Rear End

I have a 73 Convertible with a stock 351 C 2V and a C6 trans. The current rear end is original,(not sure what size), but it is an open rear end with 3.00 gears. Curious if anyone has had the same set up and upgraded to a trac loc rear end with 3.55/3.73 or similar gears. Would it be easier/less expensive to place new parts in the current rear end or can I swap an entire rear end/axle unit in ? Any gear recomendations ? Want it to be driveable ... just a little quicker off the line. Not concerned with adding disc's in the rear unless it was part of a swap in. More concerned with cost and having a reliable set up. Thanks

You should have a 9" rear end. The entire gear assembly is part of the pumpkin.



This makes swapping gears and traction methods 'easy'. <<< relative term. Some folks call them the poor mans quick change.

'for the most part' you can swap in any 9" pumpkin. But your axles have a specific number of splines that need to match.

Anyways, that said. Depending on how much you drive and where you drive you might opt for a 3.25 instead of a 3.50.

Are you sure your current gears are not 2.73?

Just change the pumpkin. I'd but a 3:25 posi. (Limited-slip)

You should have a 9" rear end. The entire gear assembly is part of the pumpkin.

This makes swapping gears and traction methods 'easy'. <<< relative term. Some folks call them the poor mans quick change.

'for the most part' you can swap in any 9" pumpkin. But your axles have a specific number of splines that need to match.

Anyways, that said. Depending on how much you drive and where you drive you might opt for a 3.25 instead of a 3.50.

Are you sure your current gears are not 2.73?

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Thanks for the info. The current gears are 3.00. I may upgrade the motor in the future nothing extreme. 4 barrel carb/intake, maybe headers. Car is not raced.

Just change the pumpkin. I'd but a 3:25 posi. (Limited-slip)

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Is limited slip the same as traction loc ? Is traction loc a Ford name/product ? What is the difference between the two ... Thanks !

Right now you are probably around 2600 RPM at 65 mph. With 3.50 gears you will be closer to 3100. At 75mph you will go from about 3000 to 3500 RPM.

That doesn't seem like much but the higher RPM's get old after a while. Drive for a mile or so in 2nd gear at 60mph now and you will have an idea of what 75 mph is with 3.50 gears.

Fords name for the "Limited Slip" was "Traction-Lok Differential". This is how it is spelled on my window sticker.

As they have already stated there are 28 and 31 spline axles and custom ones with even more. I am not 100% positive about the axle bearing outside dia. and thickness but if I recall you cannot put 31 spline axles in a 28 spline housing. Will someone refresh my memory on that? The previous owner of my 72 Q convertible put the next step up in it, 31 spline "Detroit Locker". It is I guess what you would call a positive traction. There is a ratchet mechanism in the rear that keeps both axles pulling no mater what. It will make a clicking noise in tight turns where the Traction-Lok has the clutches to slip in turns. It was an option in some of the High Performance models. In 73 the Traction-Lok option would have cost you $42.64.

If you do put the Pumpkin in with Traction-Lok be sure to put the friction modifier additive in the gear oil.

Another thing to note Ford put the 9" in lots of vehicles so you don't have to just look for one in a Mustang. I have a 69 Ford van that has a "N" case 9" 28 spline in it. Pick ups came with the 31 spline axles more than the cars did. The housings for other vehicles are different widths and offsets than the Mustang but the center sections will change out. I think the first year Ford used the 9" was 1957 so lots of vehicles to look into.

Which every you go with you will have to get use to driving it. The car will swap ends with you if you are taking off and turning at the same time as spinning the wheels. It makes it more fun to drive and much easier to power slide or drift.

A contractor here where I live got a Viper and after crashing it twice because he lost control when the rear wheels were spinning. He sold it and did not drive 200 miles, lol. A little oil, sand or a bump in the road under acceleration will do strange things quickly.

David

I have a car with 28 spline axle and 2:73 gears, found it to be boring so swapped it out with a 3:90 third member and some 31 spline axles. Much more exciting now. 28 and 31 spline axles swapped no problems in the same housing.

I have a car with 28 spline axle and 2:73 gears, found it to be boring so swapped it out with a 3:90 third member and some 31 spline axles. Much more exciting now. 28 and 31 spline axles swapped no problems in the same housing.

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Hello,

Little confused ... did you go to a traction loc or did you already have one ? The 31 spline are stronger I guess. Did you buy all new components or get Ford used or new Ford. Cost ? Thanks for the info. !

naa10104,

Here is a good site to read about the Ford 9 inch.

Everything you've ever wanted to know about Ford 9 Inch Differentials!

https://www.fordmuscle.com/archives/2002/02/nineinch/

mustang7173

I change mine fromn 28spline axles to 31 spline axles.

Inside the differential you have to change side gears and the "hat"

I just called Randy's Ring and Pinion, told them what I wanted to do and they put together a parts list and shipped it all out. Not a big deal if you can assemble a differential unit or have someone that knows how.

If throwing a 31 spline center section into a car that had a 28 spline unit, then all you need to change are your axles and axle bearings-the seals should be replaced, but are the same size (parts counter monkeys will look for seals and find ones that say for 31 spline axles, but they are wrong-measure your axles before buying seals!)