stock 8" and rear end gears?
- Thread starter mean78
- Start date
The chunk is OK, Everything else that bolts to the housing, including the housing, is scrap.
MUSTANG J
Member
3.73= 3.80 in 8" land 
I have not managed to kill an 8" (yet). Joe morgans Turbo Pinto was running 10's with the stock axles!! From what I have seen and heard failures seem to happen to stick shift cars with high horsepower and rarely happen to automatic cars. Many four and six cyl Mustang II's had numrically higher gears.(3.55's and 3.40's) V8's generally got crap gears like 2.79's. Since the 4 and 6 cyl cars did not have the power to kill gears, it is not unusal to find perfect condition gears in these 30 something year old cars!
http://mustangii.org/decoder/axle/
Remember a Mustang II is not a Fox Mustang, 3.55's are mild in a Fox with a 5 speed but, high winding in a II with no over drive and generally much shorter tires.
http://www.miata.net/garage/tirecalc.html
Calculator shows 195/70/13's are 23.7" tall Stock 5.0l Fox tires were 225/60/15's 25.6" tall. It generally gets worse because most II's have 205/60/13's on them (because they are one of the few near-wide 13" tires still around) Only 22.7" tall.
Depending on what you are running for tires and wheels, You may consider 3.40's (very popular in V6 Mustang II's)
Summit has "summit brand" 3.55's for an 8" for $125.95!!
I have not managed to kill an 8" (yet). Joe morgans Turbo Pinto was running 10's with the stock axles!! From what I have seen and heard failures seem to happen to stick shift cars with high horsepower and rarely happen to automatic cars. Many four and six cyl Mustang II's had numrically higher gears.(3.55's and 3.40's) V8's generally got crap gears like 2.79's. Since the 4 and 6 cyl cars did not have the power to kill gears, it is not unusal to find perfect condition gears in these 30 something year old cars!
http://mustangii.org/decoder/axle/
Remember a Mustang II is not a Fox Mustang, 3.55's are mild in a Fox with a 5 speed but, high winding in a II with no over drive and generally much shorter tires.
http://www.miata.net/garage/tirecalc.html
Calculator shows 195/70/13's are 23.7" tall Stock 5.0l Fox tires were 225/60/15's 25.6" tall. It generally gets worse because most II's have 205/60/13's on them (because they are one of the few near-wide 13" tires still around) Only 22.7" tall.
Depending on what you are running for tires and wheels, You may consider 3.40's (very popular in V6 Mustang II's)
Summit has "summit brand" 3.55's for an 8" for $125.95!!
I am using a 3:55 chunk from a v-6 car in mine. hasn't given me any issues yet, but it has also only been one summer, and i didnt drive it all that much. unless you are building a monster motor with some kind of unlimited amount of torque, the way i understand it the 8" will hold up just fine. i would worry more about the rad-4. again, this is what i have, and again for only one summer, but it is still working. it does have some kind of vibration at higher speeds, and i have narrowed it down to the tranny. i guess what i am trying to say is go ahead with the chunk swap and try to get that 5 speed swap done as soon as possible!!
MUSTANG J
Member
My II has 300Hp plus a 100Hp nitrous kit. I beat on my car like its my Job, and The rebuilt 3.55 pig from a 1974 Mach 1 V6 (with a mini car spool) has never broken. I put 25000KM on it last summer without any problems. Those in the Know think the C4 Automatic is the only reason the 8" is still alive. 
Drastic weight reduction and BF Goodrich T/A's (low traction) likely help too.
Drastic weight reduction and BF Goodrich T/A's (low traction) likely help too. 
Dano78
Founding Member
I'd just hunt for another chunk. It'll probably be pretty spendy to have someone rebuild it, but.... then you got all new stuff, and not a 30+ yr old question mark.
Randy's Ring and Pinion, Summit, Jegs, all should carry what you need.
Richmond and Motive Gear have a pretty good gear selection, even if they don't list them in the catalogs.
I'm still running the II 8" and a while back approx 380hp 302 (now a 366hp 289) with a mini-spool. Never had any troubles with it .....yet. Naturally it doesn't hook as nice as it should but does hook up pretty good with the SSM bars. I'm betting that if I were to launch it a few times at 3500rpm on slicks, it might frag it, or bust an axle.
I've got 3.50:1 gears and 235/60/15 tires. It turns a little over 3000 RPMs on the freeway (65mph) with a C4 auto. but that's right where the Tunnel Ram likes it too.
Randy's Ring and Pinion, Summit, Jegs, all should carry what you need.
Richmond and Motive Gear have a pretty good gear selection, even if they don't list them in the catalogs.
I'm still running the II 8" and a while back approx 380hp 302 (now a 366hp 289) with a mini-spool. Never had any troubles with it .....yet. Naturally it doesn't hook as nice as it should but does hook up pretty good with the SSM bars. I'm betting that if I were to launch it a few times at 3500rpm on slicks, it might frag it, or bust an axle.
I've got 3.50:1 gears and 235/60/15 tires. It turns a little over 3000 RPMs on the freeway (65mph) with a C4 auto. but that's right where the Tunnel Ram likes it too.
Dano78
Founding Member
Oh! also wanted to add that you might just want to just re-set the backlash.
I've been finding quite a few 9" rears on 1/2 ton trucks with pinion yokes walking right off! (excessive rear u-joint wear, vibrations, etc..) Just check the torque on that nut and see if it takes anymore turns. If it's loose you might be able to re-torque with the current crush sleeve and possibly cure the backlash. The 9", i believe, is 100ft lbs, the 8" has to be pretty close if not the same as that.
that makes alot of sense, ill give it a try tommorrow at work, ya i really want to build a AOD or atleast a t-5......i dont know of anyone who has done a AOD tho
well this summer im tearing it down for paint, but im also going to do knew leafs and bushings all around, and a posi but not sure what gears yet, so the backlash isnt that big of a deal
i picked up a 9" a little while back that a guys had, he said i could just take it, but i probably dont need that for now
oh and also, you said something about those ssm traction bars, (i think thats what they are)
i hear alot about those but im not a big fan of low hanging traction bars, but i noticed they curve up with the leaf, could i get a link to a pic or something?
what do you think of them?
thanks for the help
i hear alot about those but im not a big fan of low hanging traction bars, but i noticed they curve up with the leaf, could i get a link to a pic or something?
what do you think of them?
thanks for the help
MUSTANG J
Member
SSM went tits-up years ago. Someone's buddy on the forum makes them though.
This dude:
http://www.stumpysfabworks.zoomshare.com/2.html
He makes SSM style lift bars and pretty cool lookin' Mustang II frame connectors. (wish I had a time machine). Someone sold me Comp Pinto frame connectors and said they would fit. They did, but it took a spool of mig wire and a plazma cutter LOL
This dude:
http://www.stumpysfabworks.zoomshare.com/2.html
He makes SSM style lift bars and pretty cool lookin' Mustang II frame connectors. (wish I had a time machine). Someone sold me Comp Pinto frame connectors and said they would fit. They did, but it took a spool of mig wire and a plazma cutter LOL
SSM went tits-up years ago. Someone's buddy on the forum makes them though.
This dude:
http://www.stumpysfabworks.zoomshare.com/2.html
He makes SSM style lift bars and pretty cool lookin' Mustang II frame connectors. (wish I had a time machine). Someone sold me Comp Pinto frame connectors and said they would fit. They did, but it took a spool of mig wire and a plazma cutter LOL
haha well ill have to take a look, does anyone have any pictures of these parts?....while installed?
this really is a cool sight for us II guys
take a look on page 6 of members rides. there is a shot of my cobra, and you can see them. ill try to get out to the garage and take a few closer ones for you later on, let me know what you want for pics. mine are the old ssm bars, and i had to modify them just a bit to get them in.
i used the ssm connectors in an old coupe i once had. still have the connectors, hopefully have them in this car this summer. my ex wife wrecked the old coupe...probably the only things that really saved her life. anyways, if stumpys are anything like them, i thought they did the job. stiffened her up pretty good.
stumpys sub conn are just like a set of custom made conn.
they fit very tight to the floor. bolt to the rear spring perch and fit over the top of the front rail giving you more area to weld up. i removed my ssm conn and will be installing stumpys in a few weeks. he sells them as weld in or bolt in and the hardware is included.
they fit very tight to the floor. bolt to the rear spring perch and fit over the top of the front rail giving you more area to weld up. i removed my ssm conn and will be installing stumpys in a few weeks. he sells them as weld in or bolt in and the hardware is included.
ya i noticed that he sells them in bolt on and in weld in.
what is different from the ssm conn`s vs. the stumpy made ones?
Steel Steeds
New Member
The Stumpy's bolt-in and weld-in are the same, one just comes with bolts. I bought the bolt-ins so that I can install them, then drive the car somewhere to have them welded into place professionally.
I hope to be installing them (along with the lift bars) next month, after I get the rebuilt 351 and T-5 dropped back into the King's engine bay.
I bought one of those Auburn Pro differentials, set up with 3.80 gears. I know they aren't the best, but it was a good price, so I figure I'll run those until they die and then pony up for a True Trac. I was thrilled to find those for the 8".
I hope to be installing them (along with the lift bars) next month, after I get the rebuilt 351 and T-5 dropped back into the King's engine bay.
I bought one of those Auburn Pro differentials, set up with 3.80 gears. I know they aren't the best, but it was a good price, so I figure I'll run those until they die and then pony up for a True Trac. I was thrilled to find those for the 8".
Dano78
Founding Member
The SSM ones are more or less junk. I have them on my car too along with the traction bars. More or less the SSM frame connectors are 2 straight pieces of square tubing that you mickey-mouse onto the front and rear subframes with a few gussetts. They hang down and if your car is lowered (like mine is) they hit on stuff occasionally. Not really worth the $122 I paid.
Stumpy took the idea a few steps further and really makes a nice clean tight connector. I'd buy his, and probably go with a weld-on set if you're a welder. Once they are on, you're gonna want to leave them on anyways and welding them in is just a bit stronger.
The SSM slapper bars, I really like. They work GREAT. They are straight pieces, not curved but they do stay tight to the spring, not hanging down like some Lakewood universals do. I had chrome Lakewoods on a '78 T-Top Cobra I had and they didn't fit bad either... not hanging down.
But since SSM is no more, Stumpy's lift bars are the ones to get. They are basically the same as the SSM bars.
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