gear ratio?
gear ratio?
Laughing Gas
Joined: Jan 2002
Posts: 1,008
Likes: 1
From: Tucson
If someone has not removed it, there should be a tag on one of the bolts. If not, you can figure it out in a number of different ways. Matter of fact, I used one of them Saturday on my son's Suburban.
1. Jack up the rear end (both wheels off the ground);
2. Attach a big plastic tie to the drive shaft and arrange it so the tie's tail sticks straight up at 12 O'Clock;
3. Mark the tire with chalk;
4. Turn the driveshaft and count the times the tie goes by;
5. When the tire has rotated one full turn, the number of driveshaft turns is your gear ratio.
In my case, for example, it went around more than 3 1/4 turns but just slightly less than 3 1/2 turns so I figures it's a 3:42. Not exact but you can guess correctly by ascertaining the available ratios.
Good luck.
jor
1. Jack up the rear end (both wheels off the ground);
2. Attach a big plastic tie to the drive shaft and arrange it so the tie's tail sticks straight up at 12 O'Clock;
3. Mark the tire with chalk;
4. Turn the driveshaft and count the times the tie goes by;
5. When the tire has rotated one full turn, the number of driveshaft turns is your gear ratio.
In my case, for example, it went around more than 3 1/4 turns but just slightly less than 3 1/2 turns so I figures it's a 3:42. Not exact but you can guess correctly by ascertaining the available ratios.
Good luck.
jor
Postmaster
Joined: Jul 2005
Posts: 3,248
Likes: 0
To determine gear ratio, and alternative process Approxiamately.
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Try locating a gear ratio tag on the side of the front or rear covers on the axles, the tag mounts to one of the cover bolts. Post all the tag number and we'll help you.
Alternative way of checking gear ratio:
Items you need to check the rear and front gear ratio.
Duct tape
Rope, string, or ribbon.
Flat driving surface.
On driver side tires, where the tire make contact with the flat driving surface, place a strip of duct tape.
Then place a some duct tape at one end of the rope (or ribbon, etc..., or something that will wrap around the driveshaft) and tape it to the very bottom or the very top of the driveshaft. Then drive the truck forward until the tire make one complete revolution. Then count the number of times the rope has wrapped around the driveshaft PLUS the amount the tape has rotated from where you started. For instance, If rope was taped to the very bottom of driveshaft and the rope wrapped around 3 times plus now the tape on driveshaft is facing at the very top of drive shaft (the driveshaft has turned half a turn). 3 rev plus a half turn = 3.50:1 gear ratio.
Try locating a gear ratio tag on the side of the front or rear covers on the axles, the tag mounts to one of the cover bolts. Post all the tag number and we'll help you.
Alternative way of checking gear ratio:
Items you need to check the rear and front gear ratio.
Duct tape
Rope, string, or ribbon.
Flat driving surface.
On driver side tires, where the tire make contact with the flat driving surface, place a strip of duct tape.
Then place a some duct tape at one end of the rope (or ribbon, etc..., or something that will wrap around the driveshaft) and tape it to the very bottom or the very top of the driveshaft. Then drive the truck forward until the tire make one complete revolution. Then count the number of times the rope has wrapped around the driveshaft PLUS the amount the tape has rotated from where you started. For instance, If rope was taped to the very bottom of driveshaft and the rope wrapped around 3 times plus now the tape on driveshaft is facing at the very top of drive shaft (the driveshaft has turned half a turn). 3 rev plus a half turn = 3.50:1 gear ratio.
Elder User
Joined: Mar 2005
Posts: 709
Likes: 0
From: Mesquite, Texas
You can find the original gear ratio in your vin code. My axle code for a 67 F100 is 17 so that equals 3.25-1 gear ratio. Then I checked it in a similar way as described above and it is original.
Posting Guru
Joined: Dec 2003
Posts: 1,391
Likes: 0
From: South Central Boise
That is true you can find out what the truck originaly came with from the tags, but in the 38 or so years that have gone by, who knows what previous owner put what gears in there. Just a thought.
