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Engine keeps eating thrust bearings

20K views 32 replies 9 participants last post by  KEVINS 
#1 ·
I'm running a 4r75w with a Circle D triple disc converter behind my 4.6. I first installed the setup around 2 years ago, and it ran excellent for 8000 miles or so.

I never had an issue with the stock shortblock, so I yanked it and swapped to a MMR rotating assembly in a new block. After 200 miles, my thrust bearing did this:

Crank end play on that engine was .007, and converter pullback was 3/16th. The machinist who did the work on that shortblock was less than professional, so I figured there was a metal shard that he and I had missed had gotten in around the bearing and chewed it to pieces. Bummer, better start again.

So this time, I put together another bottom end. Reused my stock crank, and block, got the converter inspected by Circle D, etc. Crankshaft endplay was .0065", converter pullback was 1/8th" (I quadruple checked), I used one of the best machinists in my area and I cleaned every oil port religiously after the work was done.

The result? Thrust bearing failed even more catastrophically than last time, this time in 150 miles.

I'm confident that my shortblock was assembled correctly since I did the work myself. I'm also confident that my converter was healthy (it was freshly rebuilt), and the pullback was in spec. With that said, the obvious culprit was my transmission killing these thrust bearings. The best theory I have heard thus far is that my transmission cooler was clogged or restricting flow, causing converter charge pressure to rise and wiping out my thrust. This is possible since I am still using some hard lines in the trans that could have been beaten up or pinched during the engine install.

I'm going to grab some new pistons and a crank to fix the shortblock, and when I put it back together I'm going to throw a pressure gauge inline to check my charge pressure on initial start. If I can confirm it's high, I'll swap the whole trans cooler setup out for something huge with AN lines.

I'm wanting your all's input on any other theories on what is going on. I'd be sick if I built this thing for the 3rd time only to have it die within 200 miles. I still have the dead shortblock in my garage so I can do all the forensic work required.
 
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#2 ·
From what you have said and shown in the pics, I believe your analysis of what went wrong (high charge pressure) could very well be the culprit here. I definitely would not reassemble without at a minimum cleaning out the existing lines and looking for kinks or flow restrictions. If it is an OEM transmission cooler it has adequate flow capacity as long as it is not clogged up with clutch pack or other foreign material. While you could go to an aftermarket cooler I don't think it is necessary unless there were an obvious deficiency in the OEM cooler's physical condition, capacity or flow.

The other thing you might want to check into is the transmission builder. Explain to him what has happened and ask him about how to manage the charging pressure to a level that does not push the converter as forcibly towards the crank.

In auto cars there is a particular benefit to running a flanged upper and lower #5 thrust bearing. Check out Joe Goffin's excellent Aluminator Gibtec build thread in the Terminator Table of Contents (TToC). He describes a very economical way to do this.

Sean Hyland in his book on How to Build Max Performance 4.6L Ford Engines illustrates the process of drilling the #5 main oil supply hole to provide increased lubrication to the rear thrust surface of #5 main. The illustrations are on page 13 of the original release of the book and page 17 of the newest (blue cover) release of the book.

Ed
 
#6 ·
Are you using a block plate? What flexplate are you using? Possible converter pilot bottoming out. Bolt the flexplate back on and set the converter on the flexplate. Make sure the mounting tabs on the converter sit flush and see how far the converter pilot engages the crankshaft.
 
#7 ·
Just a couple things to comment & add.

First i have a question. What is the power adder and does the car still have a stock crank pulley support system? With big blowers those can actually tighten up and the support PULLS the crank forward.

Cooler circuit pressure is absolutely the first thing I would check (after the stock crank support). But I'd like to point out that cooler circuit pressure is not the same thing as line pressure. They are related but are checked separatly. Line pressure should be checked right after cooler circuit (or at the same time if you have 2 gauges)

Personally I feel like the full flanged thrust isn't going to live through a trust issue like this. It's more like a bandaid on a severed artery.
 
#8 · (Edited)
Eric (Swerve) is correct about the fully flanged thrust not being able to correct for a mechanical malfunction. The fully flanged thrust requires the engine transmission combination to be free of mechanical malfunction. When it is free of mechanical malfunction the fully flanged thrust will provide superior service to the multi-piece thrust solution. Very importantly it will not correct a mechanical malfunction.

That said, some converter transmission combinations use higher than necessary charging pressures that can cause the converter to move forward and damage the thrust bearing. If you can, it is to your advantage to lower those pressures. Most of the transmission / converter providers are familiar with the phenomena and know how to address it. I would contact the folks you purchased the converter from explain what is happening and listen to what they have to say about their product, your transmission and this phenomena.


Ed


p.s. Eric's other point about the stock lower support (if you are using it) is spot on. As the OEM supports have aged some have displayed a predisposition to screw onto the crank front pulling it forward in the block. The upshot of the whole shebang is a dead thrust bearing.

If you are using a OEM snout support I would consider going to a Metco or similar lower. If you stud the crank snout you will substantially improve your crank's snout life. There is info over in the TToC about how to do this in the Engine subsection. The two threads are Crank Tech I & II.

Other than a billet crank with a redesigned snout there is no absolutely certain way of knowing the snout will not break off — that's the bad news. The good news is that while the stud solution is not perfect, no using it has yet to report a snout failure. An extra added attraction available at no extra cost is the headache reduction associated with not having to wrestle with the OEM crank support any more when you work on the engine.
 
#9 ·
Sorry for the thread revival. Work has been crazy and I'm just now rebuilding my shortblock.

From what I'm reading, I will need the King MB5353SI for my Romeo iron block (although I've seen MB5281SI commonly listed, the part number comes back for an aluminum block), and the tangless thrust out of the MB5219SI set.

Can anyone confirm that the 5219 thrust will work on a Romeo iron block? I'm wanting to get these ordered today if possible.
 
#10 ·
Sorry for the thread revival. Work has been crazy and I'm just now rebuilding my shortblock.

From what I'm reading, I will need the King MB5353SI for my Romeo iron block (although I've seen MB5281SI commonly listed, the part number comes back for an aluminum block), and the tangless thrust out of the MB5219SI set.

Can anyone confirm that the 5219 thrust will work on a Romeo iron block? I'm wanting to get these ordered today if possible.
The 5219 thrust will not work on a Romeo block.

Ed
 
#12 ·
More importantly, what was done to correct the thrust issue?

There is nothing wrong with the washer setup. Many people have gone a lot faster than I with that setup. If you have something thrusting the crank to excess, neither bearing setup will survive.
 
#14 ·
There are none. More to the point though is what Eric asked which is, what was causing the problem and what has been done to rectify it?

Ed
The thrust bearing was actually not harmed during this last engine failure! I assumed it was a thrust at the time I made the original post because the previous engine died under very similar circumstances (~200 miles post rebuild, metallic ringing sound at idle, bearing material in the pan, etc.).

I initially checked the oil pan, saw massive amounts of bearing material, and misdiagnosed it. After I tore into it a few weeks ago, I found that the thrust was actually perfect. It was a rod bearing that had failed. I checked the bearing clearances several times during assembly and they were within spec, so my only other culprit was assembly error on my part.

I was asking about the thrust bearing mod in the post above as a "while I'm in there..." preventative measure.

Thrust bearing:

Rod bearing:


As far as corrective actions, I swapped my transmission lines to some -6an Aeroquip hose. Also swapped to a TruCool transcooler with 3/8ths ports. Darrin at BCA assured me that these things combined with correct converter pullback would keep the thrust alive with my current setup.

Corrective actions for the rod bearing include more measurements, not working on the shortblock late at night, and a 3 beer limit during engine assembly. :)

Thanks for the input, everyone. I will run an aluminum block eventually, and I'll be sure to use the thrust mod when the time comes.
 
#17 · (Edited)
In the sequence of oiling, the oil travels from the main gallery to the main bearings and then through the oiling passages in the crank to the rods. The entire system is a controlled leak. By carefully managing clearance at the mains a percentage of the oil supply is allowed to 'leak' through the clearance between the crank and the bearing to provide lubrication to the main journal and the rest of the oil is routed to the connecting rod journal to lubricate the connecting rod bearing.

Some builders like to manipulate the clearances at the mains and rods. This is generally playing with the primal forces of nature. When you increase main clearance it is at the expense of oiling to the rods. When you increase rod clearance it is at the expense of the mains. In 99.99% of builds it is to your advantage to build to Ford specs.

A single rod failure is typically an obstructed oiling passage from main journal to rod journal. This is easy to check for and clean with a brush if necessary. If the oiling passages are not blocked or obstructed then small particulate matter in the oil that has escaped the filtering process and found it's way to the rod bearing is the likely culprit. The particulate matter would have to be larger then the oil clearance. If it were then it would be wedged between the rod journal and bearing and do its deed.

The best protection against this on a new engine build is the use of a full flow filter that does not have a bypass valve. Most all over the counter filters have this bypass. The bypass can shunt as much as 50% or more of the oil around the filter's media allowing it to return to the engine w/o any filtration. The quick fix is to use one or two full flow filters on newly built engines to insure any particulate matter is trapped in the filter.

After you are comfortable the oil in the engine is in fact free of foreign matter you can change over to a conventional filter. Jomar Performance sells what they call a Professional Filter that will filter 100% of the oil all the time. The can be used as a regular filter but it needs to be maintained regularily so it does not clog up and reduce oil flow as it traps junk in the oil, including fibers from your build rags. After a few hours of continuous or near continuous use you should change the filter either to a conventional bypass filter or a second Jomar filter if you are a little paranoid.

If you wish you can run the filter instead of a bypass filter between oil changes. After initial break in on engines like ours I would attempt to change the filter every 3500 miles or less at each oil change just to be safe. Operation for that length of time will not clog up a full flow filter and you have the confidence of knowing that all the oil is being filtered all the time.

Here is the link to the filters => Jomar Professional Filter One other benefit of the filter is that it has a very high burst strength somewhere north of 600 psi.

Ed
 
#18 ·
Ed,

Thank you yet again for the information. Like I said, I'm not completely ready to call myself faultless for the rod bearing failure, but I do know for a fact the clearances were within spec. That foreign material theory does make sense, although I was careful to clean the block to the best of my ability. For $15, the filters you mentioned are definitely a no brainer for the first 3 oil changes.
 
#19 ·
As fastidiously as we clean engine components prior to assembly it is really amazing the junk that gets trapped inside an engine prior to first start. We are on the same page with respect to first start protection, the Jomar filter is just good cheap insurance.


Ed
 
#20 ·
I wanted to update this again.

Let's recap over my last 3 builds really fast:

1st engine:
Crank end play on that engine was .007. Used MMR rotating assembly with an 8 bolt Freddy Brown SFI flexplate. 2004 GT transmission cooler/radiator with the stock hard lines out of that car. Circle D triple disc converter. Result: catastrophic thrust failure.

2nd engine:
Crankshaft endplay .0065. Used factory Ford 6 bolt flexplate to fit the GT crankshaft I threw in this engine. .125" converter pull back. Same converter, same transmission, same tune, etc. Result: thrust was fine. Rod bearing died but that's another story.

3rd (current) engine:
Crank endplay: .0065". Used FB flexplate from 1st build since I used a Cobra 8 bolt crank. Converter pull back was initially .28", so I machined 4 spacers to bring it to .14". Same tune. Same trans. Same converter (verified good by Circle D in between builds). I did upgrade to a B&M cooler with -6 lines to verify no converter charge pressure issues.

This engine has 15 street miles (rings seated) and about 20-30 minutes combined of idle time. I began hearing a clanking sound at idle. I eliminated all possible sources of the sound outside the engine, and yanked it two days ago to begin checking bearings. Everything looks great. No bearing material in the pan, all rod bearings look healthy, etc.

Then I got to the thrust bearing. Attached is what I found. It appears to me that the thrust washers has had some pressure on it. It looks worse at 15 miles than my factory engine did at 77k, and than the last engine build did at 500 miles. This also explains the clanking noise I heard--the crank being pushed forward does make a hollow-metallic-thud, and also will be seemingly random in relation to RPM in my experience.

With that said, I'm still trying to find the root cause. I am almost positive the connection between these thrust bearing failures is the aftermarket 8 bolt flexplate that I am running, considering the trans, clearances, coolers, lines, tunes, etc have all been verified as good. I'm not sure how the face of the flexplate could be warped enough to cause me issues, but that's seriously my best guess right now.

I have a new thrust washer on order since my crank still looks great, and I am going to pickup a Navigator flexplate from Tousley. (Circle D converters allow you to use the larger bolt pattern or the smaller on the flexplate.)

I'm pretty sure I'm doing the right thing here, but was hoping for some input since it sounds so bizarre.
 

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#23 · (Edited)
Line pressure hovers right around 200psi at WOT. Which is what I was told to set it at.

I've not measured converter charge pressure yet.

I sort of doubt it is the flex plate, Jake. My suspicions are going the same place as Eric's. Usually it is high pressure that forces the converter forward pushing the crank into the thrust and killing the rear thrust face. Although it sounds like you have reasonable forward clearance on the converter to crank spec, what does your converter manufacturer call for?

Way back, probably 15 years or so, when the first powerglides were being used behind the engines these sorts of failures first began to appear. At the time Hyland used a modification to the rear thrust face of #5 main. The modification essentially drilled a hole through the thrust face into the #5 main bearing oil feed. The additional oiling helped somewhat but in the end the real fix was adequate clearance and proper pressure.

Your converter manufacturer should have more than a little experience with these sorts of problems. I would give him a call, explain the problem and listen to his suggestions. A properly installed and operated converter should not be giving you these sorts of problems.

Ed
Circle D called for 1/8th to 3/16th clearance on the converter, which is why I thought my setting of .14" was pretty nice. Brian actually mentioned that the 4r70s were exceptionally forgiving, and one could probably run as much as .25" pull back without an issue. I've spoken to Circle D, and they're suspicion was line pressure.

On any other given day, I would agree with you guys. However I have used these exact same transmission parameters for 2 years and 5000 miles before I put in the built engine. If there was going to be a transmission issue, it surely would have occurred during that time. I just find it odd that I run with a factory Ford plate for all those miles. Swap in an aftermarket unit, kill a thrust. Go back to the Ford unit, have no issues. Then swap back to the aftermarket one a final time and have issues yet again. All while on the same tune, with the same trans/converter, and similar clearances.

As soon as I get it together, I'll do some datalogs of the line pressure at idle and cruising around to check those incase something wonky is going on. I'll try to rig up something to measure charge pressure while I'm at it and report back.
 
#22 ·
I sort of doubt it is the flex plate, Jake. My suspicions are going the same place as Eric's. Usually it is high pressure that forces the converter forward pushing the crank into the thrust and killing the rear thrust face. Although it sounds like you have reasonable forward clearance on the converter to crank spec, what does your converter manufacturer call for?

Way back, probably 15 years or so, when the first powerglides were being used behind the engines these sorts of failures first began to appear. At the time Hyland used a modification to the rear thrust face of #5 main. The modification essentially drilled a hole through the thrust face into the #5 main bearing oil feed. The additional oiling helped somewhat but in the end the real fix was adequate clearance and proper pressure.

Your converter manufacturer should have more than a little experience with these sorts of problems. I would give him a call, explain the problem and listen to his suggestions. A properly installed and operated converter should not be giving you these sorts of problems.


Ed
 
#24 ·
It certainly does seem strange, Jake. If the dish in the aftermarket plate were greater than stock the converter's pump hub would bottom out in the front pump. When you cinched up the trans to the block it would push the converter into the correct position (approximately) but would also apply a significant push against the back of the crank as the after market flex plate dish was compressed back to approximately the OEM dish offset.

Th significant deal here is the additional force used to 'flatten' the aftermarket flexplate is also applied directly to the back of the crank pushing it up against the rear thrust face on #5 Main. That would easily account for the thrust damage. That said it is definitely worth the effort to make sure your charge and line pressures are not so high as to create the problem.


Ed
 
#25 ·
It certainly does seem strange, Jake. If the dish in the aftermarket plate were greater than stock the converter's pump hub would bottom out in the front pump. When you cinched up the trans to the block it would push the converter into the correct position (approximately) but would also apply a significant push against the back of the crank as the after market flex plate dish was compressed back to approximately the OEM dish offset.

Th significant deal here is the additional force used to 'flatten' the aftermarket flexplate is also applied directly to the back of the crank pushing it up against the rear thrust face on #5 Main. That would easily account for the thrust damage. That said it is definitely worth the effort to make sure your charge and line pressures are not so high as to create the problem.

Ed
That can't happen without being obvious when you check converter clearance.
 
#29 ·
The third engine that I posted the picture of in post #20 was fine and lived for another year with no issues. I'm actually still using the same rotating assembly in my current Teksid build. That level of thrust bearing wear seems to be pretty consistent with the engines I've built since then. I use a transbrake a lot, and never see it look any worse than the pic I've posted, even after 50-75 passes.

The clanking sound I was hearing turned out to be a misfire on cylinder #7 echoing out the large open downpipe like a trumpet. I never found the root cause (tried swapping coils and injectors to that cylinder with no change), but when I switched to Holley EFI from the stock PCM it went away, so I'm assuming it was the stock wiring or ECU in some way.

Converter charge pressure with the 4r70W trans and -6 lines going to a large B&M Supercooler was around 55-60psi at most. Still using the same cooler and haven't had a thrust bearing failure since the first one years ago.
 
#30 ·
Awesome thanks for the reply. Were you not registering the misfire on the stock PCM? and/or how did you know that.

Darrin at BCA did my trans/cooler setup. I run stock lines. So it wasn't your pressure/tc/trans for you (did you check pressure before upgrading those lines by chance)?

Thanks again.
 
#31 ·
Awesome thanks for the reply. Were you not registering the misfire on the stock PCM? and/or how did you know that.

Darrin at BCA did my trans/cooler setup. I run stock lines. So it wasn't your pressure/tc/trans for you (did you check pressure before upgrading those lines by chance)?

Thanks again.
I datalogged 'misfires per 1000rpm' or a similar PID for cylinders 1-8 with the stock PCM and that is how I was able to trace it to number 7. It was reading much much higher than the others.

I did not check the pressure with the stock lines, no. They should be fine unless they got crushed during engine install. The only funky thing I really had to deal with was the old Freddy Brown flexplate that I was using before. It's possible that the converter snout could've been bottoming out in the crank before the pads touched the flexplate face, but from what I've seen since I posted the pic in post #20, I think that level of thrust wear is just from dry starts and not really anything to worry about.

As long as your converter spacing is right, you are using transmission lines that do not kink or do anything weird, and have a good flowing trans cooler, you're probably not going to hurt a thrust with a 4R. Most of the horror stories you hear are from TH400s or Glides that have not been set up right and have a ton of line pressure.
 
#32 ·
Yep exactly what Ive been told and reading about 4R70W's. I just dont think my trans and (rebuilt new)TC are magically making more pressure after 5 years to kill a fully built motor. Im tempted since everything is out again, to just run some new transmission lines like you did. Ill talk with Darrin before doing anything like that.

I wondered if the new flexplate was it. but so many people run them I just cant see that (though Ill have it tested/sent back as well, they are a local CA company).

Again thank you for the replies and your time. Much appreciated.
 
#33 ·
Silverfox (Dan Gilsdorf) built my 4R70 and he simply locked the pressure. No adjustment at all. It runs 220-240psi around 3000rpm.


ks
 
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