Mystery vvibbrraation • The Dodge Challenger Message Board

by **charliek** » 02 Feb 2009 22:18

I finally got the car altogether. Took it for its first drive. Engine pulls strong and feels great except when it gets to about 65 mph i feel a vibrations through the pedals and my but. I checked the driveshaft and I felt a little play in the rear u-joint which I tightend up. It got a little better Any ideas? I was going to have rear wheels rebalanced but it was fine before I took the car apart. Any help is greatly apprciated :s006:

.Charlie

by **Moparman1972** » 02 Feb 2009 23:05

Get all 4 wheels balanced would be my suggestion. If it does it at a certain MPH, instead of RPM, then the problem lies with tires, driveshaft, rotors and drums, etc, not the engine or transmission.

by **dave-r** » 02 Feb 2009 23:06

If it is speed related (rather than rpm) it has to be either driveshaft (or one end of) or pinion angle, or wheel balance.

If the wheels are the same as before this happened then it is not them.

If the pinion angle (or rear ride height) has changed I would suspect that.

If there is anywear in the UJs i would suspect them.

You might also try turning the driveshaft 180 degrees on the pinion in case it did not go on the same way around as before.

by **drewcrane** » 03 Feb 2009 0:14

You might also try turning the driveshaft 180 degrees on the pinion in case it did not go on the same war around as before.,yes i created my own vibration by not asssemyling the drive shaft the same way it was before, i now have them indexed with a stamp to remember :blushes:

by **charliek** » 03 Feb 2009 0:21

Thanks I will try turning the driveshaft to see if it helps

by **dave-r** » 03 Feb 2009 8:50

I have to say. On my car, turning the driveshaft has never made the slightest difference to the balance.

Maybe mine is just well balanced.

by **drewcrane** » 03 Feb 2009 12:47

Maybe mine is just well balanced.,well if you remember the reason why i joined this forum was i had , and still kinda have a drive train vib,
i have an aluminum shaft now and have had it balanced to a nats ass ,and if i install it 180 off it will vibrate,im still a little perplexed cause it still vibrates above 4000 rpms,,ive balanced the tires,rotors,had it on a frame rack and noticed the frame was slightly bent up on the right side, fixed that, still have a harmonic vibration at speed and when i shift it to neutral it stops ,but it now seems like a body shimmy,it has not been fun, this spring i will replace the rear springs,and change the 3 rd member to a different ratio and see what that does :frown:

by **Moparman1972** » 03 Feb 2009 13:02

Maybe something you dont want to hear....but my 65 mustang had a 4 speed, and it sometimes had a vibration at high RPM's, and it would go away when you pushed the clutch in. Turns out the pilot bushing was torn up pretty good. You could get the vibration to go away by pushing in and letting out the clutch until everything seated right, and then you'd have a vibration-free gear until the next shift. :s008:

by **dave-r** » 03 Feb 2009 13:15

Drew I would check your pinion angle.

Make sure it is only slightly nose down from parallel with the engine angle.

by **Jon** » 03 Feb 2009 16:08

Just rebuilt the trans on mine (including new tailshaft bushing) and picked up a new vibration at 55 MPH. It's coming from the back of the car though. I am going to try Drews idea and 180 the drive shaft. Will let you know.

by **dave-r** » 03 Feb 2009 16:44

Hey hang on! I suggested it first! :lol:

by **drewcrane** » 03 Feb 2009 18:14

Hey hang on! I suggested it first,yes dave has helped me alot with this problem ,he gets alot of kudos for all the help thanks dave

also you have jogged my memorie now, i have 3 shims as i played with alot of different angles,

however i did find 2 other transmission crossmembers from a 72 ,and a 74 e bodie, i found the mounting holes to be in different places on all 3 crossmembers, the 2 later units had the transmission down at a lower angle,so i opened the holes on my unit(the other 2 units were borrowed),and i did manage to get rid of alot of the vibration just by doing that

,i have used 3 different angle finders and its kinda hard to be accurate but i did go by the book and the angle is at about 4 degrees,right with in the 2 to 7 degrees area form that link you posted here,

maybe you can pull that up again to show what im talking about, i think you had some diagram that was really help full,again dave is the knowlegable one here,use his advice cause it helped me :thumbsup:

by **dave-r** » 03 Feb 2009 18:53

I think you mean these diagrams?

When driving you want the pinion at the same angle as the engine so they are parallel as in the first diagram. However the pinion rises slightly (how much depends on how stiff the front section of the springs are) so you should drop the pinion a couple of degrees down from this position with the car at rest.

The resulting angle between the driveshaft and the trans/pinion at each end should not exceed 3 degrees.
If it does then you need to raise the trans and lower the pinion so that they are more in line.

by **drewcrane** » 03 Feb 2009 20:53

yes thats one of them , it seems like i saw another diagram that said between 3 and 7 degrees,i thought i saw it in a mopar book but i could be mistaken,but none the less that angle needs to be ideal,in order for the drive shaft to spin smoothly under power,so if there things like old, loose motor mount it can cause the drive train to move more than it should,i hope you can fix it jon, and post here what you came up with :nod:

by **dave-r** » 03 Feb 2009 21:48

drewcrane wrote:yes thats one of them , it seems like i saw another diagram that said between 3 and 7 degrees,

That might be to the floor rather than to the driveshaft.

You have to realise that if the two UJs are at different angles, they have to rock at different speeds or frequencies. That means you will get "harmonics" at certain speeds.

So try to get the pinion angle right so that with a little rise it's Uj has the same angle in it as the one at the trans. That way they are at the same frequency and "in tune" with one another.

by **drewcrane** » 04 Feb 2009 3:00

"harmonics" at certain speeds.that is pretty much what i have gotten used to ,i drove it today and its not bad,im probably sensitive to it since i know when is vibrates some people cant feel it,but if they drive it they can feel it a little
,oh well,i have a few options left :nod:

by **Alaskan_TA** » 04 Feb 2009 4:00

There is a factory TSB on hunting down vibrations, it is 20 pages long. :shock:

You can read it at this link;

http://www.hamtramck-historical.com/197 ... ndex.shtml

Drop down to Chapter 25 & find 25-02-74D, just click on each page number 1-20 to view it.

Best of luck!

by **Jon** » 04 Feb 2009 4:30

Went to town today and really concentrated on the vibration issue. Turns out it is consistent at 2500 RPMs in any of the 4 gears including neutral.

I Looked through Barry's info an have a game plan. I suspect its the engine or trans mounts in bind, maybe bent something when tilting the motor down to remove the trans is another thought. I'll be going through all of the possibilities.

Thanks :thumbsup:

by **dave-r** » 04 Feb 2009 8:41

Jon I would suspect it is something on the engine balance. Something between the crankshaft pulley and the clutch. Or it could be just that the crank is not balanced as good as it could be.

I had one bad vibration once that was nothing more than a run of engine paint on the damper. It meant that the crank pulley was not seated perfectly and gave me a vibration.

A mate of mine accidently bent his crank pulley slightly when he removed his manual transmission. That had the same effect.

by **drewcrane** » 04 Feb 2009 12:08

holy moley alaskan ta thats some good info, now i will read and maybe get some answers ,thanks :thumbsup:

by **drewcrane** » 04 Feb 2009 12:12

i have already found something that may cause some of my vibration. according to article 15 , i have seen my power steering pump has a wobble in the pully it looks bent, i will look in to that some time this week, again thanks guys for the help it has been very informative to say the least! :thumbsup:

by **Jon** » 04 Feb 2009 14:35

dave-r wrote:Jon I would suspect it is something on the engine balance. Something between the crankshaft pulley and the clutch. Or it could be just that the crank is not balanced as good as it could be.

I had one bad vibration once that was nothing more than a run of engine paint on the damper. It meant that the crank pulley was not seated perfectly and gave me a vibration.

A mate of mine accidently bent his crank pulley slightly when he removed his manual transmission. That had the same effect.

The motor is balenced so not too concerned there. The vibration happened after the trans R&R so that is where I plan to start. Transmission went back in without a hitch but I had loosened the solid mount on the driverside and not the rubber one on the other. Maybe tore it or bent that pully you mentioned.

It's gonna start raining here tonight so plenty of garage time coming up.

by **Jon** » 04 Feb 2009 22:27

Well the passenger side is torn. I can't understand physically how it might translate to a vibration but it needs to be replaced. We shall see if it solves the problem.

Now, whether to go solid or rubber again. Worried about the possible additional vibrations from the direct contact but it's not the first rubber motor mount that's done this. The others were always the torque up (driver) side though.

Given it may have been my fault for not loosening it before lowering the back of the motor i will do some forensic analysis to see how fresh the tear is. That will probably determine which mount to use.

by **drewcrane** » 05 Feb 2009 0:54

They have semi solid motor mounts now they are very street friendly , i have never broken one,also rep[lacing the mounts may not solve the problem but you need to replace it any way,and did yot replace the transmission mount?ill stay tuned

by **Jon** » 05 Feb 2009 3:06

Thanks Drew, do you have a source for those motor mounts? Sounds like what is needed. Them lauches just tear the cheap stuff apart on the driverside that's why I went solid.

Yes, I did the trans mount with original rubber and bracket from Mopar last year. It has a lot of cushing with the pockets in the grommet and all.

by **dave-r** » 05 Feb 2009 8:34

I would be suprised it that passenger side mount was the source of the problem as that mount is always in compression unlike the drivers side.

You don't need a semi solid type mount on that side.

by **drewcrane** » 05 Feb 2009 12:38

dave is right you will only need a semi solid mount on the drivers side, i think mancini racing has them,if not i will look for them and get back to you :lol2:

by **Jon** » 06 Feb 2009 15:43

Anyone know if the rubber block portion of the mount fits either side? I have a spare from the driver side I could use to replace the passenger side. Napa shows only one part number fits both sides.

by **Alaskan_TA** » 07 Feb 2009 0:10

The isolator is the same for both sides.

by **Jon** » 07 Feb 2009 1:31

Cool Barry, I have the replacement in and it fit no problem. Both sides are the same. Saved a couple of bucks there.

Loosened all the mounts and let the motor and trans settle into place so no binding.

Once it stops raining, and our dirt road drys a bit, I'll give her a try.