IdahoDoug

So, I've had this clunk since buying the car 5 years ago. It's the center rear mount allowing the rear of the rear diff to lift and drop on clutch takeup. I don't drive it much and have adapted to it with gentle clutch takeup at first. However, my 16yo son hero worships this magnificent car and I've let him drive it here and there and will more this spring. So I thought I'd take a crack at something I wanted to try to avoid the hassle of replacing it so he'll get the satisfaction of driving the car.

I bought an aerosol can of black RTV at NAPA, and a chunk of rubber hose I could barely fit onto the nozzle. Yep, you know where this is going. There are two rubber ears on the worn bushing facing the rear that will block access. I used my soldering iron's cutting tool to slice the rear two off (one on each side). Then I used a small pry bar to move the bushing through its range up and down while firing about half a can of brake cleaner into and through it to remove grease and any grit. Just wash it out.

Then I used a heat gun on low for a half hour or so to dry it out - again moving it up and down to open cracks and gaps to dry them. Now that the entire fitting is warm, it was perfect in my cold garage to go right into filling the mount with RTV. I again held it up with the floor jack to maximize the opening up top and used the pressurized RTV and hose to fill the entire gap and let it flow down the sides a bit. You can push the rubber hose all the way through the gap and start filling and slowly pull the hose back through, leaving a completely full gap. It was the perfect density RTV. Flowed forward and rearward and came out both sides. Then I took slight pressure off the jack, which then squeezes a bit out, again ensuring the gap at the top of the mount is full between the worn rubber and the metal housing. A popsicle stick was then used just to wipe the RTV flat for appearance sake and I think spreading it fore and aft will complete the connection from the edge to the bushing for a nice load distribution. So the top half of the mount now looks like a solid hockey stick of RTV and the original bushing rubber is fully encapsulated. If you're in a warm climate then just leave it over night. I have an old fashioned incandescent light bulb trouble light tucked up there to keep it warm overnight to cure as its winter up here.

Tomorrow I will take all the pressure off it, then use a prybar to gently pry the diff downward, opening up a gap on the bottom of the rubber and fill that. It worked so well so far that I can tell already this is going to be a win. No more diff clunk by Monday. I will report back to confirm, but I've been snickering to myself all evening about how easy that was. I probably have $10 in the fix and less than an hour. Be sure to buy a foot of the rubber hose as you'll need 6" for the top, then throw it away as it will be full of RTV. You'll use the other piece of hose for the bottom, then the 2nd popsicle stick to level the RTV if you want to. I think its important to let it fully cure so you don't tear it loose accidentally doing the bottom half. The liberal brake cleaner use will provide good bonding. I suspect it would still stop the clunk, but why mess with it if you can leave it for a full 24 hours, ya know?

If one day you opt for a new bushing, it may add 15 minutes to push the RTV out with the old bushing - a non event IMO.

Doug

IdahoDoug

So, I completed this and the car sat for a couple days before I had a chance to pull it out of the garage for a spin. Perfect. No clunk at all. I filled up the bottom half and did the same thing. I will make one suggestion. Overnight, my hydraulic jack lowered, so I did not get the full benefit of fresh RTV on the top half - some squeezed out. Mind you it's still solid and the gap is full (in fact more excess squeezed out). But I had planned to move the diff back up to its original center in the sagging rubber mount. Instead, it is in the sagging position, but the mount is solid again. So I'd use a mechanical jack, or brace it in the up position so the typical jack creep does not affect things from exactly where you want it.

Anyhow, cheap and fast hack for the rear diff clunk!