I'm in the midst of a slow (re)build of my '84 GS (original 12A)

2015: The car rested in the side yard of the house across the street from my father's for around 20 years. I offered the owner $500 and he accepted. Loaded it onto a trailer and towed it from CT to MI. Cleaned out the acorns and droppings from the chipmunks and it started! Made various basic mods to include a Rotary Engineering intake setup. Drove it on a daily basis for 3+ years during the non-salt months here in MI.

2022: I had Chip's Motorsports rebuilt the engine with a streetport (I've rebuilt many engines, but didn't have the time to do this one with my work schedule). Now I'm chipping away at a long list of items
to improve performance and appearance. One of those items is the suspension bushings. So far, I've done the rear lower control arms (LCAs), and I'm working on the upper control arms (UCAs). I realize this has been done many times before, but I add my flavor:

1. Burning out the bushings is the way to go! It's relatively fast, removes the paint and any contaminants, and it's no effort. I put mine in the fireplace -- no odor, no mess.
2. I bought the Energy Suspension full kit, which supposedly includes all the bushings -- we'll see . . .
3. People use many types of grease, but after reading many reviews, I'm convinced that Energy Suspension or Prothane silicone grease is the way to go. They're both formulated for the application, resist wash-out, and are extremely tacky. Prothane grease can be purchased in grease gun tubes, which work well with the grease zerks mentioned in the title.
4. Once the urethane bushings are lubed and installed, there's a valley between the left and right bushings that's a natural home for the grease zerk so you can load it up with grease to prevent squeaking or add more at a later date if it does begin making noise.
5. I ground a recess into the welds to allow the zerk fittings to lie as close to parallel with the control arms as possible and avoid interference.
6. I used 1/4-28 stainless zerk fittings, mostly because I already had some. I think any size / material would work fine.
7. I installed new class 10.9 M14x1.5 screws, torqued to the correct spec (140 ft-lb). I like shiny stuff and one of the original screws was brinelled.
8. Once everything was installed, I topped off each end link with grease injected through the zerks.
9. This grease is very thick and very tacky. You'll need a good grease gun with a secure coupler that won't blow off the zerk.

More to come . . .

 

If you haven't already done the upper arms, leave them with the factory rubber bushes! It will help prevent binding. Even in race cars they leave these in rubber and sometimes even drill holes in the rubber bushes to prevent better articulation.

Many will say you shouldn't do the lower trailing arms either as it also adds to binding tendency as well as unnecessary harshness. I found using poly in the lower arms was fine (using SuperPro which have pretty favourable NVH characteristics compared to other brands of poly bushes), but I left the uppers in rubber.

 

Since mine is a street car and never sees the track, I went with Mazda Factory arms with factory rubber bushings. The trick to making them last is to be sure to drop the cars weight onto the suspension before tightening them down to torque spec. This ensures the rubber is NOT constantly held in tension from being tightened when the suspension was drooping from sitting on jacks / stands. If they're tihtened with the suspension drooping, when the car is lowered into normal position, the rubber bushings are stretched just sitting. Replacement with OEM arms and bushings restored the factory feel, and I still have the poly bushings sitting on the work bench and my old arms sitting out in the back yard if I ever get the urge.

OP, your car has had some modifications done already from looking at your rear axle shots - so curious to get your impressions once it's back on the road.

 

This is a very good tip.

 

Also, very clever on the zerk fittings!

For others playing at home, there is an alternative to stop them squeaking and not needing to ever grease the bushings again: teflon tape. See this vid for example instructions:
Or you can get SuperPro brand poly bushings which never squeak and never require regreasing.

 

I believe the bushings in my original 40 year old control arms were stiffer than they were originally, so I saw three options to improve them:
1. Buy new control arms
2. Pour my own urethane bushings (I did this already for the trans mount)
3. Use aftermarket poly bushings, which is obviously what I chose.

PTFE "Teflon" tape: I've see numerous videos on this, and I don't believe it will permanently prevent squeaking. I actually sell that stuff and have extensive lab experience with it. Under shear it breaks down into microscopic fibers (or fibrillizes). This process is irreversible and will eventually leave you with different material properties. But more importantly, they don't do anything with the sides where the bushing rides against the mounting clevis. Unless you install PTFE washers there too, those areas will squeak once the grease is depleted. Remember that the steel inner bushing doesn't rotate while the polyurethane bushing and control arm do. The fact that the video advises putting PTFE tape around the polyurethane bushing tells me he doesn't understand the mechanics. Won't do any harm, but won't do any good either.

SuperPro: There are numerous posts that complain about those squeaking too. I think they put their pants on one leg at a time like everybody else.

Suspension Binding: I was aware of this concern, but assumed a part of the problem was the resistance to rotation inherent in the rubber bushings. Poly bushings eliminate that effect, so I'm hoping there will be less binding. I'll let you know how it works out.

Ride: When you eliminate the resistance to rotation caused by the rubber bushings, the ride changes. The harshness of road impacts will depend on the durometer of the urethane replacements, but the overall feeling on smooth or undulating pavement is more supple and I Iike it very much.

Mods: Torsen LSD from a Miata (love those things), stainless brake tubes and PTFE hoses (an experiment since I already had the rear axle torn apart), lowering springs (slightly lower than OEM), foam bump stops (an OEM GM part that avoids the hard impact at full jounce that the originals delivered), old school Konis.

 

@elwood What's the part number for the foam bump stop if you don't mind sharing?

 

Thanks for these observations. It will be interesting to see how you go!

The tendency for binding and snap oversteer is not due to the resistance in rotation. It is mainly down to the upper and lower links being uneven lengths and the fact the upper links not being parallel (they angle in from the rear of the car). This is then compounded by the uneven length watts link with a very high roll centre.

Thinking only in terms of freedom to rotate is looking at things two-dimensionally.

The arms don't just rotate and they do not move in parallel. Due to the arms angling in, they have to move not only up and down, but also twist and pivot left and right. The poly bushings may allow the upper links to rotate more smoothly around the joint, but only in that direction. It will introduce greater stiffness in every other direction. You have greater torsional and deflection stiffness which has the overall effect of increasing resistance to roll and oversteer. The idea of leaving the rubber is to introduce more compliance in the upper links to twist and deflect and allow the rear end to roll more easily. This was also the idea of the old PB&J mod. The page is gone now but I managed to find it on Wayback Machine! It has a good description of the issue and possible solutions: https://web.archive.org/web/20060708...uspension.html

Of course you may never push the car to the point where any of this is an issue, in which case new poly bushes might provide a much nicer feel then old rubber bushes and they are a superior solution for you.

 

Here's my post from 1996: https://www.rx7club.com/1st-generati...mpers-1101898/