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JTCN

Rear end vibration under throttle in gear

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So I'm experiencing a bad vibration when I apply throttle in gear.

It's mostly noticeable in 3rd gear and higher, but if I really push it in 1st-2nd gear it'll vibrate.

It doesn't matter how much I push the gas pedal, any throttle input at all will cause vibration in 3rd gear and up.

It sounds and feels like it's coming from the rear end. If I let off the throttle I can hear a hum or a winding noise.

There is NO vibration with clutch in or in neutral, only in gear. At any speed going down the road if I push the clutch in the vibration stops immediately.

I had my diff rebuilt not even a year ago at a transmission shop when my diff was making a loud humming noise constantly, so there shouldn't be an issue with it.

My first thought was the driveshaft ujoints, but after getting under the car and checking the play it doesn't seem to be that bad. I'll have to take it the trans shop to be sure.

I took a look at the engine mounts, but only in neutral and revving. There was slight shifting but it seemed normal.

I'm going to check the mounts at load tomorrow and check the trans mounts too.

Also checked the driveshaft bolts and they were very tight. No flange to flange play. Halfshafts too.

 

I don't know when exactly this started happening, so I can't pinpoint what I did that started the vibration. Just went down the road one day and felt the shaking.

I don't drive the car very hard, never clutch dumping or launching it.

Anyone else have this issue before? What fixed it for you?

If any of you need more info I'll provide it. I'm going to take it down to the transmission shop soon to see what they think, in the meantime I'd love for y'all to suggests some tests for me to do to narrow down the issue. Thanks

Edited by JTCN

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You didn't mention the differential mounts, so I would check those as well...this includes the front mount at the nose of the diff and the rear mounts/mustache bar.  Even if the nuts and bolts are tight, you can get movement and vibration if the bushings are worn.  Most people replace the OEM stuff with poly bushings.

And don't forget to check your lower control arm mounting points, as well.  I had a rear vibration under similar conditions as you a few years ago and it was driving me nuts trying to track it down.  Turned out to be worn rubber bushing on the inner spindle bolts of the LCAs.  Replaced all four of them with these guys, and problem solved.  http://www.energysuspensionparts.com/7.3104

Good luck with it.

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8 hours ago, jhm said:

You didn't mention the differential mounts, so I would check those as well...this includes the front mount at the nose of the diff and the rear mounts/mustache bar.  Even if the nuts and bolts are tight, you can get movement and vibration if the bushings are worn.  Most people replace the OEM stuff with poly bushings.

And don't forget to check your lower control arm mounting points, as well.  I had a rear vibration under similar conditions as you a few years ago and it was driving me nuts trying to track it down.  Turned out to be worn rubber bushing on the inner spindle bolts of the LCAs.  Replaced all four of them with these guys, and problem solved.  http://www.energysuspensionparts.com/7.3104

Good luck with it.

Thanks for the help. I couldn't get under my car and try anything yet today though, but tomorrow I'll try everything I can.

Also just realized I think I posted in the wrong forum. Anyway I can move this to the Drivetrain section?

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I didn't post earlier because you said that you were taking it to a transmission shop, but you might compare 3rd gear to 4th gear.  4th is powered straight through the transmission. while 3rd uses the countershaft.  If you have a bad countershaft bearing you won't notice it as much when in 4th under power.  You might also drain the fluid and check the drain plug magnet.  Not uncommon to find bearing retainer pieces on the magnet.  The adapter plate bearings go bad.

Just noticed that you said 3rd or higher.  There are also main shaft bearings in the adapter plate.  The two in the front cover go bad also.  Either way, draining and checking the plug will tell you something.  Easy to do.  Remove the fill plug first, to be sure that you'll be able to refill it.

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I just got back inside from working under the car for a while. I didn't discover much except that I think my rear passenger side wheel is severely unbalanced.

I had the rear jacked up and in the air and there's a little bit of play when shaking the wheel. About a month ago I had to replace the tire on this wheel because it literally wore down to the cords, the other tire was just fine and they were the same brand and put on at the same time. I also felt what I think is a brake shoe dragging inside my wheel hub when spinning the wheel, it doesn't spin freely like the other rear wheel.

Had my dad come and see what he thought and he's convinced the vibration is from the unbalanced wheel.

I'm going to take it to get balanced soon, I'm not sure if this is what causes the severe shaking in my car but it'll help.

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An out of balance wheel generally vibrates at a certain speed due to harmonics.

if the wheel can move while bolted to the hub, your hub is loose or your suspension is loose.

that would mean the rear hub bearings are bad or your suspension is not properly attached (worn bushings, loose attachment hardware).

 

you may also have a worn U-joint, but I would expect that to more be like a “bump” or jolt when transitioning between acceleration / deceleration. 

Edit: worn wheel bearings could contribute to the “dragging brake shoe” and uneven tire wear.

Edited by jthom5147
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2 hours ago, JTCN said:

I had the rear jacked up and in the air and there's a little bit of play when shaking the wheel.

You say unbalanced but you describe loose.  Sounds more like a bad bearing or bad suspension bushings.

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I took the brake drum off today and took a look. Nothing is out of the ordinary except my brake shoes were really holding on to the drum.

After removing the drum I tried spinning the hub to see if there's any catching/dragging, and there was nothing. Wasn't too hard to spin either.

I also tried wiggling and pulling on the hub and felt no play at all this time. Maybe I didn't have enough leverage to really pull it though.

Slapped the drum on and the dragging was there again. So I don't think I have an issue with my wheel bearing, it's just the brake shoes rubbing inside the drum brake.

What's weird to me though is that it only drags when you spin it to certain spots. Could the drum be warped?

Next I have to try adjusting the brake shoes and see where that gets me.

edit: I probably have my terminology wrong, when I say "hub" I'm referring to the end of the axle with the studs in it.

 

Edited by JTCN

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I'm going to ignore the "brake dragging" issue because it honestly isn't that bad and I read that S30s have much tighter brakes than normal cars.

I tightened the lug nuts on the wheel as much as I could and there's no more play in the wheel; I also had to replace a stud, I think the bad stud wouldn't let the lug nut tighten all the way down and causing the play. All good now though.

I'm just going to focus on the vibration. I'd love to just rip all of the rear end out and replace the bushings but unfortunately I don't have a torch or a press to get the bushings out.

Even if the bushings aren't the problem I'm sure they need to be replaced. What tools did you guys need to burn out your bushings and press in new ones? I can pick up a propane torch no problem, but I can't get a press.

Edited by JTCN
edit: I'm referring to the lower control arm bushings and diff bushings, or any other bushings in the rear.

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17 minutes ago, JTCN said:

I tightened the lug nuts on the wheel as much as I could and there's no more play in the wheel; I also had to replace a stud, I think the bad stud wouldn't let the lug nut tighten all the way down and causing the play. All good now though.

I'm just going to focus on the vibration. I'd love to just rip all of the rear end out and replace the bushings but unfortunately I don't have a torch or a press to get the bushings out.

Even if the bushings aren't the problem I'm sure they need to be replaced. What tools did you guys need to burn out your bushings and press in new ones? I can pick up a propane torch no problem, but I can't get a press.

The loose lug nut thing is a big concern.  How can you drive around with loose lug nuts and not know it?  They were so loose you could feel the play be shaking the wheel by hand?  That's a lot of loose. And there shouldn't be an "as much as I could" in there.  There's either a torque value or you know from experience.  Are you running steel wheels or mag wheels?  There are many ways to have a bad wheel.  Bent steel, or wallowed out aluminum on the mag, or lug nuts that are too long and bottoming out on.  If you've identified a wheel problem, swapping to known good wheels for a test would save you a lot of time.  You should spend more time on the wheels and make sure that they're right.

I used a vise to press my bushings out, and only heated the metal behind the rubber to destroy the bond.  Burning the whole thing is neat-o but really just makes a lot of unnecessary mess.

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3 minutes ago, NewZed said:

The loose lug nut thing is a big concern.  How can you drive around with loose lug nuts and not know it?  They were so loose you could feel the play be shaking the wheel by hand?  That's a lot of loose. And there shouldn't be an "as much as I could" in there.  There's either a torque value or you know from experience.  Are you running steel wheels or mag wheels?  There are many ways to have a bad wheel.  Bent steel, or wallowed out aluminum on the mag, or lug nuts that are too long and bottoming out on.  If you've identified a wheel problem, swapping to known good wheels for a test would save you a lot of time.  You should spend more time on the wheels and make sure that they're right.

I used a vise to press my bushings out, and only heated the metal behind the rubber to destroy the bond.  Burning the whole thing is neat-o but really just makes a lot of unnecessary mess.

It really wasn't that loose. It was just a small amount of wiggle that made me concerned. My wheels are a set of Appliance mesh wheels, I think they're aluminum. The lug nuts are the proper style for the wheels, they fit fine. I've replaced probably half the wheel studs on this car already too.

I also just discovered something. I was under my car checking the halfshafts bolts were tight and I felt play in the halfshaft. It's a small amount but it's there.

It's a lot like this video (https://www.youtube.com/watch?v=2rNGmNj_-is) but to a lesser degree. It's not loose bolts because I can see the halfshaft move with the flanges, it's literally pushing about a quarter of an inch of the halfshaft into the differential. It can move 1/4" in or out of the diff.

Is this normal?

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I just found a video of a Z that's making a noise VERY similar to mine. https://www.youtube.com/watch?v=Dz84sFQBA1c

It's similar in the way that it's some kind of rattling/knocking noise in the rear end. In the video his is a lot louder than mine and more pronounced.

The video description says it's from one of the halfshafts, and that it was a bad ujoint.

I'm going to take my car to the transmission shop this week and ask them to check out the halfshafts. I think this is my problem.

Edited by JTCN

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59 minutes ago, JTCN said:

It really wasn't that loose. It was just a small amount of wiggle that made me concerned. My wheels are a set of Appliance mesh wheels, I think they're aluminum. The lug nuts are the proper style for the wheels, they fit fine. I've replaced probably half the wheel studs on this car already too.

I also just discovered something. I was under my car checking the halfshafts bolts were tight and I felt play in the halfshaft. It's a small amount but it's there.

It's a lot like this video (https://www.youtube.com/watch?v=2rNGmNj_-is) but to a lesser degree. It's not loose bolts because I can see the halfshaft move with the flanges, it's literally pushing about a quarter of an inch of the halfshaft into the differential. It can move 1/4" in or out of the diff.

Is this normal?

Some is normal.  The retaining circlip has some play in both grooves.  People have been known to lose the circlip or just not be aware that there's supposed to be one in there, and run with a loose axle.  Take the nuts off and see if the axle is retained.

You're sill misguided on your lug nut issue.  Any play in the lug nut or stud area is bad.  Any.  There's no close enough.  The wheel should be firmly attached to the flange, as if they were one piece.  That's a basic of any wheeled vehicle, no fuzzy area to think about.

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Newzed is right, any play at all is very bad when talking about wheel mounting.

I went on a trip once and the group I was with was towing a brand new utility trailer. The hub had been painted before the wheels were installed and torqued. After about 500 miles the paint had been crushed / worn away allowing enough space for the wheel to wobble back and forth, making more space. Eventually the wheel ripped itself off the hub and taking the wheel on the 2nd axle with it.

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I ripped out my driver's side halfshaft today to check the ujoints. They feel totally fine, no play at all and felt firm on the hub side and the diff side. There was a lot of grease buildup around the ujoint on the diff side. I don't know if it's from the ujoint itself or the diff though. I don't think I'm going to take out the passenger side halfshaft because it feels just as tight as the drivers side.

Honestly I'm pretty bummed it wasn't that simple. Now I guess I'm going to wait until I go to the trans shop and see what they think instead of messing with this thing anymore. If they say there's a problem with the diff after it was rebuilt not even a year ago I think I'm gonna scream, lol

I'll probably get all my wheels balanced too.

22 hours ago, NewZed said:

Some is normal.  The retaining circlip has some play in both grooves.  People have been known to lose the circlip or just not be aware that there's supposed to be one in there, and run with a loose axle.  Take the nuts off and see if the axle is retained.

You're sill misguided on your lug nut issue.  Any play in the lug nut or stud area is bad.  Any.  There's no close enough.  The wheel should be firmly attached to the flange, as if they were one piece.  That's a basic of any wheeled vehicle, no fuzzy area to think about.

Yeah it's not enough play in the diff to worry about. I felt it again today and I heavily exaggerated how much play it really was.

Trust me there's no more play in the wheel lol, I replaced the bad stud. Wheel is now firmly attached to the axle and won't be flying off soon.

So if it's not the halfshafts, what is the problem? I guess the bushings are the next thing I would worry about. I don't think it's my driveshaft but I'll find out at the shop.

Edited by JTCN

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Uhh... bad news.

I got under the car while I had it still in the air. I found the problem.

Let's just say my driveshaft definitely DOESN'T feel tight and I'm a big dumbass.

The driveshaft ujoint on the diff side is severely messed up. There's a lot of play on one of the cups when you wiggle the shaft. I recorded it, here's the video.

https://www.youtube.com/watch?v=bIL4z48Ayjo

So when I'm going down the road the driveshaft starts spinning up and this ujoint slaps and rattles the driveshaft the whole time.

I don't want to drop $300 on a new driveshaft. So I'm going to call around and try to find a shop nearby that can machine in new ujoints and balance the driveshaft. Hopefully for cheaper. Thanks to all you guys for the help. I wish I would've checked the driveshaft closer and noticed before I ripped out my halfshaft lol.

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Nissan started staking the joints in to the shaft in 1975, directing owners to replace the whole shaft if there were problems.  There are places that will modify the shafts so that the u-joint can be replaced.  That's what he's looking for.

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Just now, NewZed said:

Nissan started staking the joints in to the shaft in 1975, directing owners to replace the whole shaft if there were problems.  There are places that will modify the shafts so that the u-joint can be replaced.  That's what he's looking for.

Yep, and I had to buy a whole new driveshaft today. Driveshaft shop near me quoted $200 for each end of the driveshaft. Then I would have to switch out the differential flange to mate up with the new yoke they weld. Which is ridiculous considering the new one I bought is like $300.

Oh well at least I'll have my Z driving again and not wreck my driveline in the process.

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Somehow my driveshaft got here unbelievably fast. Seriously only took 1 day and it's here now. 

So I just removed my old driveshaft and found a problem. My old DS has a dust cover over the slip yolk, my new DS doesn't.

Do I need a dust cover? I've been trying to remove the cover from my old DS by hammering at the seam with a flathead and hammer trying to seperate it from the DS.

I see that a lot of 280z driveshafts being sold online don't have dust covers. Is that because they're not needed or because they assume you'll just use the cover from your old DS?

I need to know if I need a dust cover on my driveshaft before I install it tonight. I definitely don't want to have to do this twice.

Here's a pic of the driveshafts.

PicsArt_10-17-06.52.19.jpg

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Nissan themselves eliminated one of the two sleeves when they redesigned the 5 speed for the 280ZX model.  Leaving one on the propeller shaft but none on the the  transmission.  You'll just have opposite. The 280Z system is kind of redundant.  If you ever get a ZX transmission you might want to fab one up.  It would be easier to attach to the transmission in that case though.

If the transmission cover extends over the base of the slip yoke you're probably fine.  It will be like the ZX system in reverse.  If there's a gap, things might get dirty.  You might check fit before you get carried away.

Edit - actually, by the picture, it looks like you'll have a gap.  I'd extend the transmission dust sleeve slightly, easier.  You could just run it though, and keep an eye on the seal.  It's just going to get dirtier than if it had full coverage.

Edited by NewZed

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6 hours ago, NewZed said:

Nissan themselves eliminated one of the two sleeves when they redesigned the 5 speed for the 280ZX model.  Leaving one on the propeller shaft but none on the the  transmission.  You'll just have opposite. The 280Z system is kind of redundant.  If you ever get a ZX transmission you might want to fab one up.  It would be easier to attach to the transmission in that case though.

If the transmission cover extends over the base of the slip yoke you're probably fine.  It will be like the ZX system in reverse.  If there's a gap, things might get dirty.  You might check fit before you get carried away.

Edit - actually, by the picture, it looks like you'll have a gap.  I'd extend the transmission dust sleeve slightly, easier.  You could just run it though, and keep an eye on the seal.  It's just going to get dirtier than if it had full coverage.

Thanks man. I'm just going to deal with the gap and check it everytime I have my car jacked up.

I have a bigger problem though. The new bolt holes don't line up with my diff flange. The new DS bolt pattern has slightly more space between the bolt holes then my old one, so I can get 2 bolts in on the same side but I can't get the other 2 bolts in, because the DS holes and diff holes don't line up. So we called the place I bought the driveshaft and they're claiming that it doesn't make sense, and that for a '75 280Z coupe the driveshaft should fit. Also the bolt holes themselves are larger than on the old DS. I can wiggle the bolts around if I slide them in. I don't see why datsun would change the distance between the holes for no reason. Maybe a Z expert can chime in on that.

So now I need to find out what year diff I have I guess? Did certain years of S30 differentials have different bolt patterns on the flange? It's possible my diff and driveshaft were switched out at some point in it's life, but I don't know what year it was switched with.

Also the new driveshaft is half an inch shorter than my old one, but it doesn't make much of a difference.

I'll go take measurements of my old DS bolt pattern to help find out what kind of diff this is. Then I'll edit them in this post.

 

Edit: I measured the distance between the bolts diagnolly from the center of the holes and got 2.75". I also found this pic of differential flanges, mine is exactly like the left one. While I was doing this my dad got a call from the driveshaft shop and they said they found a flange with the same pattern as mine, and are going to custom make me one today to fit my diff flange. So hopefully everything works out and we don't have to do this a second time.

9285893905_ecdeec1baf_o.jpg

Edit2: I just found out that I might have an R200 diff. I found comparison pictures between an R180 and an R200 and the cover on mine looks just like the R200. So that explains why the driveshaft shop had such trouble. Also, I don't think it's an LSD. With the car jacked up if I spin one wheel the other wheel turns the opposite way.

Edit3: I'm only updating this still because I think this info will help people that might get in a similar situation. A lot of this seems obvious by now.

I found out that from 70-78 S30s all use that differential flange on the left. Except '75 S30s, they use the middle flange. When I ordered my new driveshaft I told them my car was a 1975 280Z manual coupe, and that was that. Never occured to me that my diff might've been swapped. So they shipped me a driveshaft meant for that 75 Z flange. Since my car has an R200 from some other Z/ZX it didn't fit, and here we are now. I'll get my new driveshaft with the proper bolt pattern soon and then everything will be fine.

 

Here's where I found the pic and the info on S30 diff flanges. http://jagsthatrun.com/Pages/Parts_DAT_driveshaft_flange.html

Edited by JTCN
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Update time.

My new driveshaft came in today, this time with the correct bolt pattern. Installed it in 30 minutes, went to the gas station, and took the Z for a long drive. It drives perfect now. No shaking or rattling noises, just smooth and slow Z power. It made me realize how slow my car is when I don't have a shaking and rattling deathshaft spinning at 3000 RPM under me.

Thanks to NewZed and everyone that helped.

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