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  #1  
Old 09-26-2002, 07:33 PM
rangerkh rangerkh is offline
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I have an 360/tf727. I swaped in another 360 in this week. I noticed as I was tightening up the torque converter to the flex plate that the replacement engine has about 1/4 in of back and forth on the crank shaft. Its not a side to side/up and down - its back and forth. I can see the pully on the front and the flex plate move back and forth. What cuases this and how do I fix this. After we got the engine running, it was put into gear and then into reverse. After it set awhile we restarted and when we tried to put it into gear there was a grinding noise. My uncle thinks that the play in the crank shaft may have pulled the torque converter out of its seat. I'm tired of having my jeep sitting and not being used, so any help on solving this would be greatly appreciated.
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  #2  
Old 09-27-2002, 12:11 AM
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crispyboy crispyboy is offline
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This sounds like a thrust bearing on the crankshaft. When my motor was built for some reason the crankshaft kept eating thrust bearings. It took the engine shop 3 new crankshafts to get it right - at their expense. They even went through the tranny. The only thing they did replace was the torque converter. I still think they did some bad machine work to make this happen. It should only have a few thousands of an inch play if I remember right.
Sorry to hear about your luck. Maybe you could get the bottom of the engine fixed.
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  #3  
Old 09-27-2002, 01:47 AM
Bob Barry Bob Barry is offline
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Just watch out; if the motor is from a '79 or earlier truck with the GM TH400 tranny, there will be a spacer sleeve in the crankshaft pilot hole that will prevent the torque-converter from properly seating, which will break your front pump.
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  #4  
Old 09-27-2002, 03:29 AM
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Crazy_Jeepman Crazy_Jeepman is offline
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Yup its the dreaded thrust bearing failure. measure it, sometimes a little bit of endplay feels like a lot, Spec is 0.0015 to 0.0065. If over that, you will need a new Crank, con rod and main bearing set.
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  #5  
Old 09-27-2002, 04:12 AM
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Retro93 Retro93 is offline
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Welcome to the AMC junk crank club. I am the proud owner of 2 360 cranks that suffer from the same problem you described. [img]redface.gif[/img] It's kind of unsettling to see the whole crank assembly slide back and forth in the block isn't it? About all you can do now is pull the pan and check the thrust bearing [#3 main] AND the thrust surface on the crank. If you find a deep groove in the crank, it is junk.

Sorry to hear of you problems.
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  #6  
Old 09-27-2002, 04:22 AM
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had same problem with my 401! talk about hard to find replacement parts! i found a crank specialist that welded up the thrust surface and reground it to spec
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  #7  
Old 09-27-2002, 02:37 PM
Mike B Mike B is offline
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I too am a member of the AMC V8 wasted thrust bearing club. Forum member Kris is a member too-on two engines in a row. Common problem. My (98,000 original factory mile) engine's crank has close to 1/4" endplay as well. On mine,after warm-up,when the oil pressure comes back down, while accelerating either moderately or hard,and only at a certain RPM,the crank moves forward and the flexplate to torque converter bolt heads contact the rear engine plate,causing a LOUD BRAAAAP! noise.I removed the inspection cover and you can see the rub marks on the plate and the shiny,slightly worn bolt heads.This noise really wakes up those driving around you! I decided to forego doing a crank and bearings,instead opting to put the Jeep on the backburner,and drive and mess with my other cars a bit, while I save the $$ for a rebuilt in the Jeep.
I still drive the Jeep around town with it's full-floating crank-if you take off really slowly it makes no noise,but my new engine should be ready soon.

The AMC V8 is a good engine,but the oiling system is basically a POS system-especially for high RPM usage. The mains and rods tend to get starved,as they are the last thing to get oiled.I talked to Randy at Performance American Style about the oiling kits he and others sell to correct this,and he said a typical low rpm motor probably doesn't need them,but I think they are good insurance.
In fairness to AMC,in my case my dad was the former owner of my Jeep,and I know him-not a car maintenance guy.Very likely my engine was run low or even very low on oil at some point,so maybe a contributing factor to my problem.

But since you have an automatic,even though you put this motor in from a different truck,just to be sure this doesn't happen again, I'd check(or have a trans shop check) your trans cooler line pressures in and out of the tranny. If there is a restriction in the cooler,the line pressure climbs and torque conerter goes forward-hard!
This will take out your thrust bearing in a rapid fashion. Check the Torque converter itself too- as a malfunctioning one can do the same thing. I intend to check and double check everything when I put in my new motor as I only want to be a club member once!
Here are a couple interesting links concerning engine thrust bearing failure,and note that AMC engines are not the only ones to have this problem.

http://www.aera.org/Tech/tb1465r.htm

http://www.gnttype.org/techarea/tran...n/trantsb.html

Good Luck!

Mike B
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  #8  
Old 09-27-2002, 06:23 PM
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Kris Kris is offline
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Quote:
Originally posted by Mike B:
I too am a member of the AMC V8 wasted thrust bearing club. Forum member Kris is a member too-on two engines in a row...
Mike B
Yep.
Did'nt loose the thrust bearing until after the 1st rebuild, really messy story.
The crank can be welded and reground, does not cause any problems.
Welcome to the club !

kris.
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AX-15 swap info threads...
http://www.ifsja.org/forums/vb/showthread.php?t=83102
http://www.ifsja.org/forums/vb/showthread.php?t=97262
http://www.ifsja.org/forums/vb/showthread.php?t=104163
Theres more but that should get you started

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  #9  
Old 09-29-2002, 03:28 PM
Setto Setto is offline
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I'm in the club too. Had the motor and tranny rebuilt and the thrust went out in about 500 miles. Engine builder and I suspected the tranny shop, tranny guy was an idiot. So we rebuilt the engine, bought a new convertor, had the tranny inspected and pressure checked out by a different tranny shop. He didn't find anything wrong with the tranny and the pressures were fine. But it looks like this one is starting to go after 100 miles. It's a pretty depressing problem given the money and time I have spent on this. Sounds like the crankshafts are just POS. So I would like to verigy if the guys that the crankshafts welded and reground are still seeing the issue. Let me know.
Jeff
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  #10  
Old 09-30-2002, 12:42 AM
andy d andy d is offline
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Mike B, i read with interest the two links you put up. esp liked the idea of chamfering the rear edge of the bearing to allow better oiling. also the part of taking a pressure reading of the trans lines before and after the coolers. good stuff there. Setto, sounds like your rebuilder is real good... at the blame game.
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  #11  
Old 09-30-2002, 04:35 AM
Mike B Mike B is offline
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Setto(Jeff),welcome to the forums!
To be honest I was somewhat horrified to hear there is yet another guy out there with the recently rebuilt engine thrust failure,especially considering what you checked.
On those links supplied there was quite a bit related to the machining on the crank too,and I'm suspecting that's the problem on your engine.
You said it's going out again-is it already making noise-or did you measure play and how much is there now?
Is your rebuilder and the machinist the same person?
Did he machine the thrust surface of the crank?
Did he use an oversize thrust?
I'm getting super paranoid about installing my new longblock without checking everything humanly posssible that could cause a failure.
and Andy D-yes that chamfering sounds like a good idea,but I'm putting in a rebuilt longblock and I bet pulling those shells out and doing that would void my warranty-but maybe worth it anyway-I don't know.
Anyway,good luck Jeff and please keep us posted as to what happens...

Mike B
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  #12  
Old 10-02-2002, 08:57 AM
vvaughn vvaughn is offline
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Unhappy

I'm in the club too. I didn't realize that these thrust bearing failures were so common. My engine amc360 just came back from the rebuilder (they welded the crank) with .05" end play on the crank. I sent it back and now they are trying to convince me that fifty thousandths is really only ten thousandths! They claim that the play can be removed by dimpling with a centerpunch to make ridges in the surface of bearing support - sounds like a bad idea to me.
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  #13  
Old 10-02-2002, 09:11 AM
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Rogue Rogue is offline
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ooooh noooo dont dimple the bearing seat! that is no good, there is a way to offset the main cap with a center punch so that the cap sits cockeyed on the block (we're only talking thousandths of an inch here) i've have seen this done to $10,000 alcohol burning racing engines we used in late model racing and they lasted an entire season with no problems
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  #14  
Old 10-02-2002, 02:18 PM
Mike B Mike B is offline
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Here is a link to a company who apparently is big with the drag racing crowd.
They make thrust bearings that are on the high side(tight) of tolerance for endplay,and they also make thrust bearings that are oversize in .010,.020, and .030-so you can machine your crank thrust surface to them.
Scroll down on the page to "Benefit no. 6 Crankshaft Endplay" to read about them.

http://www.kingbearings.com/advantages.html
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  #15  
Old 10-02-2002, 04:35 PM
JJK4666 JJK4666 is offline
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I too had this problem on a new rebuild I got from a company in CA for my 88. Everyone said that it was probably related to the transmission, but I couldn't believe it since the original motor had no such problem and a motor from my 86 that I put in while I figured this out(this is my daily driver)was fine with the same tranny. I miked the bad crank and it was identical to the new crank I bought. I ended up stripping the entire motor down and rebuilding it with the new crank and new valve springs since the ones in there were out of spec and one was actually broken! When I fit the new crank in and plastiguaged it, all of the mains were off. So I sent it out to be line honed and finished building it, installed it (same tranny) and I have not had a problem since.(1500mi.) Go figure.
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  #16  
Old 10-03-2002, 04:11 AM
vvaughn vvaughn is offline
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Thanks for the thrust bearing info! I don't want to go through this again.

Val 83 FS Cherokee
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  #17  
Old 10-22-2002, 11:35 AM
Setto Setto is offline
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I have measured the end play on the crankshaft and it is holding at .012, started with .006 from the engine rebuilder. i am currently driving and checking the end play to see if it is getting worse. Not sure what else to do right now. If it stays at .012, I guess it is alright. Not really sure. I will certainly be checking frequently.

Mike B. Answers to your questions.
Yes, engine builder and machinist are the same person.
Crankshaft thrust surface was machined and looked good.
We did not use oversized thrust bearings.

One thing to also note is that we did the bearing modification recommneded by aera on both rebuilds.
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