Pulsating vibration while cruising??

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Hansen

Hansen

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Hello guys, i'm looking for tips on where my vibration could come from.. it usually comes when driving over 40 mph, often while giving gas. seems to go away when letting go of the throttle, really hard to know (pulsating kinda speeds up when letting go). I have a 69 dodge dart with an 8 3/4 3:23 rear axle, new balanced wheels and strange drivetrain, new mounted yoke from strange. Does not vibrate when in park or at slow speeds. i have a 70s 360 with xe274H cam, new motor mounts from schumacher, used trans mount but looks good. exhaust is 14 inch magnaflows with dougs headers. As already said its a vibration that comes in pulses, a few seconds long. vibration intensifies when accelerating over 1800-2000 rpm

I have concluded with two things: the yoke is not properly mounted or the converter is missing a weight as i figured out externally balanced engines needs this.

Let me know if i'm looking in the right direction.


thanks
 
If it's the converter, it will have the vibration in park or neutral at a standstill. If not, it's in the drive line somewhere.
 
RustyRatRod said:
If it's the converter, it will have the vibration in park or neutral at a standstill. If not, it's in the drive line somewhere.
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Yes, actually realized it right after posting.. drum brakes also looks good so i might need to pull the axle.
 
Make sure the u-joints are square in the pockets.
 
Sounds like driveshaft. Recently restored my driveshaft with new u-joints and slip yoke. Had it balanced. Was told good thing I did because the chinese slip yoke was poorly made and required extra weight to balance.
 
Murray said:
Sounds like driveshaft. Recently restored my driveshaft with new u-joints and slip yoke. Had it balanced. Was told good thing I did because the chinese slip yoke was poorly made and required extra weight to balance.
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can't believe Strange could have screwed up, bought many driveshafts before no problem.. seems like i'm on the right direction tho.
 
I had a similar problem, over 2000 rpm car felt like it would shake apart or if pulling a grade hard it would do some funky shaking. Found out previous owner rebuilt Torque Converter and didn't have the external wight placed correctly. New Torque converter and built new drivline as the old one was crap. After that Smooooth ride. In park didn't notice it shake, but then again I didn't rev the heck out of it either.
 
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Sounds like a bad axle bearing to me, or bad bearing in diff ?
 
Dont overlook possible timing surge or lean condition under load .

What is your intial timing / total timing at cruise speed / total vacuum advance ?

Are you using an AFR gauge or have you pulled plugs after running a stretch of hiway ?
 
I would also check the headers and exaust and look for rubbing or contact on something under load, what kind of motor mounts are you using?
 
Update: Pulled the diff, changed the pinion bearings and put it back, still vibration.

some answers to ur questions: I have schumacher motor mounts, plugs looks pretty good. As the axle bearings where changed before i bought it (1 year ago) and can't hear anything i reckon this is good.
U joint is good in the pockets.

I know that my converter is missing the external balance weight, but didn't think it would matter this much. Anyone know where i can get these weights and where to mount them on the converter?
Also thinking front tires are bad and unbalanced as they are stock with the car so will be changing these also.
 
Scamp Fasty said:
I had a similar problem, over 2000 rpm car felt like it would shake apart or if pulling a grade hard it would do some funky shaking. Found out previous owner rebuilt Torque Converter and didn't have the external wight placed correctly. New Torque converter and built new drivline as the old one was crap. After that Smooooth ride. In park didn't notice it shake, but then again I didn't rev the heck out of it either.
Click to expand...

I know that my converter is missing the external balance weight, but didn't think it would matter this much. Do you know where i can get these weights and where to mount them on the converter?
 
Hansen said:
I know that my converter is missing the external balance weight, but didn't think it would matter this much. Do you know where i can get these weights and where to mount them on the converter?
Click to expand...

If you call up an old tranny shop they might set you up. I got a new TC with weights already on after I rebuilt my 360. Previous owner used TC off the 318 when he swapped in the first 360
 
Hansen said:
I know that my converter is missing the external balance weight, but didn't think it would matter this much. Do you know where i can get these weights and where to mount them on the converter?
Click to expand...
Should be interesting to see if you can attach a weight to the TC with it installed in the car?
Have you checked the drive line angles?
If the angle(s) are off it can cause u joints to vibrate and fail.
 
Couple simple things to try that can really help. One, remove the shaft from the pinion and turn the differential 180* and reinstall. Two. Try to make sure the bearing cap retainers are in the back so they help center the joint. I also attempted to get both retainers in about the same position. Three, tighten all 4 bolts to spec. Finally, consider the reintroduction of the tail shaft counter balance weight.
 
like_A_pike said:
Couple simple things to try that can really help. One, remove the shaft from the pinion and turn the differential 180* and reinstall. Two. Try to make sure the bearing cap retainers are in the back so they help center the joint. I also attempted to get both retainers in about the same position. Three, tighten all 4 bolts to spec. Finally, consider the reintroduction of the tail shaft counter balance weight.
Click to expand...

will try this, have been lookint into pinion angle that might have been the problem
 
I started with pinion angle and learned I had a 2* difference and thought the shim would do the trick. The car feels stronger but my vibration was still with me. So I swapped out both universals and had the shaft balanced. It was worse after that but the shop didn’t have replacement bolts and had trouble tightening the old rounded ones. I got new bolts, and a really good 3/8 wrench and tightened it up. Got really close, so flipped the shaft 180* and tightened to spec (not sure how I’d translate to metric!?) and it feels pretty good. I’d say 90% there.
BTW I was certain mine was coming from the back....have you ruled out your torque converter?
 
like_A_pike said:
I started with pinion angle and learned I had a 2* difference and thought the shim would do the trick. The car feels stronger but my vibration was still with me. So I swapped out both universals and had the shaft balanced. It was worse after that but the shop didn’t have replacement bolts and had trouble tightening the old rounded ones. I got new bolts, and a really good 3/8 wrench and tightened it up. Got really close, so flipped the shaft 180* and tightened to spec (not sure how I’d translate to metric!?) and it feels pretty good. I’d say 90% there.
BTW I was certain mine was coming from the back....have you ruled out your torque converter?
Click to expand...

i have not ruled out the converter, i shimmed it an inch up on the trans mount and its getting better, still feel the vibration coming and going in different speeds and rpms..
 
Put jack stands under the rear axle and run the car. If it stops the problem is in the front end somewhere if not and it vibrates in park like Rusty said its up front somewhere. If it’s ok in park run it up to 2000 rpm then slip it into neutral and see if it goes away. If not take off the rear wheels and try again. Next remove the drums and try again. (Be conscious about avoiding the brake pedal) I just turned the ignition off and it stopped turning. See if you get any differences without those items. While it’s up in the air make double sure there is lube oil in the differential. Ya never know....
 
I had a similar problem with my Dart (although with a 7 1/4 rear end). The pulsing got worse at higher speeds. It turned out to be a bad bearing at the rear axle. I will admit that I also had a bad u-joint in the drive shaft that seemed similar. I could feel that vibration in the hump down the middle. I checked that by throwing the car in neutral and coasting while driving. The drive shaft vibration would go away in neutral. Those are the two places I would start.
 
Solved!! it was the weight's on my converter that was missing. welded on 60 grams of iron and it was gone. i could also buy a flexplate to make this go away.
 
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