What gears do I have

I just bought a NICE rolling chassis on Ebay for $20.00 to replace the one on my '66. The one I got is a '64 that had a 4cyl. Do I use my rears or keep the '64 rears. Did they use the same gears( 4cyl vs. 6cyl.)? I know you count the teeth on the ring and pinion but whats the formula?

 

if you have the cover off, count the teeth on the ring gear and divide it by the teeth on the pinion gear. the only thing is its hard too see the pinion gear.
the ring gear should have 2 numbers stamped on it. divide the bigger number by the smaller number and you have your ratio.

 

You should easily be able to ballpark this by marking both the pinion and the hub, then counting the revolutions of the pinion for each turn of the hub. Take Glenn's list of ratios options and you should nail it.

 

If you pull the cover, most ring gears have the numbers stamped on them i.e. 43 8 corresponds with 43 tooth ring gear and 8 tooth pinion. There might also be some other numbers there as well, and it might be hard to determine which ones are for the tooth count.

 

Remember, that if you do the rotate the wheel and count drive shaft revolutions method that you have to count the number of drive shaft revolutions for TWO wheel rotations, not just one .

For example, turn the wheel two full revolutions and the drive shaft turns about 5 1/3 turns you have 5.38 gears.

I suppose you could just rotate the wheel once, but if you did, you'd have to multiply your count by two..

 

Kamel, that is dependant upon to things:
1) the differential is open
2) one wheel is jacked up and spun twice. the wheel that is not being spun is still on the ground.

correct me if i'm wrong, i'm no drivetrain specialist......

 

Y'know, that's a really good question. You'd have to have the other wheel on the ground for the test axle, otherwise you could get some really strange results, but as far as the limited slip differential question, I don't know. It would seem that the L/S would change things, but I'm not sure.

I've got an old axle in the shop that has a limited slip in it. I'm going to try it tomorrow and see what happens. I know that it is 4.27 gears, so knowing the answer up front makes it easier.

 

well if its a limited slip, you get both wheels off the ground and spin the tire once while counting the driveshaft rotations. (on a limited slip unit, both tires will spin the same direction, on an open unit they will spin in opposite directions)

if its an open differential, you have one tire on the ground, and spin the tire that is off the ground twice while counting driveshaft rotations.

 

Are the gear ratios not stamped in the web of the 44 rears like the CJ2A's? Usually there are two numbers. You divide one by the other.

 

Kamel, Did you run you're experiment yet?

 

On my "Sure-Grip" Dodge Challenger I recall getting both wheels off the ground, spinnning the wheels (both spin of course) and just counting the spins. It worked out as I thought. No X2 required as I recall.

I don't understand how it being limited slip or not matters, 4:11 gears are 4:11 gears, limited slip or not. But, I am no rear-end specialist by any means. Maybe I'll learn something.

I do appreciate a good rear-end when I see one, but I am no specialist.

 

4.11 gears are 4.11 gears, but when determining the ratio (without pulling off the cover) you have to follow different methods as they act differently.
An open differential transmits powers through the spider gears, putting all power to only one wheel - the wheel with the least resistance.
A limited slip unit (if not under a load) will transmit power to both wheels without using the spider gears.
It's not the easist topic to explain. you really need a visual to understand. I only gained an understanding after taking apart both types of differentials and seeing how they work....