1 ton gear ratio

[1955 mancave]

what the highest gear that you guys have run or heard of being run in a one tone,
thank you.

[1955 mancave]

ok now that we are in prime time. btt

[factorystock]

All 1 tons are geared low during the 60-66 era. The highest rear end ratio with the HO 7200 Lb ( removeable pumpkin ) rear axle was 4.10, was optional from 1969 thru 1972.

[1955 mancave]

thank you i will do some research to find out what year the rear end may be since for some reason i do not believe its the original unit.

[Captainfab]

In my experience with the Eaton HO52/72, the 4.57 gears seem to be the most common. If that's what is still under your truck, and if it needs work, I would switch the entire differential to a 14 bolt or a Dana 70 before I would spend much money on the Eaton.

[1955 mancave]

yep it's been changed, it's a 14 bolt, now here is the kicker, i jacked it up marked the tire and the yoke, now i checked 3 different times, so i turned the tire over and the yoke only turned like 3 rev for every time i got a full rotation of the tire, i just cant imagine it has like 3.00 gears.

[61K10]

somebody said you have to have both wheels off the ground?

[1955 mancave]

yep and i did, i even turned each side and came up with the same.

[61K10]

3.08's in a 14B?

[1955 mancave]

i agree but thats what i keep comming up with i just cant think that 3.00 gears would be in a 14 bolt

[1955 mancave]

well in the morning i will go back out and take another look, i will make sure to take a wire tie and wrap it around the driveshaft and count that way for the revolution of turning over the tire once.

[Captainfab]

The 3.08's were available in the FF 14 bolt....not very common though. If it were me, I would just pull the rear cover and look at the numbers stamped on the ring gear. The differential is one of the most neglected parts of a vehicle, and more than likely the gear oil needs to be changed anyway. It will only cost you a cover gasket and a couple quarts of gear oil. Then you will know for certain what gears you have as well as the peace of mind that your differential has fresh gear oil. This will also give you the opportunity to inspect the inside of the differential and see if there are any issues.

[1955 mancave]

i think that is what i am going to do , like you said never hurts to take a look inside anyways, i will be talking to you soon about some mounts you make.

have a great day.

[1955 mancave]

ok i figured it out with some help from another site, if you are working with a non-locker IE open rear end .

jack up the vehicle rotate the tire and count the rotation of drive line, then X that # by 2

[61K10]

6.00?

[1955 mancave]

Originally Posted by 61K10

6.00?

nope i was just rounding, after doing it this morning it came in at 4.10

[HEI451]

OK, lets get real on spinning the tire to get the rear end ratio, shall we.

On a POSI-TRACTION REAR, both tires off the ground, mark the tire with one line, drive shaft with one line, turn EITHER tire one revolution, record the turns on the drive shaft. 4.10 times, 4.10:1, 4'57 times, 4.57:1.

OPEN rear end, same procedure, but, you MUST turn BOTH tires the same amount, together. I just bite the bullet and go under the truck, mark both rear tires with a line at 6:00 o'clock, drive shaft same. I then use a hand on each tire, rotate BOTH tires the same, at the same time, and look at the turns on the drive shaft.

When an open rear end has only one tire spun, with the other tire on the ground, you are measuring both the rear end ratio, AND, the side gear ratio. NOT ALL SIDE GEAR RATIOS ARE 2:1. Even at 2:1, measuring the ring and pinion ratio isn't easy, nor accurate in most instances.

[61K10]

thanks for clearing this up--------

[HEI451]

Yeah, a lot of people just don't realize that the side gears are in play when only one wheel on an open rear end is turned to do the test, and that side gear ratio is also in play as well. So, you aren't measuring just the ring and pinion ratio, but that, AND the side gear ratio as well. Since most side gear ratios are 2:1, but not all, there can be frustration in trying to get an accurate reading.

It's just old world, low tech math, measuring with fingers and toes, not calc or trig.

[1955 mancave]

thanks for your help on this, i was not aware , of the changes.