40 ford ,56 Chevy rear end. 327/4 gear Replaced rear springs and perches. I thought I had the pinion angle right ,but maybe not. Pinion angle off give good vibration?
Yes. An incorrect pinion angle can give a vibration. 55mph is also roughly the magic number for out of balance wheels, so might be worth getting that checked out early in the investigation. Also check that everything is tight after your spring swap. And why were the springs changed? Tired perhaps? Maybe their condition was masking an underlying condition? Chris
Inspect your brake drums for balance weights. Borrow a bubble balancer and check them. I chased my tail for months on a high speed vibration with my 54 Chevy, which had a tri five rear axle. It turned out to be the brake drums, something at that time never occurred to me.
Hello, In our 327 powered 1940 Ford Sedan Delivery, it was a definite project car when we bought it. My wife and I were so happy that we initially overlooked a lot of problems in driving, handling and braking. But, after we got the sedan delivery home to our little apartment, we looked for what could cause the shaking at low freeway speeds. It got worse as we got up to 60-70, so yes, it was 45-50 all the way home in the slow lane, then off of the freeway as soon as possible to drive on the side roads. Now, it was not as noticeable. ha! But, once home, my wife took it for a drive down PCH for a test. She got about 20 miles and had to turn around. The road bumps were bad enough, but now, it was shaking at around 50. It stopped, but the pedal was long. And when she went around corners, it was strange in tire grip, etc. they were off brand tires, not the big name brands. So, I tried my best to get the front end parts that looked worn out replaced and repaired if needed. It got a little better, but still not the best. It took a while, but finally, the scope was beyond my means. Luckily, our friend who had a shop about 30 miles away had always handled our wheel balance and alignment with some accessory front end work if necessary our 58 Impala and 65 El Camino. Yes, it was a drive to get from Long Beach to the Culver City/Westwood neighborhood. When he got finished with our 65 El Camino, we were totally impressed at whatever speed the El Camino could drive and corner, without any drifting and shakes. On the freeway home, it was as if I was gripping the road, but the ride was straight and smooth. I normally drive about the same speed as others and it is part of going with the flow. One selected lane and that was it for the long haul. No lane changing back and forth. It was all about the road ahead and what to expect. We had been driving on these freeways since they were developed and open for everyone. What he had done was to have our tires shaved to correct roundness. It left a ton of black rubber on the floor. But, as the wheel spun after finishing the pinpoint shaver did not carve any more off of the tread. When he put on the next tire, as he manually spun the tire, the tire rolled about ½ way around and stopped at the shaver blade as a bump was on the “round” tire. So, he manually backed it up and began the tire spinning again, with a little shaping starting and as the tire spun, more came off of the bump and finally, it started shaving the rest of the tire for a few spins. Now, the tire was round and needed balancing on the rim. Jnaki At first sight when he did that same process to our new firestones that came with the 58 Impala, we were aghast. So much rubber laying on the ground and as each spin happened, one could see the blade scraping off more, while in a stationary position. It definitely was disheartening, but a necessity to get the so called round tires… correctly round shaped tires, as they should have been from the dealer or manufacturer. When all four tires were shaved and now “round,” the rest of the wheel spinning for balance and once attached to the car, aligned to the specifics. He also did one last check by spinning on the on the car old tire spinning, portable, moveable machine leaning against the tire on the car. As he spun the front wheels, no noticeable shakes or shimmy was noted. He did not have to make any other front end adjustments and the El Camino rode so nicely home that it almost was like no hands steering on the straight freeway surfaces. Now, no shimmy or shakes beyond 50 +. When we were on highway 395, the open road was made for long distance highway speeds and it was enjoyable to have a set of tires and a car all in line for a pleasurable drive at any speed. Shave tires, balance to specifics and align the front end is the preferred method to get the 50+ shakes to go away. Try it, you will definitely like it. Note: There are a lot of folks that look at a tire and say it is round. They do not go through the tire shaving process. So, that its their choice. But, with all of the hot rod suspension maladies, one needs to take into account, new replacement suspension parts are necessary and also a great person who can shave, balance and align your hot rod. Start with the tires and suspension. YRMV
Same tires as before. I changed springs because they were plum wore out. Gonna check it out again this winter.
First thing I'd do is get it on jack stands, be sure the axle is carrying the weight not the frame. Then put it in high gear and run it up to 55. If it doesn't vibrate balance the front tires. If it vibrates, remove the rear tires and retry. If it doesn't vibrate the rear tires and/or wheels are the problem. If it vibrates you have a driveline issue. I've used this technique to chase weird noises/vibrations for years and it works for me. BUT be sure of your jack stand placement and don't run it any faster than necessary.
Wheel end vibrations tend to be low frequency vibrations. Driveline vibrations are at a higher frequency since the driveshaft rotates 3 to 4 times faster than the wheel ends. Driveline vibrations also tend to be on drive or coast, could even be on float, but not on all three conditions. Using the throttle to creat those conditions will usually change a driveline vibration. Those three conditions do not affect wheel end vibrations. I took a trip in my Model A hot rod and had a noticeable high frequency vibration that I could feel in the steering wheel. I was sure while driving that it was driveline related. The next day the first thing I did was rev the engine, with the trans in park, to the rpm where I felt the vibration. The vibration was there just revving the engine; it's not driveline. I checked to see that the vibration damper had not spun, I checked compression to make sure I didn't have a cylinder that was low, put my scope on the ignition to check the secondary and everything was good. I even ran the engine with the belts off, no change. Next I checked both engine mounts and the transmission mounts to see they were not bound up. Finally I loosened the exhaust, took all hangers free, shook it all around and retightened all fasteners and mounts. Result; the vibration is all but gone. Since I know the rpm and frequency of the vibration I can still barely feel it. It is, however, very acceptable.
Well I shimmed rear end 2 deg down. Helped a lot. Also found that the engine is surging or hunting at higher steady speeds. Don’t know if it’s the dual point or carb. But I do have another distributor I was going to install.
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