Torque converter wiping out thrust bearing?

[thedarkside]

Hi all,

I recently had to get my engine rebuilt due to the builder finding a thrashed thrust bearing. He believes it was caused by the TC ballooning and pushing forward on the crank. I know this is known to happen but I was wondering if there are any other possible reasons for failure and is there a method to narrow down the issue?

Car is 440 with 727 TF
3.91 Suregrip
235.000 EX DUR 290-300 Cam
Edlebrock Proformer heads
Holley 770CFM carb
10.5:1 Compression
Steel crank

Motor was built before I purchased the car and I have no idea what type of TC it is running but it feels to be about a 3200 stall. I checked clearance to the bellhousing at 1/2 in. and the TC had some front to rear play. Is it possible the front seal on the tranny caused this issue? I'm still in my learning years so I really appreciate the help.

[jhaag]

the only function of the front seal is to keep fluid in the trans. most likely the convertor is ballooning, forcing the crank forward and eventually wiping out the thrust bearing. (ask me how I know) If you can't identify the manufacturer, you could send it to one of the majors and have it rebuilt, or just replace it. It is not an uncommon problem. Cheaper convertors are not made as well and are prone to this problem. (thinner metals) Stick with majors and talk to their tech guys and they will help you out. With the power you are making, you may need a convertor with an anti ballooning plate, depending on how you drive, (race?) As I said, use one of the better known manufactures and they will steer you right. Good luck

[thedarkside]

Thanks for the reply. I think that sounds like a good option. Is there a way to check if the convertor is ballooning while the trans is out? I drive pretty conservative but considering the car had a line lock and some questionable bolt holes in the floorpan I assume it was dragged frequently. Should I be worried about any possible damage to the trans from this happening?

[jhaag]

You would not be able to tell just by looking at the convertor, It would need a proffesional inspection. It will balloon when the motor is torqued up against a line lock or trans brake repeatedly. Fluid pressure builds up and it expands (balloons) front to back, in line with the crank, pushing against the input shaft and the crank. Usually wiping out the thrust bearing. Remember we are only talking hundreths of an inch here.  If the trans was working ok when you took it out you may be ok, but I would pull the pan and check for an abnormal amount of trash there or in the filter.

[Moparal]

If you had a used steel crank that came out of a 4 speed car, and it had the #3 thrust worn, and the guy didn't check the end play, then it could actually be a faulty crank needing fixed or replaced. Did your engine builder say what end play you had? This is when you put a dial indicator on the crank end and see how much it moves front to back. If the crank was worn, it would eat a bearing up faster than normal.

[73restomod]

Well in your shoes, I'd bite the bullet and buy a high quality Torque Converter; plan on spending 500 or more if you want quality. If your still paranoid about the thrust bearing, you can have it drilled in the backside for forced oiling like I do for all my manual trans vehicles.

[73restomod]

Lots of the local circle track guys do this little trick; pressure from the clutch actuation goes forward thru the motor and gets caught by the thrust bearing. At the end of a season spinning 7000rpm, the thrust bearings were allways toasted. This is handy for stopping that. You can do it yourself if your careful, or just take it to your machinist.

[thedarkside]

Well in your shoes, I'd bite the bullet and buy a high quality Torque Converter; plan on spending 500 or more if you want quality. If your still paranoid about the thrust bearing, you can have it drilled in the backside for forced oiling like I do for all my manual trans vehicles.

I agree. I plan on just buying a new converter to be on the safe side. I am waiting for the motor to be finished so I can get the cam specs and dyno sheet to determine what the best option would be. I'm also gonna talk to the builder to see about drilling a hole in the thrust bearing. Problem with the 3.91 is always seeming to be incredibly high in the revs anytime you need to go over 55.

[thedarkside]

Well to update the converter is fine. The only things I can think of which caused the failure are:

1. Bad pump in the tranny causing the converter to push forward?
2. Block not being line honed?
3. Misalignment of bellhousing dowel pins causing pressure on the hub?

I know these issues are very hard to troubleshoot but I wonder if anyone has seen these types of things happen. I would hate to wreck a 4k build for a minor issue.

[73restomod]

Well, as far as the pump being bad that would only cause the tranny to crash, but if the converter isn't seated all the way when installed it could push forward on the pressure plate forcing the crankshaft into the thrust bearing toasting it in short order. You would not believe how often that happens.

As far as line honing, if the crank was out of spec, it would have left marks on the main bearings in the babbit layer from rubbing without enough clearance for oil. In extreme cases it will leave blue heat marks on the crankshaft main journals.

A misalignment of the bell will generally wipe out the front pump bushing followed by the pump itself, a leaking front pump seal is the first sign.
I believe that the prior owner/installer screwed up when the torque converter was installed, cranked down the bellhousing bolts,  causing an interference fit of the converter to the pressure plate. It won't take long for it to wipe a thrust bearing like that.

Sent from my DROID RAZR using Tapatalk 2

[JayBee]

Just got news that my thrust bearing is shot. Crank moves .060 inch back and forth.

I'm looking at 73restomod's pic and would like to know if the drilled hole he's talking about is the one that's just left of what looks like a groove in the bearings side? Also what diameter is it?

History: 318 (904) professionally rebuilt 2 years ago. ONLY 7,000 miles on it. Line bored & crank turned during this rebuild. I rebuilt this in 1982, put 100k on it and no thrust bearing issues in that time. Using the same torque convertor BUT a 1973 904 with my original, shift kit installed, valve body. Also, this recent rebuild has a windage tray installed, just mentioning something else that was done to the bottom end.

I don't want to be doing this every 2 years or 7k miles. Any other suggestions I can give my mechanic?