Shudder when making sharp turns in parking lot

subaru
impreza
transmissions

#1

In the last couple of months, my car has started shuddering when I’m making sharp turns in parking lots. It got worse so that it was less sharp turns and not limited to parking lots.

Mechanic replaced a front axle and the rear differential. The problem has lessened but not gone away. Mechanic has no idea what to do next


#2

This is one of the MANY problems AWD systems can encounter…Try changing the fluid in the center differential. Subaru might have a trick additive or “special” lubricant to cure problems like this…


#3

You need a Subaru mechanic.

How old is your Impreza? Does your car have an automatic or a manual transmission?

Manuals use a viscous coupling between the front and rear wheels. Replacing the front differential fluid sometimes helps reduce the binding between the front and rear wheels.

Automatics have a transfer valve and clutch pack. When the transfer valve wears, which it does, it cannot reduce pressure on the clutch pack and the system binds, resulting in the shuddering you are experiencing.

The cure for this is a new valve and clutch pack. They are located in the rear of the automatic transmission. Figure about $700-800 to repair this.

Ignore it and you risk internal transmission damage, which is even more expensive to repair. A temporary fix is to install a fuse in the FWD receptacle under the hood. This will disable the AWD system and you’ll have a FWD Subaru until you get the transmission fixed.

Now, which transmission does your car have?


#4

Impreza is 1997 model, bought in 1996. Automatic transmission.


#5

Spoke with mechanic, who says this one didn’t have a clutch pack. But then, he kept talking about the rear end. Where would it be?


#6

Trust me–mcparadise knows more about this than your mechanic apparently does.

The clutch pack–IIRC–is quite small, so it is possible that he has not noticed it–especially if he is not intimately familiar with the “anatomy” of Subarus. I think that you need a new mechanic and I am firm in my belief that you need to have the clutch pack/center viscous coupling replaced.

Incidentally, this component is damaged by running the car with tires that are not properly matched, so I would suggest that you make sure you have a set of 4 perfectly matched tires installed right before you have the clutch pack/viscous coupler replaced. Otherwise, you will need to have the same repair done again in a few months.


#7

No replaceable fluid in a center diff on a Subaru.


#8

Insert the AWD defeat fuse in an automatic Subaru. Hopefully it is labeled. If you have the owners manual it will be described likely in the spare tire section.

If the shudder disappears it is your clutch pack.


#9

Now I’m SURE you need a new mechanic. ALL automatic Subarus have a transfer valve and clutch pack. They wear out over time and require replacement. Unevenly matched tires will accelerate the wear.

If your mechanic doesn’t know about this he shouldn’t be working on this car.

The valve and clutch pack are located in the rear section of the transmission, as I said in my first reply.

PLEASE find a mechanic who understands the Subaru AWD system before someone makes things worse than they already are.


#10

TO: MCPARADISE-

I missed some of your replies (I anticipated the system would email me.
Took car to Subaru dealership 90 miles away today: diagnosis: new front axles will vibrate for awhile until they (they didn’t use the phrase “are seated” but that’s what I got.) Oh, and there are mismatched tires. Replace the mismatched tires - that should take away most of it. In the interim, they put in the AWD defeat fuse.

Shudder gone. Took car to my local tire place, 2 more new tires (replaced the others prior to a recent trip.)Removed AWD defeat fuse: Return of SHUDDER!

(My apologies: I forgot to speak to the dealer of the clutch pack.) Will call the dealer in a.m. and politely “beat them up.”

AM EXTREMELY GRATEFUL for the insight. Is there a politically correct version of Butterfly McQueen’s “Massa! Massa! I don’t know nothin’ 'bout no [clutch pack]!” I think I know enough about automotive mechanics to hurt myself.


#11

Mismatched tires + automatic Subaru + high miles = new clutch pack unfortunately. It is a wear item that typically lasts the lifetime of the vehicle with reasonable care taken with tires.

The Manual transmission Subaru AWD is uses an elegant simple mechanical AWD that has few issues and uses a center differential instead of clutch pack.