Please help me diagnose a vibration in my Dart.

-
3

340_833 dart

Well-Known Member
Joined
Mar 24, 2009
Messages
657
Reaction score
1
Location
NW Arkansas
'73 Dart Sport 340.

I reinstalled the engine and transmission about a month ago and now there is some kind of vibration. Prior to the removal, the car rode really smooth.
The vibration is felt in the steering wheel and is really obvious below 35 mph. It is not steady, it pulsates. I don’t feel it in the seat of my pants.
If I stand on the gas in first gear and run it to 40 mph, then let off the gas, the steering wheel really vibrates.
I didn’t do anything with the wheels and tires; they stayed on the car. I rebuilt the entire front end two years and had the front end aligned. The tires look to be wearing evenly.
Am I looking at a tire balance issue or could it be something related to the drive train?

Thanks.
 
drivetrain issue
what was changed during the "reinstall", same everything?... different piston,different convertor, different driveshaft?
 
The engine was untouched. The only thing changed was the converter. As with the first one, the converter is for a neutral balanced engine.
I put a new front U-joint on the driveshaft as well. The caps that go into the transmission yoke just slipped right in. They didn't need to be pressed. They just slid right in.
 
Pretty sure those caps aren't supposed to "slide right in".
Thats the first place I'd be looking.
 
Yes caps for U-joint don,t usually..just slip in..they usually take some tapping to get in.I like to mark my driveshaft/yoke with a yellow marker,so that it goes back in the way it came out.Maybe pull it back out and spin 180*then reinstall.Good luck.
 
340_833 dart said:
'73 Dart Sport 340.

I reinstalled the engine and transmission about a month ago and now there is some kind of vibration. Prior to the removal, the car rode really smooth.
The vibration is felt in the steering wheel and is really obvious below 35 mph. It is not steady, it pulsates. I don’t feel it in the seat of my pants.
If I stand on the gas in first gear and run it to 40 mph, then let off the gas, the steering wheel really vibrates.
I didn’t do anything with the wheels and tires; they stayed on the car. I rebuilt the entire front end two years and had the front end aligned. The tires look to be wearing evenly.
Am I looking at a tire balance issue or could it be something related to the drive train?

Thanks.
Click to expand...


if you don't feel it in the seat of your pants, it's in the front end, and the caps on your u joints shouldn't fall in, as stated they would need to be taped in or ran in with a c clamp, the way I do them, check for a broken belt in the front tires, missing wheel weight, that sort of thing, also check the tie rod ends.
 
neutral balanced converter.....you have a weighted flexplate?

73 340 should be a cast crank and will be externally balanced....

but anything is possible since the thing is almost 40 yrs old...
 
Correct, the caps should not be loose enough to not need some type of press.
Also, the front joint can be out of phase. Chances are you installed it backwards, and if you checked the runout of the shaft you would see a difference depending on which way it was installed.
The only real fix is a new yoke and rebalance. If its a 904 with a 7260 yoke they are still avail new. Heck, I may even have on in own inventory..
 
That's a low speed for a tire/wheel vibration. You need to find somebody with a reed tachometer. A lot of high end dealerships will have one in the servier department. If you know someone there, they might let you borrow it while they ride with you. They are NOT cheap and I'm sure they wouldn't just chunk it at you and say "sure you can use it." It will tell you very quickly at what frequency your vibration is occuring. Low frequency vibrations point towards tire/wheel/axle and high frequency to a driveline vibration. Does it pulsate and drone and sound like a heard of pissed off bumble bees? That would be driveline. If it shakes the flooboard and seats and your butt, that would be tire/wheel/axle.
 
Sounds like a bubble in one of the front tires.
 
StrokerScamp said:
That's a low speed for a tire/wheel vibration. You need to find somebody with a reed tachometer. A lot of high end dealerships will have one in the servier department. If you know someone there, they might let you borrow it while they ride with you. They are NOT cheap and I'm sure they wouldn't just chunk it at you and say "sure you can use it." It will tell you very quickly at what frequency your vibration is occuring. Low frequency vibrations point towards tire/wheel/axle and high frequency to a driveline vibration. Does it pulsate and drone and sound like a heard of pissed off bumble bees? That would be driveline. If it shakes the flooboard and seats and your butt, that would be tire/wheel/axle.
Click to expand...

It pulsates and drones. I feel zero vibration in the seat or steering wheel.
I've got a 727 with 7260 u-joints.
I've got a new driveshaft yoke ordered and it should be here Monday. Plus, I've ordered new, solid, u-joints and will have a local driveshaft shop put everything together and balance the shaft. I'm keeping my fingers crossed.
 
You can diagnose in the meantime. Here's how. Get several BIG steel hose clamps. Big enough to go around the driveshaft. Maybe five or six of them bad boys. Clamp them all on the driveshaft. Doesn't matter where as long as they are all together. Clamp them all in a row stacked against each other so the screws all line up together. Run it down the road and see what you got. If it's worse, bring it back, loosen the clamps and turn them 1/4 away from their position on the driveshaft. Keep repeating this until the vibration goes away. You may need to go 1/8 at the time to fine tune it. This will confirm it is in the drivetrain. It is also an ultra cheap diagnosis.
 
Well, I had new solid U-joints and a new transmission yoke installed, and had the driveshaft balanced.
I think the vibration is gone. I still felt a little in the steering wheel but it didn't pulsate and drone like before.
I let my 21 year old son drive it while I sat in the passenger seat. It was really smooth in that seat. Then I drove it and noticed that little bit of vibration in the steering wheel.
Having the front wheels and tires balanced is next.
 
You must log in or register to reply here.
-

Back
Top