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Looking for a Posi 3.50 9 inch 3rd member

W

Waffles

Member
Well, I had a good deal worked out for a rear end; guy ended up f#$#^ng me. It's a long story. Anyway, I need a 3.50 traction lock 3rd member. I have the correct housing, but need axles and the third member. I have two options;

I can buy a 28 spline posi 3.50 3rd member, use my existing 28 spline axles from my 8 inch, as well as brakes at, but still only have 28 spline axles

OR I can buy a 31 spline 3rd member, have to buy new brakes and 31 spline axles, but have the 31 spline, and try to sell my 8 inch complete for like $80-100 to try to offset my cost a bit.

Any advice?
 
Why do you need 31 spline axles? I forget what motor you're running.

Unless you've got some monster motor under the hood, I'd pick up a TrueTrac and run the 28-spline axles.
 
It's a 28 spline 2.80 open. Nothin too special, unless you're looking for fuel economy.

I'd be interested in that 4.11.... if it wasn't 4.11... I want it to be quick, but I do a fair amount of freeway driving. I'd like to stay at 3.25-3.50

What're you asking for it? I could always swap the ring and pinion to 3.50...
 
Oh, a 408? Err...yeah, I'd think about 31-spline axles at that point:) Urban Cowboy on Mustangforums breaks enough stuff with his 383.
 
What transmission are you going to run behind the 408? Unless it's a VERY stout C4, a C6 or a TKO, you'll trash the tranny long before you have to worry about 28 spline axles. If it's a TKO-600 (or equivalently geared), you're going to want something steeper than a 3.50:1 rear. I started out with a 3.50 in my '69 behind he 408/TKO-600 and didn't like it. I put a 3.89:1 in, and it's a MUCH better fit. First gear is still useable, I can accelerate EASILY in 5th gear, and I'm still only turning 2k RPM's at 75 mph.

You do NOT need to change the brakes to swap from 28 spline to 31 spline. The only difference in the axles is the number of splines. I bought Superior axles from Summit for my '69. They were a fraction of what everyone wanted for 40 year old, abused original 31 splined axles.

Do you not have a 9" chunk now, so you're looking for everything? If you have the chunk, you can always go Detroit locker and change out the gears/bearings.

You should be able to find a decent 9" traction-lok chunk, though, on ebay for less than $300 if you're patient (paid $250 + shipping for my 31 spline, 4-pinion one).
 
"Waffles" said:
It's a 28 spline 2.80 open. Nothin too special, unless you're looking for fuel economy.

I'd be interested in that 4.11.... if it wasn't 4.11... I want it to be quick, but I do a fair amount of freeway driving. I'd like to stay at 3.25-3.50

What're you asking for it? I could always swap the ring and pinion to 3.50...
Click to expand...
make me an offer, It was bought new by a friend who put it in his truck that he towed a boat with. After a couple weeks he yanked it back out. It doesn't have hardly any miles on it. He bought it thru Ford. I bought it from him several years ago and it's been in my garage ever since (in a 5 gallon covered bucket).
 
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