9" rear end

Echo_7 · November 15th, 2011, 09:42 AM

OK guys, I have an opportunity to grab a 9" rear end with out gears for a 100 bucks. I have a 69' FB at home i am trying to build. my question is i know for my car 59.25 is the width thats magic, but what length can i go with out doing much mods to it? i.e shortening or lengthening it?

MustangOne · November 15th, 2011, 09:46 AM

It all depend on your rear rim size and tire width.

It is easy Measure what you have now and know if you add 1 more inch what it will do to your tire placement.

Echo_7 · November 15th, 2011, 10:02 AM

The guy is double checking the width for me. He was going to put it in a nova.

I have another bid on a 9" out of a half ton truck. guy thinks it is 61". as far as wheels and tires I'll have to decide when i have the rear end.

Echo_7 · November 18th, 2011, 10:52 AM

my car has an 8" rear end in it now. I bought a rear end it is 61" with 31 spline axels but no third member. I can get a 9" third member out of an 82 bronco. will this work?

Echo_7 · November 18th, 2011, 04:28 PM

correction, I meassured with my own eyes from flange to flange inside to inside. It meassures 60"

Echo_7 · November 23rd, 2011, 11:07 AM

ok can any of you guru's tell me, if a 9" third member out of a 87 f150 has big or small bearings in it. Just by feeling it seems it is fairly loose ( back lash wise) when i spin the pinion by hand. I am thinking a third member that old will need freshening up. so on to question two. can anyone recomend a good overhaul kit for it? Is there any trouble shooting i can do to see if the ring and pinion gears can be reused or the posi. Thanks for the input.

MustangOne · November 23rd, 2011, 11:20 AM

The big or small bearing is on the axle at the end of the tube.

I get the rebuilt kit from my local parts house.

Echo_7 · November 23rd, 2011, 01:32 PM

thanks mustang1 you are the bomb. when you say parts house you mean like oreileys or auto zone? thats really all we have around here.

frdnut · November 25th, 2011, 10:40 AM

The rear end housing length you need for your car is 54 1/4 long..That is measured end to end with no backing plates...A rear end out of a truck will be too long for your mustang unless you shorten it....You have to pay attention to the bearing size at the outer axle end but also at the side gears of the carrier..31 spline axles require a larger bearing there as well....I got my rebuild kit from summit..

Echo_7 · November 29th, 2011, 08:57 AM

OK I think I may have lead you astray. Let me clearify. I have a 69 FB with an 8 " rear end. After looking on the internet at rear end lengths i found that my rear end is supposed to be 59.25" wide. I bought a rearend housing that measures 60" with 31 spline axles and drum brakes. It has no third member. I bought a third member out of a 87 f150 with 3.50 gear ratio and posi.

I know this isn't the best way( out of a truck) but I plan to rebuild the rear end anyway and put new bearings and seals in it. Is there a way to tell if the Posi unit is good or will need to be replaced?

frdnut · December 1st, 2011, 04:23 PM

Originally Posted by Echo_7

OK I think I may have lead you astray. Let me clearify. I have a 69 FB with an 8 " rear end. After looking on the internet at rear end lengths i found that my rear end is supposed to be 59.25" wide. I bought a rearend housing that measures 60" with 31 spline axles and drum brakes. It has no third member. I bought a third member out of a 87 f150 with 3.50 gear ratio and posi.

I know this isn't the best way( out of a truck) but I plan to rebuild the rear end anyway and put new bearings and seals in it. Is there a way to tell if the Posi unit is good or will need to be replaced?

Where are you measuring from to get 59 1/4 inches?...I just put a 9 inch in my 68 and the 69 cougar housing that I got measured exactly the same as my old 8 incher at 54 1/4 across the bare housing.. 67-70 mustang/cougars are the same width...Does the housing that you have narrow down at the outer ends of the axle tubes?..If it does then it should be the small bearing..Actually getting a third member out of a truck is an excellent low buck way to get a decent gear ratio as well as a trac lok unit..You also usually get 31 spline version as well...

Echo_7 · December 5th, 2011, 07:33 AM

I got my numbers from this site Rear End Widths. No the Rearend housing does not narrow it is straight all the way across axel tubes. This is why i bought the 60" rearend housing. Then the third member from the truck. I will just freshing the bearings up and such with a rebuild kit and get it going.

Can you magna flux the ring and pinion gear to make sure there are no cracks or stress like you can blocks?

frdnut · December 7th, 2011, 10:35 PM

I really don't think there is any need to magnaflux the gears unless they got banged around..It is rarely the actual gears that fail..

Echo_7 · December 8th, 2011, 11:16 AM

well i figured it out and almost ashamed. well as you all probably already know axle length and axle housing length are different. I know that now. Lol so I am off to buy NEW axles and cut my axle housing down to size. yeah!!!

November 15th, 2011, 09:42 AM	#1
Echo_7 Newbie Join Date: Mar 2010 Posts: 37 iTrader: 0 reviews	9" rear end OK guys, I have an opportunity to grab a 9" rear end with out gears for a 100 bucks. I have a 69' FB at home i am trying to build. my question is i know for my car 59.25 is the width thats magic, but what length can i go with out doing much mods to it? i.e shortening or lengthening it?

November 15th, 2011, 09:46 AM	#2
MustangOne Lost in the 60's 1968 GT 500 Super Snake 12.6 @ 114.3 Join Date: Mar 2008 Location: Sapulpa Oklahoma Posts: 2,053 iTrader: 0 reviews	It all depend on your rear rim size and tire width. It is easy Measure what you have now and know if you add 1 more inch what it will do to your tire placement. __________________ MustangOne's Car's How to post Photos in Your Thread. Vote for your Favorite Ride of the month, Every Month Modded Mustangs Facebook

November 23rd, 2011, 11:07 AM	#6
Echo_7 Newbie Join Date: Mar 2010 Posts: 37 iTrader: 0 reviews	3rd member ok can any of you guru's tell me, if a 9" third member out of a 87 f150 has big or small bearings in it. Just by feeling it seems it is fairly loose ( back lash wise) when i spin the pinion by hand. I am thinking a third member that old will need freshening up. so on to question two. can anyone recomend a good overhaul kit for it? Is there any trouble shooting i can do to see if the ring and pinion gears can be reused or the posi. Thanks for the input.

November 23rd, 2011, 11:20 AM	#7
MustangOne Lost in the 60's 1968 GT 500 Super Snake 12.6 @ 114.3 Join Date: Mar 2008 Location: Sapulpa Oklahoma Posts: 2,053 iTrader: 0 reviews	The big or small bearing is on the axle at the end of the tube. I get the rebuilt kit from my local parts house. __________________ MustangOne's Car's How to post Photos in Your Thread. Vote for your Favorite Ride of the month, Every Month Modded Mustangs Facebook

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November 15th, 2011, 10:02 AM	#3
Echo_7 Newbie Join Date: Mar 2010 Posts: 37 iTrader: 0 reviews	The guy is double checking the width for me. He was going to put it in a nova. I have another bid on a 9" out of a half ton truck. guy thinks it is 61". as far as wheels and tires I'll have to decide when i have the rear end.

November 18th, 2011, 10:52 AM	#4
Echo_7 Newbie Join Date: Mar 2010 Posts: 37 iTrader: 0 reviews	my car has an 8" rear end in it now. I bought a rear end it is 61" with 31 spline axels but no third member. I can get a 9" third member out of an 82 bronco. will this work?

November 18th, 2011, 04:28 PM	#5
Echo_7 Newbie Join Date: Mar 2010 Posts: 37 iTrader: 0 reviews	correction, I meassured with my own eyes from flange to flange inside to inside. It meassures 60"

November 23rd, 2011, 01:32 PM	#8
Echo_7 Newbie Join Date: Mar 2010 Posts: 37 iTrader: 0 reviews	thanks mustang1 you are the bomb. when you say parts house you mean like oreileys or auto zone? thats really all we have around here.

November 25th, 2011, 10:40 AM	#9
frdnut Newbie 1968 sprint 11.82@120.85 Join Date: Aug 2011 Location: Canada Posts: 43 iTrader: 0 reviews	The rear end housing length you need for your car is 54 1/4 long..That is measured end to end with no backing plates...A rear end out of a truck will be too long for your mustang unless you shorten it....You have to pay attention to the bearing size at the outer axle end but also at the side gears of the carrier..31 spline axles require a larger bearing there as well....I got my rebuild kit from summit..

November 29th, 2011, 08:57 AM	#10
Echo_7 Newbie Join Date: Mar 2010 Posts: 37 iTrader: 0 reviews	OK I think I may have lead you astray. Let me clearify. I have a 69 FB with an 8 " rear end. After looking on the internet at rear end lengths i found that my rear end is supposed to be 59.25" wide. I bought a rearend housing that measures 60" with 31 spline axles and drum brakes. It has no third member. I bought a third member out of a 87 f150 with 3.50 gear ratio and posi. I know this isn't the best way( out of a truck) but I plan to rebuild the rear end anyway and put new bearings and seals in it. Is there a way to tell if the Posi unit is good or will need to be replaced?

December 5th, 2011, 07:33 AM	#12
Echo_7 Newbie Join Date: Mar 2010 Posts: 37 iTrader: 0 reviews	I got my numbers from this site Rear End Widths. No the Rearend housing does not narrow it is straight all the way across axel tubes. This is why i bought the 60" rearend housing. Then the third member from the truck. I will just freshing the bearings up and such with a rebuild kit and get it going. Can you magna flux the ring and pinion gear to make sure there are no cracks or stress like you can blocks?

December 7th, 2011, 10:35 PM	#13
frdnut Newbie 1968 sprint 11.82@120.85 Join Date: Aug 2011 Location: Canada Posts: 43 iTrader: 0 reviews	I really don't think there is any need to magnaflux the gears unless they got banged around..It is rarely the actual gears that fail..

December 8th, 2011, 11:16 AM	#14
Echo_7 Newbie Join Date: Mar 2010 Posts: 37 iTrader: 0 reviews	well i figured it out and almost ashamed. well as you all probably already know axle length and axle housing length are different. I know that now. Lol so I am off to buy NEW axles and cut my axle housing down to size. yeah!!!

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9" rear end

9" rear end

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