Vibration at 50 mph

CWilson

CWilson

Senior Member
I am new to the forum, and have been reading threads for the past few months. I have a question I can't seem to find the answer to by searching previous posts. I am getting a strong (and loud) vibration from under the truck somewhere around the transmission area. I cant tell where the sound is coming from because I cant get the rpms up while laying under the truck. It also doesn't help that I've never driven another Model A other then my own so I don't know if the noise/vibration is normal or out of whack. You guys seem to know everything about these and maybe this is a common problem. Any help would be appreciated. Thanks
 
I'll assume that checked everything external around the area of the noise.

It seems as though you may have a bad u-joint.
 
Simple fix. Don't drive 50 mph. You're overdriving your brakes and your headlights anyway. If you want to go fast, get in your modern car.
 
Patrick L. said:
I'll assume that checked everything external around the area of the noise.

It seems as though you may have a bad u-joint.
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U-joint sounds like a possibility. First, pump lots of grease into it and drive it to see if that made any difference. Check Les Andrew's book for instructions on how to remove it if necessary. Happened to me once on a 34 Ford V8. Good luck.
 
Patrick L. said:
I'll assume that checked everything external around the area of the noise.

It seems as though you may have a bad u-joint.
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I cant get the rpms up high enough to make the noise while I'm laying under the truck. I read where someone said the muffler clamp can cause noise from vibration?
 
CWilson said:
I cant get the rpms up high enough to make the noise while I'm laying under the truck. I read where someone said the muffler clamp can cause noise from vibration?
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Yep, you're right. The clamp can be a problem. I was thinking you checked it. The clamp should be left a bit loose. So, I wrap the pipe with asbestos cloth or similar material so the pipe to clamp is tight but still a little loose to the frame. But, not loose enough to rattle. Make sense ?
 
700rpm said:
Simple fix. Don't drive 50 mph. You're overdriving your brakes and your headlights anyway. If you want to go fast, get in your modern car.
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Not really that helpful. I asked a question because there could be a problem with the vehicle. I drive 45 mph to and from work. The noise is at its loudest at 50 mph. Or I could take your advise and ignore the problem, and drive slower so i don't hear the problem and hope it doesn't cause a major failure. Thanks
 
Patrick L. said:
Yep, you're right. The clamp can be a problem. I was thinking you checked it. The clamp should be left a bit loose. So, I wrap the pipe with asbestos cloth or similar material so the pipe to clamp is tight but still a little loose to the frame. But, not loose enough to rattle. Make sense ?
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Yes, thank you. I will try that tomorrow.
 
Motor mount rubber may be as hard as a rock, front yoke mounting nut to tight, slide hand crank in to crank nut to check for proper alignment.
 
700rpm said:
Simple fix. Don't drive 50 mph. You're overdriving your brakes and your headlights anyway. If you want to go fast, get in your modern car.
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I agreed, 35-40mph is about what a 83 year old block should be pushed... They have only so much life left in them., heatin and cooling cycles that is...
 
To me the muffler clamp deal makes more of a drumming noise, not so much a vibration. While you're under the car grease the heck out of the u-joint too. Might not hurt to inspect the tires for out of round and the wheels for loose nuts too.
 
mshmodela said:
I agreed, 35-40mph is about what a 83 year old block should be pushed... They have only so much life left in them., heatin and cooling cycles that is...
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I guess y'all wouldn't drive on interstate 35 in downtown Dallas either, huh? :D
 
Perhaps I missed it but is the vibration only when moving or can it be made to happen just by reving the engine.
If noisy while not moving the first thing I would check would be the tail pipe clamp. Temporaraly slip a small bit of wood wedge in between the tail pipe and the clamp to see if it helps.
Maybe engine pans (if you have them) making noise.
Lot's of other possibilities.
Get someone to rev the engine whilst you crawl around under it looking and listening. Use a 1/4" dowel to push against things to see if you can stop the vibration.

If it is the tail pipe clamp use a few bits of wood wedge to get it centered in the clamp and squirt three little blobs of silicone spaced evenly apart between the pipe and the clamp. Let cure for a day and drive it. The pipe will expand with heat and break each of the blobs free from only one of the surfaces and remain tightly attached to the other. Will stop the vibration and allow movement. Silicone is very heat resistant.
 
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mshmodela said:
I agreed, 35-40mph is about what a 83 year old block should be pushed... They have only so much life left in them., heatin and cooling cycles that is...
Click to expand...

At 35-40 Mph, You are a accident looking to happen.. This even with your car lit up like a Xmas tree !!..:eek:
 
Dunno about putting hard limits on it. My coupe likes 50 much better than 40 - I get a vibration around 38 thru 45 that smooths out quite nicely above that, and it seems that driving without the vibes would be healthier for both me and the car. I don't pretend to an expert on these cars - I've only driven two coupes, mine and another, which had lots more vibration over a wider speed range. Mine has a balanced crank, which probably accounts for the difference. But I'm still learning, and I sure agree that taking it easy on these old engines sounds like a smart idea.
 
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