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Spent the day ripping out my tired old 28 spline rear axle and installing my professionally restored and rebuilt 31spline, 3.50:1 traction-lok rear axle, originally out of a 68 Shelby...

Every mechanical part was replaced with NOS ford pieces, pictures just don't do it justice. It's a work of art. Cost me alot less than an aftermarket rear axle too, even using NOS parts for everything and subbing out the labor...

Check out the pics HERE in my personal photo gallery.
 

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That's my next job on the '68. Nothing is wrong with the diff now except for the fact that I'm running a pretty agressive cam and only have 3.00 gears in the rear which totally does not do the cam justice. Gotta put in some 3.55 or higher. If I find a 9" lying around, that would be nice also!
 

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Some local fella bought my entire 9inch rear end, housing and all, as is for $300... Needs to be completely rebuilt though...

I had a 3:1 in mine too, and you're right, bog 'o rama... With the 3.50:1's in there, she's a rocket ship.

Next year, I'll probably be swapping the tranny to an AOD and switching to 4.11's....
 

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Hey Logan,
Congrats pn the new axle and the new truck!!! They both look great. I'll bet the axle set you back as much as the down payment on the truck!! Its pretty cool you sold it already. I can buy 9" axles around here for around 150 so I think you made a good sale but it depends on whats available in your area. around here the bodies fall off before the axle wears out...lol. I am going to be looking for a 5 lug axle for the 66 stang and I know they are rare as hens teeth...$$$ouch
John
wvcat
 

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3;50 REAR GEARS

YEP! YEP ! I RUN A 3:50 TRACTION LOC GEAR IN MY SPORTS SPECIAL DRIVER AND I LIKE THEM ALOT TOO. I WONDER WHAT A NICE 3.25 TRACTION LOC IS WORTH? I JUST TRADED ONE FOR A 69 XR7 PARTS CAR. I HOPE TO SALVAGE ENOUGH FROM IT TO COME OUT AHEAD. THE INTERIOR IS OK AND ONE FENDER AND THE TRUNK. PLUS SOME ODS AND ENDS. IT HAS A 3:00 OPEN CHUNK THAT I WILL USE TO TURN INTO A 4:11 DETRIOT LOCKER 31 SPLINE FOR ANOTHER PROJECT. ANYBODY NEED A DARK GREEN LEATHER 69 XR7 INTERIOR? LATER CATS...

69 SPORTS SPECIAL DRIVER
67 TRANS AM RACER
69 CONVERTIBLE CRUISER;)
 

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Hmmm...seems like someone is living right :) Everyone fawning over your new truck and no one mentioned your sweet garage!!!

Anyways, my 68 is in dire need of a rear end gearing change (2.75:1) and I'm wondering about swapping out the diff and the ring and pinion. It's a 9 incher. Not sure whether 28 or 31 spline.

Any advice since you've been through it Logan?

Also - where did you get your springs???

Thanx...

Ken
 

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most important room in the house

is the garage
 

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Bloody (leaf spring) knuckles

Hey Logan,

Did you have the rearend swap in the plans when you replaced your leaf springs? Seems like all those projects never work out to where they happen like they should, like AT THE SAME TIME! I guess the fresh bushings in your leafs allowed for an easier rear end swap though.

I'd be interested to hear about your plans for the AOD, as I am running 4:10's and could use the extra gear on the highway.

Ron.
 

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Discussion Starter #9
kvinmn, if you've already got a 28 spline 9 inch, stay with it. Just replace the 3rd member. With the 31spline rears, you need to swap housings to accomodate the big bearings required for the 31 spline axles. In short, much cheaper to do the 28 spline.

I kinda fell into my 31spline parts, so it worked out fairly cheaply. My springs are heavy duty springs from John's Classic Cougars. They're great, I love 'em.

I replaced the springs a month ago, which was a full day job in itself, I wouldn't of wanted to attack both the axle install and new spring install all in the same day...I always planned on replacing the rear axle though, it was more a matter of funds than anything. Here's hoping the wife doesn't see the check I wrote on this one... Doh.

As for the AOD, that'll be next year, but I'm not concerned about the swap. There are a ton of guys who've done it, and windsor-fox has kits to do it, so no biggie. CougarAOD can offer up some advice on the conversion for sure.

Actually I think if you do a search on this site for "AOD", it's been discussed before in great detail me thinks...

bowl, I wish I had the space for a stand-alone garage....sigh... Even with my attached 3 car, it's still a bit crowded, but I've got tons of attic space. :)
 

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31 spline is a nice upgrade, but don't feel like you are selling yourself short if you stay with 28 spline. 28 spline stock axles are still plenty strong. Logan's motor is pretty stoudt, good reason to swap up to 31 spline. The motor in my cat is probably around 350 - 360 hp and I stayed with 28 spline for cost. Of course, my entire car has about 35K original miles, so I felt pretty safe with the rest of the rear-end.

There is a semi-retired guy in my area that has been building 9 inch rear for 40 years. He only charged me $90 of labor (with me pulling and re-installing the center section). All together, the swap cost me $490. He told me not to worry about 28 spline with my application. I went from a 3.00 to 3.25, as I didn't want to sink the money into an AOD and still be able to drive long distance to shows.

Good luck.

Oops, forgot to mention, it was a 3.00 open and is now a 3.25 traction lock.
 

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jimk351c - did you notice a BIG improvement going from 3.00 to 3.25? I was planning on moving from 2.75 to 3.55 and wonder if it would be too much.

Bench racing is great fun...:)

Ken
 

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Discussion Starter #12
Jim makes excellent points. My completely resto'd/rebuilt 31 spline rear cost me about $1500 all told.

But for me it was worth it, as I wanted a completely new rear end and otherwise would've gone with a Moser or Currie custom built rear and that would've started out around $2200, nevermind labor for install...

I went from 3:1 to 3.5:1 and man what a difference! She just wants to take off now... Highway cruising isn't that bad either. My motor is built to operate in the upper RPM range anyway... At 70mph I'm turning 3300rpm or so...
 

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Ken,
The problem is, I changed the rear and cam at the same time. So, the car feels A LOT stronger. How much of that is rear-end, I honestly don't know :)

I would say 3.0 to 3.25 is not a very dramatic change. However, 351C 2v motors don't love RPMs, so I'm happy that I stayed with the 3.25. I can cruise 70mph at 3000 RPMs, just what I was looking for. Off the line, I would of liked the 3.50. But frankly, it is so easy to break the rear loose right now, that it probably wouldn't of been to huge a difference. Going from 2.75 to 3.55 will be a HUGE kick in the pants!
 

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Yeah, I figured that as well. I have a built up 390 that should be around 350-400 hp. It's just really hard to tell how well it's performing because of the axle.

Right now, 70 mph is about 2500-2600 rpm.

How about the differential...did you upgrade it to a Detroit Locker or???
 

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Yes it is...it's a 390 2V 'X' code. I knew it had the 9 inch rear end, just not so certain of the 28/31 spline axles.

I'm looking at using a new Ford Racing Detroit Locker with 3:55 gears. Consulting is picking up again so I might actually convince the wife I need it :)

I'd like to replace the leaf springs/shocks first tho as I stated b4...

Ken
 

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Hey kvinmn, You should be able to get an eassssyyyy 400hp out of that 390! I guess it just depends how much over stock you want to go..

I've got a 302 with all goodies and figure it's about 400hp (read an article a while ago about a guy who had a '68 cougar 302 with the same heads, intake, exhaust, and nearly same cam that was putting out 408hp dyno'd). Can't wait to go from 3.00 to 3.55 and see the bottom end come alive. Should be a good kick in the pants, I figure.
 
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