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  #1  
Old 12-05-2001, 03:17 PM
Moparjimbo Moparjimbo is offline
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Default Driveline vibration - need advice!

Hey guys what do you think of this. I have recently developed a rhymic repetative humming at freeway or greater speeds, like whmmmm-whhmmmm-whmmmm-whmmmm. Mostly prevalent when cruising at constant speed/partial throttle. If I give it a little more gas, the frequency picks up - whmm-whmm-whmm-whmm-whmm-whmm, if I let off, it all but goes away. Also, at full throttle it is hardly noticable seems much smoother. It does also get worse at certain/faster speeds. It sounds and even feels like its coming from right under the shifter consoloe/right in the tunnel!! Its slowly getting worse.

I have a mildly built 440, single piece stock driveshaft, 3.91 8.75 rear, MT ET streets 28 inches. It never used to do this when I first put it all together, and I have run a different set of tires and tried a different driveshaft, no difference.

Could it be rear end, trans mount, trans output shaft bearing?

Any suggestions would be appreciated.

My next solution is to hammer on it till whatever it is finally breaks and falls off!!!
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  #2  
Old 12-05-2001, 05:45 PM
Dr. Righteous Dr. Righteous is offline
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Default many things

#1 thing to check are the no brainers.
U-Joints, change 'em if you have not yet. Check all four corners of your wheel bearings. They can make a very similar vibration that will seem like it is driveline. Then of course rear end bearings. I had that same problem and did all the above and didn't fix the problem. Finally I had a CUSTOM (thick wall tube) drive shaft made with heavy duty U-Joints and all vibrations went away. I had the original drive shaft 'balanced' before. But it didn't solve the problem.
One more thing, but it usually effects 904 trannys in B bodies.
The output bushing in the tranny can wear out and cause the same vibration. Worth checking !
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  #3  
Old 12-05-2001, 07:27 PM
cudacarl cudacarl is offline
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My cousin had a similar problem on his '73 challenger. Unfortunately he noticed it after he bought it. Its an original340 car that now has a truck 440 and 727 tranny. What happened was they used the wrong torque converter i forget if he needed a balanced one or had a balanced one. He managed to buy one from summit racing were it would work on an internally or externally balanced engine. That solved the problem unfortunately after he tore up a couple of trannys and shot a drive shaft out of the car. It made that same sound your describing. If its not that, Have you done anything that would change the pinion angle of the drive shaft? It can cause the same sound and vibration.
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  #4  
Old 12-06-2001, 09:55 AM
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5th_Ave_Sleeper 5th_Ave_Sleeper is offline
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My buddy and I put a 7 1/4" from my 5th ave in his 85 ford ranger truck. We messed up when welding on the new spring perches. made the pinion stick straight forward. It made for one helluva vibration, just like you described. So he went to the local speed shop and bought a pair of 4 degree axle shims. Presto vibration gone.
There is actually quite a bit of science/engeneering that goes into drive line angles.
Its worth checking on.
Hope this helps.
5th
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  #5  
Old 12-06-2001, 11:46 AM
Blaine Peterson Blaine Peterson is offline
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Is your trans a stick or auto?
And do you get this noise/vibration when at a stop, in neutral, as you bring the engine RPM up to around 3500 to 4000 RPM?
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  #6  
Old 12-06-2001, 12:01 PM
Blaine Peterson Blaine Peterson is offline
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Is your trans a stick or auto?
And do you get this noise/vibration when at a stop, in neutral, as you bring the engine RPM up to around 3500 to 4000 RPM?
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  #7  
Old 12-06-2001, 02:17 PM
Moparjimbo Moparjimbo is offline
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Quote:
Originally posted by Blaine Peterson
Is your trans a stick or auto?
And do you get this noise/vibration when at a stop, in neutral, as you bring the engine RPM up to around 3500 to 4000 RPM?
No - doesn't vibrate at all at a stop, or at least its not noticable. Only when I get up to around 40-50 miles an hour, and like I said its really noticable when holding a consistant speed - at part throttle cruising. If I floor it, it seems to acccellerate smoothly or at least much more smoothly. If I let off gas completely and decell it smooths out a bit as well.

As far as the angle goes, I will check, but it didn/t do this for several years after I put the car together and nothing has changed back there. Its like something wore out and is getting worse. Started to do it a little, now its worse. It also coems and goes a bit, sometimes its hardly noticable, other times I feel like pulling over because I'm afraid its gonna shake apart!
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  #8  
Old 12-06-2001, 03:39 PM
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tuffbird tuffbird is offline
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Well, if it sounds anything like mine did, it'll be either the rearend bearings on the axles (I swapped them for the green axle bearings) or the slip yoke on the front of the driveshaft. I replaced both at the same time and the cool (my-car-is-vibrating-apart-but-damn-it-sounds-neat) sound went away.

The reason I suspect it's the axle bearings is because the slip yoke was only a little worn and caused a leak in the rear tranny seal....the axle bearings were actually so loose they made a cut in the metal of the housing.

Good luck
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  #9  
Old 12-06-2001, 04:28 PM
Dr. Righteous Dr. Righteous is offline
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Default OH! One more thing!

Here is one that is hard to nail down. One guy posted some time back about this kind of problem. After replacing everything and not fixing it, it turned out that his rear springs were worn out and that was throwing off the pinion angle. He replaced the leafs and the problem went away.
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  #10  
Old 12-06-2001, 06:54 PM
Jack Z Jack Z is offline
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Moparjimbo:

In order to try to narrow the location of the vibration down a bit, you should try to figure out its frequency. What I mean by that is, is it at the rotational frequency of the tires, brakes, wheel bearings, etc. (probably about 10 cycles per second at 60 mph)? Or is it at the rotational frequency of the drive shaft, u-joints, etc. (in your case with a 3.91 ratio, this would be probably about 40 cycles per second at 60 mph)? If you listen for a few seconds, you should be able to tell which one it is. And once you figure that out, it will point you in the area that you should be looking at.
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  #11  
Old 12-06-2001, 07:46 PM
Moparjimbo Moparjimbo is offline
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Its pretty slow - I wanna say like only 1-3 few cycles per second when cruising - like hummmmmmm - hummmmmmmm- hummmmmmm. If I give it a little gas it speeds up to a hummm-hummm-hummm-hummm-hummm like maybe twice as fast.
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  #12  
Old 12-06-2001, 09:53 PM
vanishPt vanishPt is offline
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That same thing happened to my Challenger. Changed the pinion angle 2 degrees and it went away.
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  #13  
Old 12-07-2001, 01:50 AM
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pishta pishta is offline
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So what is the concensus on the proper pinion angle? Mine is doing the same thing...I think.
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  #14  
Old 12-07-2001, 02:27 AM
BB 70 Challenger BB 70 Challenger is offline
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Hello

I´m with cudacarl and Blaine Peterson:

When cruising check the rpm where that hmmmmm...hmmmmm..hmmmmm... sound comes at worst, and then stop the vehicle and repeat that rpm when standing still = gear at P or N and get the rpms up again. So if the vibrating is there, again, then it can NOT be a driveline or rear end or such because they are NOT moving at all right now.

And vice versa: when cruising a slight downhill at that hmmmmm... hmmmmm...hmmmm... speed put the trans at N so that the rpms drop down. But the speed keeps the same! So IF the hmmmm...hmmmm....hmmmm sound went away it is likely to come from the engine BUT if the vibrating sound is still there even though the rpms are down it´s likely not engine related but speed related = driveline / rear axle...

Anyway, that´s the way I hunted my 2 vibrating engines down. The other had a wrongly balanced rotating assembly and the other had an externally balanced torque converter in an internally balanced engine.


Just my 2 cents, - BB 70 Challenge
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  #15  
Old 12-07-2001, 01:56 PM
Moparjimbo Moparjimbo is offline
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Thanks guys I'll start checking!

How do I check the pinion angle and what should it be?

What are the green axle bearings? I've been meaning to get in and look at these for awhile now, maybe I'll just get the green ones.
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  #16  
Old 12-07-2001, 01:58 PM
Moparjimbo Moparjimbo is offline
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Also, I do have a LOUSY torque converter that has a high stall speed around 3000-3500 but it is slipping like 10 mph at the top end through the traps according to eery calculator I have used. Could it be my torque converter is wiped out or has some fins broke off or whatever that through it out of ballance? Or would a TC failure be a total failure that I would know about?
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  #17  
Old 12-09-2001, 01:06 PM
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I found a pretty easy way to determine the pinion angle. Use a plastic protractor and a weighted line hanging from the center hole. Put a level across your valve cover and jack up the rear axle under the spring pads until the level is bubble up. Now put the protractors flat side in your U-joint saddles of your pinion gear. The weighted line (plumb bob) will show your angle. I am 6 off! I will be getting axle shims from the local 4X4 shop today to correct this. This method will only show negative angles, but can be adapted by using a T-square in the saddle and using the compass on the bottom (measures both + and - angles but more equipment) My vibration was at highway speeds and the faster the driveshaft spins, the amount of delta you can have in the 2 axis has to decrease, 0 being optimal at speed. If you drag, give yourself a little negative (5-7) to start with, because most of your drive will be at "spring wrap" angles (pinion climbing) Snubber settings can limit this. I hope this fixes my vibration, it cant hurt it!
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Old 12-11-2001, 06:52 PM
icycleboy icycleboy is offline
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I'm having the same problem on a car that didn't vibrate like this. I parked my fresh-drivetrain 440 bbody for six months and have been dealing with this annoying vibration since I started driving it again. This is not the rhythmic whirring (with which I'm also familiar and I think its your pumpkin) but more like the rapid vibration of a washing machine in the spin cycle. It gets pronounced at about 60-75 mph and then goes away as the car goes faster.

Balancing the rear wheels had no effect. I'm onto checking for the U-joints and pinion angle. Anybody know a professional pinion-angle adjuster in SoCal? In fact, I could also stand someone to take a look at my front alignment as well. The car sits on new torsion bars and i have a feeling they've sagged somewhat since new. Anybody familiar with any of these syptoms?
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  #19  
Old 12-12-2001, 10:12 AM
Dr. Righteous Dr. Righteous is offline
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Thumbs up Check your tires CLOSE!~

Sounds like your tires developed flat spots while sitting.
Don't trust a tire store when they say that your tires are OK and they balanced out.

Guys be sure when you go to the tire shop to INSIST that you be able to watch them balance the tire.
Tire shops will put a SQUARE tire on your car even after they balance it.
I was trying to track down a vibration problem that suddenly got WORSE after I got for new BF GoodRich T/As on put on my car. It seemed suddenly the vibration moved from the speed it was occuring and got somewhat worse. I checked and changed parts but was not able to solve the problem. Finally I went back to the tire shop to have the tires balanced again and this time I WATCHED them do it. The tires had less than 2K miles on them and one of them was completely out of round! They put a new square tire and put it on my car the last time I had it in. I went to the manager and raised a stink and they put a new tire on. Believe me, I watched them balance it!

You can balance a square tire; but you can't make it ride good.
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  #20  
Old 12-29-2001, 01:45 PM
icycleboy icycleboy is offline
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Default progress!

I had my car re-aligned, and in the process the front of my car was raised a little over half an inch. Before this I had it as low as possible for the big hot rod look, and as I was talking about in an earlier post, I felt there had been some sagging with the new torsion bars. Raising the front improved the vibration dramatically, and I theorize that it may have affected the pinion angle at the rear. If you visualize the car as a big wedge with the rear wheels/u-joint as an axis, raising the front (the engine) should open the angle of the rear u-joint by a little bit.
Now there's probably some more vibration in there. I am being told by my tire/wheel pro I have a bent rim which was improperly balanced with inside weights when it needed an outside weight. This man pointed at the uneven weight some wheel locks create, so I still have a way to go to get it to optimal specs.
Bottom line: Look at front suspension height in relation to pinion angle and rear vibration.

Good luck
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