Thread: 9 Inch Ford Rear Gear Change

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i HAVE A 9" FORD NARROWED REAR IN A 57 CHEV WITH A 350 POSI TRACT
GEAR RATIO..I WANT TO CHANGE THIS TO A 470 RATIO ARE ABOVE..WHAT
ALL IS NECESSARY FOR THIS TO BE DONE, AND WHERE WOULD BE THE BEST
PLACE TO FIND THE PARTS.. THANKS RDOBBS

I am no expert but you can get gear sets on ebay as well as the other parts you will need. You might think about putting in new bearings while you are at it and what the heck get new clutch plates for the trac-lock.
I also picked up a dvd of how to rebuild your rear end. check out www.technicalvideos.com (differential rebuilding) If you have a dial indicator, the dvd walks you right through the 9 inch.

Hope that helps.

You're also going to need the setup tools and a dial indicator. Getting the pinion depth and backlash set correctly will have a lot to do with how noisy the gears are, and how long they last.... As for selecting the best gear, depends a lot on how the car is used. A cheap gear set will not live long behind a big horse engine.....

You probably already knew that, just thought I'd mention it in case some thought changing gears was just a bolt in and go deal......

Would A 470 Gear Be To Much For 1/8 Strip..running Big Block
Capable Of 800 Hp...rd

There is too much time, labor and cost involved to leave this to chance. Do yourself a favor and get the software to nail it down before you ever twist a wrench. Scroll down halfway on this page and buy the dragstrip software....
http://www.kbengineparts.com/MotorP18.html

Originally Posted by rdobbs

Would A 470 Gear Be To Much For 1/8 Strip..running Big Block
Capable Of 800 Hp...rd

Depends on a lot of things... check out the calculator techinspector pointed to.

I know a lot of 1/8 mile racers running into the 5.30+:1 range. How big is your tire? How heavy is the car? Manual or Automatic? Where is your power band (or better yet, what do you want your rpm to be through the traps?)

As an example 3000lb car 30" tire 120MPH at the 1/8th with an automatic putting down 720HP to the pavement (800HP flywheel) should get you about 9.3 @ 145mph in the 1/4 which should be about 5.8 @ ~115-120mph in the 1/8th you want 4.73:1 gear ratio to trap at 7000rpm. If you have a high winder and want to run out to 8000rpm you want something closer to 5.43:1.

This is an example and will need adjusting to your circumstances...

-Chris