Fitting An R-200 Rear End In A 510 Sedan

It takes A LOT of power to brake a stock 510 rear end. Should you ever break your stock R-160 rear end and you decide you need something bigger but your happy with your 3.90-1 gears there is an alternative. Some of the 280zx 2+2s came with a 200mm rear end with 3.90 gears. They swap into a 510 four or two door with a little modification.

Step One: Finding the right rear end. I got mine out of a '80 280zx 2+2 five speed. Most of the 2 seaters came with an R-180 (or maybe R-190 I'm not sure). The turbo Zs came with the R-200 but I'm not sure about the gear ratios. Chances are you'll run into a lot more 2+2s than turbos in junk yards. One way to identify the R-200 is that the vent tube comes out of the top of the diff cover to the right of the two upper cover bolts if viewed from the rear of the car. Once you've got it out of the car you may want check the gear ratio. Simply hold one of the output flanges and turn the other output flange and count the revolutions on the input flange. It should go around about four times for each output revolution.

When you get it home drain all the old lube and clean the housing and cover to your satisfaction. At this point you are going to need two spare 510 rear end crossmembers. You want to cut the round ends off one of the crossmembers as close to the ends as possible. These crossmembers are pretty hard to cut. You'll need a really good hack saw blade and a good sharp set of carbide drill bits. The other you just basically want to cut the center, flat, rear end mounting area off of. Drill holes in the first crossmember so it will bolt on to the new rear end. It should be as straight as possible but if it isn't 100% perfect it isn't going to hurt anything. Drill two more hole at least 12mm in diameter on each of the end of the second cross member. Bolt the first modified crossmember to the rear end . If you are going to put new bushings in the cross member now would be a good time to do it.
Now bolt the two ends to the original points on the bottom of the car. You'll have to "massage" the suspension crossmember slightly to get the R-200 to fit. You may also have to do a little grinding on the bottom of the rear end. Now bolt the rear end into the crossmember. Raise the crossmember into the car. get the rear end, the suspension cross member, and the rear end crossmember aligned how you want them (probably as close to the original alignment as possible) and support them on jack stands. Mark the inner crossmember throught the holes on the outer rear end crossmember pieces. Remove the center piece and drill hole as where you marked. Be careful to get them as exact as possible. This could cause problems with if they aren't drilled where they should be. Bolt everything back together. Make sure you use 12mm or larger grade 8 or better bolts and self locking nuts to hold the new crossmember together.

Now you probably think you're done. Just bolt the half shafts to the output flanges, bolt on your super sticky tires and go. Well that's what I thought too. My car drove great in a straight line. But when I pushed it hard into a corner I noticed a strange vibration in the rear of the car. When I would dive enthusiatically into a corner the rear trailing arm bushings would deflect and cause the inner half shaft to "bottom out" because the R-200 is much wider then the R-160 that came out. This would put pressure on the output flange on the rear end. The flange bolts would rub on the out side of the rear end housing and would cause a bad vibration that could be felt inside the car. I had never heard anyone else mention this so it may have been some kind of fluke situation but I decided that the best thing to do in my case would be to shorten my half shafts.

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