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Re: [GMCnet] Reviving the Cad 500 [message #165466 is a reply to message #162802] |
Thu, 05 April 2012 13:19 |
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John Heslinga
Messages: 632 Registered: February 2011 Location: Edmonton, Alberta, Canada
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Ken:
Boy! Do I understand the frustration that you're having with this issue! I've been there a few times in my career. I've been following your Blog and it is clear that this issue has you ready to pull your hair out. Every time it looked like you found a viable solution and it failed, I re-lived the same feelings that I would go through.
I'm not going to pretend that I know what your problem is: but I have a couple of observations, comments and suggestions that may be of help. I understand the need to be confidant in your next repair and to be able to observe or measure an actual problem or inconsistency so you do not have to do it again. I also believe that you are working with a group of highly experienced and dedicated pros who have made some very interesting and cool observations and suggestions. (Man, would I love to work with some of them!!)
Everyone on the forum is certainly cheering for you, and it appears to be willing to do anything they can to help. (ME TOO!!!)
First: my humble observations and assumptions to give context and reasoning for my suggestions. Many may appear to be intuitively obvious to the casual observer, but can easily be ignored in looking for an annoying problem such as yours. Please bear with me.
The Cad engine that you rebuilt and installed came from a wreck that probably had a fair few miles on it, therefore It would be highly unlikely that there would be any problem with bell housing alignment or the block machining and alignment pins and the crankshaft vs Torque Converter alignment and position. Basic engine geometry should also be on no consequence including accessory loads such as pumps and your serpentine belt system. These wouldn't cause thrust loading problems. Harmonic balancing would cause other crank problems including breakage, and crank snout problems.
You've already replaced the warped flexplate on your first repair. ( My experience, born out also by my recent GMC engine / transmission rebuild and install, is that there is about 1/4 inch or more axial slop between the torque converter and the flexplate before you tighten the TC nuts to the flexplate. Therefore the torque converter is not bottoming out on the transmission pump. I think you also mentioned that you had that clearance on your second install.
The Transmission is also from a working unit with quite a few miles before this: therefore basic bell housing alignment, machining, clearances, and basic geometry should be well within design requirements.
The only thrust loading the TH425 can give is from the torque converter, pump, input shaft, and chain drive gear. All of which must expand that 1/4" or more of axial slop I was referring to earlier, to put much pressure on the engine thrust bearing. ( I would think that you would also have some thrust and surface damage in the transmission pump area and or torque converter as well, because the two pump drive ears would need to push against and pressure the drive gear of the transmission pump) The Torque converter also needs to expand, balloon, or stretch that large distance before it will create that kind of thrust pressure.
My suggestions:
The warped flex plate, install problems, or bad parts may have caused the nose of the Torque Converter or the transmission side of the TC housing to be slightly bent to cause the torque converter to whip slightly as it spins, causing a hammering thrust on the engine ( the flex plate will allow the flexing and springing action to enhance the hammering of the thrust bearing.). Slightly bent crank flywheel mounting flanges may also cause the hammer of the thrust bearing. A slightly rougher thrust crank surface will exasperate the problem and cut through the oil film during this hammer causing the crank to eat into the bearing. (if in fact this is the case)
Your engine machinist will certainly be ensuring the the crank is smooth this time and probably micro-polish and buff the thrust surface. It should almost be mirror smooth. He should also check out the flywheel flange for runout. I'm sure you will ensure that you pre-lube that surface with assembly lube.
You either have the transmission out or it is hanging in the engine bay very easy to remove. Send it to Manny in San Jose and have him put on his test stand. I've seen it and it will help diagnose the transmission completely. He can measure the Torque Converter against a known good one, check the run-out on the input shaft, pump housing, and pump bushings etcetera.
I have been with Manny working on my own transmission, and can confirm that he has the background, knowledge, facilities, attitude, desire, material, and integrity to find and establish if the transmission is at fault for your problem. I brought my tranny from Northern Canada to him and have seen the quality work he does. For your peace of mind, you want to be sure the tranny is not at fault. I believe that Manny also would love to know if the tranny could be your problem.
His test stand has a 455 driving the transmission, a prony brake to fully load the transmission, and access to all of the test ports to measure pressures, both line and cooling. He can confirm if your transmission is doing what it should do. Finally, he will give you the ultimate fix if needed.
Of course you could just replace yours with one of his transmissions to be sure, but there are a lot of people who are now curious and it would be a major let-down for everyone if the answer to your problems was not definitive.
I know you and Manny are on both sides of the continent, but transporting your transmission to San Jose and back would be worth it and if really needed, could be shuttled by so many of the people that you have helped on this forum over the years. (I know I would help but being 12 hours north of the Border won't help)
Sure hope things work out!!
Best regards
John and Cathie Heslinga
1974 Canyonlands 260
455, Manny tranny and 1 ton, 3:70 LS,
Red Seal Journeyman, DTE, BEd. MEd.
Edmonton, Alberta
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[GMCnet] Reviving the Cad 500
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Re: [GMCnet] Reviving the Cad 500
By: Dennis S on Mon, 12 March 2012 21:51
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Re: [GMCnet] Reviving the Cad 500
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Re: [GMCnet] Reviving the Cad 500
By: Kosier on Mon, 12 March 2012 22:05
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Re: [GMCnet] Reviving the Cad 500
By: sgltrac on Mon, 12 March 2012 23:42
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Re: [GMCnet] Reviving the Cad 500
By: ljdavick on Mon, 12 March 2012 23:51
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Re: [GMCnet] Reviving the Cad 500
By: Larry on Tue, 13 March 2012 09:23
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Re: [GMCnet] Reviving the Cad 500
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Re: [GMCnet] Reviving the Cad 500
By: Larry on Tue, 13 March 2012 12:58
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Re: [GMCnet] Reviving the Cad 500
By: Larry on Tue, 13 March 2012 18:58
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Re: [GMCnet] Reviving the Cad 500
By: jimk on Wed, 14 March 2012 01:23
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Re: [GMCnet] Reviving the Cad 500
By: jimk on Thu, 15 March 2012 01:22
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Re: [GMCnet] Reviving the Cad 500
By: USAussie on Thu, 15 March 2012 08:43
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Re: [GMCnet] Reviving the Cad 500
By: k2gkk on Thu, 15 March 2012 11:53
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Re: [GMCnet] Reviving the Cad 500
By: jimk on Fri, 16 March 2012 01:30
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Re: [GMCnet] Reviving the Cad 500
By: USAussie on Fri, 16 March 2012 10:09
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Re: [GMCnet] Reviving the Cad 500
By: ljdavick on Fri, 16 March 2012 01:37
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Re: [GMCnet] Reviving the Cad 500
By: Larry on Fri, 16 March 2012 07:54
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Re: [GMCnet] Reviving the Cad 500
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Re: [GMCnet] Reviving the Cad 500
By: Kosier on Sun, 18 March 2012 21:16
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Re: [GMCnet] Reviving the Cad 500
By: midlf on Sun, 18 March 2012 22:09
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Re: [GMCnet] Reviving the Cad 500
By: USAussie on Sun, 18 March 2012 22:04
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Re: [GMCnet] Reviving the Cad 500
By: ljdavick on Mon, 19 March 2012 01:05
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Re: [GMCnet] Reviving the Cad 500
By: USAussie on Mon, 19 March 2012 06:54
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Re: [GMCnet] Reviving the Cad 500
By: USAussie on Mon, 19 March 2012 07:05
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Re: [GMCnet] Reviving the Cad 500
By: Dennis S on Sat, 24 March 2012 15:32
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Re: [GMCnet] Reviving the Cad 500
By: Dennis S on Sat, 24 March 2012 22:45
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Re: [GMCnet] Reviving the Cad 500
By: Carl S. on Mon, 19 March 2012 13:08
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Re: [GMCnet] Reviving the Cad 500
By: GMC_LES on Mon, 26 March 2012 20:55
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Re: [GMCnet] Reviving the Cad 500
By: GMC_LES on Tue, 27 March 2012 07:37
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Re: [GMCnet] Reviving the Cad 500
By: shawnee on Sat, 31 March 2012 20:11
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Re: [GMCnet] Reviving the Cad 500
By: GMC_LES on Mon, 02 April 2012 18:28
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Re: [GMCnet] Reviving the Cad 500
By: Dennis S on Mon, 02 April 2012 18:43
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Re: [GMCnet] Reviving the Cad 500
By: roy1 on Tue, 03 April 2012 11:15
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Re: [GMCnet] Reviving the Cad 500
By: Larry on Tue, 03 April 2012 16:14
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Re: [GMCnet] Reviving the Cad 500
By: GMC_LES on Wed, 04 April 2012 16:34
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Re: [GMCnet] Reviving the Cad 500
By: ljdavick on Sat, 17 March 2012 20:15
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Re: [GMCnet] Reviving the Cad 500
By: Kosier on Sat, 17 March 2012 20:25
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Re: [GMCnet] Reviving the Cad 500
By: ljdavick on Sun, 18 March 2012 03:44
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Re: [GMCnet] Reviving the Cad 500
By: WD0AFQ on Fri, 16 March 2012 22:33
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Re: [GMCnet] Reviving the Cad 500
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Re: [GMCnet] Reviving the Cad 500
By: Dennis S on Mon, 19 March 2012 11:30
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By: rssbob on Wed, 28 March 2012 22:14
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By: kingd on Sat, 31 March 2012 20:08
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By: JohnL455 on Tue, 03 April 2012 19:17
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By: k2gkk on Wed, 04 April 2012 16:00
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By: Dan W on Thu, 05 April 2012 09:08
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Re: [GMCnet] Reviving the Cad 500
By: GMC_LES on Thu, 05 April 2012 07:45
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Re: [GMCnet] Reviving the Cad 500
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