Some weird vibrating that needs to be fixed!

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Thrasher

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Just took the car around the block for the first time all summer... I noticed a vibrating above 35 mph that may or may not be the driveshaft (this is my first guess) My question is, are driveshafts weighted for particular cars? I noticed a block that look like a weight near the universal. Just wondering if they typically need to be re-weighted or anything when you swap them out.

:-x
 
Drive shafts are balanced independently.
Look at the tires, then wheels/lugs.
Good luck
 
I ve never had problems with em long as they weren't cut are bent, They just balance the shaft on a machine not hooked to tranny are rear, so should be fine mabey a ujoint ARE tire ?
 
I actually had a bent rim in the back which I replaced, but it didn't make a difference. The u-joint is brand-new as well. The damn rear end was laying around in the garage for years and was the only thing I didn't rebuild :tard: I just swapped the whole drum assembly from the old rear since it was in better condition. If I was the lucky type, maybe a brake is dragging somehow or something in the brake assembly isn't quite right, but I'm not that lucky, and it wouldn't explain the fact that it only does it over 35 mph.
 
Hey Thrasher, even though the u joints are new doesn't mean that one of them isn't freezing up especially after disuse. I'd check to make sure they're nice and free and make sure the u joint nuts that clamp the u joint to the rear end yoke are tight.
Where specifically do you feel the vibration, in your hands, ***, feet or just everywhere.

Terry
 
Jack it up on stands and put it in gear and look at the rear wheels. Wobble ? Bent axle flange?
 
was the bent rim from that rearend? if so it sounds like what mguner says and that axle may be bent.
 
OK.... I thought the vibrating could have been a wheel bearing in the front. The bearings and seals looked good. Took em both off, cleaned em with solvent and packed them. No change.

However while going down the road (somehow) I did realize that the vibration ONLY happens in 3rd gear. I can drive around all day in manual 2nd and there is no vibration. I can be at any speed or rpm in third gear, and as soon as I let off the gas, vibration. There is no vibration when the car is accelerating.

When I had the tranny at the shop a few weeks ago for a valve body troubleshoot, I had the guy put in a 5.0 to 1 kickdown lever in since it was already apart and I had one laying around. He said that if the transmission shifted prematurely from first to second and I get overlap/vibration, I should back the front band adjuster off a quarter turn and send it down the road and go from there. The shift from first to second is really very good, but obviously something is wrong with third gear.

I was going to adjust the front band today, but I'm afraid of adversely affecting my shift from 1st to 2nd. Not to mention that I'm no 727 expert, and I don't even know for sure that loosening/tightening the front band would even affect 3rd gear. Any transmission gurus out there, or has anyone here ever experienced anything similar?


:help:
 
Go down the road, throw it into neutral, then shut off the engine, just to make sure it isn't a flex plate, dampner, engine,etc vibration. I had a bad dampner once that drove me crazy. I also would check your driveshaft angles. Vibrations can drive a person mad.
 
MtNemoMopar said:
Go down the road, throw it into neutral, then shut off the engine, just to make sure it isn't a flex plate, dampner, engine,etc vibration. I had a bad dampner once that drove me crazy. I also would check your driveshaft angles. Vibrations can drive a person mad.
Click to expand...

As long as you don't have to use your power brakes.lol
 
MtNemoMopar said:
Go down the road, throw it into neutral, then shut off the engine, just to make sure it isn't a flex plate, dampner, engine,etc vibration. I had a bad dampner once that drove me crazy. I also would check your driveshaft angles. Vibrations can drive a person mad.
Click to expand...
I did this and it still vibrated! So this left my problem to the driveshaft or rearend. Good suggestion :thumblef:


OK! I parked the car in neutral and took a look at the drive shaft. Lo and behold the damn yoke was loose in the extension housing. Not to mention the fact that 2/3 of the yoke was outside the extension housing. So... I took the old driveshaft from the 318/904/7 1/4 setup (which was 12 inches too long) and swapped the yoke so I could take a good measurement. Looks like it's 6" too long. So the next day I brought it right in to work, cut the yoke off on the band saw right at the old weld and cut 6" off of the drive shaft nice and square. Welded it back on with the tig machine. I two-passed it, I keyholed the whole root with a 3/32 gap and walked the cup on the cap.

The vibration I felt on the car before is totally gone, but the drive shaft could use a balancing (it vibrates just a tiny bit due to an unbalanced driveshaft, at least a vibration I am familiar with LOL). Problem solved :cheers: Beside a leaky tranny line (which I replaced with stainless 3/8 tubing and compression fittings, ALSO courtesy of my place of employment LOL) and a leaky intake gasket, the swinger is running like a very angry, re-awakened 35 year old beast :)
 
I was going to suggest a bad pinion bearing but it sounds like you`ve found it. I`m experiencing something similar and I`m searching for probable causes.
 
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