The Stovebolt Site Forums The Shop Area Engine Shop Rebuilt Engine Vibration

I got my 62 3/4 ton, stepside. longbed back with a rebuilt, 30 over 235. It is running very well except that there is a vibration. I disconnected the fan belt, checked the points/timing/cylinder balance but the vibration is still there. It is a low-pitch noisy shake that is so pronounced it shakes my mirrors to much to read the license plate of the vehicle behind me. It is worse under a load. On the expressway at 55mph if I let up off the gas the vibration is greatly reduced. It vibrates even when stopped and is worse at specific rpm's so it is not the drive shaft. It had a slight vibration before it was rebuilt but nothing this pronounced. When they put the engine back together the harmonic balancer and associated pulley were different. I don't know about the fan blade. Also they made a mistake during reassembly and had to pull my trans and remove the clutch. Whether this has anything to do with the vibration I do not know. Any suggestions?

since it was rebuilt I assume the spark plugs and everything are fine and the wires are all connected right? if the wires are crossed, the truck will shake really bad. Check to see if the engine misses. Or, it could be the wrong harmonic balancer, or when they re-built it, they either didnt balance the crankshaft, or they did it poorly. You said the shop made a mistake and you had to take the tranny off? what kind of mistake?

Hey gmcfan:

It is tuned well, does not miss and has plenty of power. That was the first thing that I did. I also checked the cylinder balance with a tach.

I don't believe that they balanced the crank. It was supposedly balanced from the factory. This motor had a minor vibration before the rebuild but now is unacceptable.

The guy left an oil plug out after he had installed the motor and dropped the tranny/clutch et to get to it rather than pull the motor again.

I do know that the harmonic balancer is different as are the pulleys. I am going to call him again today. Boy do I hope that it isn't the crankshaft........ :•(

It could be the Flywheel out of balance. Some engines are sensitive to how the flywheel is installed. If,after checking other things and you still have the vibration, you might try unbolting the flywheel and rotate it 180 degrees. ( I am ASSuming that it does not have a dowel to locate it) If the flywheel is the culprit, that will either reduce the vibration or shift it to different RPM range.

Some other thougnts: Rebuilt engine with mismatched pistons (one heavier than other), pressure plate/clutch out of balance, vibration damper, crank balance
Good luck

Ok, after my previous post I looked at the factory service manual for '59 and it says the flywheel is located by 3 off set dowels, so it will obviously only fit one way. Of course, if someone took the dowels out to chuck the crank in a crank grinder, and did not reinstall the dowels,............

Stranger things have happened.

Thanks for the help guys. I was really jazzed about getting my truck rebuilt. I painted it and it is looking really good. I can't tell you how depressing it is to have this problem.

I know that they did not put the original harmonic balancer back on and it is missing a pully. Perhaps this and the clutch out of balance?

I'm taking it back on Wednesday. The owner is a good guy and his wife of 40 years is dying of congestive heart failure. He has a lot on his mind. I think that he will do his best to solve the problem. I just hope that his best is good enough.

Tab.....Try this.....When you are driving on the highway put light pressure on the clutch.
If the vibration goes away...Re adjust the freeplay,and or put a stronger spring on the clutch
Also grab the clutch ped and try movin it left and right.....if it moves make a bush to the list above

Have you grabbed onto the driveshaft and tried to move it

I bet you got two things at once going on.....just an old guy guessin

Hey J.H.

I'll try putting slight pressure on the clutch. The problem is worse under load. When I let up off the gas at abut 55mph (clutch out) it stops. As soon as I press on the gas again it comes back. The vibration is independent of the drive shaft as it does so in idle.

Tab:
I don't mean to be demeaning of your ability, but have you re-checked the plug wires to make sure they are ordered properly? I only suggest this because it is a simple thing to check that could cause this problem and it is easy to inadvertently mix a couple of wires while concentrating on something else. And yes, I've done it (several times.

I appreciate your post but I assure you....the engine does not miss at any rpm . The motor has plenty of power that is not the problem. The vibration is worse at certain rpm and is worse under load as I drive. I think that the drive shaft may be part of the problem but it still vibrates parked in neutral.

Tab ..... It is STRANGE

So your going to get a strange idea from me. Are the bellhousing bolts tight....and bolts trans to
bellhousing. You might have a bolt or two that are bottomed out feel tight and are still letting the whole mess move.....ditto flywheel bolts

Do you see where I'm going?

Something IS loose.....and bolts may 'FEEL' tight

I don't think a pilot bush would cause this unless you left it out.Did you leave the bush out?

I don't know what I'm missing, but couldn't a simple loose motor mount cause this?

Jeff your right but it wouldn't be clutch or speed related. The got worse when the clutch is in
is a real clue....If he left out the pilot bush the clutch would center randomly and would do the shakes at idle.
I know there are other thing that can do this but as always we must guess....

I once had a noise in the 228 and vibration like this It was a chunk missin from the FAT fan belt
it slapped and knocked like a piston

Would the clutch know it was under a load? I can see where it would vibrate with clutch disengaged, but why under a load? Could the engine be lean and running rough and not really a vibration? I would think something would have to be pretty bad to vibrate a 500 rpm (idle). Is the harmonic balancer straight? What does it do at idle with the clutch in then out? did it change? How do you feel the vibration, in the steering wheel, the floor, seat of pants, clutch lever? Could be pushing the clutch in rock the motor or put strain on the mounts? Is the exhaust pipe rubbing? What about high rpm sitting still? does it get worse going through a certain rpm range? can you hold at a givin point to make it vibrate?

This is a strange problem, I just threw this stuff out. It may all be trash, just stuff I thought of. Keep us posted, Joe

It's all 'OUT THERE' cause we can't see and feel it....One guys 'tick' is another guys 'rod knock'
I kindda chose the clutch and trans cause he says the motor runs fine and the clutch ped in my 39 make a 'Hell Racket!!'
What happens is the clutch and trans are turning all the time the motor's running If the clutch
isn't centered you get a shake....it will vary a bunch if you leave out the pilot bush. Sometimes at speed it will center sometimes not.
I mentioned the bolts cause it's a easier to see if that's the problem.AND it will do just these things also.
Tab...If it all looks good ...get under back off the pressure plate bolts and try deflecting the input shaft....if it moves that's it! and look at the flywheel.If there is runout also it!

Hi Tab,

I had a very similar problem and it was due to the bolts on the flywheel. More specifically, one was so loose that it was allowing the flywheel to vibrate. Like your problem, it was worse under a load and vibrated the whole car as if something was very wrong.

Just my $.02.

Good luck.

Tab,

Check the simple stuff that has been mentioned before. Check for loose flywheel and clutch bolts, motor mounts, tranny mounts. Check for a loose water pump bearings, pulley or fan blade. Make sure the alt or generator pulley and mounts are tight. If these items are correct and not causing the problem, then delve deeper into the motor.

Now for some of the more involved and "out there" ideas:

The possibility that the front balancer and pulley are now different is a big clue. Ask the shop why they are different. If the parts are different than what the engine had when you brought it to them, then remove the balancer and have it rebalanced.

Its kind of like a tire/rim balancing. If a tire is out of balance, it'll hop up and down, right? The wheel weights on a tire/rim assembly are there to achieve "zero balance". This is so there is no heavy spot for centrifugal force to cause vibration. Same thing on a 235 front balancer. (I think)

Some balancers on other types of engines (V8s, etc) had weights in them to offset the crank weight. That way, the total system achieves "zero balance" I don't think the 235 is like this. I just think its a dampener, not really a "balancer" per se. So if the unit on your engine is not at "zero balance" it may cause some vibration due to offset weight. I may be wrong, but if so, somebody will correct me.

The front balancer/pulley assembly is supposed to "dampen" some of the torsonal (twisting)action and vibration harmonics that appear in a crankshaft when running.

If the unit has been custom balanced for a different 235, it might be out of balance on your engine. If the balancer is defective or "slipped" it may also malfunction and not cancel the crank harmonics that appear at certian RPMs in all engines. A 235 balancer is a press fit on the crank snout. There is no bolt that holds it on. So if the unit is loose and wobbling on the crank, then that is another common problem. It is very important to have a good balancer properly installed on the engine to dampen vibration.

I think a 235 is an internally balanced engine. All that means is the crankshaft counterweights are supposed to offset the weight of the piston/rod assemblies and the crankshaft throws. However, the rotating assembly should always be rebalanced during a rebuild. The new pistons, rings and bearings are going to weigh different than stock specs, throwing the "factory designed balance" off.

The flywheel is dowel-pinned to go on only one way. This makes sure that the timing ball in the flywheel always indicates TDC. I don't know if the flywheel is offset weighted or not. If not, you can have it "zero balanced".

If the flywheel is supposed to have some offset weight, then I don't know how you correct this, since the engine wasn't balanced during the rebuild. You wouldn't know how to balance the weight on the flywheel to cancel the offset weight in the engine, because it wasn't measured during the rebuild.

Checking the balancer, flywheel, and pressure plate may solve the problem. If not, then you'd have to look for an unbalanced component inside the engine.

Sorry for the novel. If I've gotten a technical detail wrong, somebody please correct it.

good luck

chip

So Tab......what happened??

somebody mentioned the pilot bushing, back up there. I once had a similar vibration problem, in a big block firebird. Neglible vibration until I put a load on it. After a lot of searching, it turned out to be that pilot bushing. Worth a check.....02c.

I can't thank you guys enough for your thoughtful comments on my problem. I still have to take it back to the guy but can't until I can get a ride back home. I may have to get a tow-bar and take my economy box with me.

I believe that as someone above said that I have a twofold or threefold problem. The fact that the original harmonic balancer and pulleys were not reinstalled is troublesome.

Again: The engine has some vibration but not at idle. When I drive the vibration gets much worse especially around 30mph in 3rd gear. I'm beginning to believe that there is a problem with the clutch/ pressure plate, the harmonic balancer and the fan.

I plan on taking it back this week and will surely let you guys know what happens.

Thanks Again !!!!!

May not be possible with your combination, but
a long time ago I had installed the clutch in backwards. This caused a chattering under load also. On 98% of the flywheels this is not possible, but there are a few that can be reversed. In my case there was just enough clearance to do it.
Good luck
Brad

Since you say it vibrates with out being driven, and vibrates differently at different speeds and worse under load. It does sound like a balance issue with the engine itself, or whatever is bolted to it, like the clutch. Having a load behind it would just amplify the shake. Since the engine did it before the question would be did it shake at the same rpms and with the same frequency? It looks like it will take a step by step process to diagnose. Sorry about that I understand your frustration.

I understand where the guys are coming from on the spark plug wires because I have a supercharged 90 MK VII and when its just out of tune a bit (like one wire or plug bad) that lack of one working pot really makes the car run rough. Because of the blower, what joe blow in his regular lincoln wouldn't really notice is quite amplified on my motor. However, in this case, its kind of a regular vibe and it is carried through out the rpm range.

With your engine running right now the old vibration or out of balance condition could be amplified more than it was in its original anemic state.

So the first change would be to put the right balancer on it and see how that helps, and then proceed from there. It may have been wrong for quite a while. Another case would be somekind of warp in the clutch, so maybe if the shop can pull the tranny off/back and run the motor and see if the vibe is there, that would be a 2nd step. Next would be pull off the clutch, and run it, if the vibe is still there, then at least you know its confined to the motor.

I thought I used to see a fludic type harmonic balancer that worked like those wheel ones that the goo distributed itself about in them to balance bad wheels, etc. Anyone ever try one of those on wheels or motor? Or are they just another magentic-fuel-line-spark-amplifier-snake oil special? :rolleyes:

Haven't taken it back yet as I have no ride back home. I am going to buy a tow bar from UHaul Monday and tow my econo box behind me to the shop. If you guys know where I can get a "old style" towbar for less than $125.00 let me know.

It is definately not an engine misfire. The original harmonic balancer had a distinct mark on it. That's how I know it is not original.

I am going to have him replace the balancer and look at the Clutch. I like the idea of removing the clutch and starting the motor.

If this problem ever gets resolved I will surely let you guys know. Hopefully this week......

Thanks!