VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1933-1936 Speedometer gearing

The Speedo has never worked on my 33 since my Dad out it together from crates of parts the first time over 25 years ago. The cable is there, but he seems to remember the internal heat was missing.

Opening it up this week- anything I should look out for? If the internal gear is missing - where do I find out the ratio? It’s. 1933 1.5 ton truck, and I can’t seem to track down much outside of the cable to replace.

Thanks

Look here. There are 3 parts manuals that go back to 1929. I found the middle one the most useful for speedometer gears, but If it were in your situation I would read the sections and look at all the illustrations that pertain to speedometer gears and the back of the transmission in all 3 books.

http://chevy.oldcarmanualproject.com/

Chevy speedometer gears were sold in sets, it was not possible to change just the pinion for different tire sizes and rear axle ratios like in more modern Chevys. The pinion and the worm (inside the transmission around the u-joint or output shaft) had to be changed together. The two come together in a box under one part number.

The good news is there is probably only one rear axle ratio and tire size for a truck that big and you can probably narrow it down to one part number for the correct speedometer gears.

Some trucks used a correction box that screwed on the transmission between the cable fitting and the cable. Be sure to check that section in the parts manual to see if it applies to your truck.

. The rear end ratio in Ton & half trucks from 1933 model "O" thru 2002 model 3500HD are 6-37 (6.17) and 7-38 (5.42). These gears interchange from 1933 - 1936. (Military used 6-40 with ratio of 6.66). .
. Part number #364163 having speedometer gears on U-joint 3-12 are for the 6-37rear ratios. Part #363575 having speedometer gears 4-14 are for 7-38 ratio.
. If you have larger rear tires adapters are available to change ratio.
. Lou .
.