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  #1  
Old 09-11-2006, 08:08 PM
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Question Can engine problem ruin transmission?

Can front-to-rear play of the flywheel (due to an internal engine problem) ruin the transmission? My car is back in the transmission shop following a rebuild at the beginning of summer. I took it back in because of a noise from a cracked flywheel, and the mechanic told me that it had already "torn up" the transmission he'd rebuilt. (When the transmission went bad the first time, he had discovered that the flywheel was cracked that time as well.) He says the transmission and flywheel will fail again unless the engine is rebuilt/replaced because the engine is producing this back-and-forth motion. It sounds plausible. It would explain a lot of mysteries. But I have no idea if it's even possible.
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Old 09-11-2006, 08:17 PM
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I don't know. I have never heard of that, but that doesn't mean that it is not true. Let's see what others have to say.
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Old 09-11-2006, 09:33 PM
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I didn't know that the engine could rock back and forth as that mechanic describes. If it was happening in the back of the engine, it would surely have to he happening at the front - is the crank pulley mucked up? Maybe one of the main bearings is out, but I've never heard of that causing the flywheel to crack.
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Old 09-12-2006, 05:21 AM
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We've had a few guys measure what seemed to be excessive (beyond OEM spec) crankshaft thrust. Then again it may have been their method of measurement as I'm not certain they had access to proper measuring tools or methods. Be that as it may, the thing to remember is that the torque convertor also has the ability to float back and forth, mimicking the crankshaft. So.... before jumping on that bandwagon I'd make certain of the existence of the alignment dowels between the engine and transmission. They accurately locate and match the two together - the bolts alone WILL NOT do that properly (at least not without an extraordinary amount of luck.) This causes the flywheel (flexplate) and the convertor to rotate in two different planes and cracking will inevitably occur.
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Old 09-12-2006, 06:55 AM
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Beav,
I had asked about the dowels before he even took a look at it. A couple days later, when he had it up on the rack with the transmission out, he showed me the 2 dowels protruding form the engine block. They were there, but I have no way of telling if their alignment is right (or even if they had been there this whole time). Is it enough to know the dowels are there? Or must I also know their precisely measured angles (and if their sockets hold them tightly in place) to be sure there's no problem with them?

Jason,
You're misunderstanding the type of motion, exactly as I did the first time he told me about it. The whole engine is not moving, and it's not a side-to-side motion. Some problem inside the engine, maybe with the bearings or crankshaft, is supposedly causing the flywheel to move front-to-back.

My engine was rebuilt 2 years ago. When it failed that time, the shop I had it at then said the crankshaft went. But they used the short block from an engine I got in a junkyard (w/160,000 miles on it) for the rebuild.
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Old 09-12-2006, 10:59 AM
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Nothing to measure or adjust, all that is required is that they are installed.

It could be that the crankshaft has enough thrust bearing wear but I'd think there would be other issues, like the engine oil pump, etc.
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Old 09-12-2006, 02:44 PM
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the technical term is crank walk... I have never heard of it destroying a tranmsission but it has definately been the cause of killing flex plates(AKA flywheel in an standard trans). Talk to SVXRide... his flex plates love him ... But seriously, I would suggest you have the clearances checked by a certified mechanic and see if that is really causing your issues or if BEAV is right when he says that your pins may not be installed

Tom
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Old 09-12-2006, 05:32 PM
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Tom,

O.K., time to show my ignorance: What do you mean by clearances? If I'm going to ask someone to check something, I should probably understand what it is.

After I get the car back from the transmission shop, is there a possibility that an engine mechanic can diagnose my problem w/o tearing the engine apart? (ie: spending a fortune)

I was already thinking that it's time to get rid of this car if it's inevitable that the transmission is going to fail again. The transmission place already told me that the next time it won't be covered by my warranty since it's an engine, not transmission, problem. If I can get confirmation that the engine is bad, then I know getting rid of it is the thing to do.

If the engine isn't the problem, I'm still up a creek, because I can't trust the transmission shop's rebuild to last, and they won't fix the transmission for free next time.
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Old 09-12-2006, 06:20 PM
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by clearances I mean the front to back movement of the crank shaft. There is a certain amount of acceptable movement but once it goes too far past this spec... it becomes a problem. I do not have the service manuals with me and cannot look up what the movement should be but maybe someone who has them handy can tell you. This movement is also known as play

Tom
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Old 09-13-2006, 06:13 PM
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It would seem to me that the oil pump, which is concentric to the front of the crankshaft, would catch a lot more hell than the flexplate. The 'flex' in flexplate is there for a reason... and as I mentioned before, the torque convertor can slide back and forth a tad on its stub into the front pump of the transmission. Also to be questioned is what would be the cause of such high thrust bearing wear in the engine, as it isn't subjected to the pressures of a throw-out bearing as it would be in a manual trans car.

Seeing how the dowels are in place I'd suspect either a torque convertor that is unevenly swollen due to TCC-induced distortion, whether mechanically or hydraulically caused, or a poor quality reman' torque convertor that doesn't spin true. Last, but not necessarily least, could be a very worn torque convertor bushing in the front pump.
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Old 09-13-2006, 09:27 PM
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Beav,

A very informative post, even if I don't understand everthing. What does the "TCC" stand for in "TCC-induced distortion"? I don't understand what you mean by "unevenly swollen" torque converter. How/why does it swell? Although I know what torque is, I'm not really sure what a torque converter is or how it works.

By the way, I do remember that the transmission "oil pump" was one of the parts that was ruined. That would be the same as the "front pump", right?
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Old 10-16-2006, 06:45 PM
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At the end of last week, 7 weeks after I took the car in to the transmission shop, they finally finished! The mechanic kept at his tired claim that it was caused by play in the crankshaft. Today I took it to a shop called Harry's Automotive in Butler, PA, which was recommended by another member, and had the play measured. It's well within spec. To be precise, it's 0.020", and according to the mechanic, spec is between 0.014" to 0.045".

That basically means that the second failure really was due to the first rebuild being a bad job. I don't know if he did a better job this time, but last time he rebuilt the torque converter, and this time he replaced it. That may be a good indication, but here's a bad indication: This time he painted the transmission case silver I guess he figures I'll think it's brand new! (I saw it when it was up on the rack today getting the play measured.) He also replaced the ruined oil pump, bushings, fluid & fliter, and of course the flywheel. He wrote on the work order: "Motor has excessive endplay in crankshaft. This is the cause of vehicle breaking flywheels...Warranty:none."

In any case, I already bought a new SVX just a day or 2 before he finished! It's a FWD 94 Laguna that was well taken care of. (It's in very good shape, especially considering that it has spent its whole life in the northeast.) Now that I have my old car back and know there's no engine problem, that seems kind of excessive. I always wanted a laguna, but now that I have my claret back, I like it better than the laguna! Maybe that will change with time.
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  #13  
Old 10-16-2006, 07:08 PM
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didn't think that there would have been enough movement to do that. I would bring back the documentation from the other mechanic showing him there is no excessive endplay in the crank and he needs to warrenty the new rebuild....

BTW painting the case silver is common after a rebuild

Tom
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