Vibration in Tractor

[Anonymous-0]

2005 Massey Ferguson 431 - has vibration between idle and 2000 RPM's. The whole tractor shakes in that RPM range. Any suggestions on what the problem may be?

 

[Anonymous-0]

Hello,
Does the engine sound like it is mis-firing? To check the top end; set the engine speed at idle and slacken each injector pipe nut in turn. The engine should show a drop in speed until retightened. Normally the bad cylinder will have little effect. Does not sound like a top end problem but its a starting point. Another possibility is a loose flywheel. Does the vibration change if you press the clutch pedal?
DavidP

 

[Jerry/MT]

Most engines installations have some critical frequencies where the vibration peaks. But nor as wide a range as you describe(Idle to 2000 rpm). Are you sure it;s not sheet metal vibrating?

Make sure that you don't have loose mounts. Usually the front axles bolts to a fitting on the engine make sure that it's tight and that your transmission bolts are all tight. Look for cracks at there mounting points. If your engine has a balancer then it may have come loose or is damaged.

 

[Anonymous-0]

Hi Jerry,
Good points about loose bolts, cracks etc.
The balancer would have been a prime possibility but I did not suggest that because my understanding is that the 431 is a 3 cylinder tractor and therefore one would not be fitted.
DavidP

 

[Geoff in Scotland]

On 3-cylinder crankshafts there are 2 balance weights....no matter what is fitted on or into an engine has the possibility of giving a problem at sometime....there is a possibility of one of the balance weights becoming slack....they have also been known to crack and break....mind you if one has broken you would have a vibration so fierce you could share it with someone....Geoff

 

[Anonymous-0]

Hello Geoff,
There are indeed two balance weights fitted on 3A.152 and AD3.152 3 cylinder cranks. However the MF 431 has a 1103C-33 Perkins 3 cylinder engine fitted. Had this been a '152' that could indeed have been a possible cause and may be in this case. I do not have any info on this tractor so it is suggestions only at the moment.
Regards
DavidP

 

[JerryMT]

my Ford's a three cylinder and it has one, David. I think only the 6 cylinders don't require balances but it's been a long time since I took a Vibrations course.

 

[Anonymous-0]

Hi Jerry,
I think that we are splitting hairs on this one a little between the balance weights and a balancer unit. The 152 has the weights so does not need a balancer because the journals are equally spaced. Four cylinder engined tractors comprising the '5' line, (135) were not fitted with balancers as they were regarded as more of a utility tractor. The '8' line, (I believe the 148 was originally going to be a four cylinder), 168 and 188 were the 'Super spec' tractors having more features. The addition of the balancer gave a smoother engine. On a four cylinder, vibrations are caused when the pistons travel from max speed to zero in 3 inches or so. There is always a 'two up, two down' stress. The balancer reduces this stress. Whatever the cause of this perhaps we should wait to hear some more from M LeBrell.
Cheers
DavidP