Ford 9 inch question...
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From: Lakeland, FL
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St. Jude Donor '03, '06, '17
Ford 9 inch question...
I'm planning in having a Ford 9 inch rear installed in my '68 Vert.. I'm getting a new engine with over 600 HP and the corvette differential will probably not hold up when running with slicks.
Now I have to decide what way to go...
Posi, Spool or Detroit Locker..
Posi would be the most streetable choice.. but how many hp/torque (on slicks) can a posi take??? I did some searches on GOOGLE, looking for any sites with HP ratings for those different types.. but didn't get any satisfactory results...
What are the strongest posi units available - and how many horsepower can they take?
How bad would the drivability be if I'd go with a spool???
BTW - I'm converting my car from my Tremec TKO 5-speed to a TH700R4 with fully manual valvebody, reversed shift pattern and transbrake...
Any information is greatly appreciated..
Now I have to decide what way to go...
Posi, Spool or Detroit Locker..
Posi would be the most streetable choice.. but how many hp/torque (on slicks) can a posi take??? I did some searches on GOOGLE, looking for any sites with HP ratings for those different types.. but didn't get any satisfactory results...
What are the strongest posi units available - and how many horsepower can they take?
How bad would the drivability be if I'd go with a spool???
BTW - I'm converting my car from my Tremec TKO 5-speed to a TH700R4 with fully manual valvebody, reversed shift pattern and transbrake...
Any information is greatly appreciated..
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From: Pettis Performance 565 with two stages of Nitrous Supply nitrous 1.082, 4.61 at 155, 7.17 at 192
Re: Ford 9 inch question... (GrandSportC3)
No need for a spool at that power level, you will be fine with a good posi. I have several buddies running in the low 700 hp #'s with heavy cars and a good posi is fine for them.
BTW chack on racingjunk.com under rearends and you will fine lots of 9in. rears ready to go. You may even be able to get something you did not think you could afford. I got as killer deal on a all chromemoly narrowed fabricated backbraced 9in. with Strange 40 spline axels, spool, brakes, aluminum 3rd member etc for about 1/3 retail. The rear was built to handle 2000 hp.
[Modified by 69 N.O.X. RATT, 8:35 PM 4/10/2004]
BTW chack on racingjunk.com under rearends and you will fine lots of 9in. rears ready to go. You may even be able to get something you did not think you could afford. I got as killer deal on a all chromemoly narrowed fabricated backbraced 9in. with Strange 40 spline axels, spool, brakes, aluminum 3rd member etc for about 1/3 retail. The rear was built to handle 2000 hp.
[Modified by 69 N.O.X. RATT, 8:35 PM 4/10/2004]
Thread Starter
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Joined: Jul 2001
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From: Lakeland, FL
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St. Jude Donor '03, '06, '17
Re: Ford 9 inch question... (69 N.O.X. RATT)
No need for a spool at that power level, you will be fine with a good posi. I have several buddies running in the low 700 hp #'s with heavy cars and a good posi is fine for them.
BTW chack on racingjunk.com under rearends and you will fine lots of 9in. rears ready to go. You may even be able to get something you did not think you could afford. I got as killer deal on a all chromemoly narrowed fabricated backbraced 9in. with Strange 40 spline axels, spool, brakes, aluminum 3rd member etc for about 1/3 retail. The rear was built to handle 2000 hp.
BTW chack on racingjunk.com under rearends and you will fine lots of 9in. rears ready to go. You may even be able to get something you did not think you could afford. I got as killer deal on a all chromemoly narrowed fabricated backbraced 9in. with Strange 40 spline axels, spool, brakes, aluminum 3rd member etc for about 1/3 retail. The rear was built to handle 2000 hp.
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From: Clymer PA
Re: Ford 9 inch question... (GrandSportC3)
Olivier:
I've been contemplating doing the same to the Corvette and caging it once I get the money. A spool on the street would be rough, I would do it but I'm just that kind of guy. You would have to be really careful going around turns otherwise broken axle city. I would tend to think a posi would be fine at your target power level. However I think you will run into nothing but problems with a 700R4 and transbrake....those are two words (IMO) that shouldn't go together. I know you want the overdrive gear but I foresee many future transmission problems. A built TH350 would be a better choice IMO.
I've been contemplating doing the same to the Corvette and caging it once I get the money. A spool on the street would be rough, I would do it but I'm just that kind of guy. You would have to be really careful going around turns otherwise broken axle city. I would tend to think a posi would be fine at your target power level. However I think you will run into nothing but problems with a 700R4 and transbrake....those are two words (IMO) that shouldn't go together. I know you want the overdrive gear but I foresee many future transmission problems. A built TH350 would be a better choice IMO.
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From: Lakeland, FL
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St. Jude Donor '03, '06, '17
Re: Ford 9 inch question... (bence13_33)
Olivier:
I've been contemplating doing the same to the Corvette and caging it once I get the money. A spool on the street would be rough, I would do it but I'm just that kind of guy. You would have to be really careful going around turns otherwise broken axle city. I would tend to think a posi would be fine at your target power level. However I think you will run into nothing but problems with a 700R4 and transbrake....those are two words (IMO) that shouldn't go together. I know you want the overdrive gear but I foresee many future transmission problems. A built TH350 would be a better choice IMO.
I've been contemplating doing the same to the Corvette and caging it once I get the money. A spool on the street would be rough, I would do it but I'm just that kind of guy. You would have to be really careful going around turns otherwise broken axle city. I would tend to think a posi would be fine at your target power level. However I think you will run into nothing but problems with a 700R4 and transbrake....those are two words (IMO) that shouldn't go together. I know you want the overdrive gear but I foresee many future transmission problems. A built TH350 would be a better choice IMO.
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From: The Top of Utah
Re: Ford 9 inch question... (GrandSportC3)
I am not familiar with the "new" Detroit Locker, but I have an old one in the rear of my pick up. They are very strong and reliable. Unlike a posi traction there are no friction clutches to wear out. It has steel, bullet, clutching teeth, that stay engaged in straight ahead travel, locking both axles together. Under no circumstance, can either wheel turn slower than the ring gear. When you go around a corner, the vehicle is driven by the inside tire and the outer wheel is allowed to ratchet ahead and turn faster. It is the strongest, most positive, differentiating device *I* know of. It can be a little "clunky" at times. On occasion, the clicking or ratcheting noise can be heard, especially in turns. It is known to be harder on tires, with the driving of only the inside wheel on turns, but nowhere near as bad as a spool. If a posi won't do it for you, the Detroit Locker, is the beefiest differential there is. Good luck, and...
RACE ON!!!
RACE ON!!!
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From: Lakeland, FL
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St. Jude Donor '03, '06, '17
Re: Ford 9 inch question... (SmokedTires)
Just by switching to the automatic will help your rear differential live longer 
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Thread Starter
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Joined: Jul 2001
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From: Lakeland, FL
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St. Jude Donor '03, '06, '17
Re: Ford 9 inch question... (CFI-EFI)
I am not familiar with the "new" Detroit Locker, but I have an old one in the rear of my pick up. They are very strong and reliable. Unlike a posi traction there are no friction clutches to wear out. It has steel, bullet, clutching teeth, that stay engaged in straight ahead travel, locking both axles together. Under no circumstance, can either wheel turn slower than the ring gear. When you go around a corner, the vehicle is driven by the inside tire and the outer wheel is allowed to ratchet ahead and turn faster. It is the strongest, most positive, differentiating device *I* know of. It can be a little "clunky" at times. On occasion, the clicking or ratcheting noise can be heard, especially in turns. It is known to be harder on tires, with the driving of only the inside wheel on turns, but nowhere near as bad as a spool. If a posi won't do it for you, the Detroit Locker, is the beefiest differential there is. Good luck, and...
RACE ON!!!
RACE ON!!!
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From: The Top of Utah
Re: Ford 9 inch question... (GrandSportC3)
I think the increase tire wear is a bit over played. I haven't really noticed it on my pick up. In sharp low speed turns you can sometimes hear that inside tire scuffing. One thing to be aware of: It can steer the vehicle, when there is a transition in the power source. Driving down the interstate and letting off the gas, makes the truck want to steer, slightly, as the engine backs down. It starts to pull in the other direction, when you get back on the gas. As a matter of habit, I slip my A4 into neutral as I cross the finish line. I don't like the forces put on the engine by the car driving the engine, especially at higher rpms. That probably isn't a bad idea with the No Spin. I don't think a lot of drag racers are aware of these. They're great.
RACE ON!!!
RACE ON!!!
Thread Starter
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Joined: Jul 2001
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From: Lakeland, FL
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St. Jude Donor '03, '06, '17
Re: Ford 9 inch question... (CFI-EFI)
I think the increase tire wear is a bit over played. I haven't really noticed it on my pick up. In sharp low speed turns you can sometimes hear that inside tire scuffing. One thing to be aware of: It can steer the vehicle, when there is a transition in the power source. Driving down the interstate and letting off the gas, makes the truck want to steer, slightly, as the engine backs down. It starts to pull in the other direction, when you get back on the gas. As a matter of habit, I slip my A4 into neutral as I cross the finish line. I don't like the forces put on the engine by the car driving the engine, especially at higher rpms. That probably isn't a bad idea with the No Spin. I don't think a lot of drag racers are aware of these. They're great.
RACE ON!!!
RACE ON!!!
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From: Lackey, my own dragstrip VA.
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Re: Ford 9 inch question... (GrandSportC3)
For the street.....Spool 
We welded up a std diff one time ( guy ready to upgrade to a 12 bolt) to show a him he wanted other than a spool for street use
He found driving it was no fun on the street. Straight was fine but tight turns.....
Detroit or Dana Locker all the way...........only metal parts to wear out vs. friction material.
I like them and have used them in quiet a few racing applications to boot.
9" very easy to work on as well. Takes a little more power to turn them, but the trade off is they live a long life when set up right
Are ya buyin a turn key and from who? 31 or 35 spline
Assure you match your u-joints to the power as well
Good luck
We welded up a std diff one time ( guy ready to upgrade to a 12 bolt) to show a him he wanted other than a spool for street use
He found driving it was no fun on the street. Straight was fine but tight turns.....Detroit or Dana Locker all the way...........only metal parts to wear out vs. friction material.
I like them and have used them in quiet a few racing applications to boot.
9" very easy to work on as well. Takes a little more power to turn them, but the trade off is they live a long life when set up right
Are ya buyin a turn key and from who? 31 or 35 spline
Assure you match your u-joints to the power as well
Good luck
Thread Starter
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Joined: Jul 2001
Posts: 182,997
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From: Lakeland, FL
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St. Jude Donor '03, '06, '17
Re: Ford 9 inch question... (ALLTHROTTLE&NOBOTTLE)
For the street.....Spool
We welded up a std diff one time ( guy ready to upgrade to a 12 bolt) to show a him he wanted other than a spool for street use He found driving it was no fun on the street. Straight was fine but tight turns.....
Detroit or Dana Locker all the way...........only metal parts to wear out vs. friction material.
I like them and have used them in quiet a few racing applications to boot.
9" very easy to work on as well. Takes a little more power to turn them, but the trade off is they live a long life when set up right
Are ya buyin a turn key and from who? 31 or 35 spline
Assure you match your u-joints to the power as well
Good luck
We welded up a std diff one time ( guy ready to upgrade to a 12 bolt) to show a him he wanted other than a spool for street use
He found driving it was no fun on the street. Straight was fine but tight turns.....Detroit or Dana Locker all the way...........only metal parts to wear out vs. friction material.
I like them and have used them in quiet a few racing applications to boot.
9" very easy to work on as well. Takes a little more power to turn them, but the trade off is they live a long life when set up right
Are ya buyin a turn key and from who? 31 or 35 spline
Assure you match your u-joints to the power as well
Good luck
[Modified by GrandSportC3, 2:47 PM 4/16/2004]
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From: Clymer PA
Re: Ford 9 inch question... (GrandSportC3)
Olivier:
I was just saying that a posi would do the trick. There are guys at my track running this setup with transbrakes. A locker is tougher, no doubt, but if you are after strength why are you going with a 700R4 transmission? A "done-up" TH350 will take the power much better....or if you want to step it up a little more go with a "done-up" TH400 (more parasitic loss than a TH350, but it is stronger). I'm just throwing some ideas your way. I talk a lot with the drag racers at my track and haven't run into one yet that runs a 700R4 (the majority of them run, TH350s, TH400s or Powerglides).
I was just saying that a posi would do the trick. There are guys at my track running this setup with transbrakes. A locker is tougher, no doubt, but if you are after strength why are you going with a 700R4 transmission? A "done-up" TH350 will take the power much better....or if you want to step it up a little more go with a "done-up" TH400 (more parasitic loss than a TH350, but it is stronger). I'm just throwing some ideas your way. I talk a lot with the drag racers at my track and haven't run into one yet that runs a 700R4 (the majority of them run, TH350s, TH400s or Powerglides).
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From: Lakeland, FL
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St. Jude Donor '03, '06, '17
Re: Ford 9 inch question... (bence13_33)
Olivier:
I was just saying that a posi would do the trick. There are guys at my track running this setup with transbrakes. A locker is tougher, no doubt, but if you are after strength why are you going with a 700R4 transmission? A "done-up" TH350 will take the power much better....or if you want to step it up a little more go with a "done-up" TH400 (more parasitic loss than a TH350, but it is stronger). I'm just throwing some ideas your way. I talk a lot with the drag racers at my track and haven't run into one yet that runs a 700R4 (the majority of them run, TH350s, TH400s or Powerglides).
I was just saying that a posi would do the trick. There are guys at my track running this setup with transbrakes. A locker is tougher, no doubt, but if you are after strength why are you going with a 700R4 transmission? A "done-up" TH350 will take the power much better....or if you want to step it up a little more go with a "done-up" TH400 (more parasitic loss than a TH350, but it is stronger). I'm just throwing some ideas your way. I talk a lot with the drag racers at my track and haven't run into one yet that runs a 700R4 (the majority of them run, TH350s, TH400s or Powerglides).
I'm planning on driving 5000 miles per year on the street with that car.. and I need a overdrive tranny, and the only affordable one is the TH700R4.. My transmission shop says that they can build it to 800 HP... I'll have 4.11 gears in my Ford 9 inch and without overdrive - it wouldn't be streetable... A posi will require more mainanance than a locker... I want to be on the save side - because I would not rebuilt the posi myself and it would cost me $$ to get it rebuilt every once in a while.. Moser Engineering says that their locker should easily last several hundred passes.... A posi probably won't...
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From: Lackey, my own dragstrip VA.
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Re: Ford 9 inch question... (GrandSportC3)
Olivier:
I was just saying that a posi would do the trick. There are guys at my track running this setup with transbrakes. A locker is tougher, no doubt, but if you are after strength why are you going with a 700R4 transmission? A "done-up" TH350 will take the power much better....or if you want to step it up a little more go with a "done-up" TH400 (more parasitic loss than a TH350, but it is stronger). I'm just throwing some ideas your way. I talk a lot with the drag racers at my track and haven't run into one yet that runs a 700R4 (the majority of them run, TH350s, TH400s or Powerglides).
Shane,
I'm planning on driving 5000 miles per year on the street with that car.. and I need a overdrive tranny, and the only affordable one is the TH700R4.. My transmission shop says that they can build it to 800 HP... I'll have 4.11 gears in my Ford 9 inch and without overdrive - it wouldn't be streetable... A posi will require more mainanance than a locker... I want to be on the save side - because I would not rebuilt the posi myself and it would cost me $$ to get it rebuilt every once in a while.. Moser Engineering says that their locker should easily last several hundred passes.... A posi probably won't...
I was just saying that a posi would do the trick. There are guys at my track running this setup with transbrakes. A locker is tougher, no doubt, but if you are after strength why are you going with a 700R4 transmission? A "done-up" TH350 will take the power much better....or if you want to step it up a little more go with a "done-up" TH400 (more parasitic loss than a TH350, but it is stronger). I'm just throwing some ideas your way. I talk a lot with the drag racers at my track and haven't run into one yet that runs a 700R4 (the majority of them run, TH350s, TH400s or Powerglides).
Shane,
I'm planning on driving 5000 miles per year on the street with that car.. and I need a overdrive tranny, and the only affordable one is the TH700R4.. My transmission shop says that they can build it to 800 HP... I'll have 4.11 gears in my Ford 9 inch and without overdrive - it wouldn't be streetable... A posi will require more mainanance than a locker... I want to be on the save side - because I would not rebuilt the posi myself and it would cost me $$ to get it rebuilt every once in a while.. Moser Engineering says that their locker should easily last several hundred passes.... A posi probably won't...
Dana has had the locker out for a few years.
I know thats why you wanted a 700R4.............and they can build them to take some
I have played with them...............had a good one in our 92rs Camaro..........it wasn't stock 
[Modified by ALLTHROTTLE&NOBOTTLE, 9:59 PM 4/17/2004]
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From: Lakeland, FL
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St. Jude Donor '03, '06, '17
Re: Ford 9 inch question... (ALLTHROTTLE&NOBOTTLE)
I know thats why you wanted a 700R4.............and they can build them to take some I have played with them...............had a good one in our 92rs Camaro..........it wasn't stock
I have played with them...............had a good one in our 92rs Camaro..........it wasn't stock
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From: B'Ville NY
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St. Jude Donor '05
Re: Ford 9 inch question... (GrandSportC3)
I missed where you said what your new engine is going to be,
If you go to a straight axle, be sure to take many pics for us 
II hope that it'll be strong enough for mid 10's ALL MOTOR on pump gas!!
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St. Jude Donor '03, '06, '17
Re: Ford 9 inch question... (SmokedTires)
I missed where you said what your new engine is going to be,
II hope that it'll be strong enough for mid 10's ALL MOTOR on pump gas!!
If you go to a straight axle, be sure to take many pics for us
II hope that it'll be strong enough for mid 10's ALL MOTOR on pump gas!!
If you go to a straight axle, be sure to take many pics for us