I've read alot of posts about 9" fords. People I talk to say they are good rear ends. Are they? I'm thinking about replacing my entire rearend with a ford 9' and multi-leaf springs. If I wanted to go with one are they easy to fit under a '67? Any opinions would help. :D

My thoughts on rears:

A factory 12 bolt is:
1:stronger
2:lighter
3:more efficient at transfering power to the wheels

A 9 inch can be made to be as strong, however it will cost a little more.
The 9 inch has the advantage of changing gear ratios in well under an hour(a full day project in a chevy).
But to do that you also need a 2nd center section which cost nearly another $1000 for a strong one. (!!!)

Randy

On a side note, ask yourself why you want to change rears. If you never plan on having more than 700-800HP or running quicker than 9 seconds in the 1/4, I would be beefing up a 8.5 in 10 bolt and saving a TON of money.

Randy

So a 12 bolt is lighter? good to know. I don't plan on racing it, but I do want the horsepower on the streets. Right now it has a 10 bolt from what I think is a 80's firebird with the mopar setup for spring perches. It's a small axel and my pinion and gears are making noises that tells me they don't have much more time on them. I just want a strong, reliable rearend that will last me for years to come. And money is an object!!

My thoughts on rears:

A factory 12 bolt is:
1:stronger
2:lighter
3:more efficient at transfering power to the wheels

A 9 inch can be made to be as strong, however it will cost a little more.
The 9 inch has the advantage of changing gear ratios in well under an hour(a full day project in a chevy).
But to do that you also need a 2nd center section which cost nearly another $1000 for a strong one. (!!!)

Randy

You're splitting hairs. I deal with 9" and 12-bolts every day, and my choice in the 9". The 9" is the small block Chevrolet of axle housings, you can get any part you want for it. If you want to do a quick gear swap, no problem with the 9". BTW, with a 12-bolt, most shops charge about $700 to change gears (which is the same cost as a beefy 9" pumpkin too), so with the 9" you get the option of easily changing back to the old gearset.

The 12 bolt is more efficient, but if you are really concerned (which you shouldn't be, the difference is within 1% in my tests) you can buy 12-bolt gears to fit a 9" pumpkin. The 12-bolt also has a slight advantage for strength, but that's in purely stock form. The 9" has WAY more potential for little money.

The weight advantage of the 12-bolt is minimal. I don't worry about it, and if you are concerned, get an aluminum center section. Can't do that with a 12-bolt.

The BIGGEST advantage of an out-of-the-box 9" is the bolt-on axle retention. Obviously GM rear ends don't have this feature, and will cost you an extra $600 (with axles) to get it. IMO, with the number of Chev housings I see with broken axles, THIS IS MANDATORY.

Matt you say there is 1% difference in parasitic drag? I have read numerous articles written by other shops which disagree with that statement. They feel it more like 4% lose in horse power.

I also note that the sell gun drilled axles with spider web flanges and lightened gear sets with aluminum center sections and front bearing supports made of aluminum to reduce that "weight advantage of the 12-bolt" Those parts aren't cheap so they are of interest to some people.

Finally one other factor that you may have overlooked is the fact that though the SBC of rear ends may have become the FORD 9", it still looks out of place beneath a first gen Camaro. In my opinion had Chevy continued to make 12 bolt rears the FORD 9" would still be languishing under SUV's with little interest in them.

NHRA dictates "C" clip elimination, it doesn't specify how. Most racer are running 9" rears without a FORD part in them, the big boys run 9" look a likes that use 11" gears. I recommend getting the remanufactured (new casting with high nickel content) 12 bolt using thicker 3' diameter axle tubes and running Furd small axle ends to eliminate the dreaded "C" clip (the most bone headed mistake GM ever made). You can buy these new 12 bolts (as well as recycled and updated original 12 bolts) set up ready to run from all of the major rear end specialists.

What I want to know is why the "Quick Change" has not made a come back yet. You can still get them, and NASCAR has been using them for years. The only advantage I see to a FORD 9" is the Hotchkiss style rear end has the inherent ability to swap center chunks unlike the Salisbury style made by Spicer/Eaton/Dana. With a quick change rear you can change your rear gear ratio as fast as you can change a spare tire.


Larger Dave

And money is an object!!


Then why dont you just look to fixing and overhauling the 10 bolt that is in there.. probably the wheel bearings making noise... if your not going to race it and only get on it from time to time, the 10 bolt will hold your current power levels.. Going with more would be a waste of money in my opinion..

If you have an 8.5 ten bolt, build it. The 8.5 are fairly strong on street and occasional strip use. If you need to buy a rear, the meager cost of a 9" (plentiful) vs a 12 bolt, and the expense of building a 12 bolt vs a 9" makes my choice a 9". But, I needed a stronger rear than my 8.2 so I got a 9" for some labor and an additional 3.91 locker and pumpkin for $500. Add a rebuild and axles and it's affordable.

I got a 9" from a ford van. It has huge 3.25" diameter tubes with beefy center section and very thick material.

Currently my car is going through a full frame off, and I'm going with a MW cast iron center section, 35 spline axles, alum. pinion support and probably moser axles. I'll be using a detroit locker also.

My car is original 12 bolt with the orig 12 bolt under, and I was reluctant to cut off the axletubes (ends) to install clip eliminators, and risking the whole axle under my heavy foot. My car sees strip almost never, it's mostly street. I still wanted to go with the "strongest there is" under my car, building this 9" costs about the same as building a 12 bolt. Especially the housing for the 9" was cheap, 100$. Finding a 12 bolt for this is truly lucky.

So to keep it short 9" is strong, cheap and I think it looks racey (especially with a rear brace)!

Dave,
Yes, my own tests confirmed 1% steady-state power loss. Actually 1.5%. But the point of the tests I was performing was not to measure efficiencies of hypoid gears or anything, but to measure advantages of synthetic to non-synthetic oils, and lightened components. So the power loss was a 'after the fact' calculation. Regardless, whether its 1-4%, that should not be of concern to 99% of the people who frequent this forum. The people who do have to worry about it probably don't have time to post threads on the internet at all...

I was speaking to a guy a while back about this same subject of 9" power loss, and I could only chuckle when he told me he was running a stall converter. Why in the world he was worrying about a minute power loss at the axle housing when he was loosing lots of energy at the torque converter?

I understand your statement about the image of a 9" under a Chevrolet, but that is just mere opinion. My opinion is that I couldn't care less if it's a 12-bolt, Dana 60, or 9"...just as long as I have the axle housing that suits my needs and budget.

If you think about it, the 8.5" is the modern-day passenger 12-bolt. It is nearly as strong and has the same available parts...but people still go to a 9". GM still uses C-clips and a fixed pumpkin which is the biggest turn-off to a 12-bolt. If they were to fix that, the Hot Rod crowd would be very happy.

But it's good you brought up the clip eliminators. They're aweful. Any of the manufacturers of these will tell you they WILL eventually leak. Mine did. I second the recommendation to use Ford bearings (you can get GM ends to use your current brakes).

About the Quick Change setups, the currently available ones are either noisy (Circle track types), or very weak (street types). The stronger Quick Change sounds like a noisy gear drive and gets very old when cruising. If somebody where to come out with a strong, quiet version (maybe with helical gears?) I'd think it would be very popular.

Good points to both sides. Yes the C-clips suck. However all c-clip eliminators are NOT the same. Strange makes Pro-Race axle sets with thier Hy-Tuff axles and TAPERED ford style timken bearings designed for heavy side loading. Not like the usual roller bearings found in most kits. Ive got thousands of miles on mine in my 8.5 10 bolt and they have proven to be bullet proof with nary a drop of a leak. They make stock axles look like twigs. And they are available for around $500. Not bad.

Randy

The guy I went to said he would charge me between 6-700 to fix it. So I was thinking about spending some more and going with a whole new rear. That way I know it will last me for years.

I think helical gears would create a lot of wear on the back plate that secures the variable drive gears in the housing; though tapered rollers, or ball bearings in a cupped race could compensate. I was under the impression that all Quick Changes were created equal (more or less like choosing who is to fab your "Ford" 9 inch with no Ford parts). I know they hold up to Busch Grand National (or what ever it is they call the big boys) cars that are routinely putting out close to 700 horse. Franklin Racing in Riverview, used to make them a long time ago, for the roundy, rounders. They've been in the back of my mind for decades, wondering.

As far as a whine goes a lot of people choose the M-22 over the M-21 to get that "HiPerf" whine, same for choice of timing gear drives instead of belts. They like that straight cut sound, and the race car mystique that goes with it.

I'm still running my twelve bolt with a 4200 pound car that has a warmed over BBC pushing close to a thousand horse on engine alone. Due to a lack of safety equipment, and disagreements with NHRA over exactly what classification to pigeon hole my street car as, I rarely get to run at the track. When I do, I usually get in a low nine second pass before being asked politely to leave. I have put about 14,000 miles on this engine on the road and the twelve bolt hasn't failed me yet. Matter of fact I've only broken one twelve bolt in about thirty years of experimentation (I mean really broke it, so that it's scrap) I've broken axles, yokes, and twisted a few odd drive shafts, and shed a tooth or two on gears, but who hasn't?


Larger Dave