Datsun used several different sized differentials in their independent-rear-suspensioned sports cars. The 510 sedans used the R160, the early Z’s used the R180, and the later Z’s used the R200. There are also several other variations out there (R190, R230, LSDs, Ks, clip-ins, bolt-ins, etc). The diff name refers to the size of the ring gear in millimeters, ie the R160 has a 160mm ring gear. Here’s a link to more info than you could ever need – Hybrid Z diff info.
The R160 and R180 are known to be direct bolt-in swaps in the 510 and the early Z, but there are a few important differences. The larger ring gear in the R180 allows it to handle higher torque motors before destroying itself, but the R160 can still stand up to some pretty surprisingly powerful motors. Also the R160 weighs about 8 lbs less and the case is 1/2″ narrower, thus leading to this story. The R160 and early R180 use the same inner bolt-in stub axles (properly known as the side flange). But since the R160 has a narrower case, it needs to use a longer dust cap. (Left – R160, Right – R180).
The dust cap size difference keeps you from being able to swap them between diffs, so don’t get them mixed up in your parts bin! Doh… The dust caps are not that critical of a part, you could just cut them off and use the stubs in either diff if you had too. When I had my CV joint adapters made, I had a R160 in my 510, but now that I have a R180 in it, they didn’t fit. So I cut off the caps, and welded on a pair of caps that I cut off some R180 stubs. Problem solved. If I use them now in my R160, they will just have a 1/4″ gap between the dust cap and the axle seal.
Thank you troy, very well said. yes the motor is pretty beastie. finally got rid of some things (unnecessary) on the car and the weight without me in it is 2460lb. so I’m happy with the engine/car. now if i can get the passenger side floor pan replaced, all will be in check. 2000 miles on the engine/rebuilt trany and no issues. i am going to be looking for a R180 4:11 diff so if anyone has one for sale you can email me at randallwayne221@gmail.com
A 4.11:1 ring & pinion is about a 14% higher gear ratio than with a 3.54 differential. It will increase acceleration across every gear since you are changing your final gear ratio, not your transmission gear ratios. You will experience a higher engine speed for a given road speed, for example if you were doing 2000 rpm at 50 mph in 4th gear, you now will be doing 2000 x 1.14, or about 2300 rpm. Sounds like a nice motor, and with the ZX 0.745 overdrive 5th to handle the freeways, you’ll enjoy the extra acceleration through the lower gears.
I’m thinking of switching my 3.54 to a 4.11. Does the 4.11 help acceleration through every gear or just first and 2nd? How much does it help ? 280Z – 3.1 stroker , 280 deg 490lift cam. 10.45:1 CR,triple mikunis, headers with 2.5″ full exhaust, blue print and ballanced,1982 n/a 5 speed (lower 5th gear).