Rear end gears

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Sep 8, 2012 | 02:34 PM

77 2wd

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Rear end gears

Is there anyway i can figure out what gears my rear end has without tearing it open? the rear end is a stock rear end out of a 78 f150, it's currently under my 77 f100, i appreciate the help!

Sep 8, 2012 | 03:49 PM

starwriter

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Joined: Jan 2008

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It's easy, turn wheels/driveshaft, count rotations of both and divide.

How to Calculate a Rear Differential Gear Ratio - YouTube

Sep 8, 2012 | 03:53 PM

smokenchoken

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From: peru kansas

one way is to use a jack and a jack stand lift up one side of the rear end and make sure to put mark on drive shaft and on the wheel or a piece of tape as a mark with the tranny in neutral rotate drive shaft and count how many times it takes to spin tire one full revolution if you turn drive shaft just a little more than 4 times then its a 4.10.... 3 and 3/4 turn its 3.73 so on and so forth only thing that would hinde it is if you have a locked rearend then you have to have both sides off of the ground

Sep 8, 2012 | 04:25 PM

77 2wd

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alright ill go do that real quick and let ya guys know, thanks alot!!

Sep 8, 2012 | 04:26 PM

77 2wd

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wow, forgot i dont have the driveshaft hooked up atm, ill have to do tomorrow, when the engine,tranny finishes up getting put in

Sep 8, 2012 | 11:11 PM

smokenchoken

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From: peru kansas

you could just mark the u joint holder you don't specifically need a driveshaft

Sep 9, 2012 | 02:04 AM

countryboyglen

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if its automatic i would say 3.54 to1 if it is stick i would say 3.73 to1 both are common in the 8.8 dana 60 and 9" rear ends.

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Sep 9, 2012 | 09:23 AM

NumberDummy

Ford Parts Specialist

Joined: Nov 2006

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From: Simi Valley, CA

Quote:

Originally Posted by 77 2wd

Is there anyway i can figure out what gears my rear end has without tearing it open? the rear end is a stock rear end out of a 78 f150, it's currently under my 77 f100.

The AXLE code is stamped on the 2nd line of the Warranty Plate-far right.

Warranty Plate located on the left door face below the latch / 1959 thru today: If the AXLE code begins w/a letter: Limited Slip / If w/a number: No Limited Slip.

9 inch: The rear axle ID tag is located at about 5 o'clock under one of the bolts that retains the carrier to the housing.

Dana axles: The axle ID tag is located under one of the bolts that retains the inspection cover to the housing.

These ID tags could be missing by now / 1976/79 F100/150's: Some have Dana 44 rear axles with/without Limited Slip. Usual ratios are 2.75-1 & 3.00-1.

After the first Arab Oil Embargo ended in 1974, you will see a lot more "high speed" ratios in F100/150's. A/T could be 2.75 or 3.00-1, M/T could be 3.25 or 3.50-1.