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Discussion Starter #1 (Edited)
2008 Whiteline Rear Subframe bushings (W0598)

Install and Impressions
The W0598 rear subframe bushings for the 2008 are inserts designed to keep the rear subframe from moving around during cornering and acceleration.
The 2008 Impreza has a redesigned subframe that uses 4 large bushings inside a large metal carriage to locate the rear end of the car. The entire rear suspension and rear differential is attached to the subframe. The bushings that are in the mounts for the rear subframe are made from a very soft rubber and have many voids in them for added comfort and reduced NVH for street driving. However, for performance oriented driving, the softness of the bushings create vagueness during hard cornering and clunking during launching and hard shifting. The purpose of the Whiteline Rear Subframe Bushings is to firm up the stock bushings to rid the car of vagueness during cornering, reduced clunking during launching and hard shifting, and to increase throttle response.
Install
Install Time: 1 hour
Tools needed: 14 & 19mm sockets, ratchet, 3”extension, torque wrench, jack, jack stands.
The rear subframe bushings are inserts that fit inside the stock bushings as seen in the following picture.

This is an easier method of install as opposed to a full bushing replacement and less expensive. The basic concept is to simply insert the whiteline bushings into the voids of the stock bushings.
To start, raise the rear of the car with a jack under the rear diff and support the car on jack stands for safety. There are four locations with large bolts that we are looking for that contains the bushings we are interested in. Two are in front of the rear suspension and two are behind it.



With the jack still under the rear differential, remove the four large bolts (19mm hex heads). The front mounts also have two 14mm hex head bolts that need to be removed.



After removing these bolts the entire rear subframe will be free to move around. Slowly lower the jack to allow the subframe to lower. The front mounts will drop about 4” while the rear will only drop 1-2”. This will give us the room to insert the bushings into the mounts.
Grease up the bushings to ease insertion (watch out for that gutter).


Once the bushings are lubed they can be inserted into the mounts. The longer bushings go in the top while the shorter ones go in from the bottom. Make sure attention is paid to the location of the slots and holes in the bushings to make sure you are inserting them properly. You may want to use a dead blow hammer to “massage” the lower bushings into place. Slide the upper inserts into the stock bushings as far as you can by hand. We will use the jack and bolts to help move them into place fully.



Insert the four lower bushings first, followed by the two forward upper bushings. Once you have these six bushings inserted, move the jack to the front portion of the rear differential (see pic below). The metal plates above the rear bushings will not be reused.


When the jack is positioned as shown in the picture above, begin to operate the jack. This will help to push the upper insert bushings in the front into the mounts and will widen the gap above the rearward mounts. Space is tight above the rear mounts and it will take some time to get the bushings into place, but they will go. Once they are started, move the jack back to the original position at the rearward end of the rear differential and jack into position such that the mounts are snug, but not too tight. You will need a bit of wiggle room to move the mount around to get the large bolts back in.
It is now time to insert the large bolts. There is no real trick to this other than to make sure the holes in the mounts are properly aligned with the holes in the frame rails. It is important to get the bolts in straight and to make sure they go in a few turns by hand first. They are VERY easy to cross thread if not lined up properly!!!!! Should they become cross threaded, the bolts are M14x1.5 thread.
When all bolts are finger tight, move to the tools to tighten them to spec (70 ftlbs).
That’s it!!
Impressions
Upon driving the car, a greater sense of connectedness was immediately felt. Handling felt more responsive in the rear and the suspension reacts better to quick transition. The clunking on launching is greatly reduced over previous conditions and clunking on hard shifting is all but gone (keep in mind the car also has the Whiteline rear diff bushing inserts). A quicker throttle response was also immediately apparent.
As with any upgraded bushing install, a bit of increased NVH is expected. The noise caused by these bushings is noticed upon throttle application and sounds like a low rumble, but is very quiet….almost imperceptible. As the RPM’s increase the noise increases as well, but nothing more than would be expected with an upgrade of this type.
Overall I am very pleased with the performance value of these bushings. For a few dollars and an hour of install time, the performance increase is great. I can honestly say that these bushings are on par with a sway bar upgrade in terms of perceived performance benefit. They really do change the performance characteristics of the car for the better!!!
 

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1) When realigning everything, did you have any problems making it work?
2) On a tedious scale, where would this be from catback to your holy grail shifter bushing set?
 

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1. Haven't realigned it yet as I have some more mods coming for it. (coilovers)
2. These weren't too bad really. An hour would be plenty of time, just make sure the bolts don't get cross threaded. I had problems with one and had to clean up the hole with a tap to get the bolt to go in smoothly. The most difficult part is threading the bolts straight after inserting the bushings.
 

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I did this today. Started out fine had to keep playing with the the jack to get the Subframe to lower and couldn't get the Top Bushings to sit down til i had the bold in and was tightening it. I haven't noticed much difference other than some noise which isn't bad But i haven't done any hard launches or hard cornering either.
 

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In case you crossthread any of those giant bolts like I did, the Subaru part number for them is 901000343.
 

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In case you crossthread any of those giant bolts like I did, the Subaru part number for them is 901000343.

Yeah, I managed to do that myself, I must have rubbed the bolt against the subframe or it had a burr or something :(

Very Traumatic experience for a noob like myself :p
 
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