Mopar thrust bearing failure
 

I keep killing the thrust bearing in my 360 Stocker after 10 passes.
Last time, had the thrust repaired on the crank, freshen the convertor, changed to another 904 trans, did away with the quik disconnects on the trans cooling lines.
After the thrust repair, I had .002 endplay.
The time before, had .010 endplay.
All the bearing look great.
Anyone else have this problem?

Re: Mopar thrust bearing failure
 

.002 is too tight it will cause a failure.

Re: Mopar thrust bearing failure
 

I agree with Lee,that is rather snug. Out of curiosity,what is your stall
speed? I have seen a real high rpm stall causing early thrust brg.
problems but I would think a stocker wouldn't hit all that hard.
All your end play etc is within specs I assume.
Good luck devo

Re: Mopar thrust bearing failure
 

And along the same lines, sure the converter isn't ballooning? Might want to ask whoever freshened it about that. Had a "other brand" that caused me some problems before changing to ATI

Re: Mopar thrust bearing failure
 

I though .002 might be too tight, I checked the service manual & it had .002-.010 for range.
It is a ATI convertor, sent it back to them. Asked about it ballooning, no concerns found. It was freshened up at that time also.
It is footbraked to 3K to leave.
Another racer was having the same problem with a 340 Stocker.
He recommended me to a guy at Pro Trans.
They have a piece called the "destructor" that goes into the convertor charge hole.
I haven't disassembled the engine from this last failure to inspect the bearing yet. Just cut the oil filter open, found bearing material & the crank has excess movement.
I checked the crank during the last race, it didn't kill it until the last two passes. Also lost a tenth at the same time.

Re: Mopar thrust bearing failure
 

0.002" is way too tight for a race engine.

0.007" is more typical for a race engine. I lot of flexing occurs under the high stresses in a race engine.

Also, please check the end play with JUST the upper bearing in place, then again with JUST the lower bearing in place to confirm the alignment of the upper to lower bearing halves.

You know the saying, "If you have too much bearing clearance you are the only one who knows. If you don't have enough bearing clearance, EVERYBODY knows."

It's best that you are the only one who knows.

Re: Mopar thrust bearing failure
 

Most likely to much cooler/lube circuit pressure. Good converters don't really balloon, but excess pressure will force them forward off the stator support. A common problem on some transmissions with a high fixed line pressure.

Tee a pressure gauge into your cooler lines. You'll want no more than 50 PSI at stall speed. Anything over that needs a restrictor installed. With a fixed line pressure in the 150-175 range, a restrictor with a .094" hole is a great place to start.

Re: Mopar thrust bearing failure
 

It is also important that you have at least .080" pull up on the torque converter . All converters will balloon a bit depending what the charge pressure is , and how many rpm's it is spun to . Having pull up will help keep the converter from binding up on the splines and damaging the engine thrust bearing .

Re: Mopar thrust bearing failure
 

Also check the hole in rear of the crankshaft
to be sure its bigger than the hub on the converter.

Re: Mopar thrust bearing failure
 

You can slide the converter back from the flex plate when unbolted, right?

Re: Mopar thrust bearing failure
 

Yes

Re: Mopar thrust bearing failure
 

Thanks for the response guys.
Got a lot of things to check out in the off season.
At least my kid won some cash in the Bracket car last night to pay for repairs on the Stocker. LOL

Re: Mopar thrust bearing failure
 

Devo,

Is this a new engine or has it run before without hurting the thrust bearing ?

The reason I ask is I had a problem with a thrust bearing in a 350 Chevy years ago. The block had been align honed and when they cut the cap they cut it crooked and it was tilting the thrust bearing just slightly. Took me a while to figure it out.

Did something change in your combination right before your thrust problem started ?

Just thinking out loud :)

Re: Mopar thrust bearing failure
 

Not a new engine. Ran the car in 2016 with no concerns. Had a trans leak, pulled it & had it looked at to be freshen. Trans guy couldn't find anything wrong. resealed it. Took it to our first race this season, lost #6 rod bearing. Had the crank ground, replaced 2 rods, new rings & intake valves. Just freshen the engine. Wasn't as fast it should have been, slowed way down after the 2nd race back. found the thrust had severe wear allowing the crank counter weight rub the main web in the block. Had the crank repaired, all the bearings looked really good. replaced bearings & oil pump. lasted for two more races, started slowing again. cut the filter apart, found bearing material. also excess movement in the crank. haven't pulled the engine yet.I still had the last oil filter from 2016. it was perfect inside. May be coincidence, started having problems after the trans was checked out.

Re: Mopar thrust bearing failure
 

do you have another transmission you can test with?

Re: Mopar thrust bearing failure
 

Are both the dowel pins that align the bellhousing still in the block . Sounds like something didn't go back together the same after the trans repair .

Re: Mopar thrust bearing failure
 

Yes, used my spare transmission.

Re: Mopar thrust bearing failure
 

Could it be a balance issue after fixing the crank? I'll be running a 340 for the first time and I'm all ears on these small engines.

Re: Mopar thrust bearing failure
 

Unlikely a balancing issue. A 340 is internally balanced and has different journal sizes than a 360.

Re: Mopar thrust bearing failure
 

Except for the 1973 cast crank 340. It has a special balancer on the front, but probably could be internally balanced with lighter rods and pistons (that part should be easy with the stock 340 slugs). All the rod journals are the same size, the 360 has larger main journals than the other SB Mopars.

Re: Mopar thrust bearing failure
 

I don't see how the trans would have caused a rod bearing issue. What did the thrust look like at that point ? Are you using the same bearings as before ? Same clearances ? Just curious.

Re: Mopar thrust bearing failure
 

I would think that BillK might be on to something here

Is this a new engine or has it run before without hurting the thrust bearing ?

The reason I ask is I had a problem with a thrust bearing in a 350 Chevy years ago. The block had been align honed and when they cut the cap they cut it crooked and it was tilting the thrust bearing just slightly. Took me a while to figure it out.

Did something change in your combination right before your thrust problem started ?

Just thinking out loud :)[/QUOTE]

Re: Mopar thrust bearing failure
 

Bent crank-- trans crooked---convertor ballooning--- insufficient oil / lubrication---dowel pins not zeroed in ---- Fed387

Re: Mopar thrust bearing failure
 

I agree the rod failure would be hard to pin on a trans issue. Not so with the thrust. 7 to 8 thou is a good number. Bump or pry the crank back and forth a few times before tightening the main cap and force the crank towards the front of the engine when torquing that cap down.

If the issue started after having the trans apart, I would have someone familiar with that unit in a race application look closely at it. Would be nice to run it on a trans dyno to verify pressures before putting it back in.

Re: Mopar thrust bearing failure
 

I wiped out the thrust bearing in my 340. After a lot of thought, I determined the failure came from
stacking the weight of the engine and transmission on the driveshaft at the hit. I had eliminated the
engine mounts and was utilizing an engine plate and OEM transmission mount to locate the engine.
After the crank repair, I added a fore and aft limiter. I've had harder launches since then and no sign
of thrust failure.


The first thing to identifying the culprit is asking, "What changed?"

Re: Mopar thrust bearing failure
 

One other thing was changed, weight of the car.
Was at 3640, now @ 3750.


Crank is internally balanced with Mallory metal.
This is why I elected to have it repaired.
To avoid the cost of rebalancing another crank.


Rob & Main bearings have been changed every time.


I am going to change out the crankshaft this time & have the line bore checked & corrected if need be.
Since I'm new to this type of racing, anyone want to recommend a crank shop?

Re: Mopar thrust bearing failure
 

where are you located?

Re: Mopar thrust bearing failure
 

Oklahoma.

Re: Mopar thrust bearing failure
 

see if mike cotton is still in the area, if anyone would know it would be him

Re: Mopar thrust bearing failure
 

Make sure the hub is not bottoming out and pulling the flex plate to the converter.I had a simlair problem.had to put washers under the converter legs to pull it out of the crank.

Re: Mopar thrust bearing failure
 

when you believe the clearance is set, I like to check the area's with a feeler gauge. just because the dial indicator says one number, the cap could still be crooked. the gauge will show if its the same everywhere..