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I'm a geneticist during my day job (plant biology and education) and occasional Saab mechanic at night and on weekends. When I undertake a relatively major repair (major to me) I try to post my experience here at Saabnet in hopes that others of similar talents and ambitions might benefit both from my mistakes and my successes.
Last Sunday it was front shock replacement. The chassis and suspension is that of a '93 900 NA 3-door. The engine is from another '93 900 and the 5 speed is from my dearly departed '88... but the chassis had ~200k mi on the clock when I took possession of it a few years ago. Unfortunately I did not have anything in the way of service records so I can't say when the existing shocks had been installed; all I new was that the lower mount bushings on both front shocks were shot-- the PS having nearly disintegrated, the DS a bit better but nonetheless seriously out of round and depleted re: rubber especially on the bottom side of the mount. The net result was that the car handled rather poorly-- not horribly, but I don't drive her very hard. Much worse was the rumble made by the front end when passing over even the slightest bump in the road. RR tracks were the worst, but even seams in the pavement translated to cabin noise that could make passengers a bit leery of riding much more than a short distance.
At the recent holidays I decided to gift myself a pair of Bilstein HD shocks to complete R&R of the front end (ball joints, tie rod ends already done). They arrived shortly after New Years, but it was only last weekend that I found the time and drive to tackle the job. I'd like to think that the delay was all about other priorities, but I will confess that there are so many horror stories on this site of shock jobs gone awry-- from needing a special tool to cinch down the top mounting bolt, to having to put a torch to the lower bolt, to breaking the lower A-arm mounting stud-- that I kept putting it off. While I could ill-afford being without the car if some worst-case scenario came to since it's my daily driver, I finally bit the bullet and dove in. The following are my experiences and observations. I apologize for the length of the post but, hey, that "back" button is just a click away.
Preparation: The shocks (P/N BIL 24-181501) were obtained from an online source (URL available upon email request) and cost $165 for the pair. I scoured this and other sites to learn what others had experienced and one tip was recurrent: hit the lower shock mounting bolt with penetrant at least a couple of times in advance of the task. I took this to heart, putting the front end up on jack stands on Saturday, removed the front wheels. and doused the nuts with PB then and again on Sunday morning.
Sizing up the job Sunday afternoon and starting on the PS, I used an impact wrench with 11/16" socket attached to a 3" 1/2" drive extension to go at the nut on the lower shock mount nut. Happily, it spun right off with the nut jammed in the socket and the washer dropping harmlessly to my garage floor. I'm glad I kept track of both, as replacements are not included in the Bilstein package.
As noted above, the PS lower shock bushing was pretty much toast, with absolutely nothing left on the bottom side. That left the A-arm mounting bolt firmly lodged against the loop at the bottom of the shock and I figured there was no way that shock was going to go easily off the mount, so I used the floor jack to unload/raise the suspension, placing the lifting head beneath the lower ball joint. I gave it a few pumps until the stud was about centered in the shock's circular bracket. With just a few taps the shock came off the lower mount. YAY!
Now came time for the scary part: how to "disengage" the upper mount from the shock tower. This site is rife with all manner of approaches, from using a special tool to remove the upper nut to using a cut-off wheel to shear the shock shaft, to bending that shaft repeatedly in and out of the wheel well until it snapped. I opted for the latter. It ultimately worked but it took a hellofa lot of swings at different angles before she finally let go. (Tip: I partially replaced the nut on the mounting stud to avoid bunging-up the threads during the back-and-forth pulls). At one point I used a Dreml to hack away at the lower bushing at the shock tower to give the pulls a little more room but I'm not sure it made much difference. In the end the shaft broke and, as advertised, the upper remnants lifted easily out of the shock tower as accessed from the engine bay.
I cleaned up the smooth part of the A-arm mounting stud with a bit of emory cloth, lubed the lower bushing on the replacement shock with a dab of Dawn detergent and proceeded to push it onto the lower stud. It wasn't going on easily, so I looked through my socket set and found one (30 mm, 16 pt) that mated nicely with the metal loop of the shock and I tapped it home. I re-used the washer and nut that I had removed earlier to hold all in place and then went about getting the top of the shock through the mount tower. I used a pry bar levered between the coil springs and the top of the shock (using the mounting nut to protect those threads, too) to compress the shock to a distance ~3-4" beneath the hole in the tower. After a couple of failed attempts I was able to compress the shock, twist off the nut, and then guide the threaded portion smoothly through the port in the shock tower.
A possibly important detail here: before attempting to cinch the top bolt, I removed the jack from beneath the lower A-arm assembly and replaced the PS wheel to (re)load the suspension. From my prior researches and from common sense, this may help to ensure that the upper threaded portion of the new shock shaft is fully through the tower and the shock itself is almost fully seated.
After installing the upper bushing and washer, I twisted the upper mounting bolt on down to the nylock by hand-- ok, by finger, there isn't much room to maneuver over there. [Another tip: have a magnetic part retrieval tool at hand.] Joining a socket attached to a couple of extensions I was able to get a pretty good shot at straight-on. It's hard to do because the power steering reservoir and some portion of the cabin ventilation/AC parts-- not to mention various electrical wires-- are in the way. I tried at first to use a nuckle down near the socket to ensure a good square fit, but the additional pivot point provided by the nuckle actually seemed to make things worse, so I ditched it and went for "close". I put the impact wrench to the assembly and, voila, the nut cinched down nicely past the nylock. The new bushing aligns almost perfectly with the circumference of the retaining washer; I gave the nut a couple more pulses with the impact wrench to tighten it until the bushing just bulged beyond the washer.
Assuming that the work at top was done, I returned to the lower mounting bolt and here's where things went wrong. Recall that I has replaced the washer and nut on the lower mount to hold things together while I went at the top. Hoping to finish the job properly, I turned to the Book of Bentley and found the torque specs for lower shock mounting nuts: 66-74 ft-lbs. I whipped out the 1/2" torque wrench, dialed it in, attached the socket and started cranking. I'd had the nut pretty tight before, but who knows what 66-74 ft-lbs feels like? So I waited for the 'click'. It didn't come. There was a brief period where successive tightenings seemed like the 'click would be coming soon, but it never did. Soon the resistance faded, it was actually easier to turn the wrench thatn on previous throws.
I thought "Crap, I sheared the A-arm stud and it's probably just spinning within the bushing". I took some touch-up paint in order to paint a stripe across the end of the stud, reasoning that the mark would rotate if the stud was actually broken but it stayed put. My guess is that the nut found a section of threads that had been beaten down by the many miles of bushingless driving and was simply not finding traction. It also wasn't coming back out but, satisfied that all was reasonably secure down there, I called it job done. Huzzah!
In re: the DS shock replacement-- pretty much the same story, but more Dreml ("More Cowbells!"). I yanked on that shock until my arms were exhausted and still it wouldn't break. I used the Dreml with a carbide boring tool to cut a clean and free segment of the lower-upper bushing away and slipped the ramainder off the shaft-- no help. The old shocks had a metal cap at the top that had to be removed unless the shaft broke above its retaining ring. I ended up using a cutting wheel to make slots to the center of the cap,vise grips to remove the wedge of material, and then a large screwdriver to spread the gap in order that the cap could slide down the shaft. I then used the Dreml to score a pretty substantial cut into the shock shaft, a couple of tugs and she was a goner.
Repeated same compression/guidance move as described above for PS and moved topside. I dropped the DS of car off of jack stands and moved the radiator expansion tank (one bolt, easily done, and no coolant spills involved, just get it out of the way) in order to get access to the DS upper shock mount. This too went pretty smoothly, the mounting nut turned right on through the nylock band and I was able to flatten, slightly, the upper upper shock bushing. I went back to finish tightening the lower mounting bolt and this time relied solely on my intuition to determine how tight was tight enough-- it's pretty frickin' tight.
I took it for a short test drive Sunday night, mainly to be sure that the whole assembly wouldn't come undone. Today, Monday, was the first opportunity I had to really gauge the impact of the repairs and all I can say is
OMG!
It's like driving a different car. Nearly all of the road noise that I used to assume was the price of driving a 20 year-old, 200k+ mile car are gone. It handles like a dream, I'm sorry I waited so long to effect this (in retrospect) simple repair. I'm not endorsing Bilsteins in this post-- I don't have the data to claim that the end result attributable to that particular shock versus an alternative brand. Hell, for all I know, I could have gotten away with replacing lower shock bushings and achieved the same satisfaction at the end of the day.
But I'm drivin' on Bilsteins, baby, and it sure feels good!
Thanks to all whose ideas I've poached and especially to RS who was kind enough to give me some advice and encouragement in advance of the job.
Scott
posted by 68.187.92...
, Wed, 20 Feb 2013 12:00:31
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