The Stovebolt Site Forums The Shop Area Driveline 58 Apache Rear End Ratio

With a lot of help from the guys in the Eng Shop I just finished installing a SB in replace for a 235.
Need to know what rear end gear ratio's came in the 58 Apache 3100? I rotated the rear wheel 0ne full turn and got one and three quarter turn on the pinion, which doesn't seem correct. From what I recall that would give me a ratio of about 1.75 which doesn't seem feasable.

3.90:1 is the most common, although there are other ratios and rears available.

yes 3.90 was standard, 4.11 came with the OD trans, and there was a 'mileage minder' option of 3.38 .... check in the tech tips for the method for determining the ratio

Bill

Checked the Tech Tips, found nothing on determining the rear gear ratio.

it's there someplace - need one wheel on the ground if it's not posi - mark the tire, turn the driveshaft 2 full turns

Bill

Here is a link to checking the rearend ratio in the Tech Tips and it is WRONG big time! Incorrect tech Tip The driveshaft of course makes many more turns than do the wheels.

I just checked it with one wheel on the ground, two complete turns of the wheel gives me 1.75 turns of the drive shart. In my start post I had both wheels off the ground. This still does not add up.
Numbers I found on the pinion housing are 707340, does this tell you anything to gear ratio??

There is an axle code stamped (not cast) on the center "chunk" of your axle. It's on the left front side on the flat surface where the bolts are. If you post it, someone here can look up the ratio for you. I have a couple '55 to '59 rears with the
code AF, wich is 3.90:1. Most likely what you will have as well.

Do you mean the axle tube?? Don't know what you are refering to as "Chunk".The numbers 707340 are stamped on the front pass side of the housing between the pinion seal and the housing bolts.

move the driveshaft 2 complete turns, not the wheel - also make sure you have the slack taken up to start - also be precise, then multiply x2, you seem to have a 3.50, not likely

the 'chunk' is the differential, not the housing, but markings are not always there and might not match what's been changed in the last 50 years ... the definitive way to tell is pull the cover and count the teeth, should be looked at anyway because it's not uncommon to find them with damaged teeth from a pinion loosening up or bearing going out

Bill

I just went and checked the whole rear again. The only numbers stamped on it are 3707340 and under that D1. the numbers run bottom to top (vertical) not rear to front (horizontal).Left out the 3 in previous post. I can post a pic but I can't find a way to post it.

a casting number won't indicate the ratio .... to use pics here you need to have them hosted someplace like Webshots, and link to them

Bill

This pic shows where the id code is stamped on the 3rd member.

There are no numbers stamped where your pic shows. The numbers I mentioned are on the housing that holds the pinion seal close to the housing away from the seal. There are three raised vertical ridges, the last ridge is shorter then the first two. The numbers (370340)are between the first and second ridge and the stamping D1 is between the second and third ridge. I did the rotation again turning the drive shaft and I get a little over two turns on the wheel. If I times it by two I get a gear ratio of about 4.11. So I now think that the rear is either a 390 or a 411. Does that seem correct?

yes, standard was 3.90 with the 3 or 4 speed, and 4.11 with the overdrive trans - if it is 4.11 you'd do better with a 700R4 OD

Bill

It's more accurate if you do 10 or 20 rotations, then do the math accordingly. My '59 has 3.90 gears.

John

see how many times it takes to spin the wheel ten times.

if it had a manual trans it was 3.9 (taks 39 turns)

If it was a manual with over drive it was 4.11 takes 41 turns

and I think the automatics were 3.23

Thanks. I will try that.