James

Hi Guys,
I follow all the issues with the lower control arm bushings closely but I would like some feedback on general wear and tear items with the front end. I have had an on-going problem that was unresolved after some reasonable front-end guys attempted to diagnose it so its best to gather some experience from other SC400 owners.

I have a 1992 and it transmits a rattling vibrations through the steering wheel at low speeds over washboard surfaces. It also feels very loose on center at high speeds (>75 mph) especially on road surfaces that have cracks. This is what I'd like you to let me know as I have inspected my lower control arm bushings and they show no signs of deterioration (cracking). When hoisted the wheels and other suspension componets are rock solid so the problem isn't obvious. This is where you can help. Please let me know what components your service outlets have changed that have ended up resolving any type of front end problems. In order of what I have heard as the most common problems with SC400 and other front ends is as follows. Please give some feedback as this may eventually happen to you and identifying the most common problems will save all of us money when we take our babies to the shop for worn front ends as improper diagnosis costs either you or the dealership money.

1) lower control arm bushings (seemingly common problem with SC's but don't seem to be my problem)
2) inner tie rod ends (common wear item on many front ends)
3) steering rack and/or linkage to steering column (less common but I'm out of ideas)
4) worn out shock absorbers (I'm grasping with this one as I don't know how this could cause my symptoms)

Cheers,
James

DoubleWhoosh

If you haven't changed your arms lately, the bushings are bad. You can't see where they are bad just from a visual inspection, it has to really be taken apart. You can't tug on it either to test most of the time, the problem only shows itself when driving.

That would probably fix all your problems. These guys don't know the car well enough to spot this problem.

Todd Matsubara
TM Engineering LLC
www.tmengineering.net

James

Hi Todd,
At least the only response I got was from one of the most knowledgable members. I appreciate that and will have them focus on a close inspection of the control arm bushes. I'll be sure to let you know the outcome of the job.

Regards,
James

DoubleWhoosh

Yeah this problem is hard to diagnose if you do not have experience with these specific cars.

I guess the best way to describe it is that the bushing is of course round, but the internals are shaped kind of like an H, with the steel sleeve and bolt in the middle. There is no supporting material at the top or bottom. This is so that the arm can rotate in position, while the center sleeve stays stationary. Unfortunately, this minimal material is what causes the failure over time, once the rubber becomes hard and brittle.

The standard grab and pull technique, and a brief visual inspection will not indicate any problems at all, which is why this problem goes overlooked a lot of times. Once you drop the arm down you will see cracks on both sides of the center sleeve. The sleeve will still stay in place, which is why the problem goes undiagnosed many times.

Once the rubber cracks you will start to have minor driveability problems, such as instability at higher speeds and odd tracking on freeway grooves. Accelerated tire wear will also become an issue at this point.

The next step of failure would be when the rubber cracks apart, and the center sleeve and bolt start floating around loose. At this point you will definitely notice bad driveability, and you will hear the telltale clunking noises when backing, turning, accelerating and/or braking. This is when tire wear will happen really fast. You should fix this asap at this point, as this is when there could be damage occurring to the arms, crossmembers, sleeves, bolts, etc.

If you have any other questions or need any other help, don’t hesitate to ask.

Todd Matsubara
TM Engineering LLC
www.tmengineering.net