How To Read the Ring for Diff Ratio

[texasz]

Can anyone tell me how to read the ring stamp to tell what the ratio is on an R180?

[mwz]

Divide the first number by the second number. So, if it says 39/11, that's 39 divided by 11, or 3.545.

[texasz]

GREAT!! Thank you, now I will know what to look for when searching for a 3.9 R180 in the junk yards.

[2ManyZs]

I made a list the other day of the marking when I was checking to make sure the 180 I just bought was what it was supposed to be.

39:11=3:54

37:10=3:70

39:10=3:90

37:9 =4:11

[texasz]

Thank you 2many, again you are a wealth of information.

Slightly different question...Is there a casting code or something on the R180 that indicates it is an R180 and not an R200? This would need to hold true for all the R180s since I'm seeking one that is not from a Z. I'm looking for the 3.9 R180 from the front of a 1/83 -6/83 Datsun 720 4x4 truck.

[texasz]

Anyone, anyone??? I have a couple that I have located and need to confirm that they are the right one. Is there a casting code on the diff case that would help at all?

[2ManyZs]

Sorry, I went looking for an old thread that might have had what you wanted to know in it and haven't found the right one yet ........so many threads, so little time.....

The easiest way to distinguish a 180 from the 200 is the rear cover. The 180 has a cover that is closer to being flat than the 200. The 200 also has the mustache mounting studs on an extended part of the cover while the 180 cover has more of just a raised flat area.

The vent is also another give away, the 180 is further to the right and closer to the mounting flange of the cover, while the 200 is more in the center and farther away due to the raised section of the cover.

There's a pic on one of the sites that has them side by side but I haven't found it yet, I thought it was on the Datsun Garage site....

[mwz]

There's a pic on one of the sites that has them side by side but I haven't found it yet, I thought it was on the Datsun Garage site....

Was it maybe this page?

http://www.geocities.com/MotorCity/Garage/6212/diffswap/diffswap.htm

[2ManyZs]

Errr yup, that's the one of them Chloe... guess I got to many pages bookmarked....:stupid: There was another pic that had them side-by-side from the rear... dunno where I put that one...

Thanks.

Guess if I wasn't so lazy, I could have just taken the camera out in the garage and made my own side-by-side pic....hate hefting those things out from under the shelves when I don't have too...

[texasz]

Does this appear to be an R180? It is said to have come out of a '78 Fairlady Z and be a 4.11 ratio.

[Ben]

That's a 180, you can tell by:

It's rectangular/oval rear section (200 is squarer).

The alloy side plates for the bearings/seals

[2ManyZs]

Looks like one to me too, but you might have to use the 280 output shafts with the clips in it and not the bolt in ones from the 240...unless it's been converted to the bolt in ones already. If it came out of a 78 it probably needs the 280 style.