General Axle/tranny swap questions

[bricud]

I have a '69 barracuda convertible with the weak 7 1/4 rearend. I was thinking about finding a 8 1/4 rearend to replace it with. There is one listed locally for $500 out of a '69 Coronet. It is open type and I would consider changing it to a sure grip type if possible. Is it worth it? I think it is a few inches wider than my A body unit based on what I read about the C body rear ends. The owner said he would take $250. To replace the guts would run about $450 if I use the same gears. It has 2.71 gear ratio. By the time I replace seals, etc I would likely have about $8-900 in it. If not this what should I look for that would work for my Cuda. I want to ne able to use as a weekend driver so I don't want super tall gears. I am not familiar enough with my options so I am hoping to get some advice. What I should really be looking for? I plan to run a 360 stroker about 450-500 hp. Can the 8 1/4 handle this or should I only be focused on the 8 3/4?

Thanks.

 

[sabre67]

8.75 would be a good choice.for parts availability and strength

 

[RustyRatRod]

I would double check that it's an 8 1/4. That's too early for them to be under these cars originally. Of course as old as the car is, it certainly could have been swapped in. Think of this though. The more work you have to do to get it to fit and fixed up like you want, the closer in dollar amount you get to just buying something from Moser, Strange, Currie or some other vendor that will FIT and be all NEW and with a warranty. If you can do the work yourself, that will help some, but parts ain't gettin no cheaper.

 

[bricud]

I managed to find a 8 3/4 rear end out of a a body that will fit well. It is an open rear end so I am now debating to change the guts to a sure grip or limited slip. Advantages of each? I would guess I should just go with the sure grip.

 

[33IMP]

A "sure grip" is only mopars name for an LSD, a limited slip differential. Just as a posi, or positraction, is chevies name for an lsd. Seems like each brand had a brand-specific name for their own lsd.
An 8 3/4 has basically two types of sure grip, a cone style, and a clutch style. Clutch is stronger and rebuilable, cone is not as strong nor as "sure" in its grip.
My suggestion would be a new clutch style SG from Dr Diff if he has them back in stock. Best advice, give him a call after new years, he can help you out with advice, and parts.

 

[bricud]

Appreciate the advice. I'll be calling him. And thanks for the info on lsd.

Brian

 

[AJ/FormS]

Is it worth it? I think it is a few inches wider than my A body unit based on what I read about the C body rear ends.

IMO; Not a chance is it worth it.
In addition; you will need Big Bolt-pattern wheels, probably with a custom offset . But even if you get the wheels on, now you are limited to running them forever, cuz the body is altrady on the tire.. And not to forget, no matter what rearend you slide under there, your driveshaft will need to be shortened. And going from 9" brakes to 10", is likely gonna need to have the brake-proportioning re-engineered to prevent rear-wheel lock-up in panic situations. and finally, yur still sitting on those weiner LD springs, so you'll be needing something to keep the pinion angle in line.

I want to be able to use as a weekend driver so I don't want super tall gears.

For your application;
IMO
Just;
1) swap in a different 7.25 with a lil more gear, I mean every HotRodder in N.America who has more than 3/8 acre of property, must have at least one of those in the stack behind the shed, lol. I got two. and IIRC one of them is a 3.23posi. out of a 68 Barracuda. or
2) install a higher stall convertor, say a 2800; I love mine, or
3) Put a lil more bottom-end power, into the engine. I mean, the slanty has a stroke of 4.125, so...........

I plan to run a 360 stroker about 450-500 hp. Can the 8 1/4 handle this or should I only be focused on the 8 3/4?

Well then, on the street with street tires, yes you should be looking at the 8.75, but you won't be needing any help from the gears, so you can run any old gears that come with it......... at least for a while.... lol.
3.23s will get you 60 mph in first gear with either of the 904/727 Torqueflites @~6500. 2.94s will bring that down to ~5900. 2.76s to 5550.
But again, a stroker is really overkill for a streeter. A stout hi-pressure alloy-headed SBM is all the tires can maybe handle, and not even very well with a 360.

 

[CudaFactHackJob]

Warranties ain't worth nothin. It has to be right the first time or it's all junk.