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Discussion Starter · #1 ·
Hey!

I have a '72 240Z that's mostly original (shot). When I take it up past about 80mph, the entire car starts to shake itself to bits. It seems like everything rattles and groans at once.

My question is, the 240Z should /feel/ like it's at home at speeds over 80, right? It should sound good and not shake itself off the road at a little over 100, right?

Thanks!
-rr
.
 

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> Hey!

> I have a '72 240Z that's mostly original
> (shot). When I take it up past about 80mph,
> the entire car starts to shake itself to
> bits. It seems like everything rattles and
> groans at once.

> My question is, the 240Z should /feel/ like
> it's at home at speeds over 80, right? It
> should sound good and not shake itself off
> the road at a little over 100, right?

> Thanks!
> -rr
> .
 

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RR You said this car is mostly original. How many miles? Have you ever rebuilt the front or rear suspension, or changed the engine or transmission mounts? Those rubber bushings and parts tend to get soft over time and could be your problem. Try replacing them with urethane bushings. And how about checking the tightness on all the bolts and nuts in the suspension. Also, any broiken bolts anywhere? How about the tires and wheels? Have you checked the tires for flat spots? Let me know. Gerry
 

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Discussion Starter · #4 ·
> RR You said this car is mostly original. How
> many miles? Have you ever rebuilt the front
> or rear suspension, or changed the engine or
> transmission mounts? Those rubber bushings
> and parts tend to get soft over time and
> could be your problem. Try replacing them
> with urethane bushings. And how about
> checking the tightness on all the bolts and
> nuts in the suspension. Also, any broiken
> bolts anywhere? How about the tires and
> wheels? Have you checked the tires for flat
> spots? Let me know. Gerry

This is a very good idea, but is perhaps only a small portion of a bigger problem. My 75 280z was suffering from exactly the same thing, and I was looking for any thing that might have been causing it, couldn't find any thing. Over time the vibration started to get worse, and at lower speeds. I was thinking that it was a loose u-joint, didn't find any, it was only when I decided to remove the diff. and inspect it that I found the problem. The rear u-joint on the drive shaft was partialy seazed. This caused a loping action, which only became evident at higher speeds. But as the u-joint got worse, the vibration got worse. I suggest that you may want to look for the same thing on your car, but it may be any of the u-joints.

Will.
 

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Discussion Starter · #5 ·
> This is a very good idea, but is perhaps
> only a small portion of a bigger problem. My
> 75 280z was suffering from exactly the same
> thing, and I was looking for any thing that
> might have been causing it, couldn't find
> any thing. Over time the vibration started
> to get worse, and at lower speeds. I was
> thinking that it was a loose u-joint, didn't
> find any, it was only when I decided to
> remove the diff. and inspect it that I found
> the problem. The rear u-joint on the drive
> shaft was partialy seazed. This caused a
> loping action, which only became evident at
> higher speeds. But as the u-joint got worse,
> the vibration got worse. I suggest that you
> may want to look for the same thing on your
> car, but it may be any of the u-joints.

> Will.

My 280z has a severe rear tow-in that causes it to shake ar speeds of 20-45. No problems above it though. Also causes it to jump sideways when one wheel hits a bump. I would recommend Urethane buchings on the whole suspension and check tie rods and ball joints. I'm doing that this weekend.
 

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Discussion Starter · #6 ·
> RR You said this car is mostly original. How
> many miles?

Ya know I don't actually know how many miles it has on it. I'd guess it's between 100 and 200k. (It has a new L28 engine in it, [20k miles]).

> Have you ever rebuilt the front
> or rear suspension, or changed the engine or
> transmission mounts?

I think the engine mounts are good, since the engine was swapped for a new one 20k miles ago. No, I've never rebuilt the suspension or touched the transmission mounts. They're probably all original and shot.

> Those rubber bushings
> and parts tend to get soft over time and
> could be your problem. Try replacing them
> with urethane bushings.

As I type, the Z is sitting in a cleared-out 3 car garage awaiting restoration that'll begin in a few months. I plan on using the urethane bushings in the suspension. So when I'm done with the car I'll post a picture of it and tell ya if it still shakes at high speeds or not. :) It's going to be bright yellow.

> And how about
> checking the tightness on all the bolts and
> nuts in the suspension. Also, any broiken
> bolts anywhere? How about the tires and
> wheels? Have you checked the tires for flat
> spots? Let me know. Gerry

That's probably one of the main problems. One of my rear wheels is bent! The tires are also funky.

I guess it's shakes are just the classic symptoms of being an old and worn out car. Time for a full rebuild! :]

Thanks for the suggestions,
-rr
.
 
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