Drivetrain vibration

-
David Dickerson

David Dickerson

Stickler
Joined
Feb 26, 2018
Messages
119
Reaction score
75
Location
New York
I have a vibration problem to solve. This issue goes way back to the 80's when I last had the car on the road. From what I can recall, the vibration was more of a problem when I had 410 gears in the rear because of the higher rpm at driving speeds. I tried putting a vibration dampener on the tailshaft of the transmission which didn't seem to do much. I went back to 323 gears which made the situation more tolerable. The motor is a 340 T/A which was balanced when I had it built. I recently did a complete restoration of the car and had the motor again rebuilt. I added a Summit dampener, Gear Vendors Overdrive, new balanced driveshaft, and 410 gears again. The only thing that went back in original was the torque converter, which is a TCI. I still have a vibration that I think is even worse than before. Could this be the torque converter? It seems to be the worst at a certain rpm range and under moderate acceleration, like going up a hill where you can maintain rpm. It will diminish if I shift into overdrive. I know my pinion angles are good. What is the best method to troubleshoot this? I wanted to isolate the engine from the transmission, but it's not possible to unhook the torque converter and start the motor like a chevy. Thinking of pulling the tranni and having the converter tested, but want to get some thoughts from people with experience first.
 
David Dickerson said:
I have a vibration problem to solve. This issue goes way back to the 80's when I last had the car on the road. From what I can recall, the vibration was more of a problem when I had 410 gears in the rear because of the higher rpm at driving speeds. I tried putting a vibration dampener on the tailshaft of the transmission which didn't seem to do much. I went back to 323 gears which made the situation more tolerable. The motor is a 340 T/A which was balanced when I had it built. I recently did a complete restoration of the car and had the motor again rebuilt. I added a Summit dampener, Gear Vendors Overdrive, new balanced driveshaft, and 410 gears again. The only thing that went back in original was the torque converter, which is a TCI. I still have a vibration that I think is even worse than before. Could this be the torque converter? It seems to be the worst at a certain rpm range and under moderate acceleration, like going up a hill where you can maintain rpm. It will diminish if I shift into overdrive. I know my pinion angles are good. What is the best method to troubleshoot this? I wanted to isolate the engine from the transmission, but it's not possible to unhook the torque converter and start the motor like a chevy. Thinking of pulling the tranni and having the converter tested, but want to get some thoughts from people with experience first.
Click to expand...
It's a total mystery to me how they can even balance a torque converter. I can't remember why(maybe I wanted to polish the neck), but I chucked up a converter in a lathe, many many years ago, and the innards were just clunking around in there. I tried putting an input shaft in it, but that wasn't enough.
 
Just a thought, Working on vibes and acoustics on aircraft interiors has taught me the vibration source can migrate to any solid or semi-solid mounted structure and be difficult to diagnose. If you have any torque straps on the engine, or trans, try removing them for test. any solidly mounted objects like exhaust, linkages, engine mounts and trans mounts can translate vibes pretty easily.
 
David Dickerson said:
I have a vibration problem to solve. This issue goes way back to the 80's when I last had the car on the road. From what I can recall, the vibration was more of a problem when I had 410 gears in the rear because of the higher rpm at driving speeds. I tried putting a vibration dampener on the tailshaft of the transmission which didn't seem to do much. I went back to 323 gears which made the situation more tolerable. The motor is a 340 T/A which was balanced when I had it built. I recently did a complete restoration of the car and had the motor again rebuilt. I added a Summit dampener, Gear Vendors Overdrive, new balanced driveshaft, and 410 gears again. The only thing that went back in original was the torque converter, which is a TCI. I still have a vibration that I think is even worse than before. Could this be the torque converter? It seems to be the worst at a certain rpm range and under moderate acceleration, like going up a hill where you can maintain rpm. It will diminish if I shift into overdrive. I know my pinion angles are good. What is the best method to troubleshoot this? I wanted to isolate the engine from the transmission, but it's not possible to unhook the torque converter and start the motor like a chevy. Thinking of pulling the tranni and having the converter tested, but want to get some thoughts from people with experience first.
Click to expand...

It's been a long time ago in the 70s...I had a similar problem...Ironically, starting at 55mph, which at the time had just been signed into law. (Nation-wide speed limit) 1965 Barracuda 273 Commando, 4 speed. (with some added bells and whistles, pristine, less than 40,000) I did everything you could think of to rid the problem. Clutch, pressure-plate, flywheel, joints, etc. One day in a moment of total frustration, I traded my car for a brand new 1975 Chevy step-side, 6 cyl. 3 on the column. (One of my more stupidest, life decisions) Afterwards I was asked by a friend, "what about the drive shaft?" "What about it? I put all new joints on it!" "Did you check to see if it was bent?"
I'm not saying that is what you are dealing with, but to this day, I believe that was what was wrong with my car. It made sense, as (shortly) prior to the vibration showing up, I tore out the rear universal, challenging a local Camaro.
Wish I could go back in time and do it all over again.
Norm​
 
The GVOD manual has 3 pages of good vibration troubleshooting. Just because parts are new doesn't mean they are good. I had my driveshaft shortened for the GV install and the u joint phasing was 3.5* off when they welded it together. I chased a vib problem for a long time. I came across a you tube video on u joint phasing and checked my driveshaft, BINGO. Make sure you have the 5/8" clearance on the trans yoke, car setting at ride height.
 
Just a thought, get a digital angle finder and check your pinion angle setup. That was the problem with my GV equipped Barracuda.
 
One thing that comes to mind is the torque converter.
If the engine was internally balanced, the torque converter should be too.
You may have gotten a converter that was meant for an externally balanced engine, but sold to you as an internally balanced one. (misboxed etc.)
The externally balanced one should have some big weights that look like 1/4'' x 1'' flat bar about an inch or so long welded to the side of it, (pretty easy to spot with the inspection cover off).
A neutrally balanced one should have no weights on it or very small ones.
It's pretty easy to knock them off with a good hammer and chisel.
Do you have a stock flex plate on it?
An aftermarket one might have weights on it or either of them could be bent.
I would contact your converter manufacturer to verify this information.............
 
grjammer said:
Just a thought, Working on vibes and acoustics on aircraft interiors has taught me the vibration source can migrate to any solid or semi-solid mounted structure and be difficult to diagnose. If you have any torque straps on the engine, or trans, try removing them for test. any solidly mounted objects like exhaust, linkages, engine mounts and trans mounts can translate vibes pretty easily.
Click to expand...
I don't have a torque strap anymore. I did have one back in the 80's and took it off because of the vibration. I did go to urethane mounts on the engine and transmission, so that is probably going to do about the same thing.
 
Dartnut said:
One thing that comes to mind is the torque converter.
If the engine was internally balanced, the torque converter should be too.
You may have gotten a converter that was meant for an externally balanced engine, but sold to you as an internally balanced one. (misboxed etc.)
The externally balanced one should have some big weights that look like 1/4'' x 1'' flat bar about an inch or so long welded to the side of it, (pretty easy to spot with the inspection cover off).
A neutrally balanced one should have no weights on it or very small ones.
It's pretty easy to knock them off with a good hammer and chisel.
Do you have a stock flex plate on it?
An aftermarket one might have weights on it or either of them could be bent.
I would contact your converter manufacturer to verify this information.............
Click to expand...
Like your thoughts here, especially since the converter was in the car back when I first built it. I believe there is a weight on the outside of the housing. I will have to check more closely. I called TCI and they did mention the external/internal balancing, so you mentioning this makes me even more curious. I think the flex plate is original, and when bolting it up, each ear seemed even with the tabs on the converter. I will also check my pinion angles again and see if there is any runout on the driveshaft. I have a lift, so I can jack up the rear tires and run it through some gears.
 
You need to figure out if its engine speed related, driveshaft speed related or wheel speed related. An engine vibration will change with engine speed, regardless of gear. A driveline vibration will be fast in your case 4 times faster than the engine speed or more due to the 4:10 gears and the OD. Driveline vibrations also quite often change with load. Wheel speed vibrations are slower and sometimes change when loaded differently, like changing lanes fast.

Garth
 
mderoy340 said:
The GVOD manual has 3 pages of good vibration troubleshooting. Just because parts are new doesn't mean they are good. I had my driveshaft shortened for the GV install and the u joint phasing was 3.5* off when they welded it together. I chased a vib problem for a long time. I came across a you tube video on u joint phasing and checked my driveshaft, BINGO. Make sure you have the 5/8" clearance on the trans yoke, car setting at ride height.
Click to expand...
I once had a problem with a vibration in my pickup which I attributed to a slightly bent driveshaft. I had a company in Seattle called Drive lines NW make me a new driveshaft. I don't remember the final cost, probably around 3bills. When I got it home and checked it, it was just as bent as the oem one. Long story short, just because it's new, doesn't mean it's correct.
 
If you put it up on jack stands and run it up to speed and have someone watch the driveline you can sometime tell if it is in the driveshaft or u joints. I had worn u joint straps and when I ran it up to 70 it was obvious where the vibration was.
 
You must log in or register to reply here.
-

Back
Top