68 rear gears

[1968k10blue]

Okay, so I did some math and I found my 68 k10 has roughly a 3.97 rear gears using rough math, so I was wondering what 68a had for options for the rear gear ratios.
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[geezer#99]

Rough math??
Tell us how you figured it out. 3.97 is pretty precise.
You could have 3.73's, 4.10's or 4.56's in there.

[67 chevelle]

should be in the glove box door , rough math dont work , especially if its a non posi

[1968k10blue]

By rough math I mean I did slot of rounding it is probably a 4.10. I don't have the paper in the glove box, it has had a cab swap
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[Fitz]

Originally Posted by 1968k10blue

Okay, so I did some math and I found my 68 k10 has roughly a 3.97 rear gears using rough math, so I was wondering what 68a had for options for the rear gear ratios.
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Here are the options for rear gearing in '68. Remember, the open carrier was base and the positraction rear was an optional extra.

Series 10 Open Carrier
3.07=HB, LL, RA, TR, TT
3.73=HA, HJ, HQ, MF, TQ
4.11=HO, HP, JQ, MI, MK,

Series 10 Positraction
3.73=HC, HN, MU, TU
4.11=HK, HL, HR, ME, MG, TS, TV

There will be a number stamped on the upper surface of the axle tube (I think on the passenger side) that uses one of the letter codes above to identify ratio and open vs posi rear. All bets are off if someone has changed the carrier.

[1968k10blue]

It's simple, my rpm at 55 is 2500, and I have 31 inch tires so you see how many rotations it takes your tires to go 55 miles, then take you RPMs and multiply it by 60 to get 55 miles per hour, so in my case I did a little more precise math this time and got 150000/36759 which ended up being 4.08 ration in fourth gear which is a 1:1 ratio
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[67 chevelle]

if you have a Manuel that might work , autos have converter slip

[1968k10blue]

It is a manual
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[Fitz]

Originally Posted by 67 chevelle

if you have a Manuel that might work , autos have converter slip

If it is slipping at constant speed it's time for a new one!

[68c10airstream]

Hi 1968K10 blue, take a bright colored crayon, mark the drive shaft to the nose of the rearend, and at the same time strike a mark straight down to the ground on the outside of the tire (at the 6 oclock position). After you have done this a few times it is very easy and has never been wrong. What i do is mark the drivers side of the driveshaft along the drivers side of the nose of the rearend so i can roll the drivers tire forward as i watch the tire and drive shaft, remember to have the truck steering straight ahead (not turning). An example is this, drivers tire makes exactly one revolution, as the drive shaft makes just past 4 full revolutions = 4.11 ratio. Ex #2 drive shaft turns just past 3 revolutions for 1 tire revolution = 3.08 etc, etc. Good luck, Brian F.