but you must have the tools, desire, talent, and ability to do so.

​I found an 8" pumpkin at my mechanic's brand new for $100.  He just wanted to get rid of it.  I got the SSBC rear disk brake kit plus bearings, etc. and installed it over a weekend.  That was before MS had his kit.  I did it  that way because my fabrication talent and skill suck.  I'm a big picture guy, not a detail person.  I do nuts and bolts, not welding or other stuff.
 

Last edited by lowercasesteve (2/05/2018 5:20 PM)


Original owner - 351w,T-5, 4whl disks, power R&P
 

2/05/2018 5:36 PM  #4


Re: New Rear Axle or Rebuild Old one?

Do you "need" or "want" to do a drum to disc conversion?  Disc's up front will serve you well and save you cash.

As for the rear...... cheaper, faster, less painful, less hair pulling, to keep and build what you already have.  Do an ebay serach. There's a reputable builder offering 8" chunks for about $900 in whatever ratio you'd like.  That plus a new gasket, fluid, and maybe new alxe bearings would have you cruising again for about a grand.  
I've got cobra disc's up front with MS's kit and drums out back......and the car stops just fine
 

 

2/05/2018 6:55 PM  #5


Re: New Rear Axle or Rebuild Old one?

X-2 what Josh sez!
Thank-a-boud-it......these older Mustangs weigh nearly noth'in compared to later models and especially new cars with all the "safety crappage" on them.
Disc/disc set-ups look plenty trick with the Torque-thrust rims ....spinning down the road and rear discs with red(naturally!) cailpers  shining through the spinning wheels. (Get where I'm going here?!)
My scarebird front discs and rear drums stop me waaaaay better than the drum/drum set-up that servered the purpose the first 40 years of the cars existence (Get where I'm going again?!)
No Kidd'in...if you want'em cause you want'em.....go for it. Do you need'em to stop good.....uhhhhhh....un-uh.
Sorta like a big lumpy camshaft in my engine(Get where I'm going?!!!)
6sal6
I'm wanting a 8" trac-loc with a set of 3.55 gears too! Pretty sure it will hold all the hosses I'm mak'in.


Get busy Liv'in or get busy Die'n....Host of the 2020 Bash at the Beach/The only Bash that got cancelled  )8
 

2/05/2018 8:04 PM  #6


Re: New Rear Axle or Rebuild Old one?

Rebuilding the 8" out of the 70 ran me about $2000 total that includes the eaton tru-trac, 3.80 gears, MS disc kit, rebuilt calipers, new rotors, bearings, gear oil. Did I need disc brakes in the rear? maybe not  but did I want them yes. I drive with a heavy foot and I can tell you I want stopping power I used to drag race and imagine stopping a manual drum car from 110 mph like I used to.

 

2/05/2018 9:14 PM  #7


Re: New Rear Axle or Rebuild Old one?

After reading all the above, I had a thought.  One of the early rear brake upgrades was installing Galaxy/big block rear brakes.  They are wider by around  1".  Straight bolt in as I recall.  They will work just as well as rear disks, and better than your stockers.  They used to be available at most Mustang vendors.  I believe that is what the Mustang racers used way back when.  And you can get them for well under $500.  Backing plates may be the most difficult to find.

​If you are not going road racing and do not care about looks, you might look into them.  Much cheaper than any disk conversion.  And I don't think you have to worry about what kind of M/C you have.

Last edited by lowercasesteve (2/05/2018 9:22 PM)


Original owner - 351w,T-5, 4whl disks, power R&P
 

2/06/2018 8:01 AM  #8


Re: New Rear Axle or Rebuild Old one?

So is it safe to say that in terms of keeping fabrication to a minimum and cost to less than $1500...rebuilding what I have is the way to go?

I don't have the setup for welding and fabrication.  One day.

 

     Thread Starter
 

2/06/2018 9:23 AM  #9


Re: New Rear Axle or Rebuild Old one?

Yes. 
Think of it this way....the stock rear end fits as engineered and works as designed.  It's a straightforward procedure to remove the third member and re-install.  The time spent will be minimal in comparison to modifying an 8.8 especially since you don't have the tools to do this yourself right now.  


 

 

2/06/2018 2:42 PM  #10


Re: New Rear Axle or Rebuild Old one?

lowercasesteve wrote:

TremendousWand wrote:

1966 Mustang Coupe, 1988 5.0 HO Swap, T5z, EFI w/ MAF

I'm looking at my rear end (chuckle).  

Should I rebuild it or but a complete new one.  It's currently a Ford 8" stock rear. 
Based on a quick internet search, looks like I can buy a complete (Option A) 9" rear for $2500-$3500 + Shipping (Option B) Pull a Ford Explorer rear and go down that rabbit hole or (Option C) Rebuild what I have with some upgraded components.

I need to do a drum to disc conversion and rebuild the differential.  So If I bought a complete rear I could "save" money on not having to but the brake kit and rebuild the rear but I doubt that nets me more than $600-700 bucks.  I'd probably have to find a donor 9", order all the parts individually and rebuild it all.  I'm not opposed to that by any means.  However, from past experience I wonder if after a month of sundays, 10 bloody knuckles. half a dozen new tools, and cursing like a sailor, I won't end up wondering if the money I saved is worth it.  In my book, anything less than $500 isn't worth replacing w/ new.

Anyone go through this and speak from experience?

​Your 8" is good to 400HP and that HO is nowhere near that.  You don't need a 9".  Rebuild the pumpkin with whatever ratio suits you and install a rear disk kit from a reputable source like MS.  Going with the 8.8 sounds good but you must have the tools, desire, talent, and ability to do so.

​I found an 8" pumpkin at my mechanic's brand new for $100.  He just wanted to get rid of it.  I got the SSBC rear disk brake kit plus bearings, etc. and installed it over a weekend.  That was before MS had his kit.  I did it  that way because my fabrication talent and skill suck.  I'm a big picture guy, not a detail person.  I do nuts and bolts, not welding or other stuff.
 

Well stated. The T5Z will probably let go before the 8" will. And before you reach that point you need to have the traction. GM use to put a 7.5" ring gear in 350 Camaros because their engineers said either the clutch or the tires will slip before the 7.5" axle let go. Heck, I wouldn't even swap discs. You don't need them from a braking standpoint on these cars. Use discs if you want something that is easier to work on but the drums will last longer then the disc pads will. The 8" is lighter for less unsprung weight and has a better axle retention system then the 8.8" does. I'm perfectly happy with my 8" and I have a free 8"  center with limited slip going in.
 

Last edited by Huskinhano (2/06/2018 2:43 PM)


I'm not a complete idiot.....pieces are missing. Tom
 

2/06/2018 3:06 PM  #11


Re: New Rear Axle or Rebuild Old one?

I've done all three, rebuilt my 8" in the 66, built an Explorer rear for the 68, and used a 9" in a 65.

Two thing to think about:
1. I don't know how much, but that 8" is a lot lighter than either of the other two.
2. Unless you have mini tubbed the back end, about a 245 series tire is all you fit under there, and unless you are planning to run a slick or some type of sticky tire, a 245 street tire will be up in smoke WAY before you ever hurt that 8", even with 1000 hp.

The 9" is great if you need it, most of us don't.

The 8.8 was a low cost way to get trac-loc & 3.73 gears for my 68. ( the parking brake set-up is a bit of a pain, and has never worked quite right)

The 8" was the best set-up if you can deal with looking at the drum brakes which work fine for our light cars.
 

 

2/06/2018 8:55 PM  #12


Re: New Rear Axle or Rebuild Old one?

Does the existing 8" have suitable gears and is it in working condition?  You have to decide the "realistic" purpose for the car.  If you just want to drive it, put the $2,500 into something that will make a noticeable difference.


Money you enjoy wasting is NOT wasted money... unless your wife finds out.
 

2/07/2018 1:44 PM  #13


Re: New Rear Axle or Rebuild Old one?

I also vote for rebuilding the 8"... but most of the folks here seem to be implying that if you keep the 8" you can't have rear disk brakes.  I think most of the rear disk kits that work on the small bearing 9" also work on the 8".  So you can have keep your 8" and have rear disk brakes too!

Last edited by Michael H. (2/07/2018 1:45 PM)

 

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