Automotive Front end question-any specialist here?

[dweller]

I'm getting ready to head out and put the wagon up on supports to try and diagnose a problem that just cropped up this morning.
I'll describe as best i can what it was doing.
it's a 2 wheel drive, automatic, 1991 subaru legacy wagon, no air suspension. Front wheel drive.

as long as the drive is engaged (moving forward at any speed) no problems that i can detect. But as soon as i take my foot off the gas and as it slows (at any speed) there is a MAJOR shimmy from the front. More like a wagga-wagga, like a tire is loose (it's not).

Braking slightens it, but not much. Also, the steering wheel reacts with the shimmy with a left-right motion which is really active.

Again, with any acceleration it stops.

Give me your best guess, i'll check back in after it's up and i've had a look.

thanks in advance.

dp

[trogdor]

1. misbalanced tires?

That'll do it. Maybe you have some dirt in the wheelwells that's throwing them out of balance.

[GOPisEvil]

2. Unbalanced wheels is my guess, too.

Could be alignment, but my first guess is have the wheels balanced and see if that corrects the problem.

[sendero]

3. I'm no expert....

... but I doubt this is a tire issue. This sounds like there is some serious 'play' in your front end. It could be in the steering, or any front end component that keeps the wheels in place. If you put it up on a jack and wiggle stuff, you might very well find it.

I know you know already but this sort of thing can really be dangerous. If you can't find it you really need to get it to a shop!

[Ready4Change]

4. Check engine mounts, too.

IMHO it's more likely something in one of the connecting points of the suspension, like a bushing. But it could be anything from loose lugnuts to a worn or broken engine mount. Also check from the tie rod ends all the way back through the steering system.

If you need to take it to a shop, consider getting it towed or flat bedded. If you must drive, plan a route through un trafficed streets and slow speeds, just incase.

[nothingshocksmeanymore]

9. Engine mounts or the drive shaft would cause shaking at any time

not just when slowing.

[Ready4Change]

10. Hmmm

I was thinking that power input would hold things tight. Then, when power is released it would free things up to knock back and forth. I had a worn universal joint in a car's drive shaft many years ago that behaved that way.

[nothingshocksmeanymore]

11. Possibly..It sounds a bit too predictable in terms of WHEN it happens

to be anything with the drive shaft. I might be wrong...will be interesting to see :D

[dweller]

5. okay, had my look

Tires are only a couple of months old, so while it could be a balance issue, most likely not.

I don't see or feel any play in ball joints, tie rod ends, an allowable minimum in cv joints, but the outer boots are shot on both sides, so that's a problem. Inner joints look fine.

The worst i can determine: while in drive or neutral the right tire is very hard to turn, so i suspect wheel bearings are bad at least, and at worst the hub may be worn out (?) thus causing the play while moving. I can't detect any looseness when i grab tire at 12/6 oclock and pull/push tho. Nor side to side.

So i'm stumped, sort of. Nothing appears as loose enough to cause a major shimmy like i felt earlier.

closest shop is a mile or two on back roads, so i will have to take it by and let them have a look, at least check balance on wheels and inspect front end suspension.

thanks for all the input, add any more if you think of something.

dp

[BiggJawn]

6. CV joint?

Holds steady under load, but when you back off and unload it, all hell breaks loose? That could be a possibility.
Not for the Shadetree Mechanic with a Haynes book in his hand, whatever it is...

[dweller]

7. that's what i'm thinking

with the bad boots, loss of grease.
I've done the job on other cars, just not this one. Outer joint is not rebuildable, inner is. Of course it's the outer that is showing the damage.

pining for the good old days of vw's and owner maintained/rebuildable parts...

dp

on edit: just got off the phone with the parts house, suprisingly they have the driveshaft, $59.95 new. That's cheaper than a single joint for some cars. I'll take care of the worst one today (right one) and save the other for another week. Hopefully it's the one causing the problem. Guess i'll find out.

[DonP]

15. Agree on the CV's

Under pressure (in drive) there might not be a shimmy ... yet.

But there could be a catastrophic failure soon, when the grease is all gone and one of the joints freezes up, hopefully not at speed.

At very low speed see if there is a faint or pronounced "clunk" when you put it in drive it's 90% that it is the CV joints. Once the boot goes, unless you catch it the same day the joint is usually junk. When it gets contaminated by dirt, dust and salt it's history.

FWIW, I just replaced two on one of our Camry's this past weekend..

Remanufactured CV joints only use the half axle and replace eveything else so it's a new system except for the hard steel componets that never wear out.

They cost about one third as much as new and come with a year warranty at most places, (but not Pep Boys). IMHO, go to NAPA dealer and get American made Re-Manned parts.

[nothingshocksmeanymore]

8. Sounds like TWO issues

Rotors will cause shaking and the rotors on Subaru's wear in an oval fashion. This causes it to shimmy when the car slows...also, there is an adjustment in the steering gear box which probably needs to be made as a result of the rotors loosening it.


Front wheel drive cars go through front rotors faster.

Rotors are cheap..about 50 bucks each plus labor and a nice mechanic will adjust the steering gear for free.

[dweller]

12. argh, nmsa...

i've got the driveshaft off, and it's pretty shot on the outer end. Definately needs replacing. Just waiting for my daughter to get home and get me to the parts house. Maybe i'll get it back on tonite, but more likely tomorrow. Test driving etc. will lend an answer.

I'm not detecting any hub/knuckle/bearing play at this point, which is what you are referring to with 'rotor' i think. But i'll take a closer look at it. It's power steering and haven't experienced any problems with that at this point. All points i checked (tie rods, bushings) appeared good.

we'll see...
dp

[nothingshocksmeanymore]

13. Well if the end of the drive shaft is worn, then that would pretty well

explain it...do you have a part's yard to pull a used one off a wrecker? or get a rebuilt one? Can save a bunch of dough if you are doing the labor yourself.

If it were the bearings, the tires would wiggle when you have them off the ground with a little force, but you knew that :D

on edit..the main reason I did NOT think it was the drive shaft is that usually causes the whole car to shake..not just the front end, and if it's worn enough, it's impossible to accelerate without MORE shaking.

[dweller]

14. There's a wrecked subaru wagon

about 45 miles from me that i was hoping to get to before this happened, i've gotten a part or two from it before. Problem is, all of the wheels are gone so it's flat on the ground pretty much. So getting the driveshafts from it would have been a chore. I will be going back to it for the roof rack tho...

even so, $60 quoted for a new shaft won't bankrupt me today...of course, a month from today, who knows? :)

dp

[nothingshocksmeanymore]

16. OK but I have to chuckle at you a little

Only a MAN would go through the trouble of ripping the drive shaft out without being certain! :evilgrin:

[CanuckAmok]

17. I'm saying CV joint, too.

And, it can often be two things (the second resulting from the first).

Example: CV joint wears out, and allows a certain amount of wheel hop during brakeing (particularly if you're braking while turning in the direction of the bad side). That causes uneven caliper pressure on the rotors, and, if not addressed right away, may cause undue wear on the pads and/or rotors. It can also put more strain on your tierod ends, so have a look at them, too.

Most of these parts are cheap, but I strongly suggest taking the car to an alighnment shop after the work is done, if you're doing it yourself. Especially with those new tires!

[dweller]

18. Problem solved (hopefully)

Test drive was fine, no wagga-wagga in the front end....at this point. Took the old blue wagon up to about 65 on the back roads here, and it performed great, that other slight shimmy at 60 has disappeared too, so it must have been the cv joint afterall.

I'm going to replace the other side in a week or two on a ideally warmer day.

and you are right nmsa, only a man would be out on a ~30 degree and falling nite laying on the ground futzing around with a car just to see if he can fix it.

so quick question for you..since females are better at math. How do i achieve 123-140 foot lbs on the drive axle nut without a torque wrench?

:)
dp

[dweller]

19. The answer

if only to shamelessly bump my own post back up...

i put the socket on a 2 ft long breaker bar and then stand my skinny 135 lb body on the bar at ~1ft and think heavy thoughts. That usually works.

mission accomplished.
dp