Need some MAJOR help with this sound- tranny/thrust bearing

[SilverXJ]

Let me describe it first. It’s a metallic knock that varies with engine RPM. Using a stethoscope I can only hear it in the bell housing, around the RMS. When the Jeep is started from cold the sound is not there. It becomes noticeable after about 15 minutes of driving and the engine is up to temp. It happens in all the gears. It seems to go away after 2000 RPM, or I can’t hear it over the engine and exhaust. The thrust bearing is also showing accelerated wear.

Youtube video of it: http://www.youtube.com/watch?v=153_r38bn9M

What has been done:
-flex plate replaced with new
-torque converter replaced with new
-transmission and torque converter replaced with a used unit.
-Transmission fluid changed, using correct Dex/Mer fluid.
-Transmission cooler moved to passenger side
-All new transmission hoses
-External transmission filter added with cooler install
-Both transmission pumps tested
-Crank thrust bearing surface checked by 3 different companies and cleaned up.
-New thrust bearing.
-All engine clearances checked
-Side clearances on the connecting rods checked and found fine
-No valve train interference or clearance issues.
-Disabling a particular cylinder has no effect on the sound
-Clearance between crank & rods and the main girdle are at least .020”
-verified that cam was not butting up against block plug and the spring and pin were in the cam bolt.
-Torque converted installed correctly and there is about a ¼” gap between converter and flex plate before installing torque converter bolts.
-Torque converter to flex plate and flex plate to crank bolts tight and torque correctly.

These are the engine specs:
2000 block
4 wt 258 long snout crank using Hesco spacer
4.0L rods with ARP bolts; polished and shot penned
KB944 .030” over pistons (they are an early run using 2618 alloy and installed with .004” piston wall clearance)
Clevite bearings w/ rod bearing notched for rod oil squirter
Johnson/Hylift lifters
Isky cam
JP adjustable dual roller billet timing set
Smith brother’s pushrods
Harland Sharp adjustable roller rockers
Melling standard flow oil pump
Performance products harmonic balancer
Entire assembly was balanced.
Crank endplay started out at .002” and increased to .005” before being replaced
Crank and rod bearings are .0014” - .002”
Preload is .030”
Currently using Joe Gibbs BR 15w-50 oil with hot idle pressure of 28psi and hot cruising pressure of 58 psi.

The transmission cooler and hoses were changed and moved because I thought there was perhaps some restriction in the hoses or cooler which was increasing the transmission pressure causing the converter to push against the crank. I have heard of that from reading an AERA document. Install can be seen here: http://www.naxja.org/forum/showthread.php?t=1026658

I don’t know what to do anymore. The only thoughts I have is that there is still some issue with the transmission that would push the torque converted into the crank with great force. But the transmission shifts fine. Or there is some other issue with the thrust bearing that’s it is causing it to wear so fast and the crank bounce back and forth. At all times the end play was in spec but it still made that noise and continued to wear away the thrust bearing.

The vehicle runs and drives fine and the only other noise is from the roller rockers. I probably forgot to mention some items that I did as well.

[dwg86]

You stated that you had 1/4 inch gap between the converter and flexplate before you bolted it up, so I don't think the converter would have any pressure against the flexplate. I'm stumped Did you check for starter clearance?

[SilverXJ]

Yes, there was a ~1/4" gap between the converter's bolt bosses and the flex plate before I bolted it up. As for the pressure issue, I'm thinking more along the lines of hydraulic pressure from the converter/transmission pushing the crank.

I don't see anything on the starter that would be a clearance issue nor any marks on the starter or flex plate that would indicate either is hitting anything.

[SilverXJ]

This is the AERA document I referenced above with the transmission cooler pressures and torque converter pressures.
http://www.4secondsflat.com/Thrust_bear ... lures.html

I ordered a oil pressure gauge and a AN union with a gauge port in it from Jegs this evening. About $30 and I can check the cooler line pressures.

I believe the AW4 has a pressure and/or temperature bypass valve built into it. But I'm not exactly sure when it opens and closes.

And some other possible causes:
http://www.gnttype.org/techarea/transmi ... antsb.html

[yuppiexj]

Did you leave the pilot bearing (or spacer) in the 258 crank?

I found a similar case on the interwebs.

http://www.pirate4x4.com/forum/showthre ... 89&page=99

I little snip from post #607
However, what failed was not the TC or the trans. The AW4 is a fine choice for anyone looking for serious power control.

My engine failed due to 100% Corey error. Nobody is perfect.

I discovered today that I left the pilot bearing in the 4.2L crank. I have no idea how or why I did not catch this .

There was a 1/4" interference fit from the day the engine came to life.

3000km later the thrust bearing finally gave out and the block started eating the crank. It also preloaded the transmission and toasted the pump, the fluid from the TC today was not happy - not a good sign.

[SilverXJ]

No, the pilot bearing is not there.

[SilverXJ]

So I took a look at two thrust bearing pairs from the previous engine. The one that was in the engine the longer shows heavily accelerated wear on the FRONT of the bearing and some abnormal wear on the rear. The other one shows more wear on the REAR to a much lesser degree than the previous bearing's front, but was in the engine a much lesser of a time and probably spent a lot of time at idle diagnosing the cam failure. The first one was driven more.

Ok.. I can understand that on acceleration the crank will be pushed reward due to inertia... but it still shouldn't break the oil layer on the bearing and wear it this fast. Plus it doesn't explain the knocking which I can only assume is from the crank being thrown back and forth by some force.

The transmission theory doesn't fit unless some how it is creating pressure then revealing it, creating pressure then revealing it... and on and on...

Also, why would the sound not be present when cold, but start when the engine is fully warmed up? Colder oil = more oil pressure? But the oil pressure has always been good. However, the oil pressure is taken pretty much right off the pump, and it could decrease as it gets to the main bearings.... then were would the pressure go? Too much oil going through the rockers to the top of the engine? However, the rest of the bearings are fine... mains and rods. And the clearance on the mains and rods are well with in spec.

If it is a lack of oil to the thrust then I can just increase the bevel on the bearing which allows the oil to flow to the thrust surface.. however there is still the knocking sound which I assume is from the crank being thrown around. And I say assume because I have no way of measuring which direction the crank is going while it is running. If I could measure it and the dial indicator was bouncing back and forth in rhythm to the sound then I would know that that is the source of the sound. However, the best place to measure that would be off the crank bolt.. and I have no way to setup a dial indicator on the single exact center spot on the bolt and have the indicator firmly attached to the block. The flex plate is too much of an imprecise assemble to take a measurement off as it is simple stamped steel.

Would lack of oil to the thrust bearing throw the crank back and forth?

So yeah... I still have no idea

[SilverXJ]

So I don't think the accessory belt drive belt can exert enough force to push the crank reward with such force to cause my issues. However the crank is also tied to the cam by the timing set. I am also running the earlier style cam in the later block. The original cam setup on the newer block used a different cam snout, different cam gear and a a thrust plate on the cam.

Maybe the later blocks are machined more on the front than the earlier blocks to account for the cam thrust plate? What is the natural motion of the cam? To be sucked in the block by the oil pump drive resistance? Could the cam gear be set further back on the block due to the earlier cam being run on the later block, thus sucking the cam in the block which in turn would push the crank into the block via the timing chain?

[dwg86]

I am running the older style timing chain and cam in a newer block with no problems. On the newer style cam and chain, the cam sprocket didnt ride on the cam plate. I still have the newer style cam and chain I removed from my engine. I need to look and see how it was configured.

[SilverXJ]

Yeah, I know a lot of people use the older cam in the newer block with out issue.

Could it be an oil issue? The crank just bouncing off the thrust bearing.

[dwg86]

I've never seen a crank bounce off the thrust bearing without any external forces causing it to bounce. Can you get a dail indicator on the balancer or flex plate? Then the pry the crank fwd and aft to see how much play the crank has. You can do this with the engine cold and the hot to see if there is any difference in measurements. This will also see if your thrust bearing has worn beyond serviceable limits.

[SilverXJ]

I have previously taken measurements on previous end play. It will open up. However, it don't recall it being out of spec. Even with near perfect end play the noise was still there.

[SilverXJ]

Some images of the previous thrust bearings. Major wear on the front which has the most miles on it, which is the one on the left. The one on the right was in there for a short period of time and didn't see much driving time.

FRONT:






BACK:

[lafrad]

You have something majorly wrong going on.

I know you have been through this whole thing a few times... have you always been using the SAME block? the SAME crank?

has it always been the SAME transmission & torque converter?

Out of pure "what if", can the flexplate be installed backwards? Is it?


There is simply no ways to get severe pressure on a thrust bearing in a "free" motor. even with the belts and cam chain on, the fact that we have 7 mains sturdily holding the crank in place means the true "side to side" force from those is very very minimal. This really points at something in the transmission, or just faulty parts/crank/block... something that can be providing a true high amount of pressure directly at the thrust bearing.

[dwg86]

It looks like the split line of the bearing are worn more than the rest of the thrust surface, or am I looking at it wrong?. Like the bearing thrust surface at the split line is being pushed out. Maybe being pinched together. You said the thrust measurement was never out of tolerance, so I don't know if the sound would be from a worn thrust surface.