Clunk on moderate to hard take-off from standstill

[1970DCH]

Hi Eveyone - When taking off from a stop (904 Auto) with moderate to aggressive throttle, there is a loud clunk that I can also seem to feel through the throttle in my foot. I have all new suspension, mounts, etc. What could be causing this? I’m not super familiar with the 904 and respective driveline gear, but I’m not sure where to focus for diagnosing the issue. Thank you in advance!

 

[dadsbee]

Broken left engine mount?

 

[1970DCH]

Broken left engine mount?

I’ve got new mounts in there, so it’s not that.

 

[kiwigtx]

Hi Eveyone - When taking off from a stop (904 Auto) with moderate to aggressive throttle, there is a loud clunk that I can also seem to feel through the throttle in my foot. I have all new suspension, mounts, etc. What could be causing this? I’m not super familiar with the 904 and respective driveline gear, but I’m not sure where to focus for diagnosing the issue. Thank you in advance!

904 suggests you have a 318....so it can't be Horsepower.

Maybe you have a load of play in the rear end or a universal is flogged out?

 

[1970DCH]

904 suggests you have a 318....so it can't be Horsepower.

Maybe you have a load of play in the rear end or a universal is flogged out?

Okay thanks for the input.

Hah, I’m working on it ;). It’s got a 318 with a 355 stroker kit from the previous owner (no other details) but it’s actually got a surprising amount of power, in my opinion.

 

[kiwigtx]

Okay thanks for the input.

Hah, I’m working on it ;). It’s got a 318 with a 355 stroker kit from the previous owner (no other details) but it’s actually got a surprising amount of power, in my opinion.

Transmission may also have a load of excess play..... it doesn't take much at each point to add up to be an annoying noise.

 

[RemCharger]

Maybe try it in 1st, to see if its a slipping sprag.

 

[Rishi]

Pinion snubber?

 

[j-c-c-62]

The clunk has to be coming from a detectable direction, location. If you can't determine that while driving, have a spotter stand on both sides of the car at a point it is most likely to occur. It's called shrinking the haystack I believe.

 

[1970DCH]

The clunk has to be coming from a detectable direction, location. If you can't determine that while driving, have a spotter stand on both sides of the car at a point it is most likely to occur. It's called shrinking the haystack I believe.

Touché my friend. My current available options are my wife and a 17 month old . But yes, need to further isolate the source with someone.

 

[j-c-c-62]

So just make sure the wife holds the kids' hand and see what the child finds during the test. 

I apologize for the attempt of misogynic humor.

My guess, left side LCA bushing or brake strut bushing?

 

[Fran Blacker]

Pop the hood and stand on the brakes, give some gas on and a couple of times and watch the engine. You mine have gotten a bad engine mount. Bad u-joint?

 

[Don Frelier]

I didn't see exhaust mentioned?

 

[j-c-c-62]

Pop the hood and stand on the brakes, give some gas on and a couple of times and watch the engine. You mine have gotten a bad engine mount. Bad u-joint?

Bad U joints usually have a very distinct "clink" to them and it happens upon any start up, fast or slow, and why I didn't go there.
But I can't rule it out.
It's not a front ball and trunnion joint, right?

 

[Dave6T4]

Possibly transmission mount. Mine went away in my '67 R/T. Lots of clunking and vibration.

 

[pnora]

I’ve got new mounts in there, so it’s not that.

Ok so what is it.

 

[Cranky]

I’ve got new mounts in there, so it’s not that.

Just because you have new motor mounts doesn't mean they are good. Waaaay back in 1970, I broke a new motor mount and can only think the new ones we have now are any better if not worse. And my engine wasn't all that strong.

 

[pnora]

Just because you have new motor mounts doesn't mean they are good. Waaaay back in 1970, I broke a new motor mount and can only think the new ones we have now are any better if not worse. And my engine wasn't all that strong.

My 340 swinger with an automatic could break them real quick.

 

[WileE]

Something loose inside the trunk ?

 

[RemCharger]

Need more info