Advice on building a rearend

SadbutTrue · Jan 28, 2004

There are several rear-end vendors on ebay that have very high approval ratings. It seems that if I were to use my current 8" axles and brakes, I could get a rearend for a pretty affordable price and piece it together with a case of some sort, possibly from the same vendor.

Would you recommend this? How hard is it to put together a rearend, if I were extremely careful and took my time with it? What can go wrong? I can't really afford to go to my local shop and have them build me a completely new rear for $12-1500 as I've been quoted. But I need a rearend, badly.

Any advice is appreciated..

GaPonyFarm · Jan 29, 2004

Your 8" stuff won't work... but from what I see about your car, you don't "need" a 9" rear anyway. A mild 351 won't break an 8", especially with an automatic tranny. If you want positraction... you can swap in an 8" posi pumpkin - check with your local powertrain shop for a used one and put some 3.25, 3.55, or 4.10 gears in it. Should be able to get it done for $450 (parts & labor) from a good shop.

If you don't know how to setup a rearend, its virtually impossible to do correctly.

You'll be better off finding a used rearend in a boneyard, or better yet, a swap meet. It should be extremely easy to find a 9" unit is Cali.... if you really want one.

66P51GT · Jan 29, 2004

I picked up a 8" 4 spider 3.80 rear from this vendor on ebay for $555 shipped to my door. Includes new Strange gears, rebuilt 3rd member, and new clutch pack in the traction lock unit. I am mating this behind a ~325hp 289 and a T5. It is for my daily driver with occasional drags and autocrossing events.

SadbutTrue · Jan 29, 2004

well problem is i don't plan on my 351 staying like this for long...

HistoricMustang · Jan 29, 2004

I like my 9 inchers and the one in the car came from Currie. Give them a call.

HistoricMustang
www.historicmustang.com

1320stang · Jan 29, 2004

GaPonyFarm said:
Your 8" stuff won't work... QUOTE]

Not true, if he has a 9" the same width as his 8", and has the smaller housing ends and a 28 spline section in his 9" pumpkin, the 28 spline axles from the 8" and the backing plates and drum brakes will work on a 9". One of my best friends has this exact setup in his '67 coupe.

While this is all fine and dandy, 31 spline axles are stronger, so you'd have to upgrade in the future anyway if you're making a decent amount of HP. A 8" will hold up to about 400 HP small block, so I'm guessing about 300 ft/lb of torque.

TurboDoctor · Jan 29, 2004

Are you wanting the entire rear end or just to update to posi track and change gear ratios or something like that ?? I would just buy detriot locker and a new set of gears and rebuild kit from summit or jegs ect ect and just rebuild the rear end myself. All you will need beside hand tools is a good dial indicator to set up the backlash and pinion depth. Building a rear end is not really that hard you just have to take your time and make sure you get everything in spec. If you got a good repair manual and follow it you will knock out the job and save yourself alot of money. For some reason people will do every other aspect of thier car by themselfs and are scared to touch the diff.

brianj5600 · Jan 29, 2004

Most early 28 spline axles taper down in the middle. That will be your weak point imo. I'm going 8.8. Lighter, cheaper, more efficient, and plenty of fast cars running them w/o trouble.

GaPonyFarm · Jan 29, 2004

1320stang said:
GaPonyFarm said:

Your 8" stuff won't work... QUOTE]

Not true, if he has a 9" the same width as his 8", and has the smaller housing ends and a 28 spline section in his 9" pumpkin, the 28 spline axles from the 8" and the backing plates and drum brakes will work on a 9". One of my best friends has this exact setup in his '67 coupe.

Click to expand...

Are you expecting the planets to align perfectly, at the exact moment he walks upon a rearend... Remember this is a '66, not a '67 or later. 9" rears for those cars aren't just lying around all over the place like they used to be. I haven't seen a 9" housing that has the same flanges as an 8" housing...sorry.

GaPonyFarm · Jan 29, 2004

Amen to the 8.8"! ... Probably the most underestimated rearend out there. And there are millions of them around.

1320stang · Jan 30, 2004

GaPonyFarm said:
Are you expecting the planets to align perfectly, at the exact moment he walks upon a rearend... Remember this is a '66, not a '67 or later. 9" rears for those cars aren't just lying around all over the place like they used to be. I haven't seen a 9" housing that has the same flanges as an 8" housing...sorry.

Huh, I just got a '57 9" rear end for free for my '65 coupe. Complete. Maybe you need to get out more often. Sorry, I'm being a smartazz.

I wasn't saying he'll find the correct housing, but many passenger car rears have the small bearing ends on them which are the exact same as the 8" ends. Having a housing professionally narrowed and the perches placed in the correct position will run somewhere from $125-$200 with you supplying the housing. This is a fact. I have a buddy that has a race car chassis shop, he's done hundreds of rears, this is where I get my info from.

GaPonyFarm · Jan 30, 2004

1320stang said:
Huh, I just got a '57 9" rear end for free for my '65 coupe. Complete. Maybe you need to get out more often. Sorry, I'm being a smartazz.

I wasn't saying he'll find the correct housing, but many passenger car rears have the small bearing ends on them which are the exact same as the 8" ends. Having a housing professionally narrowed and the perches placed in the correct position will run somewhere from $125-$200 with you supplying the housing. This is a fact. I have a buddy that has a race car chassis shop, he's done hundreds of rears, this is where I get my info from.

Remember, nobody likes a smartazz...

'57 huh... not the best of breed, but ok for low power use. You really want the newer housing... but its certainly worth what you paid.

My guess is, if he had a buddy with a shop, he wouldn't be asking these questions. I suppose if you cut enough and weld enough, you can make anything. I have several 8" & 9" rears and none of the 8" races will fit the 9" tubes... However my main point was to question why he even needed the 9". A 9" rear with 28 spline axles is not much stronger than an 8". The axles are the weak link, not the gears, especially if he's using those cheap tapered axles.

Get your buddy to weld a girdle support on your '57 housing... you'll be glad you had it done.

Edbert · Jan 30, 2004

The bottom line recommendation is that you have your ring and pinion gears set up by a pro or at least someone with micrometers that has done MANY of them. The mesh and lash settings are very important. Too tight and they'll rob lots of power and grind themselves to death. Too loose and they'll break. The tolerances are VERY small, we're talking THOUSANTHS of an inch here, and you can't use plastigauge like you can on your crank.

1320stang · Jan 30, 2004

GaPonyFarm said:
Remember, nobody likes a smartazz...

'57 huh... not the best of breed, but ok for low power use. You really want the newer housing... but its certainly worth what you paid.

My guess is, if he had a buddy with a shop, he wouldn't be asking these questions. I suppose if you cut enough and weld enough, you can make anything. I have several 8" & 9" rears and none of the 8" races will fit the 9" tubes... However my main point was to question why he even needed the 9". A 9" rear with 28 spline axles is not much stronger than an 8". The axles are the weak link, not the gears, especially if he's using those cheap tapered axles.

Get your buddy to weld a girdle support on your '57 housing... you'll be glad you had it done.

I got it cause it was a bolt in and I doubt I'll ever make more than 400 HP or 400 ft/lb of tourque in it. Not going to be a race car, just a warmed over driver. Now my '63 Nostalgia Super Stock Fairlane will need a braced rear end. I've already got a big web pickup 9" housing ready for narrowing for it. Ladder bars and coil overs with a minitub for that car. Should end up with 700 HP FE between the notched shock towers. Crites fiberglass with me cutting as much weight as I can and a 'moly cage should get the weight down into the 2700 lb range dry.

But I digress. I agree, in my scenario, you end up with a rear that's not any stronger than the 8" it's replacing, but it will ultimately have more potential. It'll just cost more in the long run than doing it right the first time. But he was wanting a 9" as cheap as he could get it, and this is the cheapest solution I can think of, unless he runs across a deal like I did. My buddy is running a '57 9" in his '68 coupe with my 500hp 289 in it running high 11's with a C4 and 4.88 gears in a mini spool (or did he get a full spool?) on real street radials. It held up for a few passes with old slicks okay, but I bet the motor will puke before the rear, it has close to 200 passes on the Howards aluminum rods with heavy TRW 12.7:1 slugs on the ends. Cast 289 crank, but it revs to 8 grand okay with no girdle. Went 11.08@119 in a 3000# Mach I with a 2.95 (I believe) Jerico and 5.67 gears on 2 year old 9x30 slicks.

Advice on building a rearend

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