63 falcon differential identification

[thewallyllama]

I've not done work on a differential before. My falcon has the 170 cu in 6 and 2 speed auto in it. Pinion seal has been leaking for some time and wont be till Mardi Gras week that I will be able to work on it. What weight gear oil would work best for it. Also i'm wonder how do i know what size rear end it is? I've had some people ask how many bolts the cover plate has. Its 8. Thr car is just the basic base model. Looking for new bearing and seals online it seems to be either 7 or 7.25 in ring gear and such. I do need to get my hands on the service manual one of these days would answer most of my questions.

[CZLN6]

Howdy Back Wally:

While a Service Manual is an excellent idea, you could begin by identifying what rear end you have by decoding the build plate on the door frame. One of the codes will be under "ax". That will be the axle that your car came from the factory with originally. Report the code here and we can help you or by a Service Manual for a 1963 Falcon and it will tell you. that said, most '63 Falcons came with either a 6.75" or a 7.25". The number refers to the outer diameter of the ring gear.

A second option to id your rear end is to look for a stamped metal tag attached to on of the bolts that hold the cover on it.

Give it a go and let us know what you find.

Adios, David

[thewallyllama]

On the data plate there is nothing stamped under where it says axle but directly below/between axle and trans is a 3 and a 3 stamped below the trans spot. I hope that makes sense.

[thewallyllama]

I have not gotten under the car to look at the tag on the housing. Later today I will get to that.

[CZLN6]

HOwdy Back:

FYI- Both the 6 3/4 and 7 1/2" have 8 bolts holding the cover on. both covers are octagon in shape and they share the same seals. Without opening and measuring IDing is iffy. The tag is your best bet.

The "3" would indicate a 3.2:1 ratio.

Adios, David

[thewallyllama]

From the tag i've gathered a few things. First row is WBY J1. Second row is 3 20 8F4 505.

So i know its a 7.25in dif with the 3.2 ratio. Not sure how to read the date and which plant is 505.

[thewallyllama]

It just occured to me that im in the wrong part of town. Lol.
Thread was supposed to be in drivetrain not suspension. Sorry about that guys.

[bubba22349]

There you go

[1bad6t]

From the tag i've gathered a few things. First row is WBY J1. Second row is 3 20 8F4 505.

So i know its a 7.25in dif with the 3.2 ratio. Not sure how to read the date and which plant is 505.

Date code = 1st number is year...2nd letter is month...3rd letter is week. Your code reads 1968, June, 4th week. Don't know about plant code but it's the same plant code on my 63. When replacing axle seals on my 63 HT I found out I had the larger axle taxicab/sedan delivery rear end. Some 63 Falcons also came with the 7" gear. You are correct that the WBY-J is the 7-1/4". Are you sure date code starts with 8 and not 3? In '68 the codes were WC* or WD*

[thewallyllama]

Its definitely a 3 and not an 8. The tag has been banged around. Some of the numbers are sort of flattened a bit. Thanks for the help!