My son's '65 has an 8" rear end with 2.80 gears and is in need of a new ring & pinion gear. It's a daily driver with a 302, shelby intake and a Holley 600 CFM. We will also add headers and a mild cam but that's for later on. I'd like to put an 8.8" or 9" rear end in it but I've been told that the 8" should be more than enough for this setup. Any thoughts on this?

On a side note I could also use a gear recommendation. He's got a C4 tranny and his rear tires are 225/50 15.

 

For a daily driver I would stay with the 8" and go with 3.55:1 gears.

 

Yeah, you don't have enough power to the rear with your setup to warrant an 8.8 or a 9" rear.

 

I agree. You can built an 8" to withstand 400hp

 

400 HP, Drag radials, sticky track and 5000 rpm launch, then you would need anything more than a built the 8 inch

 

What kind of RPM will he get with 3.55 gears at 55 mph?

Thanks for all the great replys!

 

For a mild build, you should be ok with the 8". Just keep in mind that all HiPo "k" code 289's with 271bhp came with 9" rears. I have broken two well built 8" rears with way less than 400hp.

 

I assume he does not have OD added to that C4, so he should be running near 2K RPM at 55. His gas mileage will be between 15-20 MPG unless he has an extremely heavy foot. I get about 20 MPG on steady driving on the freeway at 70 MPH, but I still have the 2.80 gears.

 

And that 271 hp was a gross number, if measured the same way they do today it would be more like 240 hp and probably less than 200 hp at the tires. I'm usually on the conservative side when suggesting that an 8" is enough for a modified car. With what you've described I think that an 8" will be OK, esp with street tires and an automatic. For a daily driver I would stay at about 3.2 gears if you do any freeway driving. Of course if you replace the C4 with an AOD, you want lower gears... but that's another post.

 

The weak piont on a 8" rear is the lack of meat around the pinion bearing I have a 302 with a toploader 4 speed. I blow the 8" the first time like it was nothing. I plan to replace it with a 9" when I rebuild the engine, the prblem with 9" in the 65 66 cars is getting one thats norrow enough. I plan on getting a direct fit currie from jegs with gears and disc brake kit should be somewhere around $2000.