[zzubzero]

Is it an inherant problem for the automatics to obtain this vibration problem around 60 mph or more? I've owned a couple Challengers that have had this problem. Automatics only, ..do four speeds do this????
I've been through new u-joints , drive shaft, balanced ,.....the whole bit, 5 TIMES"
I'm down to adjusting the axel angle and the engine and transmission angle, I'm going to have the angle of the drive shaft lazer plotted with relation to the angle of the transmission and rear end. (i.e. is the rear end angled down and transmission angled down, the result would be a "U" shape -vs- the differential angle is down, transmission up, forming an "S", obviously you could reverse the last order up or down to arrive at the same "S".
This has been a maddening process
Anybody been through the same crap????
Help!!!!

[dave-r]

I am not sure that Dodge set the pinion angle to an ideal position.

So here is what I feel is the best way to set it.

The center line of the crankshaft and transmission output shaft must be parallel to the center line of the pinion shaft as shown in Figure 1.



You will note that there is some distance between these parallel lines. The distance is caused by the angle of the components and their distance apart.

Planning these component angles is critical. You have to set the components up so their center lines are parallel and so that the angle made THROUGH the U-joints is 3-degrees or less as shown in Figure 2.



While it is possible to run at zero degrees through the U-joints, something more than one degree and less than three degrees seems to run smoothest.

You should also point the pinion down from this ideal position slightly because under load the pinion rises slightly (depending on spring strength). Probably only a degree on a road racer rather than a drag racer.

Many drag racers get this completely wrong and drop the pinion down with relation to the ground instead of to relation to the UJ angle. They end up with pinions pointing at the ground.

[dave-r]

Even if you do all of this you could still have a vibration.

The thing is that everything that rotates from the fan at the front of the engine and back to the rear wheels can all cause vibrations.

Even your crank can have a vibration despite a good ballance job. Mainly because you can only get an ideal ballance at one rpm.

In my case I had bad vibrations at many different speeds and rpms.
I found my pinion angle was out. Putting that right helped a lot.

One other bad vibration was rpm related. It turned out that when I brush painted the block the paint ran on the front of the engine damper. This made the crank pulley not sit completely flush. Cleaning the paint off the back of the pulley and the front of the damper got rid of that one.

New tail shaft bush (where the driveshaft enters) helped slightly too.

I still have one vibration that only happens at 55mph only. But it is not bad and I can live with that. I am seldom below 70-80mph anyway.
The rear wheels are not actually ballanced on my car. The local tyre fitter couldn't get them on his machine because of the width (295s on 15x10 wheels). I might buy a cheap wheel ballancer and do it myself. Then I might be finally rid of that last one vibration.

[Jon]

I completely agree with Dave and a couple of items likely are the source of the problem. (At least these are what I plan to do next)

My car has a 4-speed and the 60 MPH vibration seemed worse when I replaced the rear transmission mount. The new one took up the slack and raised the rear of the trans. I have concluded that an alignment change between the trans and diff. occurred. Also, recently had the rear springs re-arc to give about 1-1/2" higher deck height. That would change the pinion/trans alignment also.

Secondly, my tail shaft bushing is worn and there is significant play at the yoke. Have you check for this? I image this could cause a vibration also.
Quickest and easiest would be to work with the alignment issue first though.

BTW- Anyone know where to get the leaf spring wedge/shims?

[Jon]

I forgot to add that all 4 tires were replaced a couple of months ago and that made no improvement with regards to the vibration.

[dave-r]

BTW- Anyone know where to get the leaf spring wedge/shims?

I am sure I have seen them somewhere like Mancini or Summit.

[Eddie]

Yep, Jon and Dave, www.manciniracing.com under the chassis/suspension section.

[Jon]

Thanks Dave and Eddie, been looking for those buggers for a looooong time.

In my case, (threadjacking again, sorry ) I think the pinion U-joint needs to go up. ????

[zzubzero]

Thanks Dave and Eddie, been looking for those buggers for a looooong time.

In my case, (threadjacking again, sorry ) I think the pinion U-joint needs to go up. ????

Thank you all!!! this is great info, I know it can be narrowed down to something. It will get fixed, vibrates the car apart, carb is already starting to leak

[Eddie]

Thanks Dave and Eddie, been looking for those buggers for a looooong time.

In my case, (threadjacking again, sorry ) I think the pinion U-joint needs to go up. ????

Thank you all!!! this is great info, I know it can be narrowed down to something. It will get fixed, vibrates the car apart, carb is already starting to leak

Good Luck zzubzero and keep us posted. What type of Holley do you have? I have set of Holley Blue gaskets new in the box. It's for 4150 type carb, of which I dont have anymore, you can have these fuel bowl gaskets for free if you need them, if it's that type of carb you have. If so and you want em send me your address. Eddie

[drewcrane]

im now in the right forum to talk about this im gonna try to lower the engine and trans down a bit as now i have found the correct way to measure these important angles, the drive shaft has been removed , now i can place a protractor on the steel boss where the u-joint clips bolt to and (i have 1/12 degrees shims in the front of the axel for this test) my rear pinon angle is 1 1/2 degrees pointing up,the trans tail shaft angle is zero, i have 3 trans. crossmembers ,and the origonal off the car the holes are 1/4 in higher than the two other crossmembers,also the one in has marked 74 ebody has different holes all togeather , so this means there slight variations from year to year as far as how they bolted to the frame . im gonna modify my crossmember to drop my trans tail shaft a little and try that ill be in touch...................... thanks,drew

[dave-r]

I use the pan rail on the trans and the mounting pad for the pinion snubber (snubber removed) for my levels.

Hope this info helps you sort out the problem.

[drewcrane]

actually those are good references when thr drive shaft is in stalled and i also used those points too but........ i removed the shaft and went off the trans tailshaft spline shaft and i opened the holes to drop the trans to about 2 1/4 degrees, and then on the boss for the u jointsi had a n angle shim in there and it was 5 1/ 2 degrees ....way too much so i removed that and now have it at about 2 1/4 degrees pointing up an d trans pointing down so now i have to put it togeather and see how it is so stay tuned ill be back today sometime soon with the results......thanks ,drew

[drewcrane]

ok after careful measuring i have 2 1/2 degrees down on the trans. and 2 1/2 up on pinon angle , after test drive it changed a little but still a very bad vibe above 4500 rpms, i have a source to go to next week that might have more answers cause im outta of em..........................drew

[dave-r]

Yes but the important bit is what is the angle between those and the drive shaft?

I am just wondering if you have misread the instructions? All you have done there is made the trans and pinion parallel. It is the angle between them and the drive shaft that is important.

This is why I do it with the driveshaft in place.

[drewcrane]

yes i will check this but my problem is the 3 inch exhaust is in the way , and i will have to take it to a shop to confirm these angles,asn they have a laser and a program to be more accurate, i really appriciate the in put and i will let you know for sure.thanks, drew

[drewcrane]

also my trans. is pointing down and pinon is pointing up.

[drewcrane]

i measured my drivshaft angle and its at zero, so i have some work to do , the car sits so low , in order to make accurate measurements i do some of it on the ground and some on stands ,also i have an x pipe exhaust and it is duffulcult to see the protractor tool its tight is what im saying.

[Jon]

I'm curious about the RPM reference there bro. What speed and what gear? Is your car lowered or jacked up?

[drewcrane]

ok, the car has been lowered 2 inches, the gear ratio is 3:91, i had 3:55 in before and the vibe came in at about 5 grand and then i put a different pumpkin with the 3 :91 and the vibe starts at 3500 , however i did another test run an with the currant setup and, it is a little different , so tomorrow i plan on changing rear pinon angle , and i have an idea on how to measure more accutratly and i will post tomorrow with the results, i reaLLY APPRICIATE THE INPUT GUYS ,i need all the help i can get thanks ...drew and i have had a long day and i cant spell either

[zzubzero]

I've been there Brother,.....heh,.....I've been there, l'll tell you!!!

[dave-r]

i measured my drivshaft angle and its at zero,

Impossible.

You are doing it wrong.

What you should be doing is measuring the angle difference between the drive shaft and the trans. Then the driveshaft and the pinion.

If your pinion and crank centerline are 2.5 degrees relative to the (level I hope) ground and the driveshaft is completely level to the ground (zero degrees) then your drive shaft UJ angles must be 2.5 degrees. Which would be ideal.

If this is so you need to look somewhere else.

[dave-r]

If the vibratiion only happens at a particular speed (no matter what gear you are in or what gears are in the axle) then the problem has to be in;

The trans output shaft or tailshaft bearing

The driveshaft

The driveshaft UJs

Axle half shafts

Brake drums

The wheels/tyres.

If the driveshaft is well ballanced and the UJs are in good condition and at the same angle as each other I seriously doubt the problem is there.

So all that is left is the axle, brakes and wheels.

[drewcrane]

well , this where im baffeled i changed to strange , axels, wilwood disc brakes in the rear,(as well as the front), this is my 3rd set of wheel bearings, i cheched the lash , and end play of pinon yesterday, um im still stuck on what you said about the angle, since there is no angle to the driveshaft, therefore there is no canceling angle at either point, yesterday was the smoothest i have had it , so i plan on trying to shim the rear pinon and also plan on modifying my measuring tool to be more accurate, stay tuned...........

[dave-r]

You said the trans was pointing 2.5 degrees down at the rear. The pinion is pointing 2.5 degrees up.

How can there not be an angle between the trans and the driveshaft? Or the pinion and the driveshaft?

Look at those drawings I posted above again. I know the print is small but read what it says.

[drewcrane]

actually i have about 5 different articles on the subject, basically i need to have each angle cancel the other angle equally, how ever i still feel that measuring this angle on this car is very difficult and i dont feel that my measurements are truly accurate, all i know now is that trans . angle is down more tham ever before on this car and pinon angle is up more than ever and it seem s to make somewhat of a difference, if i ever get motivated i will raise the pinon a little more and see what happens............... btw i dont understand why there is no angle at drive shaft i intend on figuring it out ................

[drewcrane]

70, 383 r/t auto, 3:55 gears, since 1992,new 440, 2nd trans., new front susp.,4 wheel dics brakes, 17 inch wheel ,and tyre,new axels,spindels,bearings, this car was not treated nice , it was driven hard , the body was bashed in or rusted, trunk floor was gone, i have put alot in to this car since it was truly a basket case destined for the crusher so just a little info on the car......drew

[zzubzero]

Yeeeeeah, I'v eowned one of them there cars afore, it weren't not a shiny nickel itself.