The Stovebolt Site Forums The Shop Area Engine Shop 1 ton rear end gearing mystery

On my 59 1 ton I have the bed off and the truck on jack stands so I decided to do the trick to count the times the drive shaft rotated versus a rear wheel to see what the ratio was. I really didn't want to run with what should be the stock ration of 5.14 (according to my books).

I took a marksalot and put arrows on the drive shaft and on the brake drum for reference so I could count revlutions easier. I have the 8 lug floating axle (like in Jerry's previous post). To measure it I put a 1/4 steel plate on one side in the lugs braced against the driveway so one wheel wouldn't turn and then went both backward and forward turning both the driveshaft and the wheel by hand.

The reason for all that testing is that the drive shaft doesn't quite make 3 rotations for the the 1 rotation of the brake drum!!!

So question is - did they really have gearing as high as that in these rears? Did I get really lucky??? I am going to ax the original owner about it and see if he remembers changing it. Would be a score if he did. The truck was last inspected in 1975, and it was regularly used, so maybe they upped the gearing or swapped for a rear end that would be more practical on the highway.

Or am i ignorant and doing the test wrong?

I'm thinking you did it right. Did you try w/out holding other wheel too? Seems like even if you had newer rear, it would still be 4.11 or higher. Is there a tag on cover bolt? Is there a stamping on a flat machined surface that's wider where cover bolts on? May have to clean it off. Is there a letter and date stamping on the top of tubes nearer brakes? May have to wire brush good to see those. Now with bed off, that's easier. Look near the vent if it has one. I use my cup brush in my 4-1/2" angle grinder to clean stuff like this up, works very well.

If you hold one drum and turn the other, you have to double the number of driveshaft revolutions because of the multiplier effect of the spider gears.

The easiest way for me is to count the driveshaft revolutions till the drum makes two full turns.

Joe

Irwin, you were just wishing for 3 to 1 high way gears

Sorry to spoil youe excitement, but this is what the results mean:

If both wheels were free and you had a 5.14 ratio, you would be turning the driveshaft 5.14 times to get the brake drum(s) to turn 1 turn, if they turned at the same rate. Since however you have one blocked, the brake drum does twice as many revolutions. Therefore with 5.14 revolutions of the driveshaft, you would get 2 turns of the brakedrum. For 1 turn of the brakedrum, you need 5.14/2 tuns or 2.57 turns, which is what you have observed. You have a 5.14 rearend.

Thanks, I figured I was doing it rong!

I asked the previous owner and he said he once did a trip to San Antonio with it going about 60 - must have been spun up pretty good!