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Discussion Starter · #1 ·
Not a chevy sbc, this is a 302 FI in my F150:

Had an oil pressure problem all of a sudden ranging from normal to 0. As I increased rpm
"slightly" the oil pressure moved toward 0 and let off the throttle it went back to normal. I removed the oil pump and screen and found the screen clogged real bad. Checked all of the main bearings/journals and they are good and within specs. Have not taken the pump apart yet. But # 3 thrust bearing on one exterior side is pratcticlly gone. Cut open oil filter and found no metal particles. But in the pan found a skin piece of the # 3 bearing thrust side metal. Bearing side worn was toward rear of engine . My guess is this happened in short order and probably the screen plugged restricted oil circulation and somehow toasted the exterior side of the bearing. I am replacing the oil screen and pump. Of course the crankshaft end play is way out.
Note, measured all of the bearings at journals are good, the engine does not have any noises...knocks etc., I'm planning on just replace the thrust bearing and if the end thrust clearance is ok, just leave the engine as is and drive it.
This is the original 302FI in my F150 extended cab, never had any issues with oil/pressure before. Been using Mobil 1. About 125K on engine.
This just baffles me how this happen without damaging any bearing surfaces? Any thoughts Phil
 

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is this a stick or automatic? how many miles? something is pushing the crank foreward and wiping out the thrust. I've seen this a few times. Could be the torque converter balloned, trans cooler clogged causing excessive pressure, belt pulleys out of alignment. Something stuck inside the input shaft of the trans. If its a stick too much having your foot on the clutch at stoplights. Also if the engine was just rebuilt the thrust clearance wasnt set properly. Just some ideas.
 

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Discussion Starter · #3 ·
Its an automatic w overdrive. have not ever had it adjusted. original trannie. changed the fluid several times over its lifetime
 

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This one is a real mystery. If the thrust bearing is worn on one side you need to be looking at what could be pushing it so hard in that direction. Most of the typical culprits have been mentioned above.
The clogged pump is a clue but I can't think of anything else specific to look for right now.
You bought the truck new and the engine has never been apart?
 

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Discussion Starter · #5 ·
This one is a real mystery. If the thrust bearing is worn on one side you need to be looking at what could be pushing it so hard in that direction. Most of the typical culprits have been mentioned above.
The clogged pump is a clue but I can't think of anything else specific to look for right now.
You bought the truck new and the engine has never been apart?
Paul, yes the engine and trannie are virgin...never been apart. I've had some replies and all seem to be leaning to a balooned converter. Saying that would exert excessive pressure against the crankshaft thrust bearing and to wipe the bearing shim side out on the trannie side of the crankshaft. Over the past few years, at times,I had a "drumming" sound at times on acceleration.No one could ever pin point the problem and trannie shops said it was other than transmission. Sooooooo I'm now thinking about a month ago the drumming dis appeared altogether. Hmmm and maybe so did my thrust bearing. Now I'm thinking the drumming may have been the ballooning and overtime just wiped the trannie side of the thrust bearing.

I never even heard of problem like this deriving from a trannie/converter. But on the other hand never had been an auto trannie guy. Just goes to show how little sometimes we do know and thanks for people with their expertise can help over sites like this and others. Thnaks 6nova4 for opening up may eyes on this and thanks Paul for your input.

BTW. I'm looking at this as being two fold: in that the converter wiped the thrust bearing out and the clogged screen was relating to the restrictive low oil pressure which in turn may me drop the oil pan and discover now the "two" differnet problems. Sometimes you get lucky and kill two birds with one stone. Were not for the oil gage the motor could have been toast.

Phil
 

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Discussion Starter · #6 ·
is this a stick or automatic? how many miles? something is pushing the crank foreward and wiping out the thrust. I've seen this a few times. Could be the torque converter balloned, trans cooler clogged causing excessive pressure, belt pulleys out of alignment. Something stuck inside the input shaft of the trans. If its a stick too much having your foot on the clutch at stoplights. Also if the engine was just rebuilt the thrust clearance wasnt set properly. Just some ideas.
Really appreciate the heads up on "ballooning". Please read the post above. I think you may have nailed it with the converter problem. The belt system is serpetine type. alignment was fine. Trans cooler factory...suppose it could be removed and checked or take it to a trannie shop for test?
Thanks, your reply would be appreciated...Phil
 

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A ballooned converter is something you might see on a high powered drag car but not a stock pickup truck. I'm not saying that isn't possible, but I've never seen that on a stock low performance vehicle. If you have a lockup converter then something may have failed internally that is forcing the converter forward and applying pressure on the crank. I would think you'd have other symptoms as well if that were the case.
I'm not sure what it is, but I'm skeptical it's a "ballooned" converter. Let us know what you find. I'll be curious to see what it turns out to be.
 

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The Ford oil problem is common in "HIGH" mileage for the 5.0/302 5.7/351w engines.

The most common problem is the valve seal deterioration. The umbrella seals will harden and fall apart. The parts of the seal will get into the oil pump screen and eventually into the oil pump.
The design of the Ford pump will not allow any trash. Pumps are know to lock up from this trash. A very small piece of anything can cause the pump to lock up. And in most cases the oil pump drive shaft will break, being the weak link.

Thrust bearing wear is also common, when the pressure in the trans pump is very high. This is caused mostly by a bad regulator pressure valve in the transmission. This pushes the converter forward. The high pressure is normal when pulling a heavy load. Normal oil pressure in the engine keeps the main bearing in good shape.

A combination of Low oil pressure and high trans pressure will have a negative result on the thrust bearing.

Unlike, Chevy. The thrust bearing in the Ford located in the center main is very soft material compared to a GM bearing. And will take most of the wear.

Chevy thrust problems usual eat the crap out of the crankshaft!


IMO
What you have is a low oil pressure problem that caused the bearing problem. The low oil pressure from trash in the pick up, maybe valve seal material!
When the transmission was under a heavy load it put the added pressure against the thrust bearing and this is the extra wear.

Good luck
Al
 

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I would have to agree with about everybody I guess.


The only thing I might add is to check the thrust surface of the crank very carefully. In my experience its very unusual to have thrust bearing failure and not damage the crank. If the crank is defective the new brg (in my opinion) is very likley to fail as well.


Also Im pretty sure the thrust brg is "adjusted" on this application by tapping the crank back and forth in the block with cap just snugged down a bit.

Im probably way crazy but I always try and just make sure the rear surface of the thrust is aligned as I have never seen a thrust fail in front. I would rather have any slight mismatch in overall brg thickness in the front. Just me.
 
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