Floating crankshaft
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Floating crankshaft
I have a 2002 f150 4.2 and while on the highway the motor sharted clanging. It was not a deep hit and it came and went but very loud. I have been told that the crank shaft is moving forward and back app. 1/4". The fly wheel is striking the block. Has anybody heard of this before?
Thanks in advance.
Thanks in advance.
Lead Driver
Joined: Sep 2006
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In some engine/transmission designs the clearence between the converter and the bell housing is quite close.
A severly worn crank thrust bearing and or crank shaft will allow the crank to move excessively to the rear and could cause the issue.
Also pay attention to what may have caused the excessive wear.
In an auto trans, it sometimes is the converter front pump has been putting to much forward pressure on the crankshaft so these things should be looked at while all is apart.
To check this, move the crank at the front and measure the movement.
If more than about .010 you need to have the thrust bearing inspected and the crank for wear.
This means the pan comes down so the main bearing cap can be removed to inspect the bearing half and get a look at the crank thrust surface.
I once had a 2.9 v6 in a Ranger with the same issue if this is the condition you have.
Good luck.
A severly worn crank thrust bearing and or crank shaft will allow the crank to move excessively to the rear and could cause the issue.
Also pay attention to what may have caused the excessive wear.
In an auto trans, it sometimes is the converter front pump has been putting to much forward pressure on the crankshaft so these things should be looked at while all is apart.
To check this, move the crank at the front and measure the movement.
If more than about .010 you need to have the thrust bearing inspected and the crank for wear.
This means the pan comes down so the main bearing cap can be removed to inspect the bearing half and get a look at the crank thrust surface.
I once had a 2.9 v6 in a Ranger with the same issue if this is the condition you have.
Good luck.
Lead Driver
Joined: Sep 2006
Posts: 7,907
Likes: 143
If the upper half of the bearing could be removed and the crank side clearance is not worn, yes but I doubt it can be done without a lot of disassembly.
The mains would be unbolted, the cam drive chain and gears come off, the trans unbolted and moto rmoved forward so the crank can drop far enough.
If going that far, consider a rebuild if you feel the truck is worthwhile long enough to make it pay.
Good luck.
The mains would be unbolted, the cam drive chain and gears come off, the trans unbolted and moto rmoved forward so the crank can drop far enough.
If going that far, consider a rebuild if you feel the truck is worthwhile long enough to make it pay.
Good luck.
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Pretty much that is the advice I have gotten is to go with a long block and be done with it. Thanks for your time and good advice.
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Fleet Owner
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If you are handy pulling the pan will show pieces of the main thrust bearing in it. It will be the bearing infront of the rear main bearing. Usually the crank needs turned and new main and rod bearing at that time. Most crank repairs fail without mic and repair to the journals. With your knocks it is may be flat spotted also withthe loss of oil pressure, if not fixable. Torque convertor pushes it out and usually the torque convertor is also worn out.
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