Rear Suspension Refurbishment

[Philipp]

Dear all,

Appreciate your support in my upcoming project. I’d like to refurbish the rear suspension. My idea is to completely remove the top link, lower link, rear hub, radius arm, etc. The plan is to refurbish parts which are not easily accessible. Therefore I’d like to skip refurb work on the brakes for example… will be done later.

That means I’m going to replace the trailing arm bolt with an Inconel one. I also like to blast and powder coat the bigger parts such as top and lower link and the radius arm. And there is my first question already:

With the search engine I tried to figure out whether it is worth to install the PU bushings instead of the regular bushings. But I couldn’t find the information I was looking for… Since price for top and lower link (with the regular bushings already installed) is moderate I guess it is not worth to sandblast and powder coat these parts just to install new regular bushings. On the other side if there is a clear recommendation for PU bushings (may be also in conjunction to the Inconel material for the trailing arm bolt…) I certainly do the refurbishment of the old parts and install the PU bushings afterwards.

I’m not looking for a ‘hard’ ride feeling. Thus from my perspective I do not have to install them. I just do not like to do this job and regret not to have done this modification afterwards.

As part of this refurbishment I will also remove the drive axles and will overhaul them.

Apart of the trailing arm bolt, the bushings and the drive axles any other suggestions for work that could be done when rear suspension is out?

May thanks for your support!

BR
Philipp

[Mark D]

From what I've read over the years on various forums, it's generally not recommended to use poly bushing on the rear suspension links.

The design of poly bushings require a lip on each half of the bushing so they don't push through the hole in the link. This extra material protruding past the end of the link doesn't seem to play well with the design of the frame which encapsulates the bushings on both sides.

The stock OEM rubber bushings are tapered away from the center tube of the bushing so as link deflects, it maintains clearance between the rubber part of the bushing and the frame. I'm not sure if that was intentional or just typical of the design of rubber bushings.

If you look at your suspension links as currently installed you'll probably be able to see visible deflection in the axis of the center part of the bushing vs the outer bushing shell with the car just sitting there at rest. To align the rear suspension properly those bushings need to deflect from a completely unloaded position.

So with poly bushings, that outer lip of bushing material on the outside of the link will be compressed between the link and the frame. From what I've read this tends to cause squeaks between the bushing and the frame over time. I've also read that ride quality ends up being harsh. Poly is already a stiffer material than rubber, and then you're adding in the design considerations where the fit into frame no longer allows the bushing to flex freely.

DMCH has reproduction rubber bushings for the rear links made to OEM specs, so that is what I opted to go with on my suspension rebuild ~10 years ago. I felt more comfortable with new rubber than 30 year old NOS that had run out of stock anyway at that point.

So that's my 2 cents anyway. My research was from quite a while back so I'd be interested to hear from anyone with more recent experience installing poly bushings.

[Philipp]

From what I've read over the years on various forums, it's generally not recommended to use poly bushing on the rear suspension links.

The design of poly bushings require a lip on each half of the bushing so they don't push through the hole in the link. This extra material protruding past the end of the link doesn't seem to play well with the design of the frame which encapsulates the bushings on both sides.

The stock OEM rubber bushings are tapered away from the center tube of the bushing so as link deflects, it maintains clearance between the rubber part of the bushing and the frame. I'm not sure if that was intentional or just typical of the design of rubber bushings.

If you look at your suspension links as currently installed you'll probably be able to see visible deflection in the axis of the center part of the bushing vs the outer bushing shell with the car just sitting there at rest. To align the rear suspension properly those bushings need to deflect from a completely unloaded position.

So with poly bushings, that outer lip of bushing material on the outside of the link will be compressed between the link and the frame. From what I've read this tends to cause squeaks between the bushing and the frame over time. I've also read that ride quality ends up being harsh. Poly is already a stiffer material than rubber, and then you're adding in the design considerations where the fit into frame no longer allows the bushing to flex freely.

DMCH has reproduction rubber bushings for the rear links made to OEM specs, so that is what I opted to go with on my suspension rebuild ~10 years ago. I felt more comfortable with new rubber than 30 year old NOS that had run out of stock anyway at that point.

So that's my 2 cents anyway. My research was from quite a while back so I'd be interested to hear from anyone with more recent experience installing poly bushings.

Thanks for sharing your experience. Makes absolute sense to me.

BR
Philipp

[painterdave72]

I have poly bushings on every suspension part on my car. i have never had any squeaks or anything like that. .but yes it is much firmer than stock and combined with avo shocks and eibach springs its a pretty good ride as i can adjust the shock stifness if need be.. Dave...ps.. i just got done installing the front lower control arm braces and am excited to see how it handles with those added...

[Drive Stainless]

I have poly bushings on every suspension part on my car. i have never had any squeaks or anything like that. .but yes it is much firmer than stock and combined with avo shocks and eibach springs its a pretty good ride as i can adjust the shock stifness if need be.. Dave...ps.. i just got done installing the front lower control arm braces and am excited to see how it handles with those added...

Same here, although I don't notice a difference in firmness.