TransAm-Z

iTrader: (39)

I had my motor up and running for about 6 weeks (500 miles and around 15 passes) and already have a thrust bearing failure. Is this a common occurrence with Turbo LS cars?

I have done some reading and have found out some causes of the thrust bearing failures, and believe it may have have to do with excessive transmission cooling system pressures due to restrictions in the my coolers exerting force at the opening of the torque converter. It may be a stretch, but I wonder if when staging the Turbo car if the converter temps are converted to higher internal pressures in the converter. I have a nice Vigilanti converter so I doubt it is ballooning out too much.

Now I need to make sure it doesn't happen again.

Has anyone ever modified there thrust bearing to directly oil the rear thrust face by chamfering the main cap at the bearing split line as suggested in the article below (Bottom of the page)?

http://www.enginebuildermag.com/Arti...g_failure.aspx

Good Side of Bearing.


Bad Side of Bearing! The copper platting was in chunks at the bottom of the pan, and a .015" groove turned into the crank. Callies crank has been repaired.


Corner to chamfer.


Thanks for the help!

Gilbert@Ace Racing

It is a common condition that needs to be managed. If you'll call me tomorrow I'll be happy to discuss it with you. I need to know the details of your transmission build. And I'll need to know your pressures. If you do not have a 0 - 300 psi hydrulic guage with a 6' or so hose on it you need to get one for testing before you go to the track again.

Been down this road more than a few times. I want to give you something to think about in the meantime... If hypothetically the engine oil pressure is at say 100 psi and your converter charge pressure is at say 250 psi, then which one wins? The converter charge does does right? Well, my point is the converter is trying to push the crank out the front of the engine. It is not an engine issue. It is a transmission issue.

g

TransAm-Z

iTrader: (39)

I will try to call tomorrow... Thanks! Am I correct to assume that the pressure coming out of the transmission right before the cooler best approximates the pressures inside the converter?

Sounds like it is time to design a bearing system that keeps the converter pulled back to the transmission!

Just for your reference the transmission is a stock rebuilt 4L80E with the heavy duty sprag clutch. It came with the car so I haven't had a chance to tear into it yet. The converter is a 3500 stall Precision Vigilante with 5 disk lock-up. The only other mod made to the transmission was a red die spring into the pump supplied with the converter.

The transmission commanded pressures in the PCM have not been touched for main line pressures or TCC lockup pressures and are from a stock truck tune. The only major shifting program change I made was decreasing the desired shifting times to 0 seconds in the PCM (Didn't notice much of a difference).

Thanks for the Help.

bonestock_442

iTrader: (1)

I have also seen this happen with a built 408 4l80e turbo car.

JL ws-6

iTrader: (50)

I have heard of this problem several times now. It's an issue with the converter, as explained above.

And being that you have a vigelante converter in the car.. I would suspect it even more.

S10xGN

iTrader: (11)

My Vig has a billet front cover, how would that balloon?

TransAm-Z

iTrader: (39)

As does mine!

I talked to Gilbert today (awesome guy BTW!) and he had a good point that I didn't think about... If the converter to flexplate spacing is too little, the end play in the transmission input shaft could push on the converter due to the helix gears in the transmission. I know for sure my gap on my setup was a little on the small side. Definitely something I will need to take a look at.

bonestock_442

iTrader: (1)

Will a worn out tranny with excessive endplay likely cause this or pressures within the converter thrusting forward?

JL ws-6

iTrader: (50)

Let me put it this way... you won't hear about it alot.. but people have issues with even the 2000 dollar neil chance converter's doing exactly what you're having an issue with...

If you think that 800 dollar vigelante isn't having the issue... you're going to be in for a big surprise when you finally get to the bottom of the problem.

The staging process of a turbo car is VERY, VERY hard on the trans and converter... talk to fireball about it.

427

iTrader: (3)

Chamfering the bearing is a very old trick that seems to help. I have used this on low power turbo engines with good results. I keep the end play at a min of .005 also, I believe this helps also. I add pressurized oil in higher power engines to cool that bearing face. The face of the thrust is made for 400lbs of force or less for short bursts only. Cars that struggle to build boost can be very hard on the thrust, if it overheats it will flake the bearing apart. Cooling this area seems to cure the problem.

Kurt

S10xGN

iTrader: (11)

No, you won't see any endplay at the pump/converter. The only thrust issues are in the gearsets and that won't affect an engine's thrust bearing...

Well, I do have a fairly low-output (11.9's) turbo Buick GN powered S-truck with a Vig and have never had a problem. You're right though, I don't hear anything about problems with PI converters. But then, I don't hang with the big dogs...

ponjohn

I had thrust bearing failure on a non LS motor.

It turns out the pull up distance of the converter to the flywheel was too much. It's my fault it was a lack of knowledge on my part.

I changed converters and thought it was fine. Car had 4 years on it with previous converter and it failed quickly with the new conv.