So I've heard time and time again that it's a common problem, the rear end mount going bad on these cars. How can I tell if mine is bad? I hear clunking and banging back there but I am still tempted to believe that it's because my shocks are SHOT. And when I say they're bad i mean really really ****ing bad. I would assume it's just that, and the fact that it's worse when i hit bumps (however slight they may be) while accelerating feels like wheel hop from the shitty struts. Still I've heard so much about these rear end mounts that I can't ignore the possibility. Any simple ways to check? I'm going to be buying springs and shocks at the end of this month, I suppose if that doesn't fix it I'll have my answer, but I figured i'd ask.

 

Worn out diff bushing or cv / half shaft "clunk" is mostly noticeable on acceleration from a stop, or starting forward after reversing.

If your struts (shocks) are shot, the car will bounce a lot. You can test by pushing down quickly on the back or front of the car a few times to see if the car bounces or if it is still firm.

 

Hmmm... I'm getting a "clunk" too. Mostly from letting off the gas (standard tranny) or downshifting to slow down.

What's that?

 

well the car does bounce a lot and if I push on it it looks like a boat in the water. I already knew they were completely blown they're covered in their own oil and everything, and I can't imagine a 29 year old spring is too stiff either. This is why I'm buying a suspension kit for it at the end of the month, I was just trying to determine if i was simply hearing/ feeling a terrible wheel hop or bad diff mount.
I do get a slight clunk (nothing too bad though) when I put it into 1st after being stopped, I'll have to look into it. Would that be enough to make a loud banging sound when when accelerating over a bump or does that just seem more like the struts?

 

I just replaced the rear end mount of my Z and I still have a noise coming from the rear end. Mine is not a clunk, but rather more of a noise coming from the backend that varies with speed beginning at about 20 mph. Its a clunking that speeds up as I drive faster. Could there be something in my differential or cv shafts causing this noise? Could it be wheel bearings? How can I check them? It is not my brake pads clicking as I just coated the pads to resolve that issue.

 

Z-Lover (crap now we have 2 Z lovers) What your talking about sounds a lot more like a Ujoint has gone bad. just lift up the car and check for play in the joints of the axles and driveshaft

 

^ +1 Yeah it does sound like, your u-joints are shot. I had that same problem before, with my '82 T-top. Luckily I had a practically low mileage rebuilt driveshaft in my wrecked '81. So less than 2 hours later. And no more noise.

So see if there are any driveshaft shops near by. Because the u-joints are pressed in. And you can't replace them individually. Good luck man.

 

Thnaks man! How many u-joints are there on my Z? There is two on the prop shaft (trans to diff). Two on each driveshaft (diff to wheel end, both left & right). This means a total of 6 per vehicle, correct? Are they all pressed in?

 

Yes theres 6. but only the ones in the axles can be changed tho. The ones in the driveshaft are not changeable.

 

Thanks Blue! Are these axle driveshafts (halfshafts) difficult to remove from the vehicle? Looking at the service manual, it appears there are 4 bolts at both the differential and wheel end. Is there a splined shaft at each end that they pull out of? Or do I have to pull my wheel bearings apart to get at them? I would like to pull them out myself and take them to a shop to have new ones pressed in.

 

If it is your driveshaft u-joints that need replacing. Which does sound like it. There are 4 12mm bolts at the rear end of the driveshaft. Which holds it on the rear end. You need to remove the exhaust and such. To get it out. It is above the exhaust pipe. Also the driveshaft is what holds your gear oil or tranny fluid at the end of the transmission. So make sure you put a thick plastic bag with a rubber band on the end. So you don't lose any fluid. Then take it to a driveshaft shop. And they will press in new u-joints for you. Good luck.

 

Wildman, what you describe sounds more the prop shaft (shaft between the trans and diff). Everywhere I look, I can only find u-joints for the half shafts. Based on this, I just assumed that these are the likely culprit. Does anyone else have any experience with this type of issue?

 

Is your 280zx an N/A or a Turbo? I don't know the difference with them on the u-joints. But on my '81 and '82 N/A. I had them make the same noises you describe with yours. Which turned out to be my u-joints at the rear of the driveshaft. When I would accelerate, the noise would get louder. So I knew that is what it was. I don't know much about the halfshaft ones. I never had any problems with them.

 

Mine is a Turbo. Do they differ? I will check all my u-joints to see if I can find the culprit. I hope this takes care of the issue!

 

Your half shafts will come out without even jacking the car up. If I remember they are 14 mm use two wrenches they tend to suck on the tire side lil clearance. I carry an extra set in the car at all times. MAY I TELL EVERYONE!!! This is a life saver!

Order an extra set 150.00 norm. Ive been known to change them on the side of the free way and kept on going. The weakest link in the z drive train. the drive shaft you can not re build. I have not met anyone that blew one with out the rear mount being compleatly shot.

If your stupid like me and have a VERY VERY trusting friend lay on your belly bout 8 ft away SAFETY FIRST have him or her spin the wheels in grass forward then backword you will see the pumpkin jump up and down .

 

I don't want to thread jack, but this seems moderately similar to a problem I recently developed.

'79 ZX manual)It would seem, that under heavy acceleration, right after a gear shift, that my passenger rear tire wants to move faster than everything else. It makes her handle a little squirley for a second or so, but after that is fine. After I felt it do that, I took it easy on her, and she did fine. Got her home and haven't moved her since. I took a quick look underleath her, and didn't see anything out of place. Anything have something similar happen? Would you happen to know what the problem is?

 

They are completely different. NA has u-joints and the turbo has CV joints which are a much better system. The main problem with CV joints are the boots become cracked or torn and dirt gets in and causes wear.

The drive shaft U-joint isn't officially replaceable but people have changed them. They have a special retaining clip that you can't really save when you press them out but the replacement U-Joint has a retaining clip that works the same way. Some drive shaft repair places will do them for you. MSA also has a light weight aluminum drive shaft that uses replacable u-joints that are quite a bit beefier. NA and Turbo both have U-joints on the drive shaft and as far as I know they are both identical.

 

I finally was able to tear down my back end and it appears that my CV joints have failed. I would like to get them rebuilt, but before I tear everything apart, do I need to release some type of clip in the differential? I have the 6 bolts at the wheel end all removed, but still am connected at the differential side. I cannot find any info in the FSM abou this.

 

If I remember right you stick a prybar between the diff casing and the CV axle and pop it out of the diff. Just like any other CV axle

 

Yup, just popped them out. Now to find a place to rebuild them. What's the best place to go?

 

So I took the CV axles into a local trans/drivetrain shop because I was not 100% certain that these are the culprits for the clunking noise that I heard that gets faster with speed. The shop owner could not say conclusively that my outer CV joints were bad. The boots were completely sealed, the joint was still holding grease. I ran the car up to 50 mph with no halfshafts and the noise did not seem to be there. In my mind, this eliminates the diff and prop shaft so that would have to isolate the noise to the half shafts. Am I missing something here? I do not want to replace my half shafts/cv axles unnecessarily.

 

Heh, I think I found out where it was coming from afterall. Not only were my struts f'ed in the a, but my tranny mount had no rubber left in it and was no longer attached to the tranny... Not sure if that was it, but I'd still like to fix that before I do much driving...

 

Sorry for the late update, but I found out tonight that is was my inner wheel bearing was the issue. Thanks all for the help!