JMortensen

There is nothing about the Z in particular that makes it incompatible with a diffuser. The cars in the wind tunnel test were all WAY too high and I'd guess too softly sprung to make good use of a diffuser, and all had relatively bad aero at the front except TitaniumZ's car and even his didn't have a rad duct so there was still a lot of air spilling underneath the car. It shouldn't be too surprising then that the expert said the diffuser would be a complete waste. Just judging by the rest of the build, I would think that Matt's car would be a good candidate or it might be said that Matt is a better candidate to get it done than most, especially if he's looking at doing a flat bottom. Toughest part about paneling the bottom of a Z IMO is the exhaust, so you might look at some GT2 style cars and how they run the exhaust through the passenger floor or sidepipes to get the exhaust out of the way. Not a big fan of sidepipes in general, but if you look at some pictures of Zs running them, it's tough to argue with the ground clearance and the space cleared up underneath. I don't know that anyone has actually done a flat bottom Z, so there are issues like driveline cooling that you'd have to break new ground on as well...

Flipping refers to the cage on the outer end of the CV shaft. Turning it around gives you about 1/4" more space before the shaft bottoms. You don't need to do this with M2 shafts, but you have to take the gear off the shaft to put it on the new shaft, so you could choose to put it in either orientation and it's not any harder to do one way or the other. It's a non issue with the new shafts.

1. Hard to find parts, I think some have pushrod motors, rust, leaf springs. 2. Ubiquitous parts, SLA suspension, weak motors. I've seen lots of roadsters done up and I think they're really cool for someone else to own and me to drool over, but I'd much rather own the Miata. If the stock motor gets boring, there are options like turbo or Monster or LSx swaps.

Nope. I should have done it right the first time.

The bolts for the CV shafts are class 10.9 10mm x 1.25 x 20mm length. I realize now that I should have worked this out ahead of time and included these with the purchase of the adapters, so I have the bolts and lockwashers on order. If you would like a set I'll send them to you when I get them Monday, or you can buy them locally. 10 x 1.25 is a bit of an oddball, so you may not find them around town. I would suggest drilling the bolts and safety wiring them. You'll need a drill fixture to do this, they can be found at places like Summit Racing. Castellated nuts might work for the driveshaft. The stock bolts are more of a stud and nut thing, so I don't think that safety wiring works there.

Available now: http://forums.hybridz.org/index.php/topic/105514-m2-cv-adapter-for-z31t-cv-280z-stub-axle/

I would say that the late ZX 5 speeds 80-83 have the best ratios for NA engines. There is a BIG hole in the 2-3 shift on the 4 speeds and early 5 speeds. Particularly if you have a high strung NA (cam, triples, etc) that 2-3 shift can put you out of the power band. I've seen it firsthand at the track. The 80-83 have much closer ratios and can use a lower final drive.

The only way to know if you have this problem is to take the spring off of the suspension and lift it up by hand and feel for resistance. It's possible that you have the problem and don't realize it, just like all those people who install an R200 in a 240 with stock u/j halfshafts and don't realize that they have essentially the same issue with the driver's side halfshaft binding. I've seen maybe 5 people even attempt to fix that problem, the vast majority just drive around like there is nothing wrong, like I used to do. Coffey explained that problem on on his website, the CV axle thing is basically the same, but I think it's probably worse in terms of the amount of bind, and the bind being on both sides of the car. The fact that both sides are bound makes it less prone to pull one way or the other, instead the suspension just doesn't work as well and the pressure on the diff and bearings is worse because the diff can't move to the right to alleviate the pressure. http://www.betamotorsports.com/benchracing/R200handling.htm

I've got tracking numbers for the adapters. They're coming UPS, so probably next Wednesday I'll have them in hand. Looks like the price on my adapters is going to be $375 per set. If you buy with the short shafts through the next group buy, you can get both pieces for $800. The same offer will apply to anyone who bought in the CV group buy. They can retroactively get the adapters for $300 as a combo price. I won't put the adapters or the adapter/cv combo on the site until I actually have them in hand and can verify that they're good. The machinist said that they came out awesome, so that's a good sign. I have 16 sets of adapters on the way, and I'm not sure if I'll make any more after this batch is gone.

If you were driving along and the brakes were getting more and more locked up, then you don't have any free space between the master and the pedal, or the adjustment between the booster and the master is wrong. If the master cannot retract all the way, then it can't let pressure out of the braking system. So you start out and your brakes are cold. Start using them and the fluid warms up and expands and causes the brakes to drag. The more you drive the hotter it gets and the more the brakes drag, until you're stopped on the side of the road with brakes smoking.

The problem is that the stock CV shaft is too long and it binds on both sides. The allowable length gets shorter as the suspension droops, but it doesn't change much throughout the whole range of travel. On my car with billet CV adapters and custom 1/2" longer control arms, I had barely enough room to fit the CV shafts in. From the measurements that I did, I think this means that just about every Z car out there that has Z31T CV shafts has them bottomed out all the time. This means that when the suspension moves, it is flexing bushings and the control arms and putting lots of pressure on the wheel bearings and stub axles, and the differential itself. A bound driveshaft works as a suspension bumpstop and prevents the suspension from moving freely through its range. I think it's a big problem, and we've seen some people complain that they've ruined their LSD, and say this is the reason. Here is a thread about different CV options where it became apparent that this should be a real problem for Z's running stock control arms. I gave all the measurements for these shafts as I was figuring them out on my car, etc. http://forums.hybridz.org/index.php/topic/100094-cv-axle-discussion/ Here is a nice install thread with excellent pictures: http://forums.hybridz.org/index.php/topic/103391-z31-axle-swap-r200-clsd-m2-differentials/

Shipping will be free. I can't give you an accurate price until I get the total from the machinist. The parts were supposed to be ready to ship Monday, just got off the phone with the machinist and he's trying to get ahold of the cad plating guy. I should have just left them raw, but I thought plating would be a nice touch so that they don't rust. When I get the parts and figure out the best price I can give, I'll put up a vendor thread and post on the other various related threads and PM's I have going regarding these parts. If I can remember this one I'll post here too.

Sounds like you need larger pilots.

Go look at what 510's do, and ape that. 510s have basically the same suspension, but they have a spring/shock combo in the rear instead of the coilover setup like the 280ZX. 510s are a very popular autox car and almost all of the same tricks apply. You can do springs/shocks/swaybars and make it handle better. If you just want better, that is a pretty good suggestion. If you are really wanting to be competitive, you'll need different springs and shocks, and more modifications than that. By researching now, you can save yourself from having to buy parts twice later. Frank's thread on the rear suspension is very good. I'd look hard at it, and in the 510 world the "penultimate crossmember" if you want to really get serious with it.

There are other ways, like cutting access holes through fenders and door jambs for the torch. I think in this case he's talking about the main hoop backstays, and I don't think that will work. That is a tight spot. Coffey would be able to tell you if you can tig it where it sits or if one of his adjustable mig tips would work. If none of that works, my solution would be to cut the backstays off, change them so they hit closer to the leading edge of the strut tower, and then you would have plenty of room for the torch on the underside there.

Don't forget about fluids. You'll be leaking oil, trans, diff, clutch, brake fluids if you just put it on the rotisserie and turned it over. I wouldn't trust the 240 bumper mounts to hold 1100 kg. Definitely pull the drivetrain before you try and spin it. I spun mine with the drivetrain pulled and the hood and hatch and doors removed, and if you don't have the balance right it is not an easy job. You'll either need one of those crank setups for mechanical leverage, some counterweights to balance it properly, or some friends to help. With a bare shell and the pivot points correct, the car is easy enough to turn by yourself.

I'll have some soon, and will be doing a discount for people who buy the adapter and the shorter CV shafts through me. The shafts are expensive, and the adapters aren't much cheaper, so if $400 scares you away you're probably not going to like my price on both pieces. The stock Z31 shafts really are too long for the S30 though...

Depends on the angle of the TC rod, doesn't it? Even if there was a little bit more stiction at normal ride height, the angle might have changed under braking to the point where it was level or pointing up from the TC rod to the LCA, and the turn in from the increased caster might be worth the stiction at corner exit or down the straight, and the stiction under braking would be REDUCED by the more severe sweep of the TC arc. I can tell you for sure that my TC rods angled up to the LCA in my car. I moved the mount back to stock to keep the caster more consistent and get rid of the "semi-leading arm" effect that you have from the shorter TC rod.

Thanks for the correction. I though they switched in 74. Guess I was wrong.

Not a direct swap. The latches are different, and I think you'd have to do some surgery to make it work, and the 280 doors are probably 20 lbs heavier than the 240 doors too.

Z cars are prone to clunking noises when they transition on and off power. There are many causes for the clunk, but the most common suspect that is almost never guilty is the differential itself. Time and time again we read about someone who "checks the backlash" in the differential by rocking the driveshaft back and forth, or jacks up one wheel and rocks it back and forth and thinks that they've found the source of the noise. Occasionally one of these people will take the diff out and wonder why they can't reproduce the clunk with the diff out of the car, or how it is possible that the backlash is in spec. Some more unlucky people go to the trouble of replacing the whole differential with a known good unit or worse, replacing all of the bearings in the differential, which is an expensive job, only to find out that the clunk is still there when they're all done. Checking backlash with the diff installed is very very difficult; I would say impossible. If you grab the driveshaft and turn it back and forth, you're probably not going to be able to isolate the feel the backlash because of everything else moving, and you probably can't move the pinion enough to isolate the backlash without everything else also moving. First you have to overcome the resistance in the transmission, and by the time you do that and the shaft starts to move, you've already put too much force on the pinion to just move the pinion alone without also moving the ring gear. So when you move the driveshaft, what you're likely doing is moving the transmission gears until they lock solid, the driveshaft splines and u-joints, the pinion flange and pinion splines, the ring and pinion, the pinion gears and the cross pin shaft, the diff output stubs and the side gear splines, the CV joints or u-joints on the halfshafts, the stub axle and companion flange splines, wheel bearings, and any brake slack that might get taken up. It's not a good test of backlash, and is probably only good for finding a very big problem somewhere such as a u-joint that is about to fall out. Likewise on the jacking one side of the car up and twisting the raised wheel back and forth. You're going to feel any and all slack from the wheel on one side to the wheel on the other. Slack could be coming from stub axle/companion flange splines for both sides, wheel bearings for both sides, CV or u-joints for both sides, output stub to side gear splines for both sides, and spider gears (and there is more slack in the spiders if it's an LSD). Some of this slack or gear lash is absolutely necessary. The transmission gears, ring and pinion, and spider gears in the diff MUST have lash, otherwise they'll burn up. Even on a bench with the cover off and rocking the ring gear to check backlash you need to be a little careful. The 87 FSM says backlash on the R200 is .0051" to .0071", and getting the carrier to rock back and forth such a small amount without turning the pinion requires a bit of attention. There are cases where diff backlash is a problem. There are many more cases (common enough drag racing issue that it shows up on the forums from time to time) where the cross pin shaft on the carrier wallows out its hole, and this leads to a larger amount of pinion rotation before the outputs begin to move. More likely though, the ring and pinion is not the cause of your clunking. So what is? Well, it could be any number of things, but we can make a list of the most common issues pretty easily. 1. Diff strap/front diff mount. It’s hard to imagine that Nissan sold a million Z cars with this kluged design, but they did. The diff mount is below the front of the differential housing and the nose of the diff wants to lift when you apply power to it. The mount is rubber and tears pretty easily, so Nissan added a strap over the top of the diff to limit the movement. This is a less than satisfactory fix in practice, and over time or with added power the straps break and the mounts tear, and the nose of the diff can lift surprisingly far up. It can raise up so high that the driveshaft hits the transmission tunnel. Solutions: Ron Tyler’s diff mount (which he designed but other people are now producing), clamshell design diff mount addition where a bottom half is added to the diff mount which curves under the diff crossmember and prevents the mount from moving up, solid diff mounts also work but are generally not recommended because they put a lot of noise into the cabin and can cause stress at the crossmember causing it to break, and beefier replacement straps (usually metal or chain). 2. Mustache bar bushings. The diff hangs in the rear on the mustache bar. The mustache bar is insulated from the frame by rubber bushings, and they can wear out. These are typically replaced with polyurethane, which might solve a clunk but also transfers more diff noise into the car. 3. U-Joints. Worn driveshaft or halfshaft u-joints will definitely clunk on accel/decel. Replace as necessary. Just as checking backlash is difficult with the diff installed, I find checking u-joints on installed shafts damn near impossible. I have a friend who swears he can do it, but I always take the shaft out. 4. Control arm bushings. If the control arm bushings are worn out, they can allow movement which can cause a clunk. They are a royal pain in the ass to replace. Search: “spindle pin†for more details. 5. Loose bolts. A lot of these clunks are caused by the two big nuts that hold the diff to the mustache bar coming loose, or loose driveshaft bolts. Also check diff cover bolts and suspension mounting bolts. If you have a clunk and you’ve gotten to this point and haven’t found the source, you’re into the weird stuff. At this point you need to work your way through the whole driveline looking for problems. Look for loose splines on drive shafts and axles, bad driveline mounts, anything. Arne over at www.classiczcars.com even reported that his clunk turned out to be caused by a woodruff key inside the transmission. “Mine was in the transmission itself. The woodruff keys that locate the drive gear on the front of the countershaft were worn, allowing the the gear to move on the countershaft. Clunk once under forward torque, and thud back under the reverse. Sounded for all the world like the clunk was coming from much farther back.†Dealing with a clunk is like pulling the spindle pins on the rear control arms. It's a not so glamourous rite of passage that most of us go through. I'm hoping others will add their oddball clunk causes as well.

The hand brake is not totally releasing so that the pressure can escape to the fluid reservoir (or the rest of the system if that's how it works). If you look you'll see several other threads where people complain that as they drive the brakes come on more and more until they're sitting by the side of the road with smoke coming out of the wheel wells. They have the linkage to the master cylinder adjusted incorrectly. I did the same thing with a clutch years ago. The longer I drove the hotter it got the more it expanded the fluid and the more the clutch slipped until it was undriveable.In your case it sounds like a rear only problem which would indicate that it has to do with the handbrake, not the master cyl.

I was rear ended at 50 mph by a (drunk?) lady in a Firebird that didn't see me and never even touched the brakes in my first Z. She hit me right in the passenger tail light and that pushed me across the road into head on traffic, where I hit an Acura Legend at a combined speed of probably 50+ again. The head on impact offeset to the driver's side, and was hard enough that the car spun 270 degrees. The rear end pushed in about a foot and a half. The low nose of the Firebird meant that the impact was largely underneath the hatch. The tail end of the hatch was bent down, but none of the glass in the car broke. The taillight lens broke, but all of the lights were still on after the crash. The front end crushed quite easily up to the core support, then the frame rails tweaked off to one side a couple inches. The unibody was bent enough that the passenger door wouldn't open and my wife couldn't get out of the car. In one of those adrenaline fueled strength episodes I was able to open her door and get her out. My wife hit her head on the dash. I broke my nose on the steering wheel. All in all, I think the Z did pretty well, but I think I got particularly lucky in that the car that hit me had such a low nose. If it were lifted 4x4 my wife would probably be dead. I know Mike Kelly got rear ended by a big semi or garbage truck or something in a Z and lived to tell the tale as well. I really don't think they're that strong on a side impact though. I have a friend who was T-boned in his 510 by a truck that ran a red light. He had a roll bar, and that probably saved him because he took the hit right across the B pillar where the bar was. The door was pretty well smashed in, but the roll bar held up well enough that he walked away. He was pretty beat up but escaped serious injury.

Does this really cut down danger though? Normally you can crank in more rear brakes when it is raining because you don't have the weight transfer in the wet. So compared to an open diff, you now have greater stopping distances and sketchier handling, because the wheels are still locked together so one of them is going to be sliding when you're cornering.

If you can't properly install the axles without them hitting the case, I would consider that a manufacturing defect. Stripped splines means that the splines are gone. You would know if this was the case. If you jack up one side in the rear and move the tire back and forth, you're potentially feeling any slack in the splines on the stub axle to companion flange that you're moving, wheel bearings, u-joints or cv joint slop before you even get to the diff. Once inside the diff you've got the splines on the stub shaft to the side gears, the side gears which move in and out normally as a regular function of this kind of diff, and all the lash between the side gears and the helicals, the helicals on one side and the other, the helicals from the opposite side and its side gear, the side gear to the splines on the stub shaft, the u-joints or cv joints, the splines to the companion flange and the wheel bearings on the far side. Because rocking the wheel back and forth will allow you to feel play in any of these parts, it's not a good test. When you jack up the opposite side, you're feeling the same thing from the other wheel, so you should get the same result. Maybe you have a brake dragging or something that makes it not move, but this test should feel the same from either side. I think you're barking up the wrong tree with the "side shafts too short" idea. Much more likely that the OBX has the grooves for the circlips machined in the wrong place.