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Reply #15 – May 01, 2013, 10:51:18 PM

In a automatic trans the torque converter is pressurized with fluid, so it's always exerting pressure by trying to push it's self away from the trans, into the flexplate... If pressure is high enough(as in trans with a shift kit), this foorce will cause excessive wear on the thrust bearing... Only time there is pressure from a manual trans is when the clutch is depressed...

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Reply #16 – May 02, 2013, 05:33:15 AM

It has been explained to me that auto trannys do not put any excessive loads on the thrush bearing. Franky Loupo FAIRBANKS RACING TRANSMISSIONS has dun tuns of units for us over the years and he explained that normally auto trannys pull the crank back to the rear of the engine rather than the front that a stick car does. Other than an LT1 pull clutch this seems to hold true. A normal clutch pushes the crank forward. And yes heavy clutch covers adds more pressure as spring pressure is increased. But having thrush issues is rather rare because most of the time the clutch is released. Thats why i never hold down a clutch in gear waiting for a light to change. Over the years i have inspected many a thrush bearing and this seems to hold true. Some fords only use a single half bearing for the thrush of the crank. Thrush failures are rare other than some fords. On the 2.3 it is not an issue and we do not see to many issues. If you inspect a bearing from an auto car you will notice the wear on the front side other than the rear side of a stick car. This is just me could be wrong.

Diaphragm clutches have reduced this issue by leaps and bounds as they take very little force to release them and there clamping force is high when engaged. The old style 3 finger clutches are long gone and ford long style clutches as well.

Example a TH400 exerts app 225-260 LBS of line pressure in reverse and run at app 225 in drive ranges. Normally pressures do not increase to much by adding a shift kit Normally most auto trannys run somewhere around 200 PSI line pressure even with a kit. So having a line pressure of a normal and or a performance tranny would not wipe out a bearing. There are millions of trannies on the roads today weather auto or stick that dont wipe out a thrush bearing. I know Ford has some issues with the 302 with this but i think CLEVITE designed a bearing to fix that issue. Lack of oil is what we have found that is the issue. You need to get more oil behind the thrush bearing surface. A small hole is all that is required. IT WORKS with the newer designed bearing by clevite and remember to polish the crank surfaces in the direction of rotation.

NOTE a ballooning converter can wipe out a thrush bearing. But i have not ever had this issue

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Reply #17 – May 02, 2013, 08:41:28 AM

For some reason it surprises me that the converter snout seal can hold that much pressure in LOL. Converter didn't seem to fit into it super-tight.

Tom - are most new/aftermarket cluches diaphragm clutches? Obviously the manufacturer probably specifies that in the catalog/online/whatever listing right?

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Reply #18 – May 02, 2013, 12:47:02 PM

Yes the most of what i see are now Diaphragm clutches. The old style clutches are no longer used in cars. That is i have not seen them in years. And we do a good amount of clutches. The front seal as i was told does not control line pressures. But then again my auto tranny knowledge is skimpy at best. The front seal to my thinking could never withstand those pressures. And the tranny coolers as well as it was explained to me that the pressures are low. Not 100% on this as i am not an auto tranny guy and i only have one car with one!!