: Fixed my "Corsa rattle issue"



PJGross
06-08-12, 07:37 AM
I, like some, have had my Corsa cat-back rattle like crazy if I went through water puddles. I had first thought it was hitting my BMR cross bar, so I lowered that. I then saw/read that it was probably the driveshaft. I would get loud bangs over the biggest bumps.

The front of the resonator welds went (known issue) so Corsa sent a new front section. Installing on the lift the guys showed me that the DRIVESHAFT bushing was very loose and the new piece put the pipes VERY close to the shaft.

The driveshaft bushing is not available separate so the OE answer is a new $1000+ 2 piece shaft.

My fix is something anyone could do.

The shaft bearing rides inside a ring of rubber. You just have to jack up the shaft to center it, then fill the lower part of the bushing with urethane (like windshield adhesive), allow to cure, and then enjoy the silence!

I happened to have some 2 component elastic urethane at home, so I used that. I didn't have the dispenser so I mixed by hand and applied by hand. I would only fill the bottom to allow more flex. Essentially my strategy was to have a "block" so the shaft would have to compress the urethane to go down.

It was a pain working between the pipes.

If you use a 1 component moisture cure windshield adhesive, I would let it cure at least a day before taking away the support for the shaft. Pics are tough but I'll attach them. My drive shaft was sagging very low in the rubber bushing. The adhesive just bridges from the outer metal sleeve to the inner metal sleeve. I used a primer to ensure adhesion but it really wouldn't be necessary. My 2 component material was cured in less than an hour.

I will load some pictures when I can resize them correctly.
This would be a very easy fix for sloppy OE driveshafts.

-PJ

PJGross
06-08-12, 10:17 AM
Here are the pics, first the sagging bushing, note the stretched, dryrotting rubber:
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Here is the bushing centered using a jack under the driveshaft:
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Here is the filled area. It is a little sloppy since I had to fill it with about 10 finger tip fulls b/c I didn't have a 2 component dispenser at home last night:
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I purposefully only filled the bottom and slightly around to the sides. I could get the shaft to bang laterally on on-ramp/off-ramps so I wanted a bit of lateral support. I wouldn't fill it all the way around as it would become much stiffer than probably needed.

Here was the tell-tale sign of the problem:
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For me, it really started as severe banging when going through big puddles. Then it was around sweeping turns, and whenever going over large bumps in the road.

I think this would be a great alternative to a $1000 drive shaft. I would use polyurethane instead of silicone. And I would suggest if using a one component moisture cure product that the shaft remain supported for at least 24 hours before removing the support. This will ensure enough curing to support the weight of the shaft. 2 or 3 days will probably be needed for full cure, as you only get about 4mm/day from the outside in. Windshield adhesive would be nice stiffness but I'm sure even polyurethane sealant from home depot would work.

JDB
06-08-12, 04:39 PM
I accidentally fixed that issue when Corsa sent me a new resonance section and I didn't line it up straight comparing left and right sides... so, it's not perfectly horizontal. Drove through some heavy storms recently and no banging (since the new section).

CadzillaTN
06-08-12, 05:20 PM
Good work. I love that windo weld stuff. 3m makes a tube that's about $25 at autozone. It's shore 65a and hardens into a nice flexible rubber but still fairly stiff... I filled the gap in my transmission mount with it and just last weekend made some cardboard molds and filled the voids in my cradle bushings in tandem with the diy wheelhop mod. I'm considering shooting the holes in my lower control arm bushings as well.

The only downside is the stuff is pricey for one tube. It starts to get hard when opened so there's a shelf life. If you do get some be sure to check the expiration date on the tube, the first one I bought was from 2010...the date should be months in advance of the purchase date.

PJGross
06-08-12, 07:35 PM
Just as an FYI, if you find a local autoglass repair shop, you can do much better on a tube of room temperature applied windshield repair adhesive. You can also get a small primer repair stick to prime metal/painted surfaces as well.

One other thing, you need at least a 12:1 caulk gun, typically 18:1 is preferred for manual application.

You were reading my mind on the cradle bushings and the rear diff urethane block. If you spray the area with white lithium grease, then caulk, you will get a cured chunk that won't stick to anything. Best to work in layers < 1/2" thick and wait 24 hours between applications to ensure reasonable cure time, though.

To save a partial tube, you can get a piece of Saran wrap, then gun out a just smaller than golfball sized wad of adhesive at the end of the tip. squeeze all the air from the Saran, and rubber band the Saran around the tip, burying the end of the tip in the adhesive. The adhesive is moisture cure, so the only way it cures is from the outside in. Saran has very low moisture vapor permeability, and with a large chunk of adhesive, the curing will take a long time to get through the wad at the end and down into the tip, ruining the cartridge. You can do the same thing with Silicone tubes as well.

-PJ

SevillianSTS
10-23-12, 09:56 PM
Is the windo weld supposed to get fairly hard? Seems pretty rubbery to me.

PJGross
10-23-12, 10:43 PM
Windshield adhesive is fairly soft, about shore A 60 or so. However, in a "block" and constrained by the surfaces it is sticking to, this is actually fairly stiff due to a decent modulus and tensile strength. Not sure what the EPDM rubber mount is, but they typically limit the mass (hollow or thin sections) so it acts as lower modulus and transfers less vibration beween parts. The polyurethane adhesive is higher modulus than the rubber and you will be adding a significant amount of mass, so even if the same hardness, it would take more force to move it the same distance as the stock rubber mount.

Bottom line is that it might seem pliable, but in a large mass bonded to two surfaces and constrained, it will greatly stiffen the part. The main force is in compression to get the driveshaft to bottom out and it will preven that from happening (after several days when it cures all the way through, you can test this out by going back under and hanging on the driveshaft to get it to move. :) If there was still too much movement for your liking, you could always fill the top as well. That would essentially double the stiffness of just filling the bottom since the top would have to stretch in tension at the same time. If you added the sides for a 360 fill, you would essentially create a solid mount.

I believe most of the polyurethane "inserts" you can buy are in the range of 60-80 shore A. When cured, these pourable 2 component urethanes end up with essentially the same cured properties, it is just the curing mechanism and adhesion capabilities that are different. Plus, you can use windshield adhesive upside down if you want to and it will stay where you put it. :)

I suggest going to a windshield repair shop b/c they won't rip you off like Lowes, etc. I would guess 1 tube should be less than $10 and they should give you a "black primer stick" for free if you ask.

-PJ

AAIIIC
10-24-12, 09:28 AM
I've never had issues with my driveshaft (knock on wood), but this seems like a good preventive maintenance kind of thing. I've got the car up on jack stands now, I'll have to take a look at my carrier bushing to see if it's degrading.