98 V79 NA front end vibration (control arms replaced) Topic is solved

[98v70dad]

It occurred to me today that maybe at higher speeds that shroud is fluttering in the air stream and causing my vibration issue or at least adding another component to it. Has anyone ever had an issue with that part fluttering if its damaged?

It might. Mine still clips into place to the air dam, however the rear plastic tab broke off. I added a new one using some metal mesh from a drywall repair kit. Quite stout. I also used this to repair both port & starboard ends. It's held up well.

I've been experimenting a bit with "plastic welding" to fix these problems.

I cut the aft plastic tabs off on both sides and replaced them with galvanized steel simpson strong ties. This was due to the complete air dam devastation caused by my daughter driving the car over a 4 lane highway median about 4 years ago. My repair isn't going anywhere either. Being loose at the forward side is a new development. Someday I'll post some pictures. I have a couple of things I'll call 98V70's redneck cheapo repairs that work better than OEM. I've been waiting for things to stop breaking/wearing out to post them. Unfortunately it hasn't happened yet.

[98v70dad]

Feeling "twitchy" or "squirrely" on the highway is characteristic of bad rear bushings.

I have no familiarity at all with the back suspension. I replaced the rear shocks about 18 months ago. In the last few months the passenger side rear has started an occasional deep rattling going over bumps. I have no idea what it is but its coming from the wheel well area. I guess I'll have to pull out the haynes manual and do some reading.

[kcodyjr]

Probably the outer bushing. My 97 is doing that.

The rear suspension consists of two arms that reach across the width of the car. There is a round-ended bushing at the end of each arm where it meets the wheel, and block-shaped bushing holding the arm down and allowing toe adjustment. So, the adjustments are on the opposite side of the car. One loosens the driver's side block bushing to adjust passenger's side rear toe. (Watch an unsuspecting alignment tech on his first P80 Volvo try to figure this out sometime. Almost feel bad for the guy.)

If by "deep rattle" you mean "heavy piece of metal slapping into another heavy piece of metal whenever the road changes the rear geometry", that's probably it.

Rear suspension does tend to get neglected. There seems to be an attitude that it doesn't really matter. I beg to differ. Rear end wiggle *is* a steering input in a car with delta link rear end, so it gets "squirrely" long before it gets "slappy".

[sleddriver]

When dealing with vibration, always start from the bottom up.
- Tire
- Wheel
- Bearing
- Control Arm
- Tierods
- Strut and all of its mounting hardware
- Steering Rack

Found this while digging around.....

[98v70dad]

Yep. Found it myself 6 months ago. I've replaced everything but the bearing and control arm. At
this point I suspect the control arms. Bearings usually make grinding noises when they are bad.

[sleddriver]

I thought it interesting the rack was mentioned, alebit last.

[98v70dad]

I thought it interesting the rack was mentioned, alebit last.

Actually my last post wasn't accurate. I have not replaced the rack. I didn't notice that on his list. Replacing the rack is more of a PITA than I want to bother with if it is the source of my trouble. I'm sure that ireplacing it is also way more than I want to pay someone. I'll only be driving the car for a few more years so if that's whats wrong and it doesn't get worse I'll just live with it and slow down a bit.

I do have my doubts about my current rack being OK. If I jack up the car and grab the wheel and torque it with a 3 oclock 9 oclock push pull it moves a little before the rack engages. The movement is on the rack side of the bellows which leads me to believe that its internal to the rack. Other people have told me that this is normal but it doesn't seem right to me. Maybe it "tightens up" when the engine is running and there is hydraulic pressure on it - don't know. I am ignorant of the steering rack internals and also how its adjusted. The movement isn't in the tie rods though...I just replaced them about 6 weeks ago. They are tight..

I had the steering wheel off a few years ago to replace a bunch of broken things in that area and got it back on but off by about one tooth in the splined shaft. When I got new tires the last time(18 months ago) the guy who installed my tires said that I didn't need an alignment but he tweaked it for me whatever that means. When I picked up the car the steering wheel was straight. I'm wondering if he made some sort of adjustment (or his "tweaking" broke it) that straightened out the steering wheel but left a little play in the rack. The vibration started shortly after he screwed with it. It was only a slight vibration and I attributed it to a slight wheel balance issue. Its gotten progressively worse.

[sleddriver]

I noticed, but let it go. My rack is old as well (replaced at 80,000). One alignment guy refused to do align due it being "worn". Not sure what that means. He didn't offer me back for a hands-on while up-in-the-air. Odd that....

The replacement rack did come with a lifetime warranty to the owner when installed. But with AT-205 fixing the leaks, I have other things to spend $$$ on. I have yet to do the test with someone in the drvr seat, holding the SW, while I tug on the wheels.

If it has indeed gotten "progressively worse", then something is indeed amiss.

Some chassis are indeed sensitive to certain tires, fine balancing, etc.. Others? Not so much. Given our sleds exhibit interior road noise, we feel everything. Thus, we're going to notice little things....if we're attuned to such. Other chassis completely isolate one from road noise: quiet as a church.

Your Michelins are better tires than my BFGs. Mine are non-directional, thus I plan on regularly cross-rotating them to ensure even wear, minimize noise and extend life. I'll also carefully and closely be watching each corner.

Frankly, I don't understand, in 2016, with tire manufacturing being 100% a computer-controlled, automated process and with "ISO 9001" and "sixth sigma" in the lexicon, why a truly round tire cannot easily be produced! Particulary since Michelin owns BFG! Go figure........

[98v70dad]

Your Michelins are better tires than my BFGs. Mine are non-directional, thus I plan on regularly cross-rotating them to ensure even wear, minimize noise and extend life. I'll also carefully and closely be watching each corner.

Frankly, I don't understand, in 2016, with tire manufacturing being 100% a computer-controlled, automated process and with "ISO 9001" and "sixth sigma" in the lexicon, why a truly round tire cannot easily be produced! Particulary since Michelin owns BFG! Go figure........

I got rid of the Michelins because they were 5 years old and had cracks in the sidewalls. I just replaced them with Continental True contacts. These are awesome tires for the money ($95 each). I had BFG Advantage TAs on the front for about 18 months. They were a bargain tire but the did not last very long. The tread wore very quickly.

I have an aircraft tire being manufactured up close and personal standing right beside the guy pushing the buttons, etc. It was over ten years ago but I expect that they get out of round while they cool. After they come out of the heated die I don't remember anything special in the process to ensure that they cool evenly. That said, I saw it the one time and don't know that much about it.

The last few days I've been reading your posts on this topic and have concluded that we probably have the same or similar problem. Last night I was focusing on the two universal joints in the steering shaft. I started looking at this because it is the one thing in the steering that looks like it could be a weak link. You've got two possible wear points that get no maintenance and they are out of sight, out of mind. They are also attached with splined connections that could just plain come loose and slip. There was a post earlier in the thread about it and I'm just now getting around to looking into it.

It also possible that the whole rack is just loose. I haven't checked that either. I don't know if its mounted in bushings, but if so they are probably cracked and loose. I'm doing an inspection of these areas Sunday. If all checks good, I'm going with new control arms followed by sub-frame bushings if no joy from the control arm replace.

[sleddriver]

I'd read good things about Conti's + Volvos. Odd local DT won't carry them. Could have bought and shipped & M/B'd but that also adds up. Given my experience with BFG, no more of these. Rubber rot is a fact-o-life in the South. Tires need sunscreen.

Re: U-joint. Good eye. Haven't bothered to check mine as it's out-of-sight-out-of-mind.

Re: Rack mounting. "loose" meaning internally, not externally. Where R&P meet is one point. So would be the outer sleeves (metal? Plastic?) where it's guided in-n-out. Then the seals. If I had a rack in hand, I could inspect and figure it out.

Passive steering rear end delta links: This would explain unexplained RE vibration. Particularly when aggravated by rear tires that are not smooth round. These tires transmit vibration to the axles/ bearings/hubs, then to the delta arms where over time they enlarge the rubber pieces.

Do this long enough, over enough rough roads, in hot, humid weather, where black asphalt reaches 160°F , which is constantly radiating heat upwards while I'm stuck in damn Cen. Tx. traffic, in an area with only two seasons: Summer and Feb. and it all adds up.

I remember as a kid what would happen when the rubber bushings would rot in my skateboard trucks. I'd get the wobbles going fast and wipe out! Thus regular replacement was necessary to remain stable at speed and keep my skin off the pavement!