Can engine problem ruin transmission?

Brian · #1 09-11-2006, 08:08 PM

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.

ensteele · #2 09-11-2006, 08:17 PM

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.

Manarius · #3 09-11-2006, 09:33 PM

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.

Beav · #4 09-12-2006, 05:21 AM

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.

Brian · #5 09-12-2006, 06:55 AM

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.

Beav · #6 09-12-2006, 10:59 AM

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.