With reference to my previous posts in which I shared that I have replaced the MkI control are bushings, the strut mounts and bearings, install Bilstein HD struts, and replaced a ball joint all to no avail in eliminating the vague front end handling, I now share this:

I removed the lower halves of the bushings from the rear corners of the front subframe. The rubber was still bonded to the metal just fine, but it was hard to determine if the bushings were worn. Just for diagnosis purposes, I found some metal washers of the 50mm ID x 64mm OD dimension to install between the lower side of the subframe and the upper side of the lower halves of the bushings. With the bushings shimmed in this manner the subframe rear attachment points are clamped tighter. The result is that I can definitely feel an improvement in the handling.

I am pretty certain that the problem with the handling from 30,000 miles onward has been the fault of worn front subframe bushings. It has been very frustrating that the dealership service department and an independent Bosch service center have not been able to diagnose this problem for the past six years.

Recently, I was quoted a price of over $700 to replace these bushings and perform an alignment by the Bosch garage. They are assuming that they will have to drop the subframe to R&R the upper halves of the bushings. Is this correct, or can the subframe be pried down enough to exchange the uppers? Thanks!

 

Unless the entire subframe was not torqued correctly and was moving around. The front of the front subframe bolts solidly to the chassis (#3). There should be no movement. The rear bushing would appear to be for NVH reduction in the vertical plane only. There should be little to no stress on those bushings and they really should not go bad..

Poor alignment could contribute to vague handling as could issues with the steering rack and tie rods..Tires too..

<img src="http://images5.fotki.com/v63/photos/7/7305/776256/suspension-vi.jpg">

<img src="http://images7.fotki.com/v109/photos/7/7305/1232358/subframe1-vi.gif">

 

did he mean the top of the rear bushing of the front control arm? first, whty not just replace the bush, and second, there shouldn't be enough tolerance in there to do that...

 

He was describing the Rear "Front" subframe bushes...#4 here..

<img src="http://images7.fotki.com/v109/photos/7/7305/1232358/subframe1-vi.gif">

 

ah - that makes more sense, as does your response.

 

I'm guessing that the alignment shop must have messed with it and never torqued it correctly when I had my suspension done.

 

Like you, I thought that with the solid front attachment points there should be little chance for flex. However, the front attachment points (perches) formed into the pressed steel subframe stand up rather tall. So, I suspect that the perches flex under load. If the rear bushings are worn then the subframe is not securely triangulated to the body. Also, with the control arm rear pickup point very near the subframe rear attachment point, there may be quite a bit of lateral and longitudinal force on the bushings. All I know is that this car darts and hunts all over smooth but slightly "rutted" asphalt, it didn't so that when new, and I've replaced everything else (including the rack under warranty).

 

usually the cause of such behavior..

You're also describing a characteristic called Tramlining which is caused by this as well as other factors....The quality of the roads you drive can exagerate this, even on roads that "appear" smooth. Truck traffic subtly (sometimes obviously) alters the road contours.

Dunno.<ul><li><a href="http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=47">Tramlining discussed..</a></li></ul>

 

Thanks for the tramlining discussion link. That describes my car's symptoms pretty closely.

Does anyone know if the bushing uppers can be R&amp;R'ed without dropping the subframe?

 

But it's really not that hard. For a shop that knows how (i.e. taking care of the steering rack) it would only take an hour to swap out those bushes. The time is gonna be taken up in the alignment. When I do mine, I'm typically in for three hours if I'm moving the subframe side to side.

I dropped my subframe to put the front sway bar in. It was easier than twisting the sway bar in.

I'd be more inclined to think whoever did the steering rack replacement didn't torque the subframe bolts correctly. Not the first time that's happened to folks here. It really is hard to do going that extra 1/4 turn. As a result, you may have worn bushings since things could have been moving.