Elusive Vibration
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Elusive Vibration
Hey guys,
I've got a 2WD '92 F250 W/302 CID engine and E4OD tranny. This truck has a very fine vibration in it that I just cannot find. Here is what I have done: Front end alignment, new tires all around, front wheel bearings packed, new drive shaft installed, rear differential drained and gears checked (ok). The transmission was rebuilt, but the vibration was present before the rebuild. A new torque converter and flex plate were installed during the rebuild. About the only thing I haven't replace are the shocks. The harmonic balancer seems to be ok. I have had several different mechanics check it (including dealer mechanics) and they cannot find the vibration. Like I said it is a very fine vibration that I feel come on at around 30 mph. It continues at all speeds while the engine is under load. If I let off the gas the vibration disappears. Ease on the throttle and it comes back. Truck has not been modified in any way and it has never been wrecked. I don't know what to look for any more so I hope some of you guys can help me out here.
I've got a 2WD '92 F250 W/302 CID engine and E4OD tranny. This truck has a very fine vibration in it that I just cannot find. Here is what I have done: Front end alignment, new tires all around, front wheel bearings packed, new drive shaft installed, rear differential drained and gears checked (ok). The transmission was rebuilt, but the vibration was present before the rebuild. A new torque converter and flex plate were installed during the rebuild. About the only thing I haven't replace are the shocks. The harmonic balancer seems to be ok. I have had several different mechanics check it (including dealer mechanics) and they cannot find the vibration. Like I said it is a very fine vibration that I feel come on at around 30 mph. It continues at all speeds while the engine is under load. If I let off the gas the vibration disappears. Ease on the throttle and it comes back. Truck has not been modified in any way and it has never been wrecked. I don't know what to look for any more so I hope some of you guys can help me out here.
Elder User
Joined: Nov 2005
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When you say "If I let off the gas the vibration disappears", it screams to me differential pinion carrier bearings.
I chased a similar vibration last year. Finally replaced the outer bearing, and problem disappeared.
Let us know how you come out please.
Good Luck Frank
I chased a similar vibration last year. Finally replaced the outer bearing, and problem disappeared.
Let us know how you come out please.
Good Luck Frank
Fleet Owner
Joined: Aug 2005
Posts: 23,666
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From: Easton,Ks
Sounds like low oil pressure in the transmission.
Low oil pressure can be caused by a lot of things out side the transmission:
Bad TPS.
Bad wiring to the transmission or plugs.
VSS sensor, PSOM and their wiring.
Bad PCM.
To name a few.
You need to put a gauge on the transmission that you can see as you test drive it and watch the pressure. This will tell you if it is pressure or not.
Do not over look the fan and fan clutch either.
I take it you have done a complete engine tune-up, wires, plugs, cap and rotor plus timing.
Any codes?
Low oil pressure can be caused by a lot of things out side the transmission:
Bad TPS.
Bad wiring to the transmission or plugs.
VSS sensor, PSOM and their wiring.
Bad PCM.
To name a few.
You need to put a gauge on the transmission that you can see as you test drive it and watch the pressure. This will tell you if it is pressure or not.
Do not over look the fan and fan clutch either.
I take it you have done a complete engine tune-up, wires, plugs, cap and rotor plus timing.
Any codes?
Last edited by subford; Apr 15, 2007 at 07:36 AM.
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Originally Posted by subford
I take it you have done a complete engine tune-up, wires, plugs, cap and rotor plus timing.
Any codes?
Any codes?
Thanks to all for the tips. I'll start checking or having them checked to eliminate what I can. Thanks.
