VCCA Home Forums TECHNICAL - GENERAL Mechanical - Engine, Trans, etc bad thrust bearing?

anybody ever had a thrust bearing go out on a small block v-8? after having two mechanics listen to the clanking noise this engine makes, they both walked away scratching their heads. after much thinking about it, i can only deduce that's what it might be. heavy,random clanking noise until i put it in drive (automatic) then it stops. also does not make the noise while in neutral when cold but starts clanking when it warms up. i've checked the converter to flywheel bolts. they were tight. could the crankshaft counterweights be hitting the block?

Firstly Automatics dont have thrust bearings as such.
It is possible that the flex plate has cracked try gently prying the flex plate towards the trans, it should not move very far.
Tony

As Tony mentions a flexplate that is cracked / broken around the crankshaft mounting flange will make some noises that you mention. I have seen the thrust bearing go bad on a small block, the torque converter ballooned when it went bad, thus pushing forward against the thrust bearing. The pickup had a factory reman engine installed and went bad in 5oo miles. It was changed out under warranty but when the second engine did the same thing they dug in and determined that the torque converter ballooning was the culprit.
Don

tony--i'm talking about crankshaft thrust bearings.
don--what causes the torque converter to baloon? funny you should mention that because the transmission has now gone out.

My apologies about the thrust bearing mix up.
Now that the trans has give up it may well be the flex plate was only partially cracked and now has totally give out. Does the engine start if not try turning the flexplate by hand, if it turns without turning the engine start looking for a new flexplate.
Tony

Take a look at this. It does a great job of explaining things.
http://www.artcarr.com/page/news/1.acpp
Don

the engine starts and runs. the trans hasn't completely given up but started shifting funny and sounds like gravel sloushing around inside of it when you put it in drive.
i have had a flexplate completely break before on another car, so i know what that's like.

i read that article don. very good info. i think i'm going to just pull and replace both the engine and transmission and be done with it.

I didnt read all of the article but I think there is a heavier thrust load on the crank with a manual transmission by way of the clutch action. With automatic trans when the torque convertor is disconnected from the flexplate it is easily moved towards the transmission therefore next to no thrust load on the crankshaft.
Of all of the crankshaft thrust spacers I have seen it is only the manual trans that have had any noticeable wear.

If the noise only occurs when drive (or reverse) is selected I doubt the engine is the problem. As someone (I think MrMack) suggested the torque convertor could be the culprit. The fins inside have been known to become detatched allowing debri to float through the rest of the trans.
Tony

Tony,
I agree that the force put onto the thrust is probably greater with a manual transmission when the clutch is released. However the force is a limited period of time while a torque converter that is "ballooning" is putting force against the thrust as long as the vehicle is driving. The issue with torque converters has become more prevalent in the last 10 - 15 years. The bottom line is if a motor has issues with the thrust many things are possible, but some more than others. Don