Torque converter to flexplate position relationship?

[jmonica]

Hi Everyone, I have a question I am hoping someone can shed some light on. I recently replaced the engine in my '06 Envoy. The repair manual said to mark the position of the Torque converter to flexplate position and reinstall it in the same position. I'm assuming due to the way it is balanced? Well my questions are, what does one do if they install a new torque converter to ensure proper balance? I replaced the engine with a used engine that had the flexplate attached and my partner convinced me to leave the flexplate on the replacement engine and install it, while I should have listened to myself and swapped them and installed it with the marks lined up because I swear I feel a slight vibration when the trans is in drive now. It bothers the heck out of me that I allowed myself to be talked out of doing what I knew to be the right thing to do just because the person I was working with just wanted it to be done. Now I have to deal with a lifetime of vibration and any problems that may come from it over time. So what happens when one installs a new converter? Is there some procedure for balancing it to the flexplate/engine? If not, how is proper balance then achieved and why did the stock one need to be replaced in the same position? Or does one need to buy a flexplate/ converter as a matched pair in order for them to be in balanced or take the flexplate off and have the two balanced to one another outside of the vehicle? I've never heard of that procedure, but what the heck do I know? Not much obviously. Sorry, I do not know much about how it all works. Any enlightenment would be greatly appreciated. Thank You

 

[Mooseman]

The manual says to do that but, as you mentioned, it's not realistic to balance the assembly with a new converter. I don't even think they are balanced as an assembly but separately. If you really wanted to, you could unbolt the converter from the flexplate and spin it to another position.

Personally, I wouldn't bother. You might just be experiencing hyper sensitivity knowing what the manual says. Did you replace the mounts when you replaced the motor? Vibrations at idle is usually because of the mounts.

 

[Wooluf1952]

+1 ^. There are 3 bolts, so it would take two position changes at most if it really bothers you. Just be sure to rotate the converter in the same direction each time.

 

[mrrsm]

It might be helpful to take a step back and assess the Replacement Engine Bolt-Ons first before looking too closely at the Flex-Plate-To-Torque Converter mate-up. I'll pose a few questions that may prompt you to check a few of these areas out:

(1) Have you tried pulling the Serpentine Belt? (battery must be fully charged and in good shape...with the Head Lights turned off) and listen to the engine at idle and during a very brief drive on the highway for the same vibration symptoms)? If the vibrations are absent... the culprit could be bad bearings in either the Water Pump or Alternator...or perhaps the idler or belt tensioner pulleys as well.

(2) Did you install the Starter, Alternator and Water Pump from your Old Engine or choose new components?

(3) Did you install New Motor Mounts and Transmission Mount?

(4) Did you clean any adaptive components such as the CPAS or the Throttle Body?

(5) Did you R&R the Harmonic Balancer or replace it with a brand new one? Following the factory install procedures and torque specs on this item is very critical... as it has no Woodruff Key to make it behave should the bolt get unfastened and allow the HB to be loosely riding the nose of the crankshaft right now. The mischief this can cause includes destroying the engine in very short order... or killing someone... should it decide to go off on it's own all of a sudden.

Just an FYI... Torque Converters are generally constructed out of mild steel shells with fixed and rotating shaft vane assemblies welded into a fluid tight unit that are balanced and counterweighted on a lathe at several speeds to ensure that they do not shake and vibrate as hydraulic fluid is pumped in and then slung around to influence the shifting of the various transmission gear clusters. Also... it is highly unlikely that merely attaching the three bolts to the TC pads would have caused a vibration issue unless you seriously over-torqued the three bolts. And if you did not replace the Flex-Plate with a new one...unless you broke off teeth on the Fire Carbon Steel Gear Ring... that would also not present you with a vibration problem.

Depending upon the mileage and the pedigree and care of the Replacement Engine... going at this step by step will save you some time, money and aggravation as well. You would be surprised at what can be found in the way of loose exhaust manifold bolts and other similar attachments that can get overlooked during any swap-out. Gather your thoughts about everything you did during this work...itemize a check-list... and go back and check everything...one variable at a time.

 

[jmonica]

Wow thanks for all of the great info and suggestions. It could very well be that I am being hypersensitive as suggested. Very possible indeed. I replaced the Water pump with replacement engine and the started about 2 months later. Alternator is the original OEM with about 250,000 miles on it. I did replace all motor and trans mounts. I didn't think this engine has a harmonic balancer though? Did I leave a part off?

I did thoroughly clean everything following instructions found on this site. Throttle, CPAS etc... I installed all new Fuel injectors, plugs obviously. I even went as far as to install new knock sensors, new O2 sensors even though none of them seemed to be bad. New battery as well.

I could try to remove the drive belt and see if that makes a difference for the small amount of time it would take to do the test but I really don't think it's going to reveal any vibrations from bearings on anything like the Alternator etc. because the vibration is only present when in Drive or Reverse.

Granted I understand that a vibration of that kind might be amplified when the engine has a load on it, but I can tell that the vibration is coming from underneath the vehicle, not from the front of the engine compartment.

I have to say that the new engine fired up instantly before i even got a full turn on the ignition key and it runs very smoothly in neutral and park. Just a small vibration in drive or reverse.

I know what it felt like before the swap and i also had another Envoy same model for 4-5 years prior to this one so I've been driving an SLT Envoy daily for over a decade. I put 550 miles a week on it plus a few hundred per weekend on average. My point, and I do not mean to sound like I'm tooting my own horn in any way shape or form, is that I can usually almost instantly tell when something is out of order, doesn't feel or sound right and well this vibration is not normal. It's so slight it probably wouldn't even bother most folks so I probably just need to leave it alone as suggested.

I really was just curious why they tell us to mark the position in the manual. It just bothers me that it doesn't work as perfectly as it did from the factory. Knock on wood even with regular maintenance, the transmission will eventually need to be rebuilt or repaired I'm sure, so I will install a new converter at that point more than likely.

OH BTW, there aren't any broken teeth on the flex plate.


Again, I can't thank you guys enough for all of the great information and tips. It is very much appreciated!

 

[mrrsm]

Welcome Aboard the Good Ship "GMT Nation" @jmonica

It will help us all if you could occasionally punctuate your text with a paragraph line say...every inch and a half deep to allow us the chance to breath...and pause ...and collect our thoughts about each important aspect of what you are trying to convey. Otherwise...a "Wall of Words" can become an exercise in bewilderment when trying to..

"Separate the Fly Sh*t ...from the Pepper..."

...so to speak. :>)

There is no doubt that you will need to run this vehicle over to the local "Stealership" and pay the $99 Fee for what is called a CASE Relearn since you changed out the Knock Sensors. There are only a handful of reasons to do this.... but your PCM may be inadvertently causing these slight vibrations as a result of the need to reset the PCM and have the GM dealership update any software instructions at the same time. This should done after investigating what follows first.

And as it regards the 250,000 Miles on the Alternator... Please watch this entire video from one of our leading GMT360 Guides and Mentors... @MAY03LT to learn how he diagnosed the problem with his ever-abundant common sense and solid approach to Mechanical Problem Solving - 101... a book that in time, you will no doubt come to appreciate that he has shared substantially as an Author of its contents:

 

[jmonica]

Message received. I edited the post to allow readers to take a moment to digest my long winded message between thoughts.

Having watched the Alternator diagnosis noise video, I am going outside to remove the drive belt and see if that's the cause of the vibration. I hope it is.

Thanks again for all of your help!

 

[Mooseman]

There is no doubt that you will need to run this vehicle over to the local "Stealership" and pay the $99 Fee for what is called a CASE Relearn since you changed out the Knock Sensors. There are only a handful of reasons to do this....

Just saw this and I want to clarify that there are very specific reasons for a CASE relearn:
- You replaced the PCM
- You replaced or disturbed the crank sensor
- You replaced something in the timing chain system (chain, tensioner,sprocket, VVT cam phaser) and/or
- You are getting a P0014 and/or P0345 because of any of the above.

Knock sensors have nothing to do with this. Even replacing the CPAS doesn't require it.

 

[mrrsm]

As ever @Mooseman... You are Absolutely Right...

But in this OPs present circumstances... The actual reason to get a CASE Relearn is to prove that it is even possible to do it... in the first place. My reasoning is that should his New Knock Sensors misbehave or turn out to be of the Wrong Flavour for any reasons... getting the PCM to accept a CASE relearn may not even be possible (In spite of the fact that this link involves a V8 Engine... in principle.. .the sketchy behaviour of ANY suspect Knock Sensors would have the same effect because the two events involve the swapping in and out of different engines with different years of manufacture):

http://gmtnation.com/forums/threads/knock-sensor-question.11364/#post-282672