Crank Thrust Bearing

[Black 98 Joe]

My engine is at the re-builders shop right now being rebuilt. At 140,000 miles my 3.8 developed a rod knock. He reports that the crankshaft thrust bearing is trashed which in turn caused the crank to move forward and cover the oil hole which then caused the rod bearing to not be lubricated properly and spun the bearing. Has anyone else experienced this type of problem? Apparently some external force pushed the crank forward, maybe a bad torque converter, bad transmission. Any ideas? I need to figure out this problem before I put everything back together. I hate to have a repeat occurrence of this situation from something I missed. Thanks

[bigbrian442]

Re: Crank Thrust Bearing

It is normal for the trans to push the converter forward if there is play in the thrust. If the trans is pushing the converter forward and that is what took out the thrust, look for restricted cooler lines.

[WarShrike]

Re: Crank Thrust Bearing

That issue also happens when using a really high pressure clutch.

Maybe look into a good torque converter as well that has an anti ballooning plate.

[rod knock]

Re: Crank Thrust Bearing

I have never rebuilt a 3.8 before but from what i have seen in other engines i didnt think it was possible for the crank to move forward enough to block off an oil port, is it ?

[ssms5411]

Re: Crank Thrust Bearing

I don't think it will.

[rod knock]

Re: Crank Thrust Bearing

I don't think it will.

Do you happen to know of any common reasons why an otherwise perfectly running 3.8 would develop a rod knock ? Im an oil changing nazi who drives like an old woman and my 2002 3.8 firebird developed a rod knock recently.

Im curious to know if there are any mods that can be done to prevent this from happening again if i rebuild mine.

[WarShrike]

Re: Crank Thrust Bearing

Rod Knock,

The biggest issue is the oil filter bypass will get wedged open with particulate matter and cause the crank to get washed with unfiltered oil. We all know what happens when that goes down...

[ssms5411]

Re: Crank Thrust Bearing

'they make a oil PSI mod with a stiffer spring , you can do some mods to the oil bypass that will help oil PSI. I forget but someone has done a write up on it either here or FTV6.

[FirebirdGT]

Re: Crank Thrust Bearing

'they make a oil PSI mod with a stiffer spring , you can do some mods to the oil bypass that will help oil PSI. I forget but someone has done a write up on it either here or FTV6.

http://shop.zzperformance.com/store/...olume-Kit.aspx

.

[rod knock]

Re: Crank Thrust Bearing

Rod Knock,

The biggest issue is the oil filter bypass will get wedged open with particulate matter and cause the crank to get washed with unfiltered oil. We all know what happens when that goes down...

'they make a oil PSI mod with a stiffer spring , you can do some mods to the oil bypass that will help oil PSI. I forget but someone has done a write up on it either here or FTV6.

'they make a oil PSI mod with a stiffer spring , you can do some mods to the oil bypass that will help oil PSI. I forget but someone has done a write up on it either here or FTV6.

http://shop.zzperformance.com/store/...olume-Kit.aspx

.

I read some where on this site to just cap off the bypass, I assume this kit just makes the bypass stiffer ?

[rod knock]

Re: Crank Thrust Bearing

I was always under the belief that the oil bypass was there to allow some unfiltered oil to pass when the oil filter couldnt process all the oil being pumped under high rpm conditions, is this true ? And if so wouldnt blocking off the bypass put you at risk of exploding an oil filter?

[ssms5411]

Re: Crank Thrust Bearing

I belive its just blocked off on the one way to leave the other hole open to let more oil go through, yes the spring is stiffer.

[rod knock]

Re: Crank Thrust Bearing

If the bypass is the cause them im a little worried about the cam bearings too, I was considering just doing a crank kit but now im not so sure about that plan.

[ssms5411]

Re: Crank Thrust Bearing

I'm sure the crank kit will be more than enough, with good oil and maintance our 3800's will last along time.

[bigbrian442]

Re: Crank Thrust Bearing

If the engine is apart replace the cam bearings too.