DontKnowJack
Full Access Member
What gears do I have?
16 driveshaft revs = 8 rear wheel revs
- Thread starter DontKnowJack
- Start date
most of these trucks had 3.55 or 4.10 gears. by your count they would be 1.2 and i have never heard of those. can you read the rear axle tag, it should be located on the rear cover bolts.
another thing about counting wheel turns is both rear wheels need to be turning the same speed to get an accurate count. if one is spinning faster it will throw things off.
another thing about counting wheel turns is both rear wheels need to be turning the same speed to get an accurate count. if one is spinning faster it will throw things off.
sle2115
NRA LIFE MEMBER
A 4.10 ratio means the driveshaft (pinion) has to turn 4.10 times for the ring gear to make one complete revolution (Ring has 45 teeth, pinion has 11 for instance). You are losing some multiplier in your spider gears I'm guessing.
If you have RPM's/MPH and tire size, it can easily be entered at Randy's Ring and Pinion and it will tell you.
If you have RPM's/MPH and tire size, it can easily be entered at Randy's Ring and Pinion and it will tell you.
DontKnowJack
Full Access Member
Tags and door sticker say 3.55 but I'm getting 2500 rpms at 55 mph and believe they have been changed. I was only turning one rear wheel, maybe I did it wrong.
Knuckledragger
blowing chunks and grabbing porcelain
That you did. These trucks mostly had open rear ends, so by raising the wheels off the ground, you will notice that turning one will make the other turn in reverse rotation. That is a function of the side and spider gears creating the "differential" motion that allows you to go around the corner without scrubbing off rubber from the inner or outer tire. To find the ratio, you must make both rear wheels turn at the same time in the same direction. It is far easier just to remove the rear diff cover and count gear teeth.
DontKnowJack
Full Access Member
So how many teeth should there be for 3.55? And if it's more or less?
jam0o0
Full Access Member
there should be 3.55 teeth for every tooth on the other gear. cant remember how many off hand.
but if you take you original findings and divide by 2 you get 4:1 which is about 4.1:1. with open gears if you kept one tire still and turned the other one you get twice as many rotations of the tire as you would if both tires were turning.
but if you take you original findings and divide by 2 you get 4:1 which is about 4.1:1. with open gears if you kept one tire still and turned the other one you get twice as many rotations of the tire as you would if both tires were turning.
DontKnowJack
Full Access Member
Thanks jam. Just didn't want take it to a shop asking for 3.55's and find out that's what was in it.
DontKnowJack
Full Access Member
Quote:
Originally Posted by DontKnowJack
What are my rear gears?
Was that with both wheels rotating or just one? If one wheel was on the ground and the other spinning then that would be a 4:1 ratio.
__________________
Mark
Former Automatic Transmission Engineer 1988-2007
From another forum.
Originally Posted by DontKnowJack
What are my rear gears?
Was that with both wheels rotating or just one? If one wheel was on the ground and the other spinning then that would be a 4:1 ratio.
__________________
Mark
Former Automatic Transmission Engineer 1988-2007
From another forum.
icanfixall
Official GMM hand model
The way I did mine was lift just one rear wheel. Block the other both directions. Mark the drive shaft and the inside wall of the tire off the ground. Now hand turn the drive shaft and count how many turns it takes for the tire to make one complete turn. You might make a mark on the ground at the tire too. Can't get any eaier than that....
