Feeling Vibrations

[skokie]

I started the truck last night and let it warm up. After 5-6 mins I kick the gas once and it drops down to 750. I slowly rev it up through 1800 -2000 and at 1400-1500 I am feeling a vibration coming through the truck. This is with the truck not moving. I dont think its the mufflers. They are stock.
Any suggestions?

Thanks

[Tx Firefighter]

Check motor mounts and trans mount to make sure they're not sagged or broke.

Also, follow the exhaust all the way from front to back to make sure it's not hitting the frame when the engine revs up. As the engine revs, it will rock slightly, and if one of the pipes is real close to the frame, it will hit when the engines moves. Also, make sure your exhaust hangers are all rubber isolated. Occasionally, someone bolts the pipes directly to the frame and doesn't use any form of rubber to isolate it from the frame.

[skokie]

I went through it last night. Montor and trans mounts look good. Hangers have rubber on them and the pipes are not touching. What else could this be?

Thanks

[67ChevyRedneck]

If the engine is not making any noise, possibly a bad balancer? I put a used one on my rebuilt engine to save money...which was STUPID I ended up replacing it a few months later. Truck all of a sudden started vibratin like a son of a gun. If the balnacer is bad is usually causes a leak around the shaft where it goes into the timing chain cover.

[skokie]

The engine is not making any noise. I noticed it (not sure when it started) when I converted from long waterpump to short and its only from 1300-1500 that I feel it the vibration.

[Brainchild]

Check the crank pulleys make sure they are tight,anmdnot bent or wobbling.And might as well check the crank bolt to make sure it's tight too.

[skokie]

Thanks Brainchild. I will do that tonight.

[skokie]

I forgot to mention this in the original post. The vibration starts at around 1300-1500 and will go away and come back. Can that be nailed down to flexplate, balancer or pulleys? Or would it be best for me to replace the pulleys first and work my way to the flexplate?

thanks

[franko72]

when was your last tune up? could be the carb. a dirty spark plug.Dist. cap or button, points etc.

[skokie]

Carb is 5 months, new fuel filter as put in when the carb was installed, plugs, cap and rotor are also new. It is a hei not points. Is there anyway I can look at the harmonic balancer and see if anything is wrong?
Thanks

[franko72]

look to see if there are any cracks in the rubber or any rubber sticking out between the metal parts on balancer.does it happen when you drive it?could be a valve sticking

[skokie]

I will check it out. It happens when the truck is sitting still.

[skokie]

OK I got a good look at the balancer when its at 1300 rpm. It looks like the balancer is hopping up and down just a tad. When I rev it up to around 1600-1800 it stops. Is this normal or is this the culprit?

Thanks

[jhow66]

Could be a bent fan blade- remove belt and try it.

[franko72]

when you converted the water pump, did you correct the offset alignment for the pulleys to the crank? can you get someone to rev the motor to the problem RPM zone and take a visual look at the tracking of the belt or belts.you said that the problem was there after you converted the pump, something may be in a bind, maybe the belt is to tight, but I dought that is the problem.Trial and error is tough. good luck.

[skokie]

Jhow66 I dont think its a bend blade since that is a brand new fan and fan clutch but anything is possible. Frank072 I am not sure what you mean? I did get the pulleys from a short waterpump setup before I did the swap over on the water pump.

[jhow66]

Go ahead and take belt off and try it. This way you can narrow it down some. (not fan, water pump or alt. bearing.)

[franko72]

Try what jhow66 suggested. remove the belt and try it. If you already have changed to the proper pulley then the belt alignment should be tracking straight and evenly from the additional pulleys.Try a new balancer?

[skokie]

Well I checked the flexplate and it looks ok. I dont see any cracks. I removed the belt and the vibration is still there at 1300 then goes away for 2-3 seconds then comes back and so on. The harmonic balancer seems to be bouncing a little. I noticed it more in the daylight than I did at night. I think it may be time to get the balancer replaced but that will need to wait a bit. The qjet rebuild is getting my money next week .

[chickenwing]

Just tossin this out there. Torque converter?

Post #13 states balancer is hopping up and down.... Would say no that is not normal. If you can actually see a hop or vibration with the naked eye it would have to be way off.

[skokie]

New torque converter was installed when tranny was rebuilt. I wish I could get a video of this hop. Its a little hop but you can see it. Ok next question how do you swap out a balancer?

Thanks

[skokie]

I took the crank pulleys off today. First thing I came across was a not very tight harmonic balancer bolt. I put the crank pulley back on and tightened the bolt as tight as I could before the engine started turning over. I need to get a tool to stop that while I torque it down. I started it up and the vibration is still there. About half as bad but still there. Off to the tranny shop I go to have them check the torque converter.

[70 shorty]

Try tightening up the balancer with a balancer installation tool. Look back last week, there was a thread where someone tried to tighten the balancer with the bolt and it broke the bolt. That's why there are harmonic balancer installers. You'd have a mess on your hands if the bolt broke.

[jhow66]

Lossen the balancer bolt back up and see if you can move it back and forth. If it moves the key way is wallowed out. This will cause the balancer to shake which is probably your vibration.

[skokie]

Jhow66 I will do that and 70 shorty I will tighten it up with the tool. I think the parts store has one. I will have to head down there tomorrow and get one. Jhow66 if the key is wallowed out then what is my next move?

Thanks