Worn Thrust bearing ............again

[Kevin Johnson]

Keep an open mind re tweaked rods. They have already been found before in this engine. Maybe one was borderline in a way that was not apparent during the rebuild.

[user-3597028]

The thrust surface finish on the crank is important. If the grinder touched it and it has "fish scale" or sweeping grind marks, that will tear up a thrust. Eagle had this problem years ago, lots of come backs.

I would also check, or better yet, correct the transmission dowel pin index to the crank. I use the BHJ fixture and do every GM that comes thought the door. I literally have the custom dowels made 300 at a time because I do so many.
If the tranny is out of index, it will try to "corkscrew" the crankshaft one way or the other because of the side load. This has been the fix for a lot of thrust eaters in the past for me.

[Kevin Johnson]

The thrust surface finish on the crank is important.

I think shops that dealt with the crankwalk issues on the 2nd gen 4g63 would heartily agree with you. Once a surface has developed an adverse finish or texture it will greatly accelerate wear against newly presented parts.

[MotionMachine]

We've all seen thrust surfaces that have been burned on cranks that have been turned. This is because the operator just side plunges the wheel into the surface. Most volume shops never dress the sides, it's a PITA to keep the side of the wheels dressed, takes forever, you can't take much off per pass with the diamond and you have to dress the wheel as far back as you can reach so the step won't hit a counterweight. If a thrust needs to be touched up or ground for an oversize length bearing, the wheel needs to be backed out, moved over a thou or whatever is required, then plunged in slowly. This gives a much better finish. Of course it takes longer this way and it's one of the many reasons I have for hating crankshaft grinding.

[donc]

Converter or misalignment with trans. Or maybe cam walking out pulling on chain allowing crank to move forward? Some of the early 327s had terrible lifter alignment.

[Fordracer347]

Once everything is checked and the engine cleared for reassembly, you can drill a small hole from the oil feed directly to the thrust face. Just like they recommend on BBCs for the cam sprocket. Since this assembly has proven to be problematic, a little added insurance isn't going to hurt.

I agree that this doesn't solve the original problem but it sure couldn't hurt to have some peace of mind.

[cpmotors]

We've all seen thrust surfaces that have been burned on cranks that have been turned. This is because the operator just side plunges the wheel into the surface. Most volume shops never dress the sides, it's a PITA to keep the side of the wheels dressed, takes forever, you can't take much off per pass with the diamond and you have to dress the wheel as far back as you can reach so the step won't hit a counterweight. If a thrust needs to be touched up or ground for an oversize length bearing, the wheel needs to be backed out, moved over a thou or whatever is required, then plunged in slowly. This gives a much better finish. Of course it takes longer this way and it's one of the many reasons I have for hating crankshaft grinding.

Exactly!
This is a Nash crank I just ground a few weeks ago that needed the thrust face touched up. I may go in and polish it a bit more.



On thrust bearings I have always filed a small chamfer from the oil groove to the rear on the upper shell to direct just a bit more oil to the thrust face.

[MotionMachine]

Very nice job on the thrust AND the radius. As a fellow grinder, I feel your pain....

[ProPower engines]

Keep an open mind re tweaked rods. They have already been found before in this engine. Maybe one was borderline in a way that was not apparent during the rebuild.

Rods have been rechecked as part of the inspection to rule out any internal component issues contributing to the failure.
Main bearing and thrust bearing alignment has been checked and no issues there either.

Belhousing flange to crank flange has been checked for runout as well and is amazingly paralell. They are with in .0015 on the full diameter of the belhousing flange so no issue there as well
I will add the belhousing flange was off quite a bit which is why it was machined during the 1st build because it had the same issue with the thrust bearing.

[ProPower engines]

Just to add the thrust faces were polished very well to avoid any possibility of machining marks chewing the bearing up as mentioned.

[cpmotors]

Thanks Dale-

What is the minimum out of parallel the bell housing face can be from the crank before it starts to have a negative effect?
What do you guys shoot for?
I would suspect with a flywheel/clutch vs a flexplate/converter it would be less tolerant of being out.

[peejay]

If it hasn't been pulled yet check pressure before and after the cooler.
Had a local shop not believe that. The first two engines didn't make it off the lift. After the 3rd gratis NAPA rebuild he finally got to checking it. Shore nuff!. He didn't believe me the first time because a tranny shop told him that was impossible due to the pump relief in the tranny. Guess what? It can't dump off that much.

There's a direct correlation between thrust load and pressure in the trans cooler.

We ran into this too, engine ate the thrust in a very short period of time, sent the trans back to the shop that built it, who swore up and down that there's no way the trans could do that... And after we put it back together, everything was happy so whatever "wasn't wrong" with the trans was killing the thrust.

I see it in simple terms. There's basically no load on the thrust except from the trans, so if the thrust dies then it's the trans's fault. Proof is the thrust ALWAYS dies on the backside from "something" trying to shove the crank forward.

[Warpspeed]

Just a thought....
If this is caused by the converter pressing into the crank, would it not be only the front thrust face that showed damage ?
If the thrust forces were coming from the rods, or if it was an installation problem, surely both thrust faces would show about equal distress.

[lorax]

Just a thought....
If this is caused by the converter pressing into the crank, would it not be only the front thrust face that showed damage ?
.

REAR thrust face???

[Tuner]

It’s not the transmission’s fault when the cooler circuit is restricted by a plugged cooler, a kinked line or a fitting with a restricted orifice that found its way into the car out of the junk drawer in someone’s tool box…..

A common deal is the add-on cooler retained with those zip-ties through the radiator which has slipped down and kinked the rubber hoses which are used to splice it into the system. Or, a chunk of the deteriorated hose has made a flapper or shredded itself into a fitting.

The torque converter slippage is the source of nearly all the heat in the transmission. The source of oil to the cooler is the converter exhaust. If the cooler circuit is restricted the back pressure in the converter makes the area of the stator support a piston in the hydraulic jack which pushes the converter forward. It is just that simple.