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Discussion Starter #1
I have a 69 Cougar with a 9 inch rear end. Right now it has a 2.80 non locker in there. I am assuming it has 28 spline axles.

Is there an easy way to tell for sure if I'm a 28 or 31 spline?

Can I keep the 28 spline axles, or should I just look at upgrading to 31 spline? What's involved in that, how much, where to get it, etc?

How high do the ratios go in 28 spline lockers? I've heard they don't generally go over 3.23, is that true?

I plan on building my engine up to around 375hp. I'd like the rear end to be able to handle this, and right now I'm hoping to run 3.73-4.11 gears. Probably keep those around for when the engine is built up, as well.

Anyone have any suggestions, or glaring errors in my master plan?

Thanks
 

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If you want to do it once go with 31 spline, I started with 28 in mine, well I had to do it over, and now I have 31, go figure I twisted a Mosier with a stock 89 5.0.. You can get any ratio you heart desires up to 6:50 or so, that is a lot of gear.

Gears are the same for 28 and 31 spline

The only way to tell if you have a 31 or 28 is to pull one of the axels and do some counting, 31 spline axels are noticeably larger in OD than a 28.

If you have a 9" you can run 31 spline with any gear ratio you want.

You can contact many reputable axel company`s out there. I cant think of any other than Mosier right now.

Good luck
 

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The easiest way to tell is to look at the axle flange. If it has an oval shaped hole in the center it is 28 spline. If it has 2 holes and, I think, a dimple in the middle(hole, dot, hole) it is 31 spline. Odds are with that engine and gears you have 28 spline axles, unless someone before you changed it.
 

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Discussion Starter #4
Everything else on the car has turned up original down to the air cleaner, so I'll assume I have 28 spline. I think I'll just pick up a 31 spline locker with the gears I want and buy new axles.

How hard is it to swap the axles?

Thanks again
 

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pretty darn easy. pull the the wheels off, knock the drums off, 4 bolts hold a little cover over the end of the axle - pull that off and the axle will slide out.
 

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Just like sleeper67 says it is easy, but here is a helpful hint. Once you undo the axle retainer plate and the axle is stuck, take your drum and secure it on backwards on the axle flange with a wheel nut and pull hard. It will come out but make sure you have a good balance or you will go flying backwards (from experience). Also if you are removing the axles while in place put the car on jack stands, then raise the axle only on the side you are going to do first about 2 inches. This will keep any fluid from running out the axle tube. Then with the axle out put a pan directly under the axle tube opening. Lower that side and go to the other side and raise that side about 2 inches and let it drain for awhile. You can now remove the other axle with it still raised or lower it then remove the axle. This way there will be no mess what so ever. IF you are going to use the 31 spline axles and trac loc try and make sure you use the carrier that takes the large 3.062" bearings instead of the 2.895" bearing carrier. I was told to use the larger one for my 28 spline trac loc (3.50)because it was stronger.
 

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simplest way to unstick an axle it to rap it pretty hard one time with a fairly big hammer flat on the center that sticks thru the brake drum. Has never failed to work for me.
 
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