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Discussion Starter · #1 · (Edited)
How do they hold up? What's their power/torque limits?

Seen people running them behind some pretty seriously built motors,....even big blocks.....other's say even built, they'll grenade once power/torque levels start getting up there.

Just looking for some personal experiences......It may take awhile for me to find and set up the 9" I want for my Falcon, but I've got an 8" that's all ready with mini spool, 4:11's and aftermarket axles that'll bolt right in. If I do use the 8", I'm going to replace the spool with a standard posi 3rd member I have. The car's going to mainly be Street/Show, but it'll still have a moderately built dual quad 429 w/ Muthr Thumpr cam, C6 with stall converter and either M/T 28X11.50-15 ET Streets, or M/T 275/60/15 outlaw drag radials with Competition Engineering slapper bars (no massive Gasser Ladder bars until I float the leaf springs.....but that's another thread LOL)
 

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I ran an 8" for a while in a car I used to have. I didn't have that kind of engine though (360" AMC). Like a Ford guy I knew told me, Ford never used them with anything more than a 302 in front of them.
 

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I think the key is the tires, and how well they hook up. Considering how well those M/T tires will hook, and how wide they are, I'm afraid you might end up with some problems if you really get into it. Unless it's been reworked to 31 spline axles, the 28 spline axles will be a weak point, and may snap one. If you haven't purchased those tires yet, you should also be aware they're a very thin tire. Sidewalls are like a wrinkle wall, and "tread" is extremely thin and flexible. My buddy got a pair for his '35 Plymouth coupe, and you can actually wad them up with your hands. Can't imagine they'll last long on the street, or resist foreign objects well. The MT Sportsman would be a better street tire, with heavier tread and sidewall.
 

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Discussion Starter · #4 ·
Yeah, the ET Streets are a pair I originally bought for my '65 427 Biscayne project. And yes, after seeing how "doughey" they are, they're not going to be the primary tires on the Falcon. Since I just bought a complete set of newTorq Thrust Ds (15x4 front, 15x10 rear) the rear rims are actually a little wide for the ET Streets. So, I'll probably be going with some Sportsmans for regular street use. I have an "old school" wheel combo set (15x4.50 Appliance Cragar-style 5-spokes front, 15x8 chrome reverse steelies in back) that I'll proobably mount the ET Streets on for show until I can afford a pair of those mega-over-priced piecrust cheater slicks for the old school steelies.,....As for the rear's spline count, I'll have to check if the 8" was upgraded to 31-spline axles......I know the the rear was beefed up specifically for drag racing, and has aftermarket axles....but if 28-spline axles are a significant "weakness" on 8" rears, would a 28-spline be as much a weakness in 9" rears, or do their other HD strengths make up for it?.......I know a LOT of people who've put long-term major HP and torque on their 28-spline 9-inchers with no problems.

My whole question may be moot.....I've got a line on a complete drum-to-drum 9" from a 57 Ford for about $200-$300, which is 3/4 of an inch narrower than a Falcon rear.....but that's $200-$300, and I'm still looking at the cost of a posi/locker and gears.....the 8" is already mine, already built, and from a Maverick (an inch-and-a-half narrower than a Falcon rear) but I'd still need a posi/locker to replace the spool.

What I'll probably end up doing is using the 8 to get the car on the road (and take it easy on the rear), while I put the 9 together for eventual replacement....

That's assuming getting the engine set in, steering worked out, wiring done, and everything else it takes to put together a gasser goes without a hitch! LMAO!! Yeah, right!
 

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A 28 spline axle is weaker than a 31 spline, no matter what brand or model of axle it is. The more splines, the tougher they are.
There are inherent weaknesses in some rear axles with smaller ring gears, but an 8" ring gear shouldn't be a issue in strength itself. I'm running a 7.5" 10 bolt in my Austin, with Dutchman 28 spline axles, and a posi. I was worried about the 28 spline axles, but Dutchmans said the car was so light it wouldn't be an issue. The Pontiac axles actually had to be cut down in diameter to be re-splined to fit into the side gears when it was narrowed 20".
If you're on a tight budget, and want a really cheap, and tough rear axle; I'd consider a 8.8" Ford. At regular price they're $200 for a 3.73 or 4.11 posi here, and on holiday half price days, I buy them for $100. Drum rears are 58.5" wide and disc rears are 59" wide. Get an Explorer and they can be cheaply narrowed 3" by doing the short side axle swap, and just have the tube cut on the long side. You can probably sell the 8" and get enough to buy a 8.8" posi rear axle.
I used the stock width drum rear on my Falcon, and like the slightly extra width. I have a spare with short side axle, in case another project pops up, and I want to narrow it.
 

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As usual VALL is right on the $$$$. Very often how much tires hook-up is not included in the formula a hot rodder will use to try & figure out what needs to be done to make everything work together. Let us never forget how "variable" tires can be. Also, how easily how the rear suspension works can be altered by simply changing tire size, width or not paying attention to how "worn" a set of rear tires becomes which can tremendously effect the performance whole rear suspension. KEEPTIRES in the equation !!!!
 

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The 8" I had was from a Maverick. When I went to a 9", I had the housing made to the Maverick dimensions and used the 28 spline axles and the Maverick brakes. I guess my main reasoning was that the parts to go posi with a better ratio in the 8" would cost as much as going to a 9". The guy that did my work said I wouldn't have trouble with the axles but, as I said, it was a pretty mild engine turning "real" street radials.
 
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