Those who took out the thrust bearing.....

What was/is your converter clearance? What tranny?

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Blazer406

Mechanical Engineer
Joined
May 2, 2002
I would like to investigate if converter clearance between the converter mounting ears to the flexplate has anything to do with those people that have had an engine thrust bearing failure. If you had a thrust bearing related failure, do you think it was caused by using a transbrake? Did you check your converter clearance to the flywheel prior to the failure? What was that clearance? Please post your tranny... and approximate power level or ET. Maybe this can be of some use.....
 
My thrust bearing failed shortly after an engine rebuild a few years ago. Engine probably had about 500 miles on it when I noticed the crank pulley moving in and out as it idled. Not willing to accept the fact that it was the crank moving around, I replaced the balancer. Didn't fix it. The converter was a ProTorque that I had sent out and checked - it was fine. Not sure what took the thrust bearing out but the engine was re-rebuilt and washers were put between the converter and flex plate. I've since switched converters (twice) and ditched the washers but it's been fine. Probably have 6-8k miles on the engine at this point.

HTH

Jim
 
Im still too new & green to be given input on this but i bought my trans from dynotech had my engine rebuilt last yr. which eventually made my trans take a dump, so thats when i went to dynotech i bought edgeracing convertor & had a partner who had his engine rebuilt the same place as mine now his thrust bearing failed due to the machinest putting the bearing cap on backwards or something to that nature. but any way when i got the trans & torque convertor in i was also concerned about failure & all ,,i didnt know what to do.so i just took both to my mechanic who fixes my truck & wifes car & ask how much would we he charge to put it in ($200) i checked up under the car no washers or nothing in my flex plate (no clearance???)on the convertor side i cant see the oposite side but i keep records of how many passes at the track & back road racing ive been doing so far im up to 29 spaced out least amount of runs at the track (3) most i went (9) the last time i went so far no issues.i was picking up knock retard while idling after 2 hard runs dont know if it was exhaust or trans related but it went away the same night hasnt repeated so far. i dont know if this was correct or not but i told him to make sure he knew what he was doing he said he's been doing it 20yrs:biggrin: (now i didnt vote because i dont understand if your talking about the distance between the conver & trans itself or the convertor & the flexplate which is none on that one)
 
Clark6 said:
.......... (now i didnt vote because i dont understand if your talking about the distance between the conver & trans itself or the convertor & the flexplate which is none on that one)
Click to expand...

When you unbolt your converter from the flexplate... you can slide the converter toward the transmission a small distance until it bottoms out.....when it bottoms out... you should have some small distance between the mounting ears of the converter ... and the flexplate. around 1/4" in most cases... this is the amount you have to slide the converter back toward the engine to bolt it up......

I read threads where some people shim this clearance out... and some have taken out the thrust bearings because of that.... I'm just trying to see if there is some correlation between too tight converter clearance and wiping out the thrust bearing......

Hope this clears up your question.
 
Even the slightest amount of clearance is still OK. You definitely do not want a PRELOAD condition. The best way to tell if there may have been a preload condition would be to check the front pump of the transmission. If the preload condition was present, it would hurt the crank thrust AND the front pump of the transmission. In fact, since the front pump is made of aluminum, the damage should be more prominent at the transmission side.

Now, if you want to talk about torque converter charge pressure, there should be an old thread that I discussed this at good detail.
 
DonWG said:
Even the slightest amount of clearance is still OK. You definitely do not want a PRELOAD condition. The best way to tell if there may have been a preload condition would be to check the front pump of the transmission. If the preload condition was present, it would hurt the crank thrust AND the front pump of the transmission. In fact, since the front pump is made of aluminum, the damage should be more prominent at the transmission side.

Now, if you want to talk about torque converter charge pressure, there should be an old thread that I discussed this at good detail.
Click to expand...

I read that Don....it was very informative. I will check mine when I get it back together. I am really wanting to put a stagerite style transbrake (for economical reasons) in lieu of an electric style brake..... and I hear people comment... "it will tear the thrust bearing up in your engine"...... obviously I don't want to do that....so I am reading everything I can get my hands on to try and figure out the common link if there is one for those who have had thrust related issues.

Don are you saying.... that if converter back (or is it converter feed pressure??) pressure is too high... it is acting like a hydraulic piston pushing on the crank.... trying to push it out of the block? At least this is how I understand it...... If this is the case....why would a trans brake launch put anymore fluid pressure/volume in the converter than foot brake launch.....In any case... it seems to me if the pressure is kept in check.... there shouldn't be an issue.

This actually makes the most sense to me (at least on the tranny side) of things that could push on the crank that would wear the thrust surface.......

I guess inside the engine..... as long as the machine work was done properly... there really shouldn't be an issue.......
 
I think you've got the idea. The area in square inches of the ID, of the torque converter hub times the pressure of the fluid, measured in psi, in the torque converter is the amount of load that the crankshaft thrust is dealing with. Understand that in a normal situation there is always pressure in the torque converter and because of that always a forward load on the crankshaft. The crank thrust bearing is designed to deal with a certain amount of thrust load. It is when that load becomes excessive for a long enough time period that overheating and wear of the crank thrust takes place. All steps must be taken to control torque converter feed flow and internal pressure buildup. Unfortunately, there are some mods in the transmission market that aggravate torque converter pressure. I once traced the hydraulic circuit of the Stageright brake. It was a long time ago and don't remember whether line was boosted during transbrake condition. If it is, that's OK as long as other mods had not been done to increase flow to the torque converter or restrictions put in place to keep a free flow of fluid exiting the torque converter. Pressure BUILDUP in the torque converter is the problem. Internal torque converter pressure should always be much, much lower than the transmissions main line pressure.
 
Another thing I've run across over the years. Crank thrust problems from engines that did not have a history of thrust problems. Never rule out problems in metalurgy and/or hardening treatment.
 
ow, if you want to talk about torque converter charge pressure, there should be an old thread that I discussed this at good detail.
Click to expand...

Donnie, is there anyway you could help us dig that post up & post a link to it? I went back to look but could not find it. Great post as I remember & I should have printed it.
 
My understanding is when you push the converter all the way into the transmission whereby it cannot go in any further.. at that time you pull it out between .125 and .187 of an inch. Any space left over is made up with shims. The pilot of the TQ converter must move freely in and out of the back hub on the tranny, if it doesnt and binds.. bye bye thrust.

I've killed two thrusts now.

First was an older Art Carr converter that did not have the anti-ballooning plate.. used the T-brake with the converter.. guess what happened.

Second and most recent was due to a machine shop error in the way the thrust cap was cut when they set it up for a line hone. In essense they cut the bottom at an angle tilting the cap rearward. Had they tilted it forward, probably wouldnt of happened. I didnt catch it upon assembly.. so it was my fault.

New machine shop is being used :D

One learns from mistakes.. and reading the mistakes others have made. Hope this helps someone. Measure that thrust clearance CAREFULLY when putting her together.
 
When the torque converter is fully stabbed into the transmission, the T/C is stopped by the drive lugs of the pump rotor, or inner pump gear for a 400. These drive lugs have bottomed out in the slots that are cut into the end of the torque converter hub. A rookie may partially stab a torque converter where the input and stator splines have engaged, but the pump drive lugs are riding on the end of the torque converter hub and have not dropped into the grooves of the T/C hub. A rookie would install the transmission, tighten the trans to the engine, force the T/C around, not paying any thought to the fact that the T/C is jammed against the flexplate, and will bolt the T/C to the flexplate. The T/C is so well jammed between the engine and transmission, that the flexplate is bending towards the engine. Quite a bit of force to do that. Possibly even the pilot of the T/C is bottomed out against the end of the crankshaft. The rookie puts some fluid in and starts the engine. Finishes filling the trans and goes for a test drive. If he's lucky, he'll make it back to the garage. But, eventually, the transmission will neutralize and not go into gear. The reason this happens is because the spring action of the bent flexplate is pushing the T/C back against the transmission's pump drive lugs that are still riding on the top of the T/C hub. The pump rotor or inner gear are pushed back into the pump cover and the cover wears at a very fast rate until the push force has stopped. Usually, that means the pump rotor or gear has ground into the pump cover anywhere from 1/8 to 1/4". With the excessive face clearance in the pump cavity, the pump becomes inefficient and will no longer build pressure. The funny thing is, when this occurs and the transmission is rebuilt and installed properly, the engine (in my experience) never has needed attention. Bear in mind that the bent flexplate was pushing the T/C back against the pump rotor or gear, AND it was pushing the crankshaft forward. For every action there is an equal and opposite reaction. A basic law of physics.

This explanation is meant to show how much more sensitive the front pump of the transmission is than the crankshaft thrust in a situation where both have been mechanically jammed and a thrust force (equally) is applied to both.

If the crankshaft thrust surface is damaged, but there is no sign of the pump rotor or gear being forced back into the pump cover, then the thrust force that damaged the crankshaft was NOT mechanically born. It was caused by the torque converter being forced forward from the transmission by hydraulic action. Ballooning of torque converters is caused by hydraulic action also, but is a bit more complicated than just the pressure that is pushing the T/C out the front of the trans.
 
It is not a problem to have to pull the T/C 1/4" to the flexplate. There is still plenty of engagement of the pump drive lugs to the T/C drive slots cut in the end of the T/C hub. One half of an inch, I would view as a problem and you should use shims or more properly send the T/C back to the manufacturer and have them lengthen the hub. I just don't like using shims. I know people have used them with no problem, I would just rather not. Remember how reliable ring gear spacers are? If you have to use spacers, use hardened spacers.
 
Donnie,

Do you think that vigilante converters are HD enough to not have to worry about balooning? If so....It seems simple enough to ensure that you don't have a preload condition....don't have a converter that will balloon..... don't have excessive converter feed pressure....and that you really check out your crank fittment in the engine....

I am really gunshy..... it appears most people that have had problems either don't figure out what the root cause was.... or didn't pay attention to detail to ensure it didn't happen.

Thanks for all the valueable info.
 
I have not heard of any ballooning problems with the vigilantes. Do not use the cooler line fitting with the reduced orifice. That can cause back pressure in the T/C.

One final suggestion. Make sure the crank thrust bearing is seated properly. The mallet on the crank deal.
 
Ok i had a thrust problem that caused me alot of grief .I learned alot by looking at my parts and finding the flaws .I will say this most ppl miss a very important part of installing a convertor the hub and face need clearance too , most miss this .I have run a few different convertors and most where ok but not all the distance between the cheek of the crank and the torque convertor face should be .125 or so and the 1/8 to 3/16 between the legs and the flywheel .I had none of these and still ate my thrust 3 times . For the thrust to be taken out it needs a constant push to squeeze the oil out . I found my problem to be the input shaft splines it had splineloc and thats where the convertor locked on to pushing forward not the pump , once you put the least little bit of load it had constant pressure on the crank (remember that to push the crank forward it has to stake or bottom out on something like the pump or splines or misalignment ). Laz
 
Donnie, I had some warranty trans work done at a local GN shop recently. It seemed to be getting stuck between 2nd & 3rd gear. Well I'm a mechanic myself and hate warranty jobs, so I figured while he was in there, I'd pay him to instll a trans brake. Not something I had to have but, I hate to see someone work for nothing, so I figured I'd throw him a bone. The first and only time I used it I lost the thrust bearing. My engine only had 3k on it and ran really good up to this point. what do you think??
 
Dr.drivability said:
Donnie, I had some warranty trans work done at a local GN shop recently. It seemed to be getting stuck between 2nd & 3rd gear. Well I'm a mechanic myself and hate warranty jobs, so I figured while he was in there, I'd pay him to instll a trans brake. Not something I had to have but, I hate to see someone work for nothing, so I figured I'd throw him a bone. The first and only time I used it I lost the thrust bearing. My engine only had 3k on it and ran really good up to this point. what do you think??
Click to expand...
It would be impossible for me to pinpoint a cause without being able to look at the transmission. I see you use the Vigilante. Were you using the restricted fitting that comes with the T/C? What line pressure is the trans running? Was the PR valve modified? What is the normal cooler line pressure? Does the cooler line pressure change drastically during the transbrake application? What was the crankshaft endplay right before the transbrake application? Was the thrust already wearing and the transbrake just finished it off? What kind of pump and valvebody mods have been done? It's just not that easy to come up with a quick answer for you. Sorry.
 
I had the thrust bearing taken out on my 3.8l from an inferior torque convertor. I hot lap my GN at the end of the night of a test and tune. After packing up to drive home, I noticed the oil pressure at idle was down to 10 psi. It was always 20 psi. The convertor balooned. Fixed the engine and replaced the convertor with a d5.
 
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