JMortensen

Pinion bearing preload is effectively setting the distance between the two tapered roller pinion bearings. If you are missing a shim, the distance set is too short, and when you put torque on the pinion nut it pulls the bearings hard into the the races and locks it up. Adding shims will decrease the load on the bearings when the pinion nut is tightened. Too many shims will leave the pinion loose. There is a spec in the Factory Service Manual, I can't recall what it is and I don't have the FSM anymore, but if you find that spec it will tell you how much drag there should be at the pinion nut. In order to test the drag, you need a 1/4" torque wrench. Using a 1/4 to 3/8 and a 3/8 to 1/2 adapter, you put your socket on and turn the pinion nut as slowly as possible for you to get a smooth measurement. As I recall the FSM has specs for with pinion seal installed and without, be sure you use the right one. I don't think you're to this point yet, but It is possible to have the pinion seal installed but not bottomed, and in that case the little dust seal can hit the pinion flange and drag a lot. I experienced that one myself. Your work on the LSD is premature. You need to get the pinion spacing corrected, THEN do the LSD. If you don't have the pinion right and for instance you have too many shims in there so the pinion can move around laterally, that might cause the lockup you're describing. If you have the pinion secured, installing the LSD should be next, and then you check the backlash. Backlash won't change based on you turning the pinion shaft, so your experience there means that something is wrong with the pinion. I have disassembled and reassembled a couple R200s, swapped the ball bearings twice, changed seals, added clutches and shimmed the LSD's. I believe there are a couple people on here with more experience than me, Mike C and zcarnut and maybe SATAN being the ones that come to mind. They might have some insight that I do not. John Coffey has suggested Unitrax as a shop that can build R180s and R200s in the past. If you get really stuck you can probably ship it to them and have them fix it. You might consider buying another diff, swapping the ball bearing and installing the LSD and leaving the rest of it alone. The bearing swap in an R200 costs probably $400 in parts, plus shipping, plus labor if you send it off, and doesn't get you ANYTHING if the bearings aren't damaged.

Just as a matter of principle I would put the surge tank in the back next to the regular tank. Seems less likely to catch on fire in that position. Aside from that, the surge tank is just there to hold a small amount of gas so I would use a smaller pump (especially if you haven't bought one yet, since a smaller pump will be cheaper) and a large feed and return so that you don't generate pressure in the surge tank. Your lines will be much shorter. The 5/16" line that goes to the vapor tank to the engine compartment leads to the very top of the vapor tank if I recall, and it is the one that bleeds off excess pressure in the vapor tank to the crankcase in the stock configuration. If you don't have that vent in place then I think you have an issue with the tank being sealed, so as the level goes down in the tank you might actually start to collapse the tank with the vacuum from the fuel pump. If it gets hot, a lot of pressure could cause a leak. Fix here is a vented gas cap. There are other threads that deal with the tank and getting rid of it. I would get rid of the vapor tank, run the expansion tank right next to the stock tank, and then run your FI pump from there and run a new line and return up to the front. There are differing opinions on how and whether it should be done, but that's what I would do.

I just got it myself. In browsing through, I'd say yes. It has info on building wings (that's why I bought it--gonna give that a go pretty soon). It does have a lot of repetitive info if you already have CCA, but there appears to be enough new stuff in there to justify the price. I bought it used on Amazon. There is a later version that goes for about 5 times the cost, I got the cheaper version.

That's one car on one track, and shouldn't be used as a "spoilers make your car slower" proof. C&D tested various spoiler configs on a Z car and found that they gave varying degrees of downforce and drag and some of the less aggressive configurations IMPROVED drag and mpg. What's more, if spoilers and wings made your car slower, you wouldn't see so many spoilers and wings on race cars. If you look at LeMans Prototypes though, you can see that they have more slippery, less downforce setups for LeMans than they run in other races in the ALMS for example, and this is because the higher downforce IS created along with increased drag. There is a happy medium, but they're running into it at 230 mph down the Mulsanne straight. The situation might be a little different for a stock Z car, but most of us here at Hybrid Z, if we are interested in downforce probably don't need to worry about drag too much because we have V8's, turbos, and V8 turbos powering lightweight cars, and most tracks we'll be running on max out at ~150 or so mph. Have a look at McBeath's books Competition Car Aero and Competition Car Downforce or Katz's Race Car Aero Designing for Speed if you're really interested in how it all works.

I would sand the bushings until the sleeve is JUST longer than the bushing. This will take some of the stiction out of the suspension. If that isn't enough to fit them in, then I do the two nuts and allthread as posted above.Just need to tweak the arm enough to slide the strut in.

Here you go. Nothing fancy, just a plate welded on each side of the crossmember. I drilled a hole at the two ends, and then used a cutoff wheel to connect them. In retrospect, 5/8" is way overkill for the bolt size. I would probably run a 1/2" bolt and sleeve on the 5/8" rod end if I were to do it again. I guess I won't have to worry about strength this way.

Bubble balancers do a static balance. A dynamic balance is much better. That's not to say that you shouldn't do it yourself, but you may find that your car is sensitive to wheel balance issues and the bubble balance is just not sufficient.

If you mic'd all the bearings and they're dimensionally the same, there shouldn't be any bind in the pinion. The fact that there is means that something has changed. If you missed a pinion shim, that would cause the pinion to bind up. Once you get the pinion spacing right, then you can put the carrier in and check for pinion depth. But you can't really check the pattern without being sure that your pinion is seated all the way, so that means that you'll need to figure out your pinion bearing preload first. On most diffs you don't have the front ball bearing, so it's less of a hassle. If you're completely stuck you might take it to a gear shop along with a FSM.

Read the bumpsteer FAQ post for a primer on bumpsteer. When you correct for it, you can either move the outer tie rod down, or the LCA pivot up. JTR has a spec, and various other sites and people have their spec, but I basically see them all as just guessing. In order to really figure it out you have to measure. I slotted the front crossmember and then moved the LCA up until the bumpsteer went away on the gauge. That point was when the LCA pivot had moved up 1/2". With that modification the car went from doing a sharp jerk on one particular bump at the track to being smooth as silk afterwards, and no more sawing at the wheel in long sweepers on the track. It was a very noticeable difference when I was driving at the limit. So while some say 3/4" up and 1/4" out, and others say 13/16" or whatever up, the best way IMO is to measure it and minimize it.

The one I recall had the strut tube cut and capped with a stud sticking out of it, and the UCA attached to that. I'm sure I've seen others, but that was the one that stuck with me. Not very impressive fabrication, but if it works, that's the important part. FWIW, on my car I actually measured the bumpsteer and it tuned out at about 1/2" up. EDIT--agree about Brian. Have bought parts twice from him, very good to do business with.

Angles in the rear suspension determine pro or anti-squat. You could try to affect the total amount of weight transfer by moving weight to the front or rear. Again, not dealing with drag racers, but most road racers like 50/50 or more tail heavy weight distributions as that extra weight to the rear gives better braking allowing the rear brakes to be used more, and better traction on corner exit.

Mine is a 240.

My understanding is that there is a discrepancy in the FSM which contributes to the debate about which is the faster rack. I think the FSM is showing data for what may have been used in Japan or Europe and that we got the same racks in all the Z's, but it will be interesting to see what you come up with and how it compares. I did look up my spec from another thread: "I just went and measured the Z rack at 1.8125 inches per turn of the wheel." This was eyeballing the pinion, so it isn't necessarily right down to the 4th decimal place, but it did look like 1 13/16. Maybe that will save you from crawling under 2 cars...

Looks good. Where's the tach though?

I am pretty sure that the rack ratios are the same. If you want, you can do one turn of the steering shaft and measure how many inches the rack moves (I've got one sitting on my work bench). Also I think the steer knuckles are the same length as well. I've got 280 knuckles handy if you want to measure your 240 ones, but I'm pretty sure they're dimensionally the same as 240 knuckles. Up until I actually graphed it out, I would have agreed with Ron that longer arms are better. Now that I've done the graphing, I think the difference the shorter arm makes with respect to Ackerman is pretty minimal, so if you want quicker steering that is a reasonable way to go about it, and if the relatively small gain in quickness is worth the relatively small loss in Ackerman and increase in effort, then go for it. Here is a very detailed article on Ackerman that tells you how to graph it out. http://forums.hybridz.org/index.php/topic/97426-ackerman-article-by-erik-zapletal/page__p__914846__hl__ackerman__fromsearch__1?do=findComment&comment=914846 If you skip to the end of this thread and read backwards, you'll see some of my calculations for Ackerman and rack position and steer knuckle length: http://forums.hybridz.org/index.php/topic/97092-toe-changes-for-track-use/page__st__80

Nobody is saying that the occurrences are isolated, but their effects through the suspension can be mitigated. Anti-squat is the tendency for the suspension to EXTEND under power (not weight transfer, you still might have squat because the amount of weight transfer is greater than the amount of anti-squat). Pro squat is the tendency for the suspension to COMPRESS under power (not weight transfer). If you accept that anti-squat and pro-squat exist, then it should be pretty easy to figure that there is a middle point where you have neither pro nor anti-squat, and that's what a Z has. It will still squat, but it squats due to weight transfer. The 280ZX has pro-squat, the Z32 if I recall has anti-squat.

Mountain bikers have this stuff nailed. It's not the brakes that do the work in my example, it's the engine torque. If the brakes are not applied and you put a lot of torque through the driveline from a stop, it will compress the suspension above and beyond what a different suspension system that doesn't have semi-trailing arms would do. If you "launched" in reverse, the rear end would lift more than a typical front drive car would do going forwards. The "brake" when you're driving regularly is the inertia of the car. The faster you're going, the less noticeable the issue is going to be, but the geometry of the suspension will jack it around regardless of whether the brakes are on or off. In mountain biking circles this would be akin to pedal bob, only there isn't really a bob on a car, so it is just referred to as squat. If the impulses through the crank were slow enough, it would bob, and you could see that separately from the squat caused by weight transfer. It is true that the brakes alone have an effect on the rear suspension when the car is moving, this effect is commonly described as "brake jack" in mountain biking circles. It also reduces traction by making the suspension not want to move, and also in the case of the 944 actually compresses the rear suspension under braking, so it reduces nose dive to some degree as well. When you step on the brakes hard, the whole car just lowers down to the ground. It would in theory be possible to do a "floating brake caliper" to fix if someone were really interested in it, for most situations like street driving or even road racing I don't think that's necessary, but I'd speculate that it would probably make a discernable difference in a rally car. http://2btherapy.com/index.php/bikes/brake-therapy-floating-brake-kit

Weld a clevis to the strut towers and then either make your own bar or adapt one. If you're running an L6 you need the bar to be bent, or you need to make the clevises long enough that they clear the valve cover. If you are running a V8 or a shorter motor, you might be able to use a straight bar with a lower profile clevis which would be stronger.

The reason you see so many smallblock V8s is because it makes sense to put a V8 in a Z car. If you're against putting it in because it has been done so many times, you're basically saying "I'm tired of people doing things that make sense, and I get all twitterpated when someone does something that doesn't make as much sense." The V8 motorcycle hybrid makes a great engine for a lightweight car, but I think you'd have a hard time finding gears and transmissions and clutches that would handle the heavy weight of the Z car (in comparison to a Radical or an Atom or something) and would have the appropriate ratios for a motor that can turn that much rpm. So again, it would be an expensive project to put a relatively torqueless engine into a car that is too heavy, all so someone could say that they were the first to do it. Call me crazy, but if someone ever does build one of those, I'll be wondering WTF they were thinking and why they didn't put that motor in a Lotus 7 or a Radical or something like that where it would actually make sense.

Your description that torque is transferred to the components inducing a slight squat is wrong, as is the idea that the car leaning back is a cause of the weight transfer. A gokart transfers weight even though it has no suspension at all. The weight transfer is a function of the center of gravity, the wheelbase, and the amount of acceleration g force. The car leaning back is the result of weight transfer, not the cause of it. What the suspension does depends on the geometry. I used the 280ZX as an example because it has semi-trailing arm rear suspension so it reacts to torque pretty dramatically. Other kinds of suspension (like 240/260/280Z for example) do not. On live axle cars it depends on the control arm geometry as Ron said. As far as traction goes, in theory you don't want anti-squat. Anti-anything (squat, roll, dive) works by trying to freeze up the suspension so that it won't move. This makes the suspension effectively act stiffer and stickier and makes it react to bumps in the pavement, etc more harshly, so that hurts traction. Pro squat probably isn't that great either, because the more power you have, the more likely you are to make the suspension bottom and the weight transfers regardless of the position of the suspension. Using the torque from the car to compress the suspension isn't a good idea because when it bottoms it can't move, and basically you get the same thing as you had with the anti-squat, but worse. In an ideal world, I think you want the springs to do the springing and as little anti or pro geometry as you can get so that the suspension can move freely to keep the tires on the ground. I think in practical terms a lot of really high hp cars have a little bit of anti-squat built in because they transfer so much weight when the launch. I'm not a drag racer though, so that is all road racing based info. How true it is for drag racers I don't know.

Not so fast there John. Try putting an automatic 280ZX in drive, put your left foot on the brake and step on the gas. Then put it in reverse and do the same (foot still on brake). The ass end will change altitude by about a foot, and none of it is weight transfer. The simple answer is that it depends on the geometry of the suspension.

I just used 3/8" tube cut to 1/4" lengths. I think you can probably go smaller than 3/8" rod ends, maybe 5/16", possibly even 1/4, but if they're binding I think it's just a matter of time before something breaks. I had to do 3 attempts on the rear bar in order to find a position that didn't bind. The front went better, but it was still pretty hypersensitive to position of the bar. I think part of that may have been because I was trying to make it work through the full range of motion. I later decided to run much stiffer springs. Had I known that when I started, I would have focused on a much smaller range of motion. I think with your spring rates you need to be concerned with a pretty full range though. If you plan on running the car low, you can probably disregard what is going on at full droop, but aside from that I think you'll be using most of the suspension with rates in the 2-300 range. When you test for bind, don't do it with a jack. Just take the spring off and manually push the suspension up with your hands (sway bar has to be disconnected from the other side).

Did you push the suspension through its full range to check for binding on the bar? I was surprised at how little room for error there is when I did mine. Your's might have a little more give since you presumably have sway bar bushings attaching the bar to the frame.

I think you need to read about bumpsteer and sectioning struts some more. They are in no way related. The springs you bought are intended to be used without sectioning. Lowering the car will change the part of the bumpsteer curve that the car rides in.

They probably ran over something that flipped up and hit the frame rail. Plate is a good call, or leave it alone as long as there are no tears in the metal.