The Jalopy Journal
Discussion in 'Traditional Hot Rods' started by Roger Loupias, Apr 11, 2022.
The 8" is not a bad axle, but ask yourself why Ford put the 9" behind the 271 hp 289.
I suspect the 'screaming deal' is because the seller couldn't live with that ratio on the street either and isn't finding too many takers. I wouldn't worry about longevity; if you haven't broke the 8" yet you'll be unlikely to unless you switch to stickier tires or add more power.
Ford considered the 8" as a medium-duty axle. Never installed in any full-size cars or trucks, and limited to non-HiPo 302 or smaller motors where it was used (OK, Ford did use it behind some 351Ws in the late '70s, but they were smogged to where they made no more power than the earlier 302). Keep torque below about 400 ft-lbs and don't do 'dump the clutch' starts and they'll live.
I have seen the pinion ripped out of the housing on an 8" ford. happened back in the early '70's when I had a '64 Dodge Dart GT Convertible 4 sp car ( wish I had it now) I was in a street race in Sacramento , Ca. was racing against a '64 Falcon w/ a hot 289. I had already beat his buddies stock Falcon 260. The '64 Dropped the rear on the starting line. when he popped the clutch.
Wait, you mean a set of 35s outside the fenders wouldn't look kool?
I smell what you're steppin in, but within reason there could be enough compromise. My 7.00-16s don't look hateful at all, and in fact are a popular size for rears. A radial with more aspect ratio could soften the tone of the screaming, that's why I posted what mine figures out to. Huge change? No, but maybe enough? Worth a few pokes into a ratio calculator to see.
Basically when you are done your high gear will be about the equivalent of your current 2nd gear right now. Make a deal with yourself that you will drive your car around for a month with some expressway travel involved and never put your automatic into drive. Use only 2nd gear as your highest gear and you will get an idea of what its going to be like with the 3.80 gears..............
Then think again about going to 3.80 or whatever other gear might work for you and adding an OD transmission. I know you have already said "NO" to the OD, but the laws of physics won't change just because you don't want to make the best choice for performance AND driveability. You will either have low end power or high speed driveability .............but not both if you go the route you are planning to go. Do the 2nd gear drive and then you will see if its still enjoyable to cruise.
There's not much point in having 3.80 gears, if you're not going to do "dump the clutch starts."
I’m running an 8” in my Falcon..it has a hot 289 (10.8:1, trickflow heads, Cam that’s good for 1800-6000 rpm…maybe 350+ hp ) … but I have a C4…no clutch dumping for me..I have a 2500-2800 stall converter..the 8” fit so well…was gonna go 9”, spoke to the guy in Jersey about my car, how I wanted to drive it ( not a track car…hot street car ) he felt the 8” would hold up to what I had ( light car, Auto, Not crazy hp/torque) I spring for the Eaton unit versus the clutch unit..so far so good..I also tend to do more “from a roll” fun..
It’s a 3:55 gear and with my 26” M&H on the back I can honestly say I wouldn’t want to really do a ton of highway driving with it..although it’s real fun getting on the freeway…
Also do a google search on Ford 8” you’ll find lots of opinions of them..some good…some bad..the general consensus seems to be in a light car, with less than 350 hp, no slicks, and especially an automatic they will last a bit longer than something with 475 hp that weight 4400lbs, with 3 pedal, and running big sticky tires
Less reciprocating mass= more net horsepower. Great to tool around in if you don't hook it up.
Exactly. Some people can tear up an anvil.
Because engineers add a safety factor to all of their designs. Probably 100% for automotive drivetrains, but I'm not sure. We added 100% safety factor to all designs that involved human safety when I was in design years ago.
Ok. That's a 29" tire.
65 mph, 29" tire, 3.00 ratio would give 2320 rpm.
2320 rpm divided by 3.00 = 773.333.
773.333 times 3.80 = 2938.666
Rpm with new ratio is 2939. (But only if nothing else is changed)
I have a rear end with an 8" crownwheel and it is way more than strong enough.
Hint: It is not the Ford 8"....
Pick your tire size and gear ratio in the chart below. It is for only 65 mph with a 1:1 high gear.
Add about 1/10 more rpms to approximate 75 mph. So if the chart says 3000 rpms for 65, then 1/10 of 3000 is 300....3300 rpms for 75 mph.
For a .7 overdrive high gear, multiply 3000 x .7 = 2100 rpms +1/10 (210) 2310 rpms for 75 mph
Basically this means that by putting a .7 OD trans in along with changing the rear axle ratio to 3.80, a vehicle would have a large increase in low end torque/acceleration, while expressway driving would essentially remain at the same rpm as the originall 3.00 ratio. Win/Win
View attachment 5373299
Not all 8" diff carriers were created equal. The later carrier with 3 vertical ribs is much stronger than the early notoriously weak horizontal rib case.
My brother spit the pinion out of one of the early carriers with a mild 289 and 70's era street tires.
Yep, post-'67 carrier much preferred.
Actually , slipping the clutch in order to maintain traction , thus achieving faster acceleration is very FUN ! Sitting & spinning is silly !
Thanks for your input on this.
What models were those found in?
Any post 67 Mid Sized Ford with an 8”…mainly 6 banger of the following models, Mustang, Cougar, Falcon, Comet, Maverick
Strength , nothing is built so strong it can not be broken by abuse . When I was a teenager , my 67 Fairlane had a 390 4 speed , I swapped in a 428 SCJ , it took 2 weeks to blow the carrier retaining bolts , out of the case . The next move was N case with Daytona pinion support . It lasted until I sold the car . The very strangest thing that I could not believe is the driveshaft was 2 piece , one pressed into the other with a rubber sleeve between the 2 pieces , it never gave me one issue .
Also Fairlane, Torino, Montego (each through '71), Granada, Monarch, and Versailles with a 302 or smaller motor (excluding the 289 HiPo) . The exception on the last three was if ordered with 4 wheel discs, the axle would be a 9". There were also some 351W powered versions of those three with the 8".
If you're going to the junkyard, look for the 302 powered cars. Should be able to still find one somewhere. Millions were built. I'd look for a Maverick Grabber for a complete axle swap but those are getting scarce.
For center sections also look at Mustang II's. Also Pinto and Bobcat V6's, esp. station wagons. I found a couple of 3.55 gear sets in the V6, manual trans wagons.
What key factor or factors made this post 8" greater than the pre 67's?
BITD , we used to beat the crap out of 55 - 64 Chevy rears , up to 409's ! Those chev rears are considered less stout compared to 10 bolt chev & 8" fords . 9" is POPULAR because of its NASCAR use & aftermarket support & media advertising . All that doesn't mean you have to have one !
Seriously? The difference is nil, not worth arguing about. My point is you'll spend similar money on the 9" and have the strength, too. Housing and parts availability with the 9" is great, outfits like Currie can build just about anything you want. If I had something light that would never be womped on, sure, I would use an 8" if I had it, but if I had to spend money, would try to get a 9". I had planned to use the 8" in my 65 Caliente in my chopped 51, but sold that one, so at some point will have a narrow 8" available for someone with a cruiser. At the extreme end, I have 3 narrow 9" units, a 40 spline Mark Williams with a spool, a 40 spline Strange in the Falcon, both with 4-links, and a 35 spline with a Detroit Locker/ 4.30s and ladder bars that may go in the 56 Bird
Making me nervous I have a 351w with an 8"
See post #42.
No problem if you don't hook the car up and dump the clutch @ high rpm.
Thanks for saying that. Sometimes suggestions are not appreciated, so I'm glad you took them as intended.
As for the 3rd member. I think you already have a nice looking car and don't really want to get too deep $$$ wise into doing things like upgrading to a 9" as well as possibly dropping money in for a transmission upgrade. If you search, you will come across a newer 8" third member ....or complete rear end.
What I would do is weigh the economics of obtaining an 8" and having the 3rd member built with new gears and some sort of posi type system. If you find that you can get an 8" rearend, simply swap the center section and resell it for what you gave for it. Then buy a posi (and get it built. If you just find a center section, get it built and save your old one in case you ever do tear the new one up.
There are some narrow Ford 9" rears but they are almost impossible to find and people always want lots of money if you do find one. They have smaller axles and smaller bearings, so they are not much better than an 8"....if any.
Its really better to buy a complete 9" because the odds n ends parts will get expensive. You can pick up 9' rears complete for about $150 each. I bought 3 last year in one day and gave $150 or less for each one. People ask more but they usually want to sell and will take less. Then you have bigger axles even if they are 28 spline. Narrowing a housing is pretty easy, and then get someone local to respline and shorten them........or order some quality Moser axles. By the time you buy new bearings, respline, shorten, and drill for wheel pattern......I'd just buy the new Mosers.
Then the rear end that you have under your car becomes valuable because there is always someone wanting one that will not need to be narrowed and they can just bolt it in their car. It offsets the expense of the 9". Probably get quite a bit for it because someone always wants one they can simply bolt in............
Gear ratios and posis for 9" are more plentiful and possibly less expensive.
Summing it all up..........
The simplest choice is finding another 8" with the better pumpkin. But a little more time and effort will provide a 9" and the cost can be offset by the value of your current narrow 8".
Actually, the simplest option is to find an 8.8 from an Explorer. 3.50, 3.73, or 4.10 , most with Traction Lock.
Easy to narrow.
They aren’t accepted by many here, though.
Yep, my 97 Exploder is one with the 5.0, AOD, and 3.73 TL, disc brakes. Keep waiting for the vehicle to go south and mine it for driveline, but it runs and drives great, frigid AC, just keeps chuggin
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