differential identifying by the housing?

[jlenownnab]

Can you identify what rear diff you have by the numbers on the housing?? I have a 75 280

[Zed Head]

Easier to just look at the rear cover, or the area around where the axles insert.  The R200 has a rectangular chunk of aluminum, about 1/2" by 1", underneath the drain plug and the cover is almost round.  The R180 is smaller and has a rectangular rear cover.  It also has a ring of bolts around the axles holes, where the R200 does not.  Look at some images on the internet and you should be able to tell with a glance.

If your 75 is a manual transmission coupe it's almost certainly an R200.

Or you could post a picture and we'll just tell you what it is.

[jlenownnab]

Thanks,  I need to run down to my shop and look at the housing and take a picture while I'm there should I pull the cover off the pumpkin in order to tell if it's LSD or is that not necessary I'm assuming it probably is not

[Patcon]

It is probably not unless someone swapped it. If you jack the rear of the car up and turn one wheel, if the other rear wheel turns in the same direction = LSD if it turns in the opposite direction = open diff

[Zed Head]

Here's an old picture I had of an R200.  You can just see the rectangular piece of aluminum molded in to the bottom of the cover.  And you can see the rounded corners.

[jlenownnab]

I counted 39 teeth

[Zed Head]

Somewhere on the next to the ring gear you'll find 39 and another number stamped beside it.  Like 39:11.  Looks like a run-of-the-mill open R200 with 3.54 ratio.  Could also be a 3.9, from a later model 280ZX.

[JSM]

If you're not sure which ratio R200 you have lying around the garage, check it this way: Remove the rear plate (drain the oil of course). Then rotate the large ring gear until you see these numbers stamped into the edge facing you. 

• If it's a 3.54 it will read "39:11"
• If it's a 3.70 it will read "37:10"
• If it's a 3.90 it will read "39:10"
• If it's a 4.11 it will read "37:9"

[jlenownnab]

Great information, thankyou all.