Just picked up a 7 1/4 rear, sign said it is out of a 67' cuda. Ring gear shows very little wear and the lash feels good. It is a sure grip stamped 12 27 66B. The ratio stamp is not clear, looks to me like 2.93 but I never heard of that one. Has anyone heard of that ratio? The garage "spin and count" method confirms just shy of three revolutions, but I never heard of that one.

'economy' rears could have 2.93/4 ratios... some duster 360's could be had with sure grip 2.94's....good traction for road handling and mileage....
(much nicer than 2.76's any day...)


If you have an automatic she'll be a good road gear, if you're draggin' you need 3.XX....

-D.Idiot

It is going behind a 225/904 drivetrain that currently has 2.76's and no draggin' in the plans so it should work well. Thanks DI. Any idea what horsepower a sure grip 7 1/4 will handle?

there are a couple guys that are using the 7 1/4 SG...I'm sure it'll take whatever you're going to dish out...not like you're putting a 400 ft/lbs of torque small block in front of it....


-D.Idiot

Using a SG unit eliminates the weakest link in a 7 1/4; the spiders. However, it's still a tiny differential with itty-bitty splines, axles, etc. The key to letting it live is avoiding really sticky tires and high shock loads (popping the clutch at 5000 rpm). Use the tires as the fuse; if they spin, things don't break as much.
It should live a long time behind a slant with proper care and sane driving habits.

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O==\=/==O

"A mechanic is Somebody."
- Jim Preston

I agree about avoiding shock loads on the 7 1/4 rear. But I ran slicks on the same rear from 1974 till last year, when I changed to a 8 3/4. My cars weighed from 2500 lbs to 3200 lbs, drag race and street use. It is a 3.91 sure grip unit, and was in cars, that were stock, had turbo's, nitrous, and have run as quick as 13.3 at 104 mph with turbo and 13.4 at 97 on nitrous. But with 1.79, 60 ft times, I thought that was asking a little to much from the rear, but it never broke. With an auto, no problem, but I would not run a stick, and hammer it.

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Charrlie_S
65 Valiant 100 2dr post 170 turbo
66 Valiant Signet 170 nitrous
64 Valiant Signet
64 Valiant 4dr 170
64 Valiant 4dr 225

I have over 150,000 mi on my 7 1/4 behind a built 318 in one of my 65s, and it's still going strong. Using an automatic helps cushion the drivetrain, unless you're using a transbrake .
Charrlie is a hero at getting a quart from a pint pot; 13s with 170 ci and 7 1/4 rears is awesome in any book.

_________________
O==\=/==O

"A mechanic is Somebody."
- Jim Preston

no i only typed 10% the rest was on a floppy that a buddy left here i hope it was useful info

How did we get from talking about the 7 1/4" to the 8 3/4" ?...that's like lemons and Pummelos....

Good info though, if you didn't write that article make sure you mark down who the author was so we can thank/credit him/her if necessary...

Let's get back to axle assemblies that only cost $150 and weigh less....

-D.Idiot

BTW, we had a local swap meet last week end and a '742' 3.23 with SG 'chunk' was priced at $500...you provide the rest of the assembly...

Hornet, please tell me that's a copy/paste. I feel very sorry for you if you had to type all that information out . It is good information though.

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My car may be slow to sixty, but at least it's been reliably slow to sixty for more than thirty years.