strange 'Thump"

Grasping at straws here. Last fall, Nov 2012, after a aggressive drive home I broke some stuff. I did i nice clutch dump around the corner and a sweet launch. Rubber...smoke

I managed to break 2 out of the 4 bolts that hold my pulley onto my BHJ damper, second time I've done this. No problem, put it all back together again.

So I get about a block from my house and there's quite a sudden, single THUD sound. It felt like someone dropped a small body into the truck. I thought something in fact had fallen, sub box or something I forgot was in there.

The engine didn't stutter or backfire, brand new roads that month so it wasn't that.

Turned around and parked it, hasn't moved since. I did have a look underneath though before it snowed and nothing stands out. When I did the work I only had the front of the car jacked up, thought it might be the suspension settling? I'm just wondering if I broke something in the drive train I can't see.

Was it a stock stamped steel crank pulley the bolts broke on ?

David

I know this may sound silly....but was the trunk maybe open? All it takes is a little uneven road and it'll come up and "Thump" down. If it comes down hard enough it can close the trunk, thus never being able to be tracked.

Just a thought.

Tom

I like the trunk theory but I don't think so. Since I was accelerating I don't think it would have popped up. I did seem to come from the back though if I'm honest.

I've got the billet power pulleys from SCP and stainless bolts.

my cougar would thud hard in the rear sometimes after hard cornering and drifting, it turned out to be bad U joints...

spetz01 said:

I like the trunk theory but I don't think so. Since I was accelerating I don't think it would have popped up. I did seem to come from the back though if I'm honest.

I've got the billet power pulleys from SCP and stainless bolts.

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Never heard of billet power pulleys...are those underdrive pulleys with a zero balance crank pulley ? Asking because you should not be breaking bolts on the crank pulley no matter how hard you are accelerating.

David

David Neibert said:

Never heard of billet power pulleys...are those underdrive pulleys with a zero balance crank pulley ? Asking because you should not be breaking bolts on the crank pulley no matter how hard you are accelerating.

David

Click to expand...

Agreed. My first thought on the BHJ is he needs to tap the holes deeper or get new bolts of shorter length. As Far as the thump goes. Nothing beats looking. Jack it up and and start wriggling stuff. Use good jack stands and shake the piss out of it to be sure it does not fall.

Ya its the BHJ damper from SCP and an aluminum pulley. I did use shorter bolts after I broke the original ones the first time.

I did put new universals one the drive shaft when I had it all apart. They should only have a few thousand KM's on em.

This just all reminds me when I first put bigger rims and tires on it years ago. I heard a bang, found out later I broke the front passenger spring.

I've got 2" dropped Eibachs now.

Thanks for the interest guys.

Finally got her up on stands, and spent some time having a good look.

Nothing seems out of place or broken. I even put in first gear while it was up, nothing seems wrong. I guess the thump was settling from being up?

I for sure will need to do some work on the rear end. Half shafts boots are all messy and grease is spread all over.

To the OP. Just an FYI. I read your initial post on this thread. It is never a good idea to dump your clutch while going around a corner. You can cause quite a bit of damage to your traction lok unit in the differential, especially when making right turns. Lefts aren't real good either but since the radius on a right turn is tighter it really puts quite a bit of stress on the traction lok unit.