as discussed on the Internet Z car club.
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Questions and Answers:
Q: How sturdy is the Z drivetrain? I have a 280 diff + 5 spd already.
A: If the rearend is an R200, you be ok. The R180 rearend is still strong, but the R200 is better. The R180 was used in all 240s. After that both were used at various times. In talking to the Nissan Competition department, in Long Beach CA, it was expressed to me that "you would have to do something really stupid to break an R200". I was asking them about V8 conversions at the time. They where sure that the R200 could handle it.
Q: I have a '71 240Z. Is there a modifcation to the drivetrain that needs to be done?
A: On 240s '71 or older, the rearend sits further forward than later Zs. This causes premature wear of, and vibration from, the u-joints. I beleive it only requires the use of later Z diff mounts. If you go from an R180 to an R200, you need to use the R200 "moustache bar" that bolts the diff cover to the frame,not doing so will move the diff forward slightly.
Q: Is there a way to set the toe and camber on a 300ZX?
A: The common method for adjusting toe and camber on 510 rear suspensions (300Zs have a near duplicate of a 510 rear suspension) is to slot the subframe. Basically, what you do is elongate the holes that the inner pivot on the semi-trailing arms bolts to vertically, and then reattach the arm. With the elongated hole you can loosen the bolt on the inner pivot, and raise or lower that side of the arm, changing camber. For toe adjustment, you elongate the outer hole horizontally, enabling you to slide the arm horizontally to change toe. This may sound hokey, but it is how it's done. It worked for BRE, and I suspect it would work on a 300Z. There is nothing unusual about the suspension settings you describe for IRS. If I were interested in maximum tire life I would leave the suspension at the factory settings. The manufacturers would not want people bringing their cars in under warrenty to "fix" the suspension because of tire wear problems.
Q: So how would you set up the rear suspension for an autocross car?
A: The toe-in condition at the rear is normal and is not the way one would set up an autocross car (quite the opposite). When the car is at speed the drag of the wheel compresses the suspension bushings so that the tire is running at near zero toe at speed (starting a zero toe would result in toe out at speed). A degree or two static camber is also typical and prevents the tire from rolling under too much in corners and wearing the edges of the tires excessively.
Q: Can a late model 300ZX R200 be used in a 240Z?
A: I am using an early 300Z diff in my 240. Its an R200 unit, and the usual things have to be done to use an R200 (The rear diff crossmember) plus you need to change the driveshaft and halfshaft flanges. I dont remember, but you may need a donor R200 from a 280Z to get the flanges. I'm happy with the unit; I can't say that it has not loosened up a bit since I have been using it, but I use it hard. As far as I can tell the units form a current 300Z will stil fit our cars.
Q: Could excess play in the differential cause a clunking sound on my Z?
A: Don't replace the diff.just yet... I used to get
a decent Q: Why would I want to install an R-200
diff in my 72 240Z? A: IF your engine is stock and you
don't race, there is no real reason to. A modified engine OR heavy racing
shows the inferior strength of the R-180.
Rear End Discussions
Rear End Mounts: All the companies with booths at the Annual
Z-car Convention a couple of weeks ago (tweeks, JCR, etc) had Urethane
third member bushing kits. Fairly reasonable, as I recall. I solid-mounted
mine many years ago. Only slightly more noise but NO CLUNKING. One
should also check the transmission mount. I've seen lots of these go soft
from any drool coming from the engine or transmission. Soft mounts will
allow the whole engine/transmission assembly torque around until it hits
something and CLUNKS. If you have a vibration under hard acceleration
that occurs at twice driveshaft speed, you've likely got this problem.
Misalignment of the driveshaft under acceleration causes the vibration.
---------------------------------------------------------------- It is usually
the single stud that sticks out the bottom of the mount that breaks; The
diff mount has two bolts that bolt it to the diff and a stud that goes thru
the crossmember, and that's the one that breaks. There is a sling that
prevents the nose of the diff from twisting up. You should be able to view
this stud/bolt from the bottom of the car and see if it is broken. Also if it
is an early car the diff is forward of centerline. I Did break this mount
numerious times (having >250 hp might be the reason) I did move the diff
back; required a newer rear diff mount. I also went to an R200 4 pinion
LSD, and moved it back; required a new driveshaft also. Any Q's just ask
I think I have just about reworked everything........rb
---------------------------------------------------------------- Just a quick note
about my experience with the Differential Mount. I've experienced
all the problems described here relating to loose differentialmounts.
Banging rear-end when decel and accel, vibration under hard accel, etc.
last night, I finally took a look under the car to see what there was to see.
I used a floor jack under the differential to raise the car. After raising the
tires just off the ground, I took a look at the mounting points for the bow-
shaped bracket on the rear of the differential. Hmmm, there seems to be
1/2" of clearance between the mounting bar and the bottom retainer.
Enough space to insert my thumb! Just for grins, I lowered the car and
climbed back under. I grabbed the mounting bar and wiggled it. Holy
Shit! This thing easily moved back and forth, taking the differential with it!
OK, Now how to fix it. Someone else talked of cutting up reinforced
rubber to shore this up. Well, I don't have any, and didn't feel like cutting
up and old tire. So I visited the local hardware store and wandered the
aisles until something struck my fancy. I ended up with two feet of vinyl
hose, 1" OD, 1/8" wall thickness. I cut this into 4" lengths, each length
split lengthwise. I then cut 3/4" holes in the middle of the flattened pieces,
and installed them between the lower retaining washer and the mounting
bar. Everything seems to fit nicely. Then I tried it out. WOW! what a
difference. The car accelerates smoother, shifts easier, and actually
seems faster! I'm impressed. If you think you might have this problem,
just jack-up the back of the car under the diff, and check for space in the
bushings, accessed through the wheel wells. If you've got room, stuff
something in there. You won't believe the difference! Many thanks to all
those here who helped describe this problem and the solutions!
---------------------------------------------------------------- Well kids,
if you thought THAT was exciting, the mustache bar is just one of the
problems. What is even more of a problem is the funky mount in the front
of the diff.. It consists of two peices of plate sandwiching a piece of
rubber. Under acceleration the two plates are pulled away frome each
other, which eventually rips apart the rubber in the middle. Now Nissan
wouldn't want the diff doing donuts upon separation, so they put this nifty
little fix-it idea into action. This is where it gets downright scary; in case
of separation of the front diff mount (and to limit the travel of the mount
{yeahright}), they put this strap that goes over the top of the diff, and
connects to the forward rear suspension mount (can you say
"after-thought?" I knewthatchyacould.). It looks like a thick seatbelt. Solid
diff mount look'n better every second, eh?
---------------------------------------------------------------- One of the first
things I do when I turbocharge a Z is strap the nose down with several
loops of aircraft control cable pulled very tight. There's still a little spring
which cuts down on vibration. Very strong.
Drive-Axle Shaft Discussions
Over the weekend, I replaced the inner and outer U-joints on the driver
side half-shaft (differential to wheel). It was a big pain to disassemble
the U-joints, small pain to reassemble. According to Haynes :
relubrication of the sliding splines within the shaft should be done every
50K miles. My question: should I feel guilty.. is there any real reason
to take apart the inner U-joint again and dismantle the shaft to do this
"routine maintence" chore. Please don't say anything to the effect
"well..follow the guidelines" Has anyone had any bad effects on high
mileage Z's because of washed out grease in the sliding shaft?? The
boot is intact and car has 200,000+ miles on it. It doesn't seem likely
that the grease will go anywhere so long is the boot is not torn.
--------------------------------------------------------------- If you decide
to take your axle drive shafts apart to grease them, be careful. You
might want to consider wearing rubber examination gloves. Older 240's
had a problem with the spline joints clunking, and many dealers (it is now
illegal) used a lead-based grease to dampen the clunking. A friend, who
was a Nissan Service Manager and worked for a dealership from 1968
until 1991, warned me about this. I don't know how you can tell by
looking if it is lead-based grease, but using caution is advisable. Cheryl
Kaup --------------------------------------------------------------- Hmm,
I think thaty's my problem as well.. I get a 'clunking' sound under slight
acceleration. I guess the lead-bases grease worked, but what would one
use today? ---------------------------------------------------------------
Another cause I've found are the splines in the stub axle
assemblies. The big nut (Cheryl's "clinch nut"), the one that takes 200
ft-lb that holds the half shaft attachment flange onto the stub axle. I've
seen that if I tighten this nut after loosening it first, the clinking goes
away. This clink is easy to find after you've backed the car with
considerable torque and then move the car forward. In other words, the
play in the splines of the stub axle and half shaft flange attachment is
takenup one way when backing and then taken up the other way when
moving the car forward under power. Any body else found this to be a
source of clinking or clunking?
----------------------------------------------------------------- Yeah, I think
it could be my diff. mounts.. It only vibrates under slight acceleration..
anything with power, and the clunking goes away. Lately, I've been
getting some violent clunks, that I can feel in the floor by my feet. A
Mechanic who did my safety inspect. said he didn't notice anything loose
around the axel/driveshaft/diff, ect, butthen again, I'm sure he checked
hard considering we pay a flat rate of $14 for inspections here, no matter
how much checking they do. Final
editing by Salman SHAMI