Getting started

[RJB]

Hi, I have just recently bought my first Dodge, which is a 63 Polara 500. I have alot of questions since i have converted from Ford to Dodge. Dont know much about the Dodge yet but my question is how do I tell what 3rd member I have in my rearend. Its a 8 3/4.

 

[iraqivet01]

if your talking about what your gear ratio.
chock the front wheels, Jack up the rear of the car so both wheels are off the ground, (suggest using jack stands under the differential) put it in neutral, and start turning the rear wheel, mark the pinion and count how many times the it turns in one rotation.

if it in one rotation the pinion turns 3 3/4 times, you have most likely 3.73 gears.

It will also tell you whether you have a sure grip or limited slip if both wheels turn, or if one goes in the opposite direction or stays put. Even if both turn does not mean you have a true posi. someone could have welded the spider gears together making it into a lincoln posi.

might be off a bit, but it's will get you close.

 

[Deleted member 214]

If you mean what gear ratio you have, if you are lucky the factory tag is intact. Look for a small metal tag on one of the bolts that hold the center section (the part with the universal joint yoke on front) and the ratio will be stamped on it. Second way is less accurate - get both rear wheels off the ground, turn the driveshaft until a back tire goes around once. If you turn the driveshaft around 3 and a half times to one revolution of the back tire, you have a 3.55. Two and three-quarters revolution would make a 2.76, and so on. Somebody here can chime in with a list of common Mopar gear ratios - I don't have one available. Hardest way but most accurate is to remove the center chunck and look for the stampings on the gear itself. Good luck!

 

[RJB]

So on the 3rd member can i use 741, 742, or 489? Cause mine is a single track and i really would like to keep the stock rear end just want a posi unit in there with decent gears. If any of the 3 will work i will just look for one with the right gears for me, Im just not sure if all 3 work what i need to look for.

 

[khryslerkid]

Let's train him right! It's "sure grip" not posi when referring to Chrysler products!

 

[RJB]

My bad, will all 3 sure grip's fit?

 

[Deleted member 214]

Yes, they will all fit. The 741 is weakest of the three, but fine unless you a racing or otherwise abusing it. You can retrofit any of the three with a sure grip. Have you found out what gears you have and what gears you want yet?

 

[Small Block]

Just a note to save ya headaches. When and if you order a rebuild kit, meaning bearings and the likes, yu'll need to be sure and specify to the vendor the case number as some of the internals are different. The pinion sizes are diff dia. from one to another. Get a clutch type unit if you have a choice. The rear is fairly easy to rebuild. Good luck on the build and i forgot to say. Welcome and should you need any additional info that you dont find here go over on the sister site,forabodiesonly.com, and there's a ton of great folks there also. Ready and willing to help.
Small Block

 

[RubyredSavoy]

Also keep in mind, since your car is a '63 without the sure-grip option, your axle shafts are a little too long. You will need to have 1/8" machined off of them to correctly convert them for sure grip use. In '64, they widened the rear axle to do away with this issue.

 

[RJB]

Thank you, thats good to know on the axle length. I want to go 4.30 ratio on gears, just gonna be a weekend cruiser around town.