Discussion in 'Transmission Talk' started by karolko, Jan 6, 2010.
+1 Me too JW Wheel
I don't believe you were looking beyond the table top. The table legs against the concrete floor is the crank against the thrust bearing. The table top is the flexplate. The hammer blow, converter pressure. The bushing movement distance, an example of how much force is absorbed by the table top versus the stiffer steel plate on the concrete floor.
My post mentiond nothing about instant forces. Just stating that whatever force is applied to the flexplate is going to be apposed be the crank thrust.
I think the confusion is the pressure rise vs force applied. There is a possibility that the pressure spike may never translate into a force, or at least nothing with any measurable time duration. I don't think anyone would argue that. But with this scenerio, the flexplate will not have any time to deflect and if i did, the crank thrust would have to appose it.
Enough with the table top. Explain with laws of physics and free body diagrams. Show us in equations.
I agree with that.
OK. Maybe I'm getting too far out there trying to explain this in layman's terms.
For every action there is an equal and opposite reaction.
Let's move from the table top. I guess it's too hard for some to imagine a box brace from the concrete floor to the hammer force. Scratch the whole idea. That was clearly asking for too much imagination.
Imagine a rectangular box brace made of heavy gauge rectangular tubing. Label one short side of the rectangle the crank thrust bearing securely mounted to the engine block. The other short side of the rectangle, the pump cover solidly mounted to the transmission. I think we would all agree that if you tried to push outward from the inside of this rectangle on both short sides equally, the rectangle stays in place. Or, put another way, if one were to set a hydraulic jack between the two short sides, and were to apply hydraulic jack pressure in an attempt to spread the two short sides apart, the rectangle would not move in either direction and would remain stationary. Similar to what happens with the engine block bolted securely to the transmission. Is everyone in agreement so far?
to be continued...
Does Carl's #17 post
cover these comments like a blanket?
Assuming a converter was installed to spec., Don's idea for controlling line pressures pretty much takes care of my concern for thrust bearing problems.
What else can anyone do to control bearing thrust question(s)?
If you have problems, coating/cryo treatment would be a positive unless there is excessive impact from too much clearance, which goes back to the correct TQ install and Don's idea.
Is a part of this not in understanding the why's in shimming to properly locate the TQ?
Installed TQ clearance would be interesting if anyone cares to discuss it. Is .125 the trick? :biggrin:
The small amount of installed T/C clearance to the flexplate is only to make sure you don't setup a mechanical preload between the engine and transmission components. If you did install the T/C jammed against the flexplate, you would end up with an equally spread mechanical preload between the engine and transmission components. The crank thrust bearing surface, and typically the inner pump gear to pump cover surface. Theoretically, both would wear in that circumstance, but typically the tranny pump gear to pump cover chews up much faster.
You don't want the free floating clearance excessive either. The bottoming out point of the T/C to the transmission is typically the bottom of the T/C hub notch that engages with the inner pump gear of the transmission. If the T/C needs to be pulled out of the tranny too far inorder for the T/C to mate to the flexplate, you lose some of the hub to inner pump gear engagement contact that is needed to drive the pump. If enough of this engagement is lost, premature failure of the pump drive can occur.
The amount of installed clearance between the flexplate and the T/C could be .250"+ if you could only be sure that you had enough shaft spline and T/C hub to inner pump gear drive engagement. Since it is too much work to do all that measuring, people generally accept 1/8" as a good rule of thumb.
Think of my rectangular box example. If a length of pipe were to simulate a crankshaft, flexplate and T/C all bolted together, you would use a length of pipe that could easily fit between the short sides of my rectangular box with a total of 1/8" clearance on either side of the ends of the pipe. The pipe is free to float in either direction with no mechanical preload. You can turn the pipe within the rectanglar box with no wear caused due to a mechanical preload. Of course, the crankshaft thrust bearing would actually limit the movement of part of the pipe, but to keep the example simple we'll just leave that out of the picture for now.
If we used a pipe that was just a little bit too long to fit between the short sides of the rectangular box, and did happen to jam the pipe in between the short sides of the box, we would have a mechanical preload. If we managed to turn the pipe while it sat between these short sides, we would end up with galling of the thrust surfaces at both ends of the pipe. Loads would be spread equally at both ends of the pipe. Which ever thrust surface was less prepared to handle this load would be the one to wear the most. That is why the transmission pump cover surface is the one to lose out in this battle scenario.
Other bottoming out points of the T/C to the transmission can be the ends of the shafts, or the end of the T/C hub directly to the pump cover surface, depending on the depth of the pump engagement slot in the hub.
The bottoming out point would just depend on dimension tolerances used in the manufacturing of the T/C.
This is all the explanation needed concerning the forces a thrust bearing sees. There should be no other discussion about it unless it is concerning how to control this force. Anyone who wants to post anything different than the simple law of physics Alan explained is a babbling fool. Imo this thread should be locked.
Wow. That's a little harsh. OK then. Bison says, thread is over. So be it.
the restricting orfice didnt solve my thrust issues.I installed one of Chris @ CKs modified pumps after trying other options such as a restricting orfice modifying the bearing and wiping 2 cranks .its been about 5 years now but i havent wiped another thrust since the new pump from chris.alway ran a stock flex plate .Im building a new set up now so we will see been out for 2 seasons
Did Chris find anything wrong with your old pump? Assuming Chris looked at your old pump.
I'll bet it still has a lot to do with excessive gear clearence causing excessive pressure on converter hub, 400's and 350's have had these problems for years that I can remember. Chevy's wipe thrust bearings too.
no he didnt look at it
Excessive pump gear face clearance is certainly a contributor.
Converter fill pressures
Here is a example of (at least mine) of your converter fill pressures while you go down the racetrack. There are spikes in the gear shifts for a instant. I wonder if a flex plate will help absorb this? The trans is from Rossler. We have had ZERO thrust problems with it.
Don have you logged this on your car yet? I'm curious for comparative reasons.
Hutch has done some pretty extensive testing of the converter presures if I recall correctly.
I see some interesting stuff on the cooler line pressure gauge in my test car sometimes, but I'm usually not paying close attention to it.
That graph is awesome.Very informative.
No I haven't. I've made checks on the rack, but not during a run. I have a permanent tap set up, so it would be easy to take a measurement. I'll try to remember to get it so that I can share it.
For the most part, the pressures look safe. I would imagine the crank thrust bearing can handle short duration and spikes in load. The problem comes in when the T/C pressure is a constant high value where it would eventually, over time, overheat the thrust bearing and crank surfaces.
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