SLAM! WTF?? The trunk (boot) lid on my 2005 DB9 was just hammering closed. It’s been like that somewhat from when I purchased it 7 years ago, but recently it wouldn’t even hold itself open any longer. At this point it changed from a nuisance to a hazard. Reaching in for something and the boot lid comes down on top of you.
Like most modern cars the DB9 has two gas struts that are designed to help lift and hold the trunk lid up. Like a shock absorber they have seals, and the seals wear out over time. They can wear out just sitting never being used, the seal material gets less flexible and thus less effective. The gas precharge can begin to leak away reducing the force the strut puts out. The change usually occurs slowly over time and you may not notice it right away, but one day it will bite you and you’ll know.
I had a second symptom other than just the slamming on close. When I went to open my trunk lid it would bind up on the left side between the lid and body work next to the rear window glass. This was paint on paint contact. At first I thought it might be a failing hinge. I’ve since figured out my right side gas strut was still stronger than the left, and it was twisting the trunk lid upon starting to open, binding the lid into the body work. Crap. Nicked up my fresh respray.
The good news here is that the struts are simple to replace, and not very expensive at all. You can easily fit them yourself, and let me give you a few tips to get it done right the first time.
Gas struts are very popular and its no surprise Aston didn’t make a bespoke strut but rather outsourced the struts to a German company Stabilus. You can see it right on the labelling.
I had a solid look around the Stabilus website thinking I could potentially bypass Aston for the purchase, but I wanted to be 100% certain of the part number and spec’s of the strut before I went this route. Stabilus has a ‘Spare Part’ lookup tool, and it included the Aston Martin DB9 Coupe Trunk gas struts. It’s their part 3223YB.
I figured great, I can Google that and get one off Amazon. Not so much. I certainly found some aftermarket struts that claim to be the equivalent, but I couldn’t be sure. I wasn’t able to find an exact ‘spec’ sheet from Stabilus with the dimensions and most importantly the Force rating [if you find an official one, please contact me with it]. I have measured it and the important facts are:
- Length (socket center to socket center) – about 260mm
- Shaft Diameter – 8mm
- Cylinder Diameter – 20mm
- Stroke Length – about 100mm (based on what I can see on the old ones)
- Ball Diameter – 10mm
I still didn’t know the ‘Force’ the strut was rated for. Then I noticed the line right on the label:
0031TJ 0340N 247/17 BE14
I wondered if the 340N meant 340 Newtons. Manufacturers rate the struts in ‘Newtons’ (N) of force. For the imperialists out there 1 pound of force is 4.448 Newtons of force (i.e. 10 pounds – 44.48 N). So, a 340N strut would be about 76 pounds.
I tested both of the old tired struts and the new ones. The two old struts had the same value of ~42.6 pounds. The two new struts both measured ~67 pounds.
The old struts were down by ~36% versus new. Considering the two struts, that would mean there was ~49 pounds less of supporting force holding up the boot lid. Explains why it was slamming.
Since the new struts measured out at 67 pounds, that’s 298 Newtons (N) and this doesn’t exactly match up to the label if they were supposed to be rated for 340N. I wasn’t sure if that’s what the label means, but maybe these two new struts weren’t as strong as they should be [if you get a pair and do a similar measurement test, please leave a comment down below what you get].
This is an easy one. If you have a DB9 or DBS Coupe – you need two of Aston Martin part number 4G43-406A10-AC.
You can find them online at ScuderiaParts.com
This is a rare time when the Aston parts aren’t massively overpriced. I’d recommend that you pay the couple of extra bucks to get the Aston ones for peace of mind (and a neat logo). Saving $10 on a part you change every 10+ years doesn’t make a lot of sense (IMHO).
You need very few tools and supplies to accomplish this task.
- Small Flat Blade Screwdriver
- White Lithium Grease
- Masking Tape
- Lint free shop rag
One very important tool not in the picture is a HELPER. You need someone or something to hold the Trunk lid up while you remove the struts. You’ll see me use my shoulder and do it solo, but if you can entice your Sweetie or friend to help you for 10 mins it will be even easier.
Swapping both struts will take less than 10 minutes and is pretty easy.
I checked the official Aston Martin Workshop manual and couldn’t find any specific reference to removing the struts. Other procedures mention removing them, but as “remove struts”. No details.
Learn how the Retaining Clips Work
Each end of the strut is a ball and socket arrangement. To keep the socket from slipping off the ball there is a sprung metal clip that acts as a retainer. It’s a simple matter to release once you know these tips.
You don’t need to remove the clip entirely to release it. Doing that would create a problem actually, the clip is a witch to get reinstalled if you accidentally pop it all the way out. To release the socket so it can slip off the ball you only need to retract the clip a small amount. Do this by slipping a small flat blade screwdriver in the slot on the head of the socket (see photo). I strongly suggest you fiddle with this on the bench for a minute before trying it on the car. Figure out how it works.
Just inserting it that far is enough to retract the clips far enough. Here are pictures of the socket with clips out and retracted.
Lube the Sockets
The socket mounts over a ball, and the two things pivot under load. Having some lubricant (grease) in the socket will help. Inspect your new struts to see if there is a ‘dab’ [official measure] of grease in the socket already. If not, I’d suggest you put a dab of White Lithium grease in the socket. No need to spread it around, it will distribute as the ball inserts.
With the sockets lubed and tools in hand, lets get going:
- NOTE: Do only one strut at a time. Mike Potts (Aston2209) inspired me to tackle this task, and his article on this blog shows that the lid can over open if both struts are removed and can nick the edge of the rear window glass (ouch!). We can learn from this…..
- Use the Masking Tape and lay down a protective layer beneath the lower strut mounting point. You are going to be using a pointy scratchy screw driver under some load in this area, and if it slips you could scratch your nice paint. Some extra ‘just in case’ protection is worth the 30 seconds it takes.
- Open the trunk fully. This allows the strut to be fully extended and under the least potential load. This will make your job easier. Note that it will still be under load though.
- Start with the upper connection. I do the easier connection first as it will make doing the harder one (lower) easier.
- Slip the tip of your small screwdriver in the slot under the retaining clip.
- Make sure someone/something is supporting the weight of the boot lid. Not hard, just keep a hand on it, or keep your shoulder under it from this point forward.
- Push the upper socket sideways to pull it off the ball. Should move easily if the retaining clip is released enough. Just give it a push and it should pop off.
- Keep ahold of the strut with one hand now, and change your attention to the lower connection.
- Set the old strut aside (and keep holding up the trunk lid).
- Use your lint free shop rag and clean the old dirty grease off the two old balls.
- Use a bit of white lithium grease and lube the two balls.
- Installing the new strut we start with the bottom connection first.
- Orient the strut the same was it came off, with the cylinder portion nearest the top connection.
- Insert your small screwdriver blade in advance to retract the lower clip.
- Position the socket next to the ball and then press it over the ball with a gentle push. It should go on easily if you have the clips retracted.
- After it’s seated, remove the screwdriver blade and made sure the retaining clip springs back completely in place (flush).
- Move your attention to the top connection
- I’ve found there is NO NEED to insert the screwdriver for the top connection. You have good enough access to just apply a bit of extra pressure and push the socket over the ball. The retaining clips just spring out of the way automatically as you push it on.
- Just push it onto the ball until it snaps into place and make sure the retaining clip is fully seated flush afterwards.
- Remove the masking tape
- Wipe off any grease or finger prints on the shaft or cylinder to make it all shiny
- With the first one done, repeat the process on the side. Always do them in pairs.
With both struts changed out you can give it a test close. Near the top it should be absolutely holding itself up strongly. You should notice it being much more ‘floaty’ holding itself up for at least the first third of the closing stroke. [Mine didn’t just ‘hover’ half way open (I’m not sure it should), and if you check out Mike’s video of the process his seems to. Maybe his new struts were fresher/stronger and mine were old stock? If your lid hovers half way closed, please leave comments below]
In just 10 minutes you’ve cured this issue for another decade, and all for less than $100. Well done.
If your trunk/boot struts were worn out, it’s likely the other struts in the car won’t be far behind. There are gas struts that hold open those beautiful swan doors. If you find the doors are tough to open or fall back on you, those struts need replacing. Same for the struts that hold the hood/bonnet up. Check out my articles on change them here:
Like most tasks it might help a lot to see the process rather than just read about it. I’ve put together this video for you.