[49dream]

I have a 49 Chevy pickup with a GM 10 bolt rear end

The number on the rear end is GM K11 8725899

Is there some where or some one that can tell about this rear end?
Maybe the the year or what this rear end came out of.
The gear ratio would be beneficial too.

Thanks
Marcus

[37 plymouth coupe]

jack up the rear of the vehicle. Mark the right rear wheel and the driveshaft. Rotate the wheel 1 full turn and count the the turns of the driveshaft. DO the math (divide)= ratio

[Jon]

Check the Hotrodders Knowledge Base first, that's the most likely place to find a rearend identification guide for your vehicle. Here's the relevant category: Transmission-Rearend Technical Data.

[49dream]

Plmouth coupe

I did what you said and tuned the wheel 1 full turn. The drive shaft turned
1 & 5/8 times. Are you saying i have a 1.625 ratio ?

[jimfulco]

Leave one wheel on the ground, then rotate the other wheel TWO full turns while you count. This will give you an accurate number. If you lift both wheels, the wheel you can't see will turn a little (or a lot) in the other direction and screw up the count. If you have one wheel down and rotate once, you need to double the number to get your ratio.

I believe 3725899 is an old Chevy car rear end with the drop-out center section. That type of rear end was used from '55-'64, with different widths & spring mounting hardware for different cars.

Google 8725899 rear and there's an old ebay listing with pics. Casting numbers are often mistaken, especially if they're old, rusty, dirty, etc.