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Discussion Starter · #1 ·
Hello everyone,

My name is Paul and I am from Texas. I purchased an 85 Spider I am restoring that has a rust-free body. Unfortunately it has some worn mechanical components I am dealing with. To make a long story short, I have produced a shudder that appears to be coming from the rearend of the car. This occured after the shocks were changed. I have a new flex disk, new bushing in the front of the driveshaft, new u-joints. Exhaust has been throughly checked. When you take off, you feel a shudder and then it stops. This is a good shop as they work on BMW and Mercedes. I am their first Alfa of course! They have successfully fixed things on this car, but this is eating our lunch. Anything else we need to look at? They are going to put it back on the lift and double check things. I even have another driveshaft off of an 82 model that is in good shape. Any help is appreciated! My email is
[email protected]
 

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How are the trailing arm bushes? The trailing arms locate the axle fore & aft while allowing up & down movement. If/when those bushings deteriorate the axle will move/twist. This is most likely on first moving from stopped (body at rest wanting to stay at rest, etc).

 

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Discussion Starter · #3 ·
Hi Eric,
Thanks for the reply. I had ordered some of those bushings, but my mechanic says they look good so far. This is an excellent picture here, I will send it to him. I keep thinking it is something there. I had to rebuild nearly the whole frontend on this car, so I would not be surprised if some of the rear end components are shot. Maybe when he puts it on the lift tomorrow he may figure it out. Cannot be be too complicated. Paul
 

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The bushes back there can look just fine but be utter **** AFA thier hardness.
They don't generally tear up or seperate, but they do get good n gushy and/or rot.
(dry or excessive oil exposure. either or)

If they are original or of unknown age estimated at say more than 6 years, I'd replace them regardless just out of spite and the knowledge that it would have to happen before too much longer anyway.

What does it do when you lean it firmly into a turn?
A little wallow mabe, or the vague sensation of dog tracking instead of firm grip all the way up to the point of actual traction loss?

Is the differential fluid topped up?
Ii might be just a simple thing like the limited slip juddering a bit.
 

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That drawing is from IAP's web page.

The trailing arm bushes are not easy to R/R. If not done carefully/right the arms can be ruined. Most folks excavate or burn out the rubber then carefully cut the bush's steel sleeve to remove the old then carefully press new bushes in with a press & proper support. Or buy replacements with bushes already installed.


Polyurethane bushes are available. But some say they are too harsh for street use. Research & decide for yourself.
 

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I use Polyurethane bushes, I'm happy with the result (currently, my car is on restoring process too, but I drove it 6 months after replacing all the bushings to the Polyurethane ones).
rear trailing ares bushing are really not a nice work to do...
Saar.
 

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I used to have an '85 and until we figured out the driveshaft was out of alignment we tore up several u joints. You may need to shim the driveshaft to create the proper alignment and remove the shake.
 

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When you take off, you feel a shudder and then it stops.
The transmission mount may be worn, that causes the output shaft to engage the driveshaft at too great an angle and the shudder/rumble is most pronounced when first first starting off.
 

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Discussion Starter · #11 ·
The transmission mount may be worn, that causes the output shaft to engage the driveshaft at too great an angle and the shudder/rumble is most pronounced when first first starting off.
Actually the mount is new for one. New u-joints, new center bushing in driveshaft. All that seems to be left is perhaps the trailering arms. The Rumble did not occur until the worn shocks were replaced with the new ones.

The car does not seem to lean to much into the turns, I am just getting the rumble and then a low grade vibration going down the road.
 

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I have the same problem with my 87 - a rumble under hard acceleration from a stop. When I last visited the local Alfa expert, and told him of the rumble and had him drive the car, he said that changing the rear shocks should correct it. The rear end isn't sagging much but is almost 3/4" lower on one side vs, the other. He also mentioned that I needed new front trailing arm bushings, but when I get to it, I'll change both sets of trailing arm bushings and all sway bar bushings. All this should help correct the feeling of the rear end wanting to roll when taking highway entrance/exit ramps.

As for other possible rumble related components, all are good (trans mount, rubber donut, driveshaft support bearing, driveshaft balance, differential support mount, fresh and full fluid levels).
 

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Since it seemed to be mostly drive shaft related, were the proper u-joints installed?

Were the two halves of drive shaft in the proper phase or alignment? I can't think of the term, but you don't want the u-joints to match orientation, right?
 

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Yes, U-joints must be 'in-phase' - the axis of the joints should be parallel. A&B parallel, C&D parallel. Since the length of the drive shaft must be able to vary (to allow for suspension travel) there is a splined slip joint in the driveshaft. If the splines are not assembled correctly the joint axes will not be in phase.

 
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