Lubricating Rear Control Aarms Bushings?

[Scoutdog72]

Hello all!

I'm currently restoring a 1972 GT. I am wondering about the interior surfaces of that track rods and control arm - where the bushings will fit. Should this be primed, left bare, and/or lubricated? It was a real pain in the butt getting the track rods out. It was like the bushing fused the the rubber. I had to make two cuts with the sazall to eliminate the bolt and remove them. Thanks for your input!

[okieopel]

Yes the rubber is vulcanized to the bearing/bushing surface. You will have to burn the rubber out. After that, I sandblast and paint (no primer) with Rust-oleum(yep, bushing surface too).

Here is a link to Dan and Paul on the subject.
http://www.opelgt.com/forums/showthr...5&pagenumber=2

[kwilford]

I presume you are talking about the rear suspension, not the front (which is what the thread that was linked to was all about).

I just did mine, and I chose to paint the panhard rod and lower control arms before I installed the bushings, including inside the integral sleeves. No sense giving corrosion another place to start! I used the NOS style rubber LCA bushings, since I had a brand new set, and the Poly bushings from OGTS for the panhard rod.

In either case, the bushing does NOT rotate inside the outer sleeve, so don't lubricate there. The rubber style is only physically vulcanized to the inner sleeve, and the outer LCA or rod sleeve just holds the bushing. After a time, the rubber gets stuck to the outer sleeve, but they are not "vulcanized". The rotation in the LCA with the NOS rubber bushing is made by the rubber flexing. That is why you have to have the car sitting on it's wheels, with 150 pounds in the driver seat, when you tighten the LCA bolts. The rubber bushings should be "neutral" when the car is in a normal sitting position.

With Poly bushings, the LCA bushings are "tight" to the outer sleeve, but the inner metal sleeve (which is secured to the body and spring carrier by the bolts) rotates inside the bushings. So this is where you need to lubricate, with the special waterproof grease that is supplied with the Poly bushings. So no need to worry about what position the suspension is in when the bolts are tightened, since the bushing just rotates around the inner sleeve.

As for the panhard rod, the body connection uses an inner sleeve, much like the LCA, but the connection to the differential just has the bushing (either rubber or Poly) slide over the attaching bolt without an inner sleeve. I guess the Poly style should be greased at this point, since rotation will happen here.

HTH

[Scoutdog72]

Thanks for the info - much appreciated. I'm sure many more questions will arise as this project takes on a life of its own.

[RallyBob]

Poly bushings should be lubed inside and outside to ensure they don't bind and squeak. Not doing so will ensure a much rougher ride, since the twisting motion of the trailing rods will add considerably to the spring rate at the rear of the car. The urethane relys on the rotation of both the ID and OD within the trailing rod end to ensure compliance in multiple planes. This is unique to the trailing rod bushings, and not the same as the front suspension bushings. So using a 'slippery' paint (such as POR-15) within the ends of the trailing arms and then lubricating with teflon-based grease before installing the bushings is important.

I should add that tightening the bolts to the proper spec with a torque wrench is critical. Overtightening will also create a binding condition.

[kwilford]

OK, now this is getting interesting. Bob, as I mentioned, I used the NOS style rubber bushings in my rear LCA's, so I have no specific experience with polyurethane bushings in the rear LCAS's. The standard rubber bushings have their inner sleeve locked in place to the body attaching bracket by torquing the bolt, and the outer surface definitely doesn't rotate inside the LCA outer sleeve. The rotation that you get is allowed by the rubber being "compliant". The rubber flexes in rotation, which is why they wear out. And why the bolts get seized inside the inner sleeve, since there is never any rotation relative to each other at that point, and they rust together. I can visualize that when one wheel is lifted relative to the other, the bushing also has to flex in a cross-ways plane, since the LCA (or at least the differential) is now angled relative to the body. And the flex is taken by both front and rear LCA bushings.

But if the LCA bushings made in Poly are anything like any other Poly bushings I have seen, they aren't bonded to the inner sleeve. I believe they are two piece bushings from OGTS, with a single inner sleeve (like the front spring-eye bushings). So they must still be able to rotate around the inner sleeve. I just can't see them also rotating inside the outer sleeve. Why would they? They are more like a true "bushing", in a "roller-bearing" sort of way, than the rubber bushing. But they are also "compliant", in that they will compress to compensate for the roll axis. The plane of rotation in both inner and outer sleeves is the same. And the friction surface of the Poly to the inner sleve is MUCH less that the Poly to the outer sleeve. Maybe I am missing something, but I still can't visualize the bushing rotating inside the outer sleeve. Nor why you would encourage them to do that by greasing the outer surface.

As for torquing properly, I can see if the bolts were reefed really tight, the body and differential bracket sides could impinge on the sides of the bushing, which would cause the bushing to bind. But I would guess that having the suspension at the "normal" position when the bolts are torqued isn't as critical with the Poly bushings, while it IS with the rubber bushings. Or am I missing something here as well?

Please enlighten us, oh master of the suspension black arts!

[Scoutdog72]

Boy this has gotten real interesting - it's is amazing how a simple item like a bushing can influence so many dynamics. I can only relate to what I found when I did the diassembly of the rear track rods. These were the original bushings. The inner metal bushing was vulcanized to the rubber and the bolt did not move when you moved the track arm up and down. I would think that in a new assembly that the arm would move freely. Now on the control arm (single long assembly so there is no confusion) the bolts came out easily. Then again what the hell to I know - in matters like this I defer to those with more experience - my background is electronics - besides I haven't ordered new bushings yet and as a thorough restoration these assemblies will be "renewed" as the book says, stored, and then installed in a year or so.

[Joe Van Wagnen]

i sandblasted, primed and painted mine, i lubed the outside and inside of my poly businings to aid in assembly

[RallyBob]

Keith, the dynamics of the trailing arm bushings are very different from those of a front control arm and even to that of the panhard bar. Rubber bushings twist and allow for vertical movement of the arm, as well as torsional twisting when one tire moves up and the other stays down (as in cornering or when a bump in encountered, and the axle doesn't move vertically in a perfectly flat plane). With the urethane, the inner sleeve pivoting within the bushing will work perfectly if the axle moves perfectly vertically at both ends simultaneously. But this seldom happens, and most of the time a twisting motion is encountered. But the urethane is MUCH harder and resistant to this plane of deflection, so it benefits us to put as much compliancy (in the way of rotation) into the urethane as possible.

If the harder urethane does deflect during a twisting/lateral motion (it does), isn't it going to make it more difficult for the sleeve to rotate within a distorted bushing? Lubricating the OD gives another avenue for the rotation to occur in. So I lubricate the ID of the trailing arm, the OD of the bushing, the ID of the bushing, the OD of the metal sleeve, and the ends of the bushings where they contact the chassis mounting tabs. The benefits of this can be verified by installing the bushings with only the ID greased first, installing the rear axle (sans springs or shocks or panhard bar), then with a jack under the center of the diff, turn and twist the axle along the centerline of the T/T. Now try the same experiment with a fully greased bushing. In fact, try it with OEM rubber bushings...they actually have their own 'spring rate' and will pull the axle to a neutral position when released. But compliancy is better for ride and performance.

The life of the bushings will be extended by lubricating the OD of the bushings as well, I have proven this over the years from racing Opels. I can put 5 years worth of wear into a bushing in just 3 or 4 weekends of racing (not an exaggeration!). In fact, I tested Gil's (OGTS) prototype urethane Manta/Ascona bushings in my street car many years back, and wore them out in 8 months of street driving. So this gave Gil a good idea of some potential problems after I removed them and diagnosed the causes, and he had the bushings retooled so this would not affect his customers. I have installed probably 40-50 sets of rear poly bushings, and am simply conveying my opinions so that others do not encounter problems I have had in the past. Besides, the instructions Gil provides with the rear bushings specifically state to lubricate all surfaces, including the trailing arm ID and bushing OD.....

In fact, my prefered methodology for trailing arm attachment is utilising urethane bushes at the trailing arms where the attach to the chassis, and spherical rod ends at the attachment to the rear axle. Zero slop, but less binding than all urethane, and better chassis noise/vibration isolation than all spherical bearings, with better lateral location as well. Hope this all shows some insight into my thinking.

Bob

[Travis]

When I installed the rear poly bushings in my GT it was clear that they had some bind, but it wasn't until I swapped out the bushing at the axle for rod ends that I realized how much there actually was. The difference was night and day. In addition to the better positioning that Bob mentioned, the response time of the suspension must be quite a bit better....

-Travis

[kwilford]

This discussion really demonstrates the value of this kind of forum. A simple question gets asked, a different twist gets added, and pretty soon the entire Opel Community (or at least the ones lucky and smart enough to attend this forum) are smarter. And genuinely better off for the answers.

Since most of us mortals aren't up to using "spherical rod ends" in place of the rear LCA bushings, I suspect that we will have to make do with either stock rubber bushings, or Polyurethane bushings from OGTS or other sources.

Since Poly bushings tend to bind against the inner sleeve in a rolled condition (when one side of the axle is higher than the other), I can see that reducing the binding by whatever means is available (such as greasing the outer bushing surface) is a good thing.

I assume that since rubber bushings don't rely on slipping rotation to work (the rubber just deflects), they don't need to be greased on either surface, except perhaps to reduce the rusting that occurs between the inner sleeve and the bolt. But they have other undesirable characteristics, such as deflecting in any plane they are flexed in, including backwards and forwards.

I had kind of figured out the need for two (at least) planes of compliancy, since I understood that the stock rubber bushings had to be torqued in place while they were at a "normal" resting position. The stock rubber bushings clearly add some spring rate to the axis roll (when the car leans), as well as to the bump roll (when the axle is deflected up, both sides at the same time). I presume that the rubber bushings actually REDUCE body roll (to a very small extent), and also a add very small bit of spring rate.

In short, can we say that when using stock rubber bushings on the LCA's, they simply need to be pressed into the outer sleeves? The key point, then, is to only tighten the bolts when the suspension is at a normal resting position, since this reduces undue deflection in the rubber, that might otherwise cause suspension "pre-loading".

And that when installing Poly bushings in the rear LCA's, they should be greased both internally and externally with teflon grease. And the bolts can be torqued in whatever position they happen to be in, since the bushings will rotate to a neutral position when the car is resting.

Comments?

[kent]

When the poly bushings were put in the rear of my gt they were not properly lubed and squeak very badly. I have never removed these and wonder if someone can give me a lesson? What needs to be supported? can you just jack up the rear end? Do the axles need to be supported? It should be easy but I've made that mistake before . A step by step guide would be a big help! Thanks

[opelnut10]

You need to support the rear end and drop the panard bar and sway bar if you have one. Take the trailing arms loose at the spring bucket first then from the front mounting point.

[kent]

So I need to support the diff/ rear axle ? or just lift the rear of the car ?thanks