Jump to content
Ultimate Subaru Message Board
subynut

Strong low frequency vibration in floor at slow speeds

Recommended Posts

The PandaWagon has developed this low frequency vibration below 15 MPH. It's most noticeable under acceleration, but if you push the clutch in and let it roll, you can still feel it. Kinda a thump thump thump kind of sound in the floorboards. Doesn't matter the gear. Once I'm above 15, it's smooth not one hint of vibration- even over 80. Last time I had it out, I went on about a 200 mile drive. It was fine till about half way through the drive and it showed up again and as I worked my way home, the shake was getting really bad. At one point, the shake was rattling something up front - a dull metallic sound. Again, only below 15 MPH.

 

I've always had a ever slight vibration from the rear on take off for the last 10K miles. Especially when loaded. I figured it was the rear LSD. Well, it's gotten really bad in the last 3 or 4 weeks.

All the axles have no bad boots and are quiet. I've felt the drive shaft - no play in the u-joints.

 

I've been searching around looking for similar symptoms. So far, this is what I need to look at:

 

Axles

Drive Shaft

Rear Diff

Transmission? (btw it's a FT4WD 5 speed)

Engine/Trans Mounts

Rear Diff mounts?

Wheel bearings have no play

 

Trans is about a half quart down, could that cause it? I'll be topping that off shortly.

I'm planning on changing the fluid in the rear diff, if that makes no difference, then I'll drop the driveshaft and check if there is a seized u-joint. The engine mounts are good, not sure on the trans mounts though. From reading some of the other threads around here, it could be a DOJ. I can try swapping sides to see if that makes any difference. But it's still there when power is not applied, so.....maybe not?

 

anything else I should check?

 

Thanks

Share this post


Link to post
Share on other sites

I had the rear brakes apart Saturday adjusting the parking brake. They looked good. I have not looked at the fronts yet. However, the vibration is not affected by braking as far as coasting vs braking.

Tires are worn, but no signs of funny wear. I rotated them a week or two ago, vibration didn't change.

 

Vibration is not felt in the steering as far as it wanting to swing left or right. But there is the same shake as I feel in the floor, just significantly less pronounced. I had my brother drive the car while I felt around and it is strongest in the rear.

 

 

If a wheel bearing is going, can it be quiet at highway speeds but shake at very slow speeds? Just another thought. The rear wheel bearings are a number of years old and have seen many races and many a high speed run. Still, I would have thought I would have felt that when I tried to wiggle them when I was working on the brakes back there.

Share this post


Link to post
Share on other sites

You know.....come to think of it, I thought I heard a whistle coming from somewhere around the car when I had it up at highway speeds Sunday. Maybe it wasn't a whistle, but a squeal? I better check that drive shaft! A U-Joint can do that! It did on my F350 and they didn't have any play in them either.

 

I have some wrenching to do!

 

I'll report back later.

Thanks guys!

Edited by subynut
  • Like 1

Share this post


Link to post
Share on other sites

I put her on jack stands, and let her run at idle in 3rd gear. I actually had to lock the center diff in order to get the rear wheels to spin consistently - open center diff FTL :(  I also noted that the right front tire always spins while the left front hardly ever spins. Both sides spin freely by hand with no problem. Could just be the open diff in there. Or.....dragging brake?

The rear of the trans is bouncing around quite a bit. Bad trans mounts? They don't look torn, I'll lift the trans off the crossmember with a jack to really tell.

I also discovered where I had ran the parking brake cables for the rear ebrake, they are rubbing on the drive shaft. I also found the metallic sound I heard was coming from the drive shaft rubbing on the glass pack - There's a little notch in there where it's slowly rubbing through the glass pack. :/ Gonna have to have that fixed.

Next question: Is that the shake I'm feeling? When I had the back half of the driveshaft out to relocate the cables, I checked the u-joints - felt alright, no tightness or sloppiness in them.

Hmmm....

 

More to check tonight.

Share this post


Link to post
Share on other sites

To check the bearings, grab the top of the tire and push/pull hard towards and away from the car.  If you get the klunk klunk sound, you need new bearings. There should be no play in the wheel when pushing or pulling on the tire.  You can do this with the car on the ground.

Share this post


Link to post
Share on other sites

Found it! Front U-joint is seized. And here I thought it was the middle one since that was where all the vibration was coming from! Now, to find a new one. So far, the dealer is useless. Vin number doesn't match anything, therefore, they can't help me. :angry:

So, I'm gonna see if somebody can overhaul it. Meanwhile, I may have to make a trip to Tucson and find a used one to get me by.

This last one lasted about 30K with RallyXs, AutoXs, road trips, daily driving duties, and a number of top speed runs.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

×