Good day!

Sorry for the delay, I've been busy with paperwork with my school starting soon and working.

It turns out that the sound was the transmission. I pulled the whole thing out and looked in the cover, and sure enough first gear was missing three teeth that made a whack/thunk sound once per revolution. Reverse was also missing half a tooth.

I've been calling up junkyards to find another transmission, and haven't had much luck. The lynnwood Pick-n-Pull has a rather odd specimen:

https://www.picknpull.com/vehicle_details.aspx?VIN=YV1AA8243M1453636

YV1AA8243M1453636

The website lists it as both a manual and automatic. As far as I can tell, the VIN number lists it as having an M58 five speed. To my knowledge the 50 series was never used for the 200 series. Do any of you know if this is the case?

Also, if anyone is selling an M47 in the Puget Sound region, let me know.

Thanks!

I don't envy you, Skorpa, odd sounds can be a bitch to track down in a car.

I once had a buzz on deceleration. I became convinced I had found it when I noticed that the medallion on the shifter vibrating. No such luck. The more I tried to isolate the sound, the more I thought I needed a trans rebuild.

Then, one day I happened to reach for the sunroof winder while the buzzing was in full crescendo. It was a harmonic vibration of the knob on the sunroof winder buzzing away at a certain frequency!

To say the least, I was relieved and I would have felt like an idiot if a couple astute mechanics had not also mistaken the sound as coming from the trans.

I'll save the story about riding around in the trunk of my first 240 for later. My sweetheart says that if I were to ask her to do that number again, now she would leave me locked in there.

All things are possible, but any time I have had a failed driveshaft support bearing, they have developed a whining sound at a repeatable road speed.

I assume you checked the u-joints while the driveshaft was removed. More than once for me, u-joints seemed good while in place only to be obviously queefed out once removed.

As others have said, if you have one of those dreadful over-the-axle pipes, check its clearance especially along the rear frame "rail". Volvo no longer offers the under-the-axle pipe and the last time I installed an OE Volvo, cat back kit, I remember I had to adjust the axle pipe after it started to knock (only on trailing throttle while making a left turn).

Life's can be a bitch: while I have a couple OE exhaust kits in my horde and Volvo does still honor their Lifetime Warranty on their replacement MUFFLERS, they no longer offer that unique over-the-axle pipe. So, have a mid-pipe break, install a cat back kit, in toto.

Please let us know how this shakes out for you.

Rich (near The Burgh)

If you put the car in reverse, firmly set the parking brake, and then give it some gas while starting to engage the clutch, you can replicate the same torque as that created by engine braking. It make it easier to pinpoint the offending engine/exhaust/chassis contact.

If the motor mounts are really shot might the fan be contacting the inside of the shroud?

Thanks for all the replies and suggestions, I posted this on Swedespeed and got nothing.

The exhaust could very well be the problem. About two months ago, the pipe connecting the mufflers rested apart and I replaced it with a new one. After I was finished however, I noticed that the exhaust seemed to move about more than usual, but it didn't hit. It was a month later, when I was returning from a 600 mile trip, that it started making this noise.

Now that I'm home from work I can get to testing all of your suggestions.

Really sounds like thinner metal, like a cracked aluminum heat shield above the cat. On some exhaust systems there's a welded collar at the base of the down pipe that can also break loose. Otherwise I agree with others about a broken/loose exhaust bracket.

Another thing to check for is a loose cross member, although that usually causes thunking, not vibrations, but can allow others things to get too close together. While you're under there checking the heat shield and shoving the driveshaft and exhaust system around to see if you can get metal to touch metal, do try tightening the cross member bolts as well as the trans mount bolts since the weight of the trans often makes it difficult to detect unless you can get it up on a hoist and get a pry bar in at assorted angles.

And welcome aboard. We rarely get anybody posting youtube videos of problems, terrific of you to go to that effort and make it a bit easier for us to make guesses based on our experience.
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Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now

I think it sounds like the exhaust system hitting something as well.

Perhaps you can reach under the car at several different places and see if you can force the (cold) exhaust pipe around and have it make contact with the body or chassis? The first muffler (resonator) is suspended on two rubber rings that will allow things to move around if one fails.

If a motor or transmission mount is broken engine braking could very well allow the engine and transmission to move around quite a bit. Those three mounts are what keeps the assembly in place, and losing one gives it too much freedom.

Randy
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Any twenty minute job is just a broken bolt away from a three day ordeal

Exactly the right spot. Welcome Scorpa.

If it hadn't been for the sound track, I would have guessed an exhaust manifold gasket leak, but now I'm leaning toward the motor/transmission mounting and exhaust pipe adjustment, because the rapping isn't holding a beat.

Makes you want to get a friend to strap himself under the car while you cruise the avenue. Friend might suggest you acquire or rent "chassis ears" remote microphones. But sounds like you're on the right track renewing those mounts and checking the exhaust pipes. Just wanted to say welcome.
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Art Benstein near Baltimore

Brickboard members are the most likeable, smartest, and best-looking people on the internet. [Citation needed]

Hi,

It’s just a guess and I mean, a guess, on this 5 second video, that it’s a tail pipe knock.
Sure sounds loud enough!

Check the bracket on the back of the engine/transmission area. It probably has a broken lower pipe strap or one of two or three bolts are missing from the bracket.

I’m surprised you do not have a buzz around three thousand rpms if this is a manual shift.

Another place to look is near the rear muffler. The curled in the exhaust pipe over the or under the axle can hit the body of the car on the edge of the pinch weld. It fits really close back there.
That is if it sounds like it’s more behind you than up by the seats.

And yes, weak motor mounts can let things flop excessively let alone bad rubber donuts used to suspend the exhaust system.

Happy hunting.

Phil

Yes, check engine and tranny mounts for cracks/damage. That is where I would look first.

Welcome to the board!
J
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Will I buy another Volvo??? We'll see....