Banging at 10 mph

[tempest66]

Hello guys. I am new to this site. So hello! I have a 1966 Pontiac Tempest original motor and transmission. The car runs fairly well. When driving around town and coming to a stop either stop sign or red light, there is a nice BANG that happens at approx 10 mph. I replaced the vacuum modulator and still the same thing. anyone ever experience this or have any suggestions for me? Any advice is greatly appreciated. And sorry if I posted this multiple times. Thank you. Larry

[Ron Ward]

Help us out a bit, here. What does the bang sound like? Is it a backfire? Is it a mechanical bang? What part of the car is it coming from?


Ron

[tempest66]

Hello Ron, it's not a backfire. It sounds like a mechanical bang. It sounds like its coming from the front of the vehicle.

[BBR]

Sticky drum brake?

[Ron Ward]

Larry,

I apologize, but I forgot to welcome you to the forum. Glad to have you along for all the craziness that goes on here.

Can you help us to narrow this down a bit further? Does this noise at 10mph happen during acceleration or during braking? Is it at a constant speed? Is it when you hit a bump? Describe exactly when and where it happens.


Ron

[tempest66]

Hey BBR, i have converted the front brakes to disc could the rear drums be holding? Hey Ron thank you no need to be sorry. It only happens when i am applying the brake and coming to a stop. Not going over any bumps. Only on deceleration and it happens approx around 10 mph when braking only. It does not happen during accleration. I wish I could take a video and post it but i'm lucky i even figured out how to sign up and submit posts....

[TC]

What do the control arm bushings look like?? And how about the body bushings??

[Ron Ward]

What do the control arm bushings look like?? And how about the body bushings??

I think TC is probably pretty close here. You may also wanna check out the ball joints.


Ron

[SuperBuickGuy]

starting with - how full is the fuel tank?

[tempest66]

Hey TC, the control arms bushings and ball joints are all original. They don't seem to bad or have much play. I do know the lower ball joints are definitely worn cause when we installed the front disc conversion I saw that .As far as the body mounts go i know a few have been replaced but not all. Do you really think that if the ball joints/control arm bushings are that worn it would cause a severe bang only at 10 mph while braking? It does sound fesable though...Hey Super Buick the tank right now is more then 3/4 full. But it happens regardless of the amount of fuel in it...

[BBR]

Put the rear end up on jack stands, run it, hit the brakes like you would if you were driving and see if you can replicate it. If not, it's in the front somewhere.

My opinion is a ball joint is likely to make noise at other times too as the suspension cycles.

[SuperBuickGuy]

I tend to start with the simplest things first... example, my wife complained about a "terrible noise" in the back of her car. I asked her what she did right before..... long discussion short, she'd bought a bunch of rolling dog toys; the bag had fallen over; and you can imagine what the noise was

Do what BBR suggests

Then if that's not it, put the front of the car up on jack stands and see if anything is loose in the suspension. Look for cracked metal, failed rubber bushings. After that, put your hands at 12 and 6 o'clock on the tire on each side and see if you can get any movement in the ball joints. Then do the same at 3 and 9 o'clock - observe the tie rods and look for one moving more than another (it helps if you only have one tire in the air as you check each side. Then look at the idler arm - a lot of times noise can come from that - you're looking for movement in a vertical plane. Pull in and push out on the tire, there should be no movement in the bearings. Observe the shocks, make sure those rubber bushings on top and bottom are not cracked or missing. Check the springs to see if the spring is broken..... with both tires on the ground, turn the steering wheel back and forth to see if the steering box is loose or there is a lot of wear/play.

Under the car, check the transmission mount, motor mounts (especially motor mounts - try to jack the motor out of the car with the jack under the balancer - if it moves independant of the car, you may have found a problem). with the rear of the car on the ground, check the u-joints to see if they are loose.

And whatever you do, do not stop when you think you've found the problem - often if one thing is bad; something else is as well.

[MR P-BODY]

If its a suspension issue(ball joints, bushings, ect)...
listen very closely but put the car in reverse then move
a few inches/feet then go back to drive and do the same...
you will be flexing the front end... also if you can, have
someone watch(that knows what they are looking at) and
see if the wheel assembly is rocking (signs of worn parts)
you may need to brake torque it to get more load on it to
see it flex... also check the sway bar bushings.. if you have one