gear ratios

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Jul 19, 2010 | 07:20 PM

johnboggs21

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From: Michigan

gear ratios

How do I figure out the gear ratio in the rear of my truck? Its got a 10.25 sterling. The tag on the axle is too far gone.

Jul 19, 2010 | 08:13 PM

captain p4

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From: Joppa, Maryland

If the truck is all original there should be a tag in the door with the axle code on it, get that and then head up to your specific truck forum and there should be a decoder somewhere in there. You can also figure it out by driving at a certain speed, say 65 with the tq converter locked and calculate it based on the OD ratio/tire size/engine rpm/speed (maybe verify it with a GPS if tire size isn't stock). One more way to do it is to jack the truck up and put it in neutral, then turn the tire one revolution and count how many times the driveshaft turns.

Jul 19, 2010 | 10:08 PM

fatdan460

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From: utica il

Quote:

Originally Posted by captain p4

One more way to do it is to jack the truck up and put it in neutral, then turn the tire one revolution and count how many times the driveshaft turns.

this is the only part of this post that made any goddamn sense to me. make sure both tires turn the same amount of revolutions just in case you have an open diff(it can lead to wrong readings) chances are, unless it got swapped at some point in time, it is either 3.55 or 4.10, unless it is a super duty. mark it in a spot with tape or chalk, and count the dshaft rotations until that marked spot comes back to the same position. it is not an exact science, but you get the gist.

Jul 19, 2010 | 11:10 PM

73 ford guy

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From: Victoria , BC

Pull the cover and read the stamped #'s on ring gear! Done

Jul 20, 2010 | 12:33 AM

fatdan460

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From: utica il

that works too, but i value my silicone

Jul 20, 2010 | 01:39 AM

Prozon

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From: Olympia

Not to mention then he has to get all messy with the gear oil.. easiest just to turn the tires and count the drive shaft rotations.

Jul 20, 2010 | 04:29 AM

Bender99

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Or he could tell us the tranny, tire size and how many rpm's at 65 and someone should be able figure it out. If you have a 5 speed I can probly tell ya, I've had many combo's with 5speeds