the blue pumpkin

During my transmission issues on the RB25 while in the 280z, I also swapped out the open differential, replacing it with an 87-89 300zx CLSD (clutch type). Both were R200 casings so it was a direct swap using my 280z mustache bar, translink, and front mount. I swapped the rear finned cover for a standard one so it would clear instead of buying the Arizona Z translink for a billion dollars, although it is very pretty. The CLSD already had 280z u-jointed driveshafts in it from a previous life, so I didn't have to even mess with that at the time. Every time I disassemble the rear suspension, no matter how new the spindle pins are, I've decided they hate me. As does the matter found at the bottom of a 40 year old strut tube. I think it can actually move on it's own accord.

My weak link in the 280z drivetrain went from being the clutch, to my slave cylinder (if you can count that as part of the drivetrain), to the tires. I replaced the clutch with a 4-puck sprung Competition clutch exactly one launch after getting the car dyno tuned around 18psi. Note to self, avoid the ebay special clutches and adhere to proper break-in methods. Also note, when replacing parts in a system, make sure they now work together or you will quickly find the next weakest link. The strong clutch blew the slave cylinder which caused the second gear synchros to go out the window. The second gear still looked good after disassembling a supposedly bullet-proof transmission, but it was going to cost more than buying a new one in labor and parts to fix.

After replacing the transmission with a Neo RB25 5-speed while using the push-type clutch assembly from mine, and making a few (many) runs with the open diff, the CLSD was the only way to go. Trying to go fast in a straight line, the car would literally decide to do a 360 in the middle of the road while spinning one rear wheel. I needed equal distribution of power. The tires were still the weak link and would lose traction, releasing all the power, before anything else broke. I didn't worry about the half shafts then, but running Hoosier DOT slicks now had me thinking about what was next in line.

FYI, you have to get some very large sockets on the order of 31mm (from Northern Tool as the case may be) to remove the rear companion flanges and fabricate an anti-rotation bar at least 4' long. This is also assuming you have a 3' wrench extension bar as well, otherwise you won't be able to remove the nuts holding the flange to the hub axle. 

When I lowered the differential from the 240z to swap it for the CLSD from the 280z I was more than pleasantly surprised. Lo and behold, there was an R200 open diff with 280zxt CV half shafts already installed! It took some doing to figure this out for several reasons. The diff was installed in the 240z with a flat rear mustache bar, a front mount positioned rearward, and a flat translink. Everything I've read tells me you need the 280z curved mustache bar, 280z curved translink, and front mount in the forward position. This positions the diff more re-ward reducing the half shaft angle between the diff and the hubs, and this is how I would later re-install the CLSD. The car had not been on the road yet so maybe issues of too much CV half shaft angle had not been encountered yet. Here's the article for the Nissan diff family tree.

The diff from the 240z was also black, not blue as my CLSD was even before I painted it. Putting them next to each other, at first glance I thought the blue one was bigger and just assumed the other one was a R180. To make less sense, I couldn't figure out why there were non- u-jointed half shafts on it, and if they were CV's, why anyone would put them on a R180, or an open R180 for that matter. Again, everything I read told me otherwise. I read about R180s with clip in half shafts and thought maybe that's what I had since they weren't bolted u-joints as on my 280z. I actually didn't even realize this was an R200 with CV's until I went to swap the companion flanges from the 280z to the 240z and they didn't fit. As it turns out this is a completely different issue, but it brought my attention to a seemingly modified companion flange from the 240z setup.

I quickly realized I had CV half shafts with Modern Motorsports modified companion flanges installed on 240z hub axles all mated to an R200 open diff. Amazing. After several inquiries and many hours searching online, I determined that the CV half shafts could swap over to my CLSD without anything drastic, and decided to use the modified companion flanges with smaller, 240z hub axles.

The 280z hub axles are a bit bigger in dia and have a few more splines, but have the same bearing OD's to the 240z hub axles. They're a direct swap and these would be stronger, but it would involve disassembling the rear hubs, installing new bearings, and sending my 280z companion flanges off with a wad of cash to MM to be modified in a similar fashion to the ones I had just pulled from my unassuming 240z. Reminding me of my ongoing spindle pin debacle, the previous owner kept her clean and had not changed the hub axles and I didn't want to make a mess today. You do have to draw the line somewhere with weak links in the drivetrain, but I kept the 280z hubs so that in the future if this ever is needed I would have the parts to do the swap. If I'm breaking hub axles, I have other serious problems.

Not shown below, although the cats are, the half shafts from both the open diff and blue CLSD simply pop out if you put a pry bar (see pictures above of 4' bar bolted to the rear hub during disassembly) between the casing and the half shaft and pull. Pry a bit and rotate the half shaft and repeat for better results. Not covered in most how-to's or info articles online, there are NO internal clip locks, bolts, or special tools needed here.

Helpers.