fxrtharley
Member
Hello, my first post and might not be a quick or easy answer but might be able to get some ideas of where to start.
I purchased a 68 barracuda with a swap from six to 340. The engine started but the 727 was toast so was not able to drive when purchased. I was told the engine was rebuilt (Call me naïve, the guy seemed honest but of course went ghost after I purchased) but uses oil and the tailpipe smells like a refinery.
Anyhow, got the car running and have been working on it and going to car shows. What I notice is starting around 25 MPH the car starts with a loud humming sound which sort of sounds like vibration humming through the body. The headers are loud so difficult to pin down as well since both noises are fighting with each other. Another local shop agreed and thought it was the driveshaft and sent out for repair. Replaced after balanced and still the same. Then the mechanic said the bearings were shot in the rear axle and need to replace bearings only from putting a remote microphone on the axle and driving down the street. The axle is 657 8 3/4 and does appear to be rebuilt with green bearings since it has been changed to Willwood disc brakes. I was skeptical so yesterday I put up on jack stands and took rotors off and spun manually to see if I could feel or hear a bad bearing using a ultra sensitive electronic sensor with aluminum rod against the outside of the axle by the exle journals and the pumpkin. I did not hear any grinding noise just basic bearing rollers. I even hooked up the drive shaft and started the car and put in gear and had my wife step on the accelerator a bit to get it spinning faster with still no noise. I don't think it is the rear axle.
I still think it is in the drivetrain so unless you have any other suggestions this is more to my problem/thoughts. When I first got the car I took it to a local shop and sent the tranny out for rebuild. I was asked by the trans shop if needed balanced or non balanced torque converter. I asked the shop and told me what they needed. I will have to confirm which was put in but I am wondering if the wrong flex plate or torque converter can cause vibration that could cause the what seems to be an out of balance condition that would cause an annoying noise in the car? Of course I have no specs from the engine whether forged or cast crank or what flex plate or torque converter is supposed to be married up to the engine so at a loss there. I was going off the expertise of the local shop that is familiar with Mopars and seemed confident so all may be right but have to question. I even took back to the reputable trans shop that rebuilt the transmission and they could not figure out where the sound is coming from. They said it would not be the converter. So all leaves me at a loss of where this annoying noise is coming from.
So back to my troubleshooting yesterday I am looking deeper into the engine/transmission being the culprit after while the car was in the air with the tires and rotors off, I revved the engine and there definitely was a vibration going through the car and i probably only revved to 2000 RPM whether in D or N.
I know this is a long post but wanted to give you folks as much information and history to help with further suggestions. It is dead winter in WI so not going to be able to do a lot of drives for a bit but can do what I can to investigate and mechanical suggestions.
Thank you for your time, please advise any questions or thoughts.
I purchased a 68 barracuda with a swap from six to 340. The engine started but the 727 was toast so was not able to drive when purchased. I was told the engine was rebuilt (Call me naïve, the guy seemed honest but of course went ghost after I purchased) but uses oil and the tailpipe smells like a refinery.
Anyhow, got the car running and have been working on it and going to car shows. What I notice is starting around 25 MPH the car starts with a loud humming sound which sort of sounds like vibration humming through the body. The headers are loud so difficult to pin down as well since both noises are fighting with each other. Another local shop agreed and thought it was the driveshaft and sent out for repair. Replaced after balanced and still the same. Then the mechanic said the bearings were shot in the rear axle and need to replace bearings only from putting a remote microphone on the axle and driving down the street. The axle is 657 8 3/4 and does appear to be rebuilt with green bearings since it has been changed to Willwood disc brakes. I was skeptical so yesterday I put up on jack stands and took rotors off and spun manually to see if I could feel or hear a bad bearing using a ultra sensitive electronic sensor with aluminum rod against the outside of the axle by the exle journals and the pumpkin. I did not hear any grinding noise just basic bearing rollers. I even hooked up the drive shaft and started the car and put in gear and had my wife step on the accelerator a bit to get it spinning faster with still no noise. I don't think it is the rear axle.
I still think it is in the drivetrain so unless you have any other suggestions this is more to my problem/thoughts. When I first got the car I took it to a local shop and sent the tranny out for rebuild. I was asked by the trans shop if needed balanced or non balanced torque converter. I asked the shop and told me what they needed. I will have to confirm which was put in but I am wondering if the wrong flex plate or torque converter can cause vibration that could cause the what seems to be an out of balance condition that would cause an annoying noise in the car? Of course I have no specs from the engine whether forged or cast crank or what flex plate or torque converter is supposed to be married up to the engine so at a loss there. I was going off the expertise of the local shop that is familiar with Mopars and seemed confident so all may be right but have to question. I even took back to the reputable trans shop that rebuilt the transmission and they could not figure out where the sound is coming from. They said it would not be the converter. So all leaves me at a loss of where this annoying noise is coming from.
So back to my troubleshooting yesterday I am looking deeper into the engine/transmission being the culprit after while the car was in the air with the tires and rotors off, I revved the engine and there definitely was a vibration going through the car and i probably only revved to 2000 RPM whether in D or N.
I know this is a long post but wanted to give you folks as much information and history to help with further suggestions. It is dead winter in WI so not going to be able to do a lot of drives for a bit but can do what I can to investigate and mechanical suggestions.
Thank you for your time, please advise any questions or thoughts.
