POSI rearend

Stryfe · 03-26-2001, 02:04 AM

I just had my 1970 Mach1 351 Windsor rebuilt/slightly modified. I want to put a POSI rear in it to get better traction. What do I need to accomplish this? Where can I get the parts neccessary for this? Summit? Any suggestions? I am not mechanically inclined and added to the fact I haven't seen my car since June 2000. It was being rebuilt while I received orders to Japan. It is being shipped here now. I beleive it has the 8" rear end that came stock with the Mach1. Any and all help/advice would be greatly appreciated.

David Fulford · 03-26-2001, 08:29 AM

First definitely make sure it's an 8" rear end. An ease way to tell is to look at the bolts that hold the 3rd member in. If you can get a socket on the bottom ones, it's an 8". If the bolts are arranged that you have to use an open ended wrench, it's a 9". From there I'm almost positive I've seen a posi unit in Summit. If not there try Jegs....I know Jegs has gears for 8" rear ends.

66fastback · 03-26-2001, 01:03 PM

dude, you should have a 9" rear in that car. I believe all 351 cars had nines. Use the socket test like david said to be sure.

Stryfe · 03-26-2001, 06:48 PM

Thanks for the info. This is my first Mustang and am still in the learning process. I appreciate all the assistance I have received here. I am sure I will be back again. Just another 30-45 days and I'll have my baby back to me. Thanks again.

03-26-2001, 02:04 AM	#1
Stryfe Registered Member Join Date: Jan 1999 Location: Kadena AB, Okinawa Japan Posts: 25	POSI rearend I just had my 1970 Mach1 351 Windsor rebuilt/slightly modified. I want to put a POSI rear in it to get better traction. What do I need to accomplish this? Where can I get the parts neccessary for this? Summit? Any suggestions? I am not mechanically inclined and added to the fact I haven't seen my car since June 2000. It was being rebuilt while I received orders to Japan. It is being shipped here now. I beleive it has the 8" rear end that came stock with the Mach1. Any and all help/advice would be greatly appreciated.

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03-26-2001, 08:29 AM	#2
David Fulford Registered Member Join Date: Oct 2000 Location: Charlotte NC Posts: 193	First definitely make sure it's an 8" rear end. An ease way to tell is to look at the bolts that hold the 3rd member in. If you can get a socket on the bottom ones, it's an 8". If the bolts are arranged that you have to use an open ended wrench, it's a 9". From there I'm almost positive I've seen a posi unit in Summit. If not there try Jegs....I know Jegs has gears for 8" rear ends.

03-26-2001, 01:03 PM	#3
66fastback Registered Member Join Date: Mar 1999 Location: Dallas, TX Posts: 208	dude, you should have a 9" rear in that car. I believe all 351 cars had nines. Use the socket test like david said to be sure.

03-26-2001, 06:48 PM	#4
Stryfe Registered Member Join Date: Jan 1999 Location: Kadena AB, Okinawa Japan Posts: 25	Thanks for the info. This is my first Mustang and am still in the learning process. I appreciate all the assistance I have received here. I am sure I will be back again. Just another 30-45 days and I'll have my baby back to me. Thanks again.