I posted this in the driveline section and haven't had much help. I originally thought this might be the transmission oil pump or torque converter, but now I'm out of ideas. Here are the details.

Car is a 1989 GTA, TPI 350, 700R4. 125,000km, engine runs reasonably well, little stumble on throttle tip in, otherwise, runs good, no idiot lights, new plugs, wires, coil. I was told by the previous owner that this engine has thrown a balancer at one point in time. There is no play in the balancer and I can see or feel, no knocking, oil pressure is good.

PROBLEM: With the torque converter disconnected, engine runs smooth. Bolt up a converter, the whole mess shakes. It wobbles like its unbalanced, and it looks like the converter is wobbling if you watch it from under the car, but it could be just an optical illusion.

SOLUTION: I have changed the flexplate and converter (good used and new rebuilt respectively) and it still shakes. I had the transmission oil pump checked by a local shop, they said it had normal wear on the bushing, replaced the bushing and checked the oil pump, no issues they could see. I rotated the converter on the flexplate and the shaking does change depending on how its bolted up, but it won't go away. Anyone have any idea? This is pretty much the only thing keeping me from driving this car. Is there any way that the engine could be out of balance in such a way that the converter is enough to make it shake but not enough to blow up the motor?? I would think a constant shake like this would have ate away the crank bearings fairly quickly.

 

Are you bolting up just the converter without the transmission? If you are - any amount of fluid in the converter could harm balance.

If you have the trans hooked up and it wobbles; though when you remove the trans and converter it does not wobble - I would say that you should check for a bent input shaft on the trans.

However, if the old Harmonic Damper failed... who really knows how long the engine was driven with a failing/failed inertia ring on the damper. Some people don't like to agree, but an engine with an inoperable harmonic damper is like a ticking bomb... there could be physical crankshaft damage.

Hmm.....

Of course if the crank was damaged it should vibrate all the time.

Are there counterweights on either the flexplate or harmonic damper/balancer? I'm wondering if perhaps there is a mixture of internal/externally balanced parts? That would make for some wiggle

 

Bolting up the converter while its attached to the transmission. I'm no mechanic, but I know the latter would be very bad!!

Well, I think that might be it. Is that replaceable for a reasonable price, or should I just grab another trans and stuff it in? There's one available for $400 locally. I don't want to do this trans again....I can have one out in 2.5 hours now, but putting it back in is a pain...stupid cooler lines. Also, dumb question: Does the input shaft spin with the trans in Park and Neutral?

Right...but then why does it run so damn good? I would think it would sound like a bag of hammers right now. Oil pressure is very high, no funny noises. It should have exploded by now if there was serious damage.

There's a weight on the flexplate, but its the standard one, nothing unusual. Both plates looked fine, no loose weights. I'll bet you're right on this input shaft....but how the HELL do you bend one of those?? If you're ever up here, I think I owe you a beer!

 

If it's a bent shaft you're probably best replacing the transmission as a unit.. otherwise you could get one used - from a blown trans or online - and replace only what you need. However, paying to have an input shaft replaced will probably add up to the price of a used trans.

BTW - "Oil pressure is very high" - Not always a good thing, it can indicate health or clogged passages. Try some Gunk motor flush or something similar to be safe, I love that stuff!

 

Is the motor physically shaking alot? Have you checked the condition of your motor mounts? I know I had a buddy that had an old back roading car that the mounts went out and the whole thing shook bad. We strapped it in with logging chains... LOL!
But I'm not sure how you'd get a bent input shaft. But yeah it's a possibility. And everything in an auto teans is movving when the motor is running. It all operates off of hyd pressure to activate certain clutches inside.

 

I just thought of another possibility. Have you changed the flexplate yet? The hole's where the converter bolt up could be ovaled out or the converter studs are damaged.

 

Sorry, when I say "high" I mean at a pressure I would associate normally with a high volume pump. Its just under 400 when cold...I can't remember what its measured in, but that was the same the mild SBC in my old TBI truck was at, even after 200,000km. So I'm pretty sure oil pressure is ok, but I do have some de-gunker to throw through it anyway.

 

The motor alone does not shake...it is smooth. I will check the mounts, and I am going to run it without the serp. system in place to see if that makes a difference, and then when all that fails I will swap the converter one more time with one I KNOW is ok. I did swap flexplates, no change. I rotated the converter on the flexplate (changed mounting holes) and saw some change, but it did not take away the shaking and different mounting holes definitely changed how it shook. We just took a look under the car while running and the converter is definitely rotating out of round....just have to find out why, either the converter, the shaft, or the plate. Surprised I haven't lunched the engine yet with all this vibration. SBC's can really take abuse, thank God.

 

Ok, now things are getting interesting. Started playing with all of the 700R converters I have around from parts cars and unfinished projects. I have a converter I know is good from my truck. Put it on, and it engaged on the shaft MORE than the other converters. The other converters had room to wiggle a bit, but they bolted up to the flexplate as they should. The converter from the truck was 1/4 inch or so back from the flexplate when it was engaged all the way with the input shaft. It also felt a lot more snug than the others on the shaft, but I would have had to pull it out of the trans in order to make it bolt up. I think I'm doing something wrong, but I have no idea what. I have re and re'd motors and transmissions before, never managed to screw it up like this. Anyone???? Oh, and its not the input shaft, its solid as a rock with good splines.

 

I put in new motor mounts with my engine and within a month, they shrank! They were worse than the originals. If anyone has a pic, that might help.

Sometimes exhaust can make a really wierd vibe too.

edit: but it sounds like it might be something else for you, related to trans... converter

 

First, you are installing the torque converter in the trans first, right? If you don't you will have troubles! It can't simply be forced in.

My brother has a BBC 540 with a powerglide.. He lost some teeth on the flexplate and bought a new one. He put it on backwards and it still worked, shook so bad that the alignment dowl pins came out though. lol. He also didnt realize that there is only one way that you should bolt it to the crank (I mean rotationally). But at idle and such it didn't shake!

400Kpa is fine oil pressure. 58-60PSI. Mine makes about 45PSI@1000RPMs.

Can you take some pictures of how you have things assembled and what parts you are using?

I think that would be a great help for visual inspection.

 

I think its just a crappy converter. I slapped the one out of the truck in yesterday and there is much less shake. I will try changing its position on the flexplate, but I think I am going to call this done and I'll just move faster with the WC T5 swap I have planned. Its much better than it was, just not perfect. But then again, I've never really driven a v8 uni-body car, so I don't know what its supposed to feel like.