Which axle behind a 502 Big Block???

[NDWEEDS]

So I recently picked up a 1955 second series truck with a 283 in it. The plan is to clip it, notch it and throw in a 502 Big Block! Now I'm not that educated in axles so I need some help here. Im assuming that the 12 bolt and 9" are my most viable options but it seems like the good 12 bolts are a little tough to find and cost a nice chunk of change. The 9" however seems much more readily available and cost a bit less. Am I on the right track here? If I go with a 9", should I have any concerns over strength? What do I need to look for when selecting one of these axles?

[Speedbumpauto]

You've answered your own question. Any of the 9" housings will work in your app. The early ones had a smooth "baby butt" center housing which is preferred by the street rodders. The later ones have a lump for the ring gear clearance and are said to be somewhat stronger. Your biggest concern is 28 spline axles and 31 spline axles. Many earlier units were 28 and while strong enough for most apps, parts are more readily available for the 31 and it's much stronger. You can also worry about big axle bearing and little axle bearing but unless you're going for BIG power and aftermarket axles with 35+ splines, it won't be a concern.....but bigger is better. You can also worry about a nodular carrier, but the factory ones are almost nonexistent and the standard ones will work unless you go BIG again and get sticky tires. Then the aftermarket is full of options. There is an easy to find web site on the net that will tell you everything you ever wanted to know. Just google nine inch Ford. I get my stuff from Mosier, but everyone makes parts.

[mr48chev]

While I've run a number of 12 bolts in the past they have pretty well achieved the same "rare collector piece" status as a Muncie M21 and a matching price.

I found a complete 9 inch with locker and 3.55 gears for 300 at a friend's wrecking yard the other day. it still will have to be narrowed and have the axles redrilled but by taking it down to Dutchman's I'll still be in it about 600.
I'd have to think that availability, the wide aftermarket parts choices and the ease of working on them make the nine inch rears the viable choice. Even if you don't set up your own ring and pinion you can easily take the third member into a shop and have it done on the bench while the rest of the axle and the rest of the truck sits comfortably at home in the garage.
Axle bearings are pressed on the axle and not using the axle as half the bearing. If you did happen to loose and axle bearing there is only a minute chance that you would loose an axle in the process. I've had to replace an untold number of axles on customer rigs that lost a wheel bearing in a Spicer rear end with the bearing using the axle surface as part of the bearing. It might not be bad with a stock S-10 or Camaro rear end that you can find an axle for but if you have a pair of custom axles that are narrowed and one gets ruined on the road you are either stuck or renting a trailer and tow rig to get it home.

[OldRuffiaN]

Yay my first post.Having researched this question myself for a long time,I decided on the 70-81 camaro/firebird 8.5 10 bolt.Your present rear measures 61.02" flange to flange and the 10 bolt measures between 60.5" and 61" depending on the year.Any year trans Am will get you a free posi and a late 70s-ish 4-speed Z-28 will get you 3:73 + a free posi.The Pinion shaft is the same diameter as a 12 bolt and they are tough as nails.To make them super ultra bullet proof you need merely weld the tubes to the center section and throw in some moser axles,but that`s not necessary as a rule.. This guy has been running 10`s through one with nitrous for years and it`s all stock: http://ls1tech.com/forums/carbureted...ue-street.html So you won`t break it with a 502.

They are a lot easier to find as well.If you decide to mini-tub,the 2wd 5-speed V6 s10 blazer from the late 90`s has one that`s a few inches narrower yet at 54.7.

Here`s how you tell them from their lesser brethren: http://www.novaresource.org/images/rears.jpg

[Keith Seymore]

Originally Posted by OldRuffiaN

Yay my first post.Having researched this question myself for a long time,I decided on the 70-81 camaro/firebird 8.5 10 bolt.Your present rear measures 61.02" flange to flange and the 10 bolt measures between 60.5" and 61" depending on the year.Any year trans Am will get you a free posi and a late 70s-ish 4-speed Z-28 will get you 3:73 + a free posi.The Pinion shaft is the same diameter as a 12 bolt and they are tough as nails.To make them super ultra bullet proof you need merely weld the tubes to the center section and throw in some moser axles,but that`s not necessary as a rule.. This guy has been running 10`s through one with nitrous for years and it`s all stock: http://ls1tech.com/forums/carbureted...ue-street.html So you won`t break it with a 502.

They are a lot easier to find as well.If you decide to mini-tub,the 2wd 5-speed V6 s10 blazer from the late 90`s has one that`s a few inches narrower yet at 54.7.

Here`s how you tell them from their lesser brethren: http://www.novaresource.org/images/rears.jpg

Yep - been running the original 8.5" ring gear 10 bolt in my Chevelle for 36 years.

Just under 1000 HP 555 cu in big block results in 9.80s at 3950 lbs, naturally aspirated.

K

[NDWEEDS]

Thanks guys, this is all great info. If the 10 bolt is truly up to the task, that's the way to go because of the width. I know this is a bad angle but can you tell if this is the right 10 bolt? Says it's from a 70s Malibu.

[OldRuffiaN]

Originally Posted by Keith Seymore

Yep - been running the original 8.5" ring gear 10 bolt in my Chevelle for 36 years.

Just under 1000 HP 555 cu in big block results in 9.80s at 3950 lbs, naturally aspirated.

K

Wow 1000hp! Any lingering doubts I had about this thing surviving behind my turbo 5.3 have just vanished.Thank you sir.

[OldRuffiaN]

Originally Posted by NDWEEDS

Thanks guys, this is all great info. If the 10 bolt is truly up to the task, that's the way to go because of the width. I know this is a bad angle but can you tell if this is the right 10 bolt? Says it's from a 70s Malibu.
Attachment 1251456

Most likely that`s the much weaker 7.5 incher.The only G-body that had the 8.5 that I am aware of is the turbo T-type and Grand National and those are damn rare.

[mphudak]

Be realistic, how hard are you going to run that 502 with the skinny pedal. What tire size/width, auto/manual, are you wanting posi/ locker or are you fine with open diff? Many variables of what will last behind a 502. 9" is a good choice and 31 spline alloy shafts will give you piece of mind of not grenading a shaft. Anything can last if not subjected to shock loads. 12 bolts are getting expensive. Personally i like dana 60s from my rock crawling days but i have access to set up jigs to convert to semifloat axles. If it were mine, i would look to 35 spline. I dont always drive hard but when i hit it i would hit it.

[Speedbumpauto]

Most people don't get 502's to put,put. The 9 will create more interest if and when the time to sell ever comes. Perception is often stronger than truth.

[NDWEEDS]

Is the 10 bolt really a viable option? I poked around in a couple other forms and others say don't waste your time and money with the 10 bolt. I mean, i don't plan to drag race the truck so there wont be any hard launches. Mostly just a fun tire roaster.

[Speedbumpauto]

Not is this back yard. I have a 505cid bbc that MIGHT get close to 600 hp and there's no way I would trust it to a 10 bolt. And, like I said, when/if you sell, buyers will look at your power plant then look at your choice of rear with suspicion. I believe the correct 10 will work and believe the guy with the 1000 hp drag car but 9's are too easy to find and there are too many reasonably priced parts for them even though drag race purists will say the 9 eats a little more power than a 10 or 12 due to pinion location.

[OldRuffiaN]

Lol ask 10 guys get 10 opinions.

[bowt1ed]

I chose an 8.5" (Corporate) 10 bolt out of a 80 Camaro - but beefed it up a bit with an Eaton Tru-Trac, Yukon 3.73's, Moser 31 spline axles - should easily handle the 500/475 my stroker will produce. Cheers, Jim

[mphudak]

Forgot to add, IF you decide to go 12 bolt, make sure you get a true 12 bolt, and not a Type "O". Not all 12 bolts are equal. IIRC the ring gear in a type "O" is smaller, shafts are different and not the easiest/cheapest to find parts for.

When I bought my suburban I liked the fact it had a 12 bolt to back up the drivetrain (seller built it for the dragstrip). After a while of owning it i thought the 12 bolt looked different then others I had seen. Come to find out it is a Type "O" and isn't worth it's weight.

[Keith Seymore]

Originally Posted by Speedbumpauto

Perception is often stronger than truth.

This.

K

[OrrieG]

Originally Posted by Speedbumpauto

Not is this back yard. I have a 505cid bbc that MIGHT get close to 600 hp and there's no way I would trust it to a 10 bolt. And, like I said, when/if you sell, buyers will look at your power plant then look at your choice of rear with suspicion. I believe the correct 10 will work and believe the guy with the 1000 hp drag car but 9's are too easy to find and there are too many reasonably priced parts for them even though drag race purists will say the 9 eats a little more power than a 10 or 12 due to pinion location.

I abused many a stock 10 bolt in the 60's and 70's and never broke rearend, u-joints always failed first. But I think Speedbump has a good point, in the end it will probably take the same amount of effort, time and money to do a 12 bolt or 9" and the "perception" will make you more $ if you sell. Regarding 9" rearends as someone said before, you don't just buy a stock one and bolt it in, they take modification too. Aftermarket 9" housing and tubes might be cheaper that modifiying a stock one...

Am I number 10??

[whitedog76]

How about a semi-float 14 bolt. They can be had in 6 and 8 lugs.

There's companies that can build them for 5 lug also.

I'm also partial to the semi-float D60's. Again, they can be had in just about any bolt pattern, plus there is a huge aftermarket for them.

[mphudak]

The d60 semifloat i built used jeep tj alloy shafts and ford 9" bearing cups and set 20 bearings which fit the jeep shafts. You can get tj shafts in both 30 and 35 spline for reasonable price, 300-350, and put the wms-wms at 60-61". bolt pattern is 5 on 4 1/2 or 5 on 5 1/2

[NDWEEDS]

OK, so i have access to a 71 F-100 9". The width seems about right at 61.25". Any reason I shouldn't go with this axle?

[butchp]

As long as you are running street tires and you can spin them any of the 3 will work. If you make it hook then the bigger the better. The big 10 bolt has less internal friction than the other two.