FE Power Forums
FE Power Forums => FE Technical Forum => Topic started by: 410bruce on September 13, 2020, 08:38:27 AM
-
Relatively light '67 Cougar, street tires, 4-speed.
Will the stock 8" rear live or should I be looking for a 9"?
I realize how it's driven will dictate the outcome but outside of 5000 RPM clutch drops, I would think it would last--even with a little abuse thrown at it. Am I wrong? :)
-
I seriously doubt it, if that were the case Ford would have tried. The street rod folks love them but in most of their applications GVW is less than 3000 lbs.. The other issue is cost; building both from scratch, similarly equipped the nine inch will only command about a 25% premium over the eight inch. If you elect the eight inch be sure to build into a, substantially stronger, '67-up case.
-
Depends almost entirely on how well your tires hook up.. With sticky tires a 428 probably exceeds the toque limit on an 8 inch
-
8” probably won’t last long, a friend of mine broke his with a 302 and M/T ET streets.
It had decent parts in it and the 302 was a pump gas engine.
-
Considering Ford felt the need to install a 9" in any Mustang or Cougar with over 230 HP, they must have thought the 8" was inadequate. Unless you never drove that 428 on dry roads, I wouldn`t waste any money on a 8", especially with a 428 and a 4 speed!
-
Jumping in the way-back machine, around 1980, I had a '63 Falcon sprint that I street raced 3 nights a week at least. It had a "hot" 289 and a C4 with a manual valve body and an 8" with a mini-spool with 4.62 gears. The rear tires were 29" tall L78-15 Caldwell soft rubber re-caps. They tucked up nice in the Falcon wheel wells as they were fairly narrow but tall.
That car ran mid-low 13's in full street trim. Hooked and booked. You could flat foot the throttle and the tires would spin maybe 1 revolution and then you were gone. I never hurt the 8" ever. I think the soft low end torque of the 289 coupled with no wheel hop and automatic trans kept it pretty safe. I regularly whupped up on big block muscle cars that were running the requisite T/A radials of the day or Positraction Torque Twister bias plys that were popular here in the Los Angeles area.
That said, I have destroyed more than 1 2 spider 9" Fords with relatively stock 390 Fords motors on regular street tires.
Your 8" will live fine if you drive like grandma. If it hooks or hops you'll bust it. You already knew this when you asked.
Save until you can do your 9" right. Custom width housing so you can get maximum tread width in your wheel well, good case with TruTrack or Detroit, and a Cal Tracks set up. Waste of time and money building a 500 horsepower motor if you can't hook it.
-
I would say not long i had a 67 fairlane with a 289 f 4b intake factory hyd cam headers accel dist. Not much but it run good had a 8 in with 3.50 gears m/t street tires.Came out at 3500 rpm the pinion broke out the front of the case broke the tail shaft housing and the case on the top loader.It had slapper bars and did not wheel hop.I still hear about it when some of the old bunch try to relive the old days.
-
I agree on the 8" not lasting long.
A good friend, here in my area, has broken at least 2 with not to hot 302's.
Wheel hop is a real killer with that 8".
The 9" in my factory, '65, K code, 2+2, survived a bunch of wheel hop, with 10" rear tires. All though similar designs, the 8" doesn't seem to be nearly as strong.
-
I say, drive it until it breaks!
Now, that said, I'd not spend a dime on your current 8" rear so if it's runable, use it.
-
I had an 8" 3:90 open behind a boss 302 4 speed that survived at least a hundred of 4k clutch dumps. Had traction bars set-up with preload for both wheels to spin. Never broke it.
-
Bruce: I've got a couple of 9" rear axles that would come very close to fitting your Cougar. They are 57-59 Ford housings and one 58 Edsel housing. I've got the axles as well.
Nice part is I'm only about 120 miles north of you on Hwy 101, Brookings Or. I'd go $120 for the housing and a set of axles. Don't want to ship.
I will not sell the true 57 Ford housings that don't have the dimples.
Richard >>> FERoadster
-
Well I ran several high 12's in my 85 Mustang with the weenie 7.5 rear 5 spd and slicks. Later put a 9 under it but didn't break the 7.5
-
Had a '63 Fairlane 260 4 speed 4 barrel, drive it to Daytona from MI to see the 500 race, must have been around '66. Showing off in front of the motel spinning the tires in the sand and hit clean pavement, spit the pinion right out the front of the case, didn't even break the u-joint. Paid way too much for a new pig and installed it at the motel. Seems I remember we used the motel's towels for shop rags and they were not very proud of us for that!
-
I had a '66 Fairlane 289 4 speed with 3.50 gears and posi in 8" rear that I drove with over 300 hp at the wheels. Installed a 358W 4V and headers, ported heads, intake, etc. Ran it hard for several years and never an issue with the 8" rear. Surprised a lot of "hot" mustangs with that 351 and 4 speed. Joe-JDC
-
I have a 84 mustang gt with a good little small block and have run it hard for 15 yrs and has the same t5 and 7.5 (3.73) gear never any slicks
-
Depends on how much traction you have and how hard the clutch grabs. A clutch that hits hard will break just about anything. A factory 428 car had big input/big output toploader, a 9" with N case. daytona pinion support and 31 splijne axles. Also had bigger u joints. So with the right clutch, regular street tires, and some sane driving if the 8" is in good shape I'd say will live awhile. that said I'd have on the future upgrade list at least what a 428 came with stock.
-
Wow guys, thanks for all the replies, was not expecting it.
Okay, overwhelming consensus is, bad idea. Do not use unless soft pedaling or driving like grandma. Check. ;D
Richard, Thank you for the offer, I will keep you in mind if something local doesn't show up.
Your guys stories made me think of one. Back in the '80s, a friend had a '67 Mustang coupe with a built 289, 4-speed--can't remember if it was a T-10 or Toploader--with a 4:11 traction lock 8". Well, after several years of abuse the 8" did let go. Pretty sure the pinion exploded. One too many 7000 RPM clutch pops. lol.
Thanks again!
-
1971 429 mustang, aluminum CJ heads , Comp 294 S drove several spirited years before switching to a 9 inch on a customer 71 Mustang originally a 302 car , never hurt it despite multiple one wheel peels every time he drove it .
-
Bruce,
The axles , side gears , spider gears and cross shaft are all the same 8" or 9" . YES the pinion is smaller and a potential failure point. BUT if you change the crush sleeve between the two pinion bearings to a solid spacer , the durability improves dramatically. Not to that of a 9" but certainly enough to work along with some respectful throttle application.
-
We got about 800 rounds out of a 4.11 8" running on slicks, automatic, 400+ HP. Eventually broke the pinion gear. Switched to 9" center with same 28 spline axles, got almost another season before breaking an axle. Went to 31 spline and no more problems.
With a 4 speed and that torque, no - go for the 9" now and remove a potential problem area.
8" 4.11 pinion center, 9" 4.11 on the right:
(http://raceabilene.com/misc/pinions.jpg)
When torque is applied, the main caps tend to want to spread. Those bitty teeth on the 8" will snap if the applied force moves too far out from the root of the tooth. I built a 9", C7 stock case (not N), 4.56 Richmond gears, 31 spline Mark Williams Masterline axles and that has been in the car since 1999. Thousands of rounds with all kinds of power, slicks, high stall converters, etc. Parks look just fine after all that abuse. If you really make power and use slicks, then you could consider something like a Strange iron case, which is affordable and way more stout than a old stock N unit. I have one on "my list" but the deburred C7 cases haven't failed me yet. If I got close to 600HP, then it's be a requirement. Right now at around 460 HP that rear is just loafing. I can run 4 passes in a hour at then thing doesn't even get warm.
-
Trick Flow 500-550 HP 428 will beat that 8 into dust pretty quick, however, run it if you want at the beginning, just don't put a penny in it, you are tossing it out the window
When it breaks, preferably before, build a 31 spline 9 inch, weld/box the spring pads, and it'll be fun and reliable after that
-
Awesome, thanks again, guys. There's plenty to do on the car to get it even road worthy as it sits so, I'll leave the 8" in for the time being and just use it to get the car around, while I budget for a 9" swap. 8)
-
If you want cheap an Explorer 8.8 is plenty strong. On my 65 Falcon i had a 3.55 geared 8" and broke the caps off the back, with a 200 six and automatic! Yet i had a guy come to me looking for gears in the 3.7 to 4.11 range and an 8" posi unit for his street rod. It had the stock 2.79 open diff and he was looking to race it at the Oldies drags and not cross the line half way through second gear in 14 seconds.
Turned out this street rod is a 4500lb 48 Buick with a 500" Caddy engine.... and a Maverick 8"... and huge 15" tread width, 33" tall Mickey Thompson Sportman tires. I didn't have the gears and have never had an 8" limited slip but just amazed that heavy car hadn't broken the rear end.
-
Some people can break an anvil with a rubber mallet. Others can drive cross country with a shoe string as a fan belt. I've never broken an 8" when I've owned one. I've built plenty of them too and never had one fail. NO it's not a nine inch but if respected , it will do it's job.
-
The roundy round guys used to buy any 8 inch gears I had back in the 90's , not sure what class ( Hobby Stock ? )they raced but it was a popular rear unit and I was surprised they were desireable , not sure if if it's still that way
-
As I mentioned , the only downfall is the crush sleeve that allows "pinion walk" . The more substantial 9" gear doesn't fail as easily but still suffers from the crush sleeve. If it eliminated in either diff , the "life" goes up dramatically.
-
I had one behind a 390 c6 in a 64 fairlane and the guy that sold me the assy told me if I could kill it with anything but slicks he would build and give me the 9 inch replacement when I sold the car it still had the 8 inch
-
I had an 8" behind a '79 Mustang with a turbo'd 2.3 that had some work done---including spray. The car would have no significant trouble with small-block 'vettes. I never had any difficulty with the 8". I WAS very leery of the 7.5 that the car came with.
KS