Howdy,

I have both an R200 and an R180, the 180 is a 3.36 and the 200 is a 3.55. Last time I tried to switch the rear end over to a 200 I had problems from He** and gave up, putting another 180 in to get me by. I did change mustache bars but nothing wanted to line up with the diffy mount bar. The victim is a '73. Two questions: 1; Do you need to change the diffy mount bar, originally I was told no, but now I wonder. And 2; Is the change over worth it? Stock motor, 4-speed tranny, good suspension. (Springs, bars, blah, blah, blah)

Want a 3.90 but still looking. Is there a noticable diff between the 3.36 and the 3.55?

Thanks for the info.

Have a heckuva weekend...

(And ok, three questions.)

Difference from 3.36 to 3.54 is barely noticable! Just enough to screw up your speedo, although if you are running 60 series tires on 15" rims it may actually put things back to the way they were. Unless you have to do it now, I would hold out for a different ratio, 3.7 at least, if you are going to make the swap.

What do you mean by "diffy bar?" The mustache bar is different for R200 but you already mentioned that. Unlike the early, pre-'72 240s, the rear cross member is the same on a '73 240 as that used for later R200s. I believe the front insulator can be interchanged by just turning it around 180 degrees. The only trick is getting the strap over the front of the diff to work. I have read on Zcar garage that he did it by inverting and grinding the extra threads off the end of the front diff insulator mount bolts.

Hope it helps! Corrections, questions, and comments welcomed!

Have fun!

Thanks Royce, I'll just leave everything the same then, and wait fir a 3.90. And yes, I meant front mount.

Thanks for the help, have a great weekend!

Oh and another thing is that the 3.5 R200 is very popular with the V8 Z crowd, since the 3.3 R200 seem to be just about extinct. If you wanted to you should be able to sell it without to much difficulty.

I have what i believe is a R180LSD,it has no ring gear and takes 27 spline axles,does anybody know some way to identify it or a site i can go to with information specific to R180's,thanks mick

You can shoot me the numbers and I'll compare then to the r180's that I have. That way if they are the same at least you'll know what you have...

HEY I hate to change the subject, but I was wondering what size tires you are running with the R200. Also being new at this, my question is how can I tell what my gear ratio is on my 75. I know that it was put in before I bought the car but thats about all I know.

If you get an R180 from an automatic car, the ratio is. 3.54. I have one of those I'm getting ready to pull from a parts car. FYI.

HEY I hate to change the subject, but I was wondering what size tires you are running with the R200. Also being new at this, my question is how can I tell what my gear ratio is on my 75. I know that it was put in before I bought the car but thats about all I know.

FYI it's probably better to start a new post and ask your questions rather than resurrect a thread from 2002.

I have what i believe is a R180LSD,it has no ring gear and takes 27 spline axles,does anybody know some way to identify it or a site i can go to with information specific to R180's,thanks mick

Datsun/Nissan car R180 differentials typically used 25 spline stub axles. Nissan truck H180 (live axle) and Subaru WRX STi R180s used 27 spline stub axles.

From zhome.com, Documents, Index Of Technical Articles, How To Determine what ratio a specific differential contains.

"The Following is a note related to an easy method of determining which rear end gear ratio any Z differential is - before you take it out of the car, or install it in your Z. Sent to the IZCC's "Z Car List" by: Ross Corrigan, IZCC #255

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Want to know what gear ratio that Z rear end is, before you remove it from the car or install it in your Z?

Take a buddy, and just turn it to find out. My dad and I have turned at least a dozen. Fix one rear wheel so it can't turn (pry bar and foot of the driveshaft counter, or jam it otherwise). Mark the driveshaft w/ chalk or scratch w/ a nail. rotate the other rear wheel 10 times, other person counts the driveshaft rotations. Then multiply the driveshaft rot's number by 2(and divide by ten I spose) and whammo its your diff ratio.

If 10 turns gives you (x driveshaft rotations) just shy of 17, then its a 3.365 17.5 then a 3.54 18.5 then a 3.7 19.5 then a 3.9 Each difference is at least a whole number (except 3.36->3.54, but still 16 or 17?) so this always works for us. Don't forget to grab the speedo gear out of the tranny (one 10mm bolt), even though you don't need it (w/ a 700R4 for a V8 conversion), if you ever sell it it'll help out a Datsun dude.

Others reccomend removing the rear cover plate and readig the ring gear. The number of teeth on the ring and pinion are stamped on the ring gear - so just divide one number by the other. The units I look at most of the time are still in the cars, so this "counting the turns" method works for me.

Ross Corrigan / Vancouver, Canada IZCC#255 '80 327ZX [14 February 1998] "

There is also another article in the same location that will help you identify the ratio if you have the differential cover opened up.

Hope it helps!

WOW! GREAT INFO.

Thanks. it's been lots of help. I plan on pulling it out in a couple months, step 2 on my quest to restore it.