I'm just curious. Since I bought the car I can feel a slight shimmy back & forth with slight wiggling of the steering wheel while going down the road. I'm also wondering if sidewall height makes a big difference... they aren't stock size, but they're dang close to the original diameter - 195/65/15, less than 1/4" difference in calculated height. The car already had poly arm bushings in the rear when I bought it, but it appears to still have the original cradle mounts.

How about engine/trans mounts... anyone notice a difference there? Mine could likely be replaced, the engine mount is likely deteriorating pretty bad due to a semi-significant front main seal leak.

I'll be honest, I noticed very little change.

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86 Fiero GT: 3800sc/Manual, Cam/Mods.

Have you checked your front ball joints and tie rod ends? Wiggle in steering wheel tells me something in the front is in need of replacing.

The steering wheel isn't wiggling, everything is tight up front save for a couple control arm bushings that have a little bit of rattle to them... which is not the cause, the problem isn't up front. The rear of the car doesn't feel like it can keep up with input from semi-aggressive left/right steering. Think of it as your tires only have 5psi of air in them and you're whipping the steering wheel left to right... the rear follows, but lazily.

Fiero is 25-30 years old. Many old rubber bushing will need to be replaced.

1. manual trans + rubber cradle bushing often cause "torque steer." Engine load pushes/pulls right side of cradle thanks to dog bone is mounted to car frame. Auto trans can do this too but many won't see this issue all the time. Cruise control active + stick trans can do same problem w/ soft cradle bushings.

2. poly CA bushings can/will wear out w/o noise. Sooner if not lubed at install time and often after.

See my Cave, Bushings

I only have poly for cradle. no wear or noise because cradle doesn't move and cheaper than metal.
All CA use Moog rubber.

Notice the diff? Auto trans so not much most times. Some intersections allot more.
Example:Ssouth of New Castle, DE, Hamburg Rd stop sign at Rt 9 (River Rd)
Stop sign dump you at top of a slight banked turn on Rt 9.
( https://www.google.com/maps.../data=!3m1!1e3?hl=en )
Very short... The left turn + accelerating the car + angle of road + rubber cradle bushing = car is very squirely for a few seconds.
stiffer poly cradle bushings help allot. (And car did have good alignment. didn't help.) Better shocks/struts help more when done several week later.

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Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.
(Jurassic Park)

The Ogre's Fiero Cave (It's also at the top and bottom of every forum page...)

quote Originally posted by theogre: Fiero is 25-30 years old. Many old rubber bushing will need to be replaced. 1. manual trans + rubber cradle bushing often cause "torque steer." Engine load pushes/pulls right side of cradle thanks to dog bone is mounted to car frame. Auto trans can do this too but many won't see this issue all the time. Cruise control active + stick trans can do same problem w/ soft cradle bushings. 2. poly CA bushings can/will wear out w/o noise. Sooner if not lubed at install time and often after. See my Cave, Bushings I only have poly for cradle. no wear or noise because cradle doesn't move and cheaper than metal. All CA use Moog rubber. Notice the diff? Auto trans so not much most times. Some intersections allot more. Example:Ssouth of New Castle, DE, Hamburg Rd stop sign at Rt 9 (River Rd) Stop sign dump you at top of a slight banked turn on Rt 9. ( https://www.google.com/maps.../data=!3m1!1e3?hl=en ) Very short... The left turn + accelerating the car + angle of road + rubber cradle bushing = car is very squirely for a few seconds. stiffer poly cradle bushings help allot. (And car did have good alignment. didn't help.) Better shocks/struts help more when done several week later.

I'm doing a 4.9 swap and plan on using the poly cradle bushings and Moog rubber arm bushings as you wrote in your cave.

quote Originally posted by racingfortheson: I'm doing a 4.9 swap and plan on using the poly cradle bushings and Moog rubber arm bushings as you wrote in your cave.

V8 should be fine most times if not all the time. Much of this depends on how engine/trans mounts and dog bone planing.

Hard launch for drag racing etc then might distort any soft bushings enough to get some trouble but only at launch time.
And Poly CA bushings will see this too.

Poly cradle is allot harder then rubber but does compress some. Good because could prevent breaking things.

Steel or Al cradle "bushings" can have issues too, Even if aluminum is hard anodize...
Example: Steel shell stuffed w/ aluminum could be problem from road salt etc.
Shell steel is softer then steel for cradle. Soft enough can be pressing in and deform to fit the cradle hole.
Important because Al to Steel "interface" will have voids that water etc will go into and rust from inside. If was me, I would use Super 300 etc to seal up any voids. (I do same thing for axle seals for this reason. In that case, Stopping leaking oil thru any scratches in the trans hole.)

Poly installed dry could have same issue but poly will try fill most voids where it meets the shell. Poly does get some pressure after install w/o load for car. Front Poly is push into the shell then inner sleeve is push into poly. Rear poly has metal part compressing the pieces. Poly will cold flow a bit for this reason and seal most voids. (Pulling Polly front cradle after 10+ years is not easy. I have tried.)

I do need to do engine/trans mounts too, I'm thinking the weight of the engine/trans combo could be moving around, causing the wiggle. I'd really like to do stiffer cradle bushings though, just to be safe.