rear bumping sound/vibration ?

#1 08-21-2002, 03:50 AM

Hi,

Something nasty (I think) has just started to happen with my 94 Pearly...

When I make tight turn, especially say when locking the steering wheel all the way either way, when parking for example, the back literally bumps as the wheels rotate...

I took the car to the Subaru dealer, where they had a mechanic do a roadtest. He said that it's probably the transmission - when turning tightly the computer is telling the transmission to apply most power to one side (i.e. the difference in turning speed of tires on either side is greatest) - since this is when the knocking happens, he thinks it's the transmission getting stuck - could be the solenoids, could be dirty fluid, etc.

What do you guys make of this?

I've also noticed that my power steering is getting very noisy now, I thought it may be related. He checked the oil and it hadn't leaked, and there was a lot available - which he said meant there can't be a serious problem with the power steering??

Your input is greatly appreciated!

CHeers,
Pete.

#2 08-21-2002, 06:54 AM

The 'bumping' problem which you're referring to is actually called 'AWD binding.' The transfer clutches are staying stuck at 50/50 torque split, so there is always equal power to each wheel. When you go around corners there is no play allowing for the inside wheels to spinn less and the outside wheels to spin more. This causes your car to literally 'bounce' around corners. It could be one of the Duty Solanoids, or it could be worn transfer clutches. An easy way to verify that this is actually the cause of your problems is to run the car a little with the FWD fuse in place. If the problem is fixed, it is your AWD binding.

As for the steering, I recommend you replace the O-ring between the power steering tank and the pump. This can deteriorate and allow air to leak into the steering system without any fluid leaking out. The steering system fluid is under vacuum, so when there is a leak in the system air leaks in but no fluid will leak out. The power steering o-ring is a common problem. Check the how-to locker for information on replacing this. (Very easy!)

Now that I've done my community service for the day, I'm gonna go shopping!!

-Mike

#3 08-21-2002, 08:17 AM

were exactly goes the FWD fuse??

vkykam · #4 08-21-2002, 09:56 AM

Under the hood, next to the coolant reservoir, you'll see the fuse panel. The top of the cover will have indications as to where to put the fuse. It's pretty self explanatory.

If I remember correctly, it's the bottom right side, with a 10A fuse.

VK

#5 08-21-2002, 03:34 PM

Thanks for your explanation Mike - I'll try the FWD fuse suggestion (I'm in Australia but I assume my car will have this feature).

Also, now that you explain about the power steering air 'leak' - I think the mechanic mentioned that as a possibilty, but he never mentioned the words O-ring, I think he just called it the 'seal'?

As you can probably tell, I don't know very much about cars, let alone the SVX. So thanks again!

Cheers,
Pete.

paddlesnz · #6 08-21-2002, 03:51 PM

Non-US SVX models DO NOT have the FWD fuse feature.

There is a similar fuse position but inserting a fuse will lock the car in a 50-50 split and this is NOT recommended for normal driving.

paddlesnz
Japan

vkykam · #7 08-21-2002, 03:51 PM

Oh. I don't think the Aussie cars have the FWD, as they have a different tranny and TCU than the North American cars.

There was a discussion about this by oab_au, I believe, a month of two back.

What are the tire conditions like? Are they rotated regularly? Do they have the same tread depths? Are all 4 the same model?

VK

#8 08-21-2002, 04:09 PM

Good point about the tires. I neglected to mention that. That was the first thing the mechanic looked at...

They're all in excellent condition, all the same, rotated every 3 months...

I'll have a look for 'FWD" marking in the fuse box nevertheless...

CHeers,
Pete.

oab_au · #9 08-21-2002, 04:43 PM

Quote:

Originally posted by amuse
Good point about the tires. I neglected to mention that. That was the first thing the mechanic looked at...

They're all in excellent condition, all the same, rotated every 3 months...

I'll have a look for 'FWD" marking in the fuse box nevertheless...

CHeers,
Pete.

Hi, Peter,
Don't go looking for the "FWD" fuse as it is marked "DIFF LOCK" on our model and works opposite to the US fuse, in that our fuse locks it in 50/50 drive. The US fuse puts it in front wheel drive.

It does not have the same AWD binding problems as the US model.

I would go for the O ring under the power steering pumps tank.
A cheap fix.

Harvey.

#10 08-21-2002, 05:57 PM

I was driving down rt 95 today outside of wilmington, and i yelled out "Ohh S**t!" when I remembered the difference between the RHD and LHD svx trannys. Oh well, at least you guys caught it!

-Mike

#11 08-22-2002, 05:15 AM

So Harvey, are you thinking the bumping may be power steering related after all?

Thanks,
Pete.

#12 08-22-2002, 11:28 AM

I'm experiencing this AWD binding as well. Mind you, i'm still driving with snow tires, and this only happens when the steering wheel is turned fully for U-turns and whatnot. It sounds like a loud bass note. Pretty cool sounding actually. It doesnt bother me, but is it something to worry about?

oab_au · #13 08-22-2002, 05:27 PM

Quote:

Originally posted by amuse
So Harvey, are you thinking the bumping may be power steering related after all?

Thanks,
Pete.

Could be Pete. Do you feel it in the steering wheel ? If so it's the O ring.

To be sure put a 10 amp fuse in the DIFF LOCK slot in the fuse box under the hood. This will lock the center diff into 4WD, then see if this, is the same as you feel.?

Harvey.

oab_au · #14 08-22-2002, 05:36 PM

Quote:

Originally posted by Ticallion
I'm experiencing this AWD binding as well. Mind you, i'm still driving with snow tires, and this only happens when the steering wheel is turned fully for U-turns and whatnot. It sounds like a loud bass note. Pretty cool sounding actually. It doesnt bother me, but is it something to worry about?

Well in your model you, put the fuse in to turn off the rear wheel drive, to see if the problem goes away.

Harvey.

#15 08-22-2002, 05:37 PM

I'll get the Oring replaced either way, but the it's actually the whole rear of the car physically bumping up and down as the wheels rotate that I'm experiencing, and yes it happens only when turning very tightly and moreso when tiurning Right versus turning left....

Thanks again for your input!

Would you have an estimate on how much replacing an Oring would typically cost?

Cheers,
Pete.