Hello Gents and Fellow Gearheads,
Hope everyone is doing well. I wanted your thought and suggestions on a really bad vibration that has started in my 78 Monte. Just a quick history, I have a 406 sbc,. with a TCI Super Streetfighter TH350 behind it. And at the rear, I have a GM 7.5 10 bolt. (the original) I built this as much as I could, and so far, it has done great. I have Moser 31 spline axles, an Auburn Posi from a Camero, and GM 3:73 rears installed. Brand new bearings and races in a full rebuild kit I got from RATECH. I have been restoring the car by doing a full frame off restoration in my garage. Besides the engine and trans, I have done everything myself, so it has taken me a good chunk of time to complete it. But I finally got it up and running at the beginning of this summer. But...... I only had the original driveshaft. It fit perfectly, as it should because I went with pretty much a stock set up. So, we have been testing and tuning it throughout the summer, and finally got some miles on it and got it dialed in. And then it happened....... I had to let her eat, and man was it going well. Until I let my foot off the gas and the driveshaft ripped in half due to the velocity and power. I would like to say it was a successful failure it the fact that no MAJOR cosmetic damage was done, and no one got injured. Just a hell of a lot of noise, a slightly damaged output shaft seal, a badly dented and concaved floor pan, some new exhaust pipe (Thank God I was able to find and reuse the brand-new Violator Pypes Mufflers) and it nicked the inside of the pass rear rim. Got it home and up in the air for assessment. I went and pulled out the old credit card, bit the bullet, and had a new custom driveshaft built with Spicer u-joints, and Spicer straps as well. Got it all together, and the new shaft was too long. So, I remeasured, and did some more research, and had the drivetrain shop take some length off it and rebalance it, so it is measuring at 52 1/2". It fits perfect, except it had a LOT of play kat the end of the transmission and was leaking fluid pretty badly. So removed the tail shaft housing and replace the bushing and seal. When I got it re installed it sas nice and snug and went in without any problems. started her up, topped off the fluids and off went. Right away I noticed the vibration, only under acceleration, anything over I would say, 40% throttle and up. Faster you got worse it gets. When I put it in neutral, nothing. Smooth. Let off the gas, smooth. Light acceleration, pretty smooth. But when you get to around 50-55mph, it is bad! I tore it down again, and I don't see any dents, scrapes, any anything that indicates an impact resulting in any damage. I am guessing it is internally bent. Now, I do get this strange, growly grinding feeling and noise when I turn the rear pinion flange yolk. Si I am guessing that maybe the pinion bearing, or something in the rear end is the culprit. I mean, I really don't see how the output shaft of the transmission got bent, but looking at the rear diff yolk, it was really flying around back there and may have twisted that pinion shaft or maybe tweaked the bearing. That's what I am thinking anyways. Is that a likely scenario fellas? I know it kind hard to speculate without seeing and feeling the noise or vibration, but I think it is a good place to start, ya think? Any input is appreciated like always guys. I sure do appreciate your time and look forward to hearing what you guys' opinions and recommendations are. Take care and please feel free to lmk what you think the correct course of action should be.
P.S. I attached some pics of the car just to let you guys take a look at it as well.
Bullett801
Hope everyone is doing well. I wanted your thought and suggestions on a really bad vibration that has started in my 78 Monte. Just a quick history, I have a 406 sbc,. with a TCI Super Streetfighter TH350 behind it. And at the rear, I have a GM 7.5 10 bolt. (the original) I built this as much as I could, and so far, it has done great. I have Moser 31 spline axles, an Auburn Posi from a Camero, and GM 3:73 rears installed. Brand new bearings and races in a full rebuild kit I got from RATECH. I have been restoring the car by doing a full frame off restoration in my garage. Besides the engine and trans, I have done everything myself, so it has taken me a good chunk of time to complete it. But I finally got it up and running at the beginning of this summer. But...... I only had the original driveshaft. It fit perfectly, as it should because I went with pretty much a stock set up. So, we have been testing and tuning it throughout the summer, and finally got some miles on it and got it dialed in. And then it happened....... I had to let her eat, and man was it going well. Until I let my foot off the gas and the driveshaft ripped in half due to the velocity and power. I would like to say it was a successful failure it the fact that no MAJOR cosmetic damage was done, and no one got injured. Just a hell of a lot of noise, a slightly damaged output shaft seal, a badly dented and concaved floor pan, some new exhaust pipe (Thank God I was able to find and reuse the brand-new Violator Pypes Mufflers) and it nicked the inside of the pass rear rim. Got it home and up in the air for assessment. I went and pulled out the old credit card, bit the bullet, and had a new custom driveshaft built with Spicer u-joints, and Spicer straps as well. Got it all together, and the new shaft was too long. So, I remeasured, and did some more research, and had the drivetrain shop take some length off it and rebalance it, so it is measuring at 52 1/2". It fits perfect, except it had a LOT of play kat the end of the transmission and was leaking fluid pretty badly. So removed the tail shaft housing and replace the bushing and seal. When I got it re installed it sas nice and snug and went in without any problems. started her up, topped off the fluids and off went. Right away I noticed the vibration, only under acceleration, anything over I would say, 40% throttle and up. Faster you got worse it gets. When I put it in neutral, nothing. Smooth. Let off the gas, smooth. Light acceleration, pretty smooth. But when you get to around 50-55mph, it is bad! I tore it down again, and I don't see any dents, scrapes, any anything that indicates an impact resulting in any damage. I am guessing it is internally bent. Now, I do get this strange, growly grinding feeling and noise when I turn the rear pinion flange yolk. Si I am guessing that maybe the pinion bearing, or something in the rear end is the culprit. I mean, I really don't see how the output shaft of the transmission got bent, but looking at the rear diff yolk, it was really flying around back there and may have twisted that pinion shaft or maybe tweaked the bearing. That's what I am thinking anyways. Is that a likely scenario fellas? I know it kind hard to speculate without seeing and feeling the noise or vibration, but I think it is a good place to start, ya think? Any input is appreciated like always guys. I sure do appreciate your time and look forward to hearing what you guys' opinions and recommendations are. Take care and please feel free to lmk what you think the correct course of action should be.
P.S. I attached some pics of the car just to let you guys take a look at it as well.
Bullett801
