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bofusmosby

My first expressway drive

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Well, today was the day. I decided to visit my brother about 10 miles away, so I took the old car for its first spin at higher speeds. I figured if I plan on taking it to some shows, I need to make sure that going 55 mph would be no problem. Well, the engine performed fine. No problems what-so-ever. BUT, I do have some problems. After breaking the 50 mph barrier, there came a bad hum or vibration. This vibration could also be felt in the steering-wheel. I am hoping that the front wheel berrings will take care of this. When I re-packed the berrings a couple of months ago, there were some bad spots found. I know they are bad, so before I take it for another spin like this, they will be replaced. The second thing I noticed what when I was driving on a curve to the left and would hit a bump, I would have some awful shaking. I know that the king-pin is bad on the right side, so I am in hopes that this will correct this problem. After the king-pins are replaced, then I'll have a front end alignment done. This should find any other problems that may exist with the front end. Lastly, shortly after shifting gears, I am hearing (feeling) a "bump" coming out of the rear of the car. I first thought that there was something rolling around in the trunk, but now, I believe that there is something going on there. It doesn't feel the same way as a bad "U" joint, so I am wondering if the differential could have some problems. I'll have to take care of these problems one at a time.

OK, so much for my rant. Just another wonderful day in the neighborhood! :D

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Is your rear stabilizer tight? My Buick would make this clanging noise and I finally figured out it was just the parking brake cable hitting the torque tube now and again. Those rear stabilizers will clunk around if the rubber bushing is shrunk or worn.

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OK Earl, I am new to the old car thing. Can you describe the "rear stabalizer", and does my car have onme?

I got under the car and found that the right/rear shackle is loose on one end. I am thinking that this might be causing the noise. The sound seems to be coming from the right/back.

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It will look like a piece of pipe back near the rear axle that usually bolts to one side or the other of the axle and then the other end is attached to the body to help keep the car from doing much back and forth motion. Maybe they don't need them on cars with leaf springs in the back, my '41 Buick is coil springs of course, but it seems like most of those cars had them. If you push on the back of the car like you are trying to jiggle it back and forth instead of up and down you should be able to tell how "loose" it is. Spring shackles will make noise as well and thump around. They aren't too bad to replace. The car will ride better with good shackles. On some of those cars they greased the rear springs and wrapped them with canvas and some had fancy tin covers for them, but I don't know what Pontiac did. The shop manual would explain that one.

Your car is nice looking. My Dad had a '36 Pontiac and really liked the car. You'll get the bugs worked out. One nice thing about old cars is that each component just does only one thing. Makes it a lot easier to troubleshoot. Where most new cars try to make each component do dozens of things and needs a computer to monitor the situation!

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The vibration you mention sounds like a tire out of balance or, worst case, a bent wheel. Large tire shops can true up a wheel and balance tires. The rest should be taken care of by replacing the bearings repairing the king pin refilling the shocks and getting an alignment.

The bump from the back, I don't know. Could be the shackle especially if it is a front mount.

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Thanks guys, I really appreciate your opinions. I don't believe mine has the stablizer bar in the back. As for the vibration, by listening to the frequency of the noise/vibration, I believe both are being caused by the same thing. The car is not shaking like a bad /bent rim or tire. In my old 68 Couger, I had the front berrings go bad a lot over the years. It sounded/felt like this car does right now. I guess the only way to be sure is to just replace them. Then I'll know for sure. It could also be caused by a bad U-joint, but I would think that there would have been more shaking, rather than both the vibration AND the hum to go along with it. Remember, its all a learning experience for me. The shackle that is loose from one side is the right rear/back one. I've never delt with a bad shackle before, so any noises that they will make are all new to me.

Well, you gotta take step one before you take step 2 & 3. In time, if by no other way than elimination, the problems will be worked out.

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Check the Caster! My 33 Franklin had a similar shimmy when I first got it. Everything was suggested, steering box, drag link, tire balance etc. The problem turned out to be too much negative caster. It was easily corrected by two shims and the problem has NEVER come back. Dave

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A loose spring shackle will make lots of noise, as well as causing erratic handling, due to the un-damped motion of the spring as it moves through the slack between "load" and "no-load" conditions ( going over bumps ). This is probably worse when a rubber-bushed shackle goes bad.

My '41 De Soto lost the rubber from the rear shackle on the driver's side, and the rear end of car "hopped all over the place"...

Another thing to look for: if the car has lever-type shock-absorbers, make sure they are firmly mounted to the frame, and that all the links, bushings, and levers are tight. Worn shock bushings will make noise / cause a "basket-ball dribble" in the suspension.

That driveline "hum" - I've had many an old Chevy Six that would "buzz"/ "vibrate" / "hum" between 45 and 55 mph - this was almost always the result of a bad u-joint and /or the driveshaft bushing at the top of the torque-tube. The frequency ( "pitch") of a driveshaft vibration is ( usually ) much higher than that caused by a wheel-bearing. A bad wheel-bearing is usually evident through the entire range of speed while the vehiclie is in motion; drive-shaft vibrations usually occur at certain speeds, usually above 30 - 40 mph.

If I remember correctly, Pontiacs always had open-driveshafts ( unlike the Chevy Six); easier to check-out the u-joints / rear transmission bearing/bushing.

Another thing to keep in mind, your Pontiac (like most other cars of this era) is geared fairly low probably around 4.1:1 ( "stump-puller" rear). Since the modern auto-tranny came along in the mid-1950's, most automatic cars have rear-gears in the vicinity of 3.25 to 2.70 - they turn noticeably slower than the L-head six in your Pontiac (or my De Soto). Any driveline issues will show-up at lower highway speeds than they would in a "modern" car...

If you have worn, sloppy parts in the suspension, that will definitely account for "squirrely" handling... suggest you take things gently until you become familiar with how the car behaves, particularly when you encounter bumps, tar-strips, wet pavement...

It'll take some time to find / correct all the little bugs... hang in there !

The car looks sharp !

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Thank you for the feed-back Frank. Yes, I agree that it will take some getting used to on driving this old car. Before I take it out again, I'm going to give it an oil change and lube. I am also going to replace the oil in the transmission. I am sure that it could only help, and not hurt.

You may be right about the U-Joint(s) being bad. All I know is that I will not be taking it for any long drives until THAT problem is taken care of. I am sure that the problem with the front-end shake is the king-pin bushings. When I hit a bump, I can hear the play in the wheel. When I was replacing the wheel cylinders, there was a LOT of play in the R/F wheel. This movement was caused by a lot of play at the king-pin, I could see this. The L/F wheel was good and tight. This will have to be addressed when my finances get a bit better. I already have the king-pin and bushings, but this is one thing that I will not attempt myself. Neither the knowledge or the tools do I have for this.

Oh well, it'l just take some time as you stated.

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One more thought ( for now... )

A friend just purchased a VERY nice original 1940 Chevrolet Master de Luxe sedan, with about 70k miles on it.

After going over the brakes and suspension, he got it out on the road.

I had the privilege to drive it; a very nice solid car: no squeaks, rattles, groans, loose sheetmetal... probably the nicest, tightest old car I 've driven.

That said, it sounds happiest at 45 MPH or less. Push it above 45 and things begin to sound busy under the hood.

Brought back nearly identical memories of my 50 Chevy Fleetline fastback from 1992-94, and mechanically is essentially the same car: 216 splash-oiled six, 4.1 rear-end, Huck hyrdraulic brakes.

Point being, suggest you limit your cruising speed to 45 mph, 50 mph max to prolong the engine life of your Pontiac.

There were no super-highways in 1937, and these pre-War (and some post-war) cars with "stump-puller" rears do not like being shoved down the Interstate at 60-70 MPH.

They might do it for a little while, but "the little man with the hammer" will take up residence under your hood fairly soon.

Your Pontiac will be happier / last longer kept under 50 MPH.

Good luck !

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I agree Frank, but I was hoping that I would be able to take this car on the interstate when I start taking it to shows. I really didn't want to push it to 60, but was hoping to at least get it up to cruzing at 55. I know that there were 3 different rear-end ratios that were used in my car. One was for mountain driving, the second was for normal, and the third was for "plains" driving. I was told that this car was probably always a Montana car, so I am wondering if my car could have the "mountain" rear-end. I have no idea which rear-end it actually has, but I believe that if a "plains" rear-end were installed, then the engine wouldn't have to work quite so hard. Afterall, there are no Mountains in Florida. The engine was rebuilt about 2000 miles ago, so hopefully there is quite a bit of life left to it. The speedometer goes up to 100, so going 55 is just a little over half way on the numbers.

I am in hopes that the little man with the hammer NEVER pays me a visit. I must admit though, that when I got my car up to 55, the engine sounded good, its just everything else that concerned me. I have been in contact with a guy who lives up in Maryland who also owns a '37 Pontiac. His is an 8, where mine is a 6. He is telling me that my car should easily be able to do 55 to 60 with no problems, but strongly suggested that I not go over that speed. Believe me, I don't want to do anything that causes any damage to my car. I really could care less about speed or power in general. I was just hoping I would be able to do some interstate driving in time. If she won't go at least 55, then the interstate will be off limits. When cars are going 70 mph and me going 55, that can be a bit of a hazard, but to go slower would be just asking for trouble.

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When you have checked the possible sources of vibration that have been mentioned, qnd if you still have vibration, you might consider the drive shaft & u-joints & balance. I had an ongoing problem with my '36 Plymouth P2. After checking out various sources & fixing this & that, There was still vibration. I had the u-joints rebuilt and balanced all together & reinstalled the assembly on the car. There was still vibration! Now even worse. One of the u-joints had slipped on the shaft. When this was remedied, at last no more vibration. Ah well, so goes the hobby!

Edited by Fr Mike (see edit history)

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I'm wondering if the vibration can be duplicated when the car is on a lift. I was first thinking it to be the front wheel berings, but the more I think about it, I am now more convinced that it might be a bad U-Joint. Would the car need to be under some sort of load for the u-joints to cause a vibration?

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My opinion is---No. My P2 vibration problem didn't begin to occur until about 30mph on smooth pavement.

It is my opinion that the two u-joints on my P2 provided too much "slack" to control vibration. I finally had to install a Spicer slip joint assembly. Now my P2 drives as smooth as silk, all the way up to 55 (I don't drive it faster)!

Good luck!

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One way to narrow down the possibilities of the driveshaft / u-joint vibration is to get it out on the road, and up to the speed where the vibration appears, then very slightly vary the pressure on the accelerator, going from "load" to "coast" and back to "load" again, and see if the vibration changes or goes away depending upon whether the driveshaft is under a "power" load, "coasting" load, or no load at all ( in bewteen ). You're not really changing the speed of the car.

Driveshaft / u-joint vibrations often change character during this test; wheel bearing / wheel balance vibrations do NOT change with respect to engine / driveshaft loading, but do so with changes in vehicle ground speed.

My '54 Chevy truck (4.57 rear) has a driveshaft vibration that manifests itself around 45-48 MPH. My '41 De Soto (4.1 rear) has a slight driveshaft vibration around 50 MPH. In both cases, the vibration seems to be worse when the driveshaft is under no-load / coasting load than when under power / acceleration load.

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Thanks guys. On my car, there was no difference on the vibration when I pushed in the clutch. Only when the car slowed down to about 50 did the vibration subside. Maybe putting it up on a lift is the answer. If the problem is coming from the front end, then there should be no vibration doing it this way. Since the vibration continued when I pushed in the clutch, then that would tell me that the drive shaft wouldn't have to be under load for it to vibrate. Am I correct on this assumption? Of course, if the problem os being caused by the back tires...........

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Loose kingpins will cause it to shake. Is any of the vibration coming up through the steering wheel? Or does it change when you apply the brakes while it's vibrating? My Buick was shaking like that, but the front end was tight and it turned out that one wheel was way out of balance.

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Pressing the brake pedal didn't make any diference. The frequency of the vibration was a lot higher than I believe a bent wheel rim would cause. Yes, I could feel it in the steering wheel, but then again, I could feel it all over.

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Another possibility is that the bushings in the torque tube in the car could be worn. Not sure if like the 36 Chevrolet, but there are two bushings in it that the driveshaft runs in--one in front and one in the rear. From what I've read when these are worn a vibration and hum can occur.

My 36 does that and pretty sure that is what it is in my case. Also, the oil from the transmission runs back into the torque tube. There supposed to be a rear seal in the torque tube to keep it from running into the differential, but those often leak and the rear end ends up "gaining" oil.

When cold, no noise or vibration in the 36 at speed. But after driving awhile and the oil hot and thinned out, the vibration and noise come in at about 45-50 mph. It feels like toward the middle of the car. The u-joint is new in the 36, so shouldn't be that. So far I'm putting up with vibration until get a chance to pull the rear end and put in bushings.

Being GM, the Pontiac may be similarly made.

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I'm not sure what you mean. Are you speaking of a round bearing that the drive shaft runs through? If so, then my car does not have these. There are just the 2 U-Joints I believe, and thats all. Your vibration must not be that bad. On mine, the vibration is so bad, I would be afraid to drive it when doing this. I took a look at the shop manual, and it says nothing about a torque tube, just the drive shaft.

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Jim,

The symptoms you're describing sound more and more like a drivehsaft / u-joint issue.

Looking under the car, if you see exposed u-joints at the tranny and at the rear-end, then your Pontiac has conventional open (Hotchkiss) drive shaft.

Torque-tube just looks like a big pipe connecting the tranny and the rear-end, usually with a big round collar at the back of the tranny, secured by four to six bolts.

Chevy, Buick, Nash, and Ford (pre-'49) all used torque-tube ( enclosed driveshaft), if you want to crouch-down and get a look at a local show or cruise.

If the vibration is "that bad", you don't want to drive the vehicle at those speeds until it's fixed; the condition / vibration will damage other components, or at least start to loosen fasteners all over the car ( ask Model a and Model T guys about vibration and loose nuts and bolts ! ). Plus it's just not a pleasant ride.

A NAPA store can probably source u-joints for your Pontiac.

De Soto Frank

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Thank you Frank. Yes, the U-Joints are exposed. What I really need to do is to get a cross on the U-Joints, and find the "newest" car that they would fit. All of the auto parts stores I have gone to don't have any books that go back that far. When I was looking for a fuel pump gasket, they didn't show anything for a 37 Pontiac, but they had one in stock for the 48 Pontiac, and it was the same thing. I know that I can order these u-joints from a place like Kanter, but I will have to pay a lot more for them.

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Sorry to confuse things with the earlier post. I was assuming it had a torque tube like many of the American cars of the 1930's. Chevrolet and Pontiac shared some similarities, but evidently not in this way.

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Not a problem. I appreciate you trying to help me out. Never hesitate to make a post, thinking it might not pertain to my car. You never know.:)

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Thank you Frank. Yes, the U-Joints are exposed. What I really need to do is to get a cross on the U-Joints, and find the "newest" car that they would fit. All of the auto parts stores I have gone to don't have any books that go back that far. When I was looking for a fuel pump gasket, they didn't show anything for a 37 Pontiac, but they had one in stock for the 48 Pontiac, and it was the same thing. I know that I can order these u-joints from a place like Kanter, but I will have to pay a lot more for them.

Kanter was the only place that supply me with u-joints for my'41 De Soto ( one-or two-year only, DeSoto-only part ) for some time.

A MoPar buddy who works for NAPA managed to cross-reference that "rare" u-joint to a readily available NAPA part that also fits certain agricultural equipment and Caterpillar stuff.... I ordered on through my local NAPA, and sure enough, it will work.

You may need to find a NAPA with a patient old-timer who will look through their application book and match up your joint by construction, size, etc.

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