Rear diff question

[spike188]

Guys forgive my ineptitude as I am learning as I go. How do I know what differential I have? I want to replace seals and gaskets but I want to know how i go about figuring out what I have, an 8.25 -8.75 42 or 41 or 89. In other words I don't know and want to find out how to know. If I lived somewhere where there were knowledgeable mechanics I would probably not have nearly as many learning curves as I do living on this rock in the Pacific.....

1969 Barracuda convertible, 318, 3speed auto.

I appreciate all the help I have found here and once again thanks in advance.......

Spike

 

[Dubob]

Here about halfway down shows the different housings.

http://www.forabodiesonly.com/mopar/showthread.php?t=228120

If it's an 8 3/4 the 741, 742 or 489 will be cast into the housing that contains the actual differential. This is also called a pig, chunk, or third member and pull out the front of the axle housing.

 

[rumblefish360]

If the rear has a cover, count the bolts that retain the cover.
IF there are no bolts holding on a rear cover, then you have an 8-3/4 rear where the gears are installed into the rear housing from the front and nuts onto studs hold it in the housing.
Match what you see to the chart.

http://www.forabodiesonly.com/mopar/showpost.php?p=1969905844&postcount=9

 

[spike188]

guys thanks, the fender tag shows a D31 code which would be the light duty 904-A auto trans. I have used Rock auto for parts but trying to find the right gasket and seals isn't as easy as just checking 904. I thought i ordered the right one but get it up on the lift and it isnt right. Took almost two weeks to get here and need to order a new one.......