my78z

hello just bought a 78 280z have never had a z car before have always wanted one though now i have one but im getting a strange noise coming from the rear of the car sounds like its coming from the pass side wheel area or the differential it is like a slight grinding noise but only as long as my foot is on the accelerator when i lift off it stops any ideas would be greatly apprieciated

BoulderZ

The infamous early Z driveline noise! Plan on u-joints (2 per each halfshaft), and/or a new differential mount/bracket. Depending on the noise it's the one or the other problem. More of a clunk is usually the diff mount, more of a consistent noise (sounds more like your description) is probably u-joints. It's not that bad of a project, and if you don't want to do all of it, you can often just remove the half shafts and have them done at a machine shop. Of course, as with any good car project.... *while you're at it* Think about some new struts and/or springs. Odds are the springs are stock and have lowered your car an inch or more by having an aged-to-squishy spring in there. Of course, this presents the perfect opportunity to check out your brakes and think about a limited slip diff!
Congrats on your impeccable good taste in your new purchase. The '78 280 is my personal favorite, but with a first gen Z, you're in good company with everyone on this message board.
Dave

my78z

thanx dave by the way i know its very popular for people too change to the cv joint halfshaft so my questions are
1)does my car allready have it or when did they start putting them in?
2)how hard is it ,what do you have to do?
3) is it worth it? thank you again for your reply

BoulderZ

CV shafts weren't put in stock on any S30 (first gen) Z. So, unless a previous owner did it, you've got regular 'ole U-joint half-shafts in there. I'm not sure what they used in the later Z's like the twin turbos?

I've not personally been a fan of putting CV joint shafts on Z's. If you have high-angle drivelines, CV joints are a must (e.g. front WD), but it just shouldn't be an issue on a Z rear suspension and driveline. CV joints are smoother in rotation (i.e. reduced driveshaft "whip") at those high angles than are U-joints. However, CV joints must operate in a closed, greased system. Thus everybody's favorite repair: CV boots. Repairing these is a regularly occurring pain in the rear. U-joints, conversely, have their own closed bearing surfaces, with grease fittings (on good ones). No disassembling to replace boots periodically. Just grease gun it every once in a while.

Putting in CV shafts is no harder than putting in good U-joint half shafts as long as the CV kit is good. The ends of the shafts have to hook up to the hub and the diff the same way, it's just the intermediate hardware that's different. The hardest part for either option is removal of the old parts (lots of stuck fasteners).

If you don't have a kit and have to go custom, you're talking about some decent money for two custom half-shafts at your favorite driveline shop. Like for like, U-joints are *usually* more durable than CVs, and lighter if I'm not mistaken, but it's kind of an apples and oranges comparison. IMHO, changing to CVs is a misapplication. U-joints, I think, are the better solution to a low-angle driveline. To my knowledge the Z driveline is definitely low-angle enough that the smoothness or efficiency difference between the two options should be negligible, if present at all. Maybe some others here have some hard numbers on this?

I would agree though that the stock u-joints weren't particularly great, and they certainly don't age over two decades very gracefully. I still don't like putting them in. I prefer to spend that cash on high-quality u-joints to upgrade the existing half-shafts, get a nice powder coat on them and checking the balance. Of course, others might really like the CV's, and I'd be the last person to say what someone does with their car is "wrong". Unless they're making it a hazard or crashing it . Any one here with some input in favor of the CV option?
Dave

my78z

thank you dave man the people on this site are cool on all my other cars ive had in the past if you tried to ask a question on a sight everyone treated you like if you dont know you shouldnt be messing with it or they bragged about how fast their car was jeez what is this high school any way thank you for being so helpfull and answering my stupid questions

Zpeed

I'd only go to 280zx turbo CV shafts if i had enough power to be snapping uni-joints everytime i took a hard launch,

if you shorten the shaft and some custom boots, they fit perfectly

<font color=blue>76 260z</font color=blue>
The NiteRider

BoulderZ

Thanks! I was wondering about how close those were. To your knowledge, is there any data out there on testing the failure point of a high-end CV joint vs. a high-end uni? I've never been able to find a good, quantitative answer on which is stronger. Maybe it's too hard to constrain the problem to get a valid comparison (e.g. define "high end")?
thanks again,
Dave

BoulderZ

Glad to help! I haven't been on this site all that long myself, but I'd agree that it's a welcome change from the usual high-school-ish (no offense to younger owners here!) stuff you see all too frequently in auto culture. The only stupid question is the one that isn't asked. That's how you get frustrated, break parts and cause bleeding.
Dave

my78z

Dave i just read in my manual that 75-78 drive shafts (not the axle shafts) cant have the u joints replaced is their another drive shaft that will fit that does have replacable u joints or will i just have to buy a new drive shaft every time they go bad

BoulderZ

Hmmm. Now, is that "drive shaft" the way the manual refers to it? They often refer to the axle half shafts as drive shafts. Something lost in the translation, I suppose. The drive shaft (from tranny to diff) should be okay, and indeed those u-joints aren't replaceable on the stock shaft. You'd have to get a driveshaft made up with serviceable joints, custom, or perhaps alter/use one from a 70-74.
Much more likely to wear out the half shaft (diff to rear wheels) u-joints. At any rate, no, you don't have to replace the whole half-shaft every time. You can get nice new u-joints for those, for all years. They're in Motorsport Auto, for example. They've got Spicers on p 66 for about $33 @. You need four. You can get cheaper stuff, too. I bet you could pick 'em up at NAPA for about half that. Surfing around to the various Z parts suppliers online should yield some good comparison shopping.
Dave