Vibration getting worse

[Slider]

OK, I have read all the posts on vibration I can find. Tried a ton of fixes to get rid of this annoyance turned scary shake. I am hoping there is something I have missed somewhere that one of you might be able to help point me in the right direction. First the car basics.

1969 Dodge Charger
WAS a 383 car now a 1969 440RB
Original 1969 727 Torqueflight
8 3/4 rear from a pre 64 with 4.10 gear and Dana suregrip
No idea where the driveshaft came from but it has 7290 u joint ears
    the front yoke has a 7290 setup, the yoke on the dif has a 7260 so an adapter joint is used
Bought the car about a year ago so all mods were done before I got the car

When purchased the car had a tolerable vibration at 55-60. Since then it has become rather scary. The following has been done to fix the vibration.

Found a broken motor mount (torn in half from the immense power of the 440)  motor mounts replaced with new; vibe got worse
After a good burnout and run up to 100mph started to get a hammering from the rear end
rear u joint had a small amount of play; new u joint installed; vibe got slightly better
front u joint although tight suspect at this point; new front u joint installed; vibe got slightly better
made a run to the drag strip, 110 miles highway, 4 runs down the track, 13.744 best time, 110 miles home; vibe became worse
some play in the slip yoke, yoke measured out good so replaced the bushing, bearing and seal on the tail; vibe no change
transmission mount had gone soft from the years of abuse, new transmission mount installed; vibe got worse
transmission mount was the block style for the lower HP engine, modified transmission crossmember and installed high HP trans mount; vibe got worse yet
wheel bearings in diff checked and adjusted, in great shape; vibe no change
car up on lift wheels in the air; vibe still there
car up on lift wheels and drums off; vibe even worse
checked driveline angles, dang near dead straight -1,+1
Checked the vibe from under the car while at speed, small vibe in rear end, big vibe in tranny aha, TC!
Took out Driveshaft and ran it up to speed again, no vibe, smooth like silk,  not the TC
Driveshaft balanced by local highly recommended shop; no changes required; vibe still bad
Tested car on the highway again tonight, still does a great burn out, starts to hammer as tires gain traction (not wheel hop) vibe becomes noticeable at 25mph now right up to 65-70 where it becomes intolerable

I don't know where to go with this issue next. I know some have had to throw the driveshaft out of balance to get rid of a vibe but shouldn't have to do this, no Gear vendor installed. stock type setup. Any chance a really bad vibration could come from the transmission only under load? Any help you guys could throw this way would be greatly appreciated. Fighting this vibe for a year now. Many thanks for your help!

[1974dodgecharger]

I hate vibrations.....

tranny mount? 

I have a vibration in my shifter handle at 80 plug mph and can take it up to 100mph and same amount....I contribute it to the steel shim packs on my shift packs instead of the nylon ones that were used.  I can tighten down the tranny nut mount and reduce it to nothing, but it said torque should be only 17ft lbs....

seems you done everything so try tranny mount tighten it up or get a new one?

[Slider]

I have tried 2 different mounts now. 3 if you count the original softy I replaced. The better the mount (stiffer) the worse the vibration.

The vibration is definitely stronger at the transmission when the car is on the lift spinning at 45mph. Not there as soon as I take out the driveshaft. The differential doesn't have near the vibration the tranny does when the driveshaft is in. So I am thinking the differential isn't the issue. With all the work done on the driveshaft I don't think it could be the driveshaft either.

I have heard the driveshaft needs some angle to run smooth. Could it be the driveline is too straight? I was going to try getting some angles on the shaft today. If its balanced correctly I can't see how that could be the cause though. And the vibration becomes all out washboard type hammering under full load now.

I am at the point of replacing the transmission.... Is there a transmission with overdrive that's a fairly direct replacement for the 727? I would like to keep it on the cheap so a wrecker unit out of a newer vehicle would be the ticket. Pretty good at fabricating so kickdown, shifter, mounts, things of those nature shouldn't be an issue.

Thanks for the reply and help.

[firefighter3931]

The pinion angle seems suspect. It should be 3-5* nose down at rest and yours is at zero. I would start by installing some shims and give that a try. 

I'm going to assume the rear wheel balance has been checked ? It's a simple thing that often gets overlooked...



Ron

[John_Kunkel]

8 3/4 rear from a pre 64 with 4.10 gear and Dana suregrip

Am I reading that right? You have a pre-'64 taper-axle rear end in a '69 B-body?

[Slider]

That is correct, the rear axle is from a 64 or earlier with the Dana Power-Loc in it. The axle yoke has a 7260 small yoke though and the driveshaft is a 7290 so I am running the adepter u joint. Front of the driveshaft has both as 7290's.

I double checked the slip yoke and how much more it could be inserted and it could go another 1" or so further in so it is sticking out a bit much. Small amount of play in the slip yoke still even after replacing the end bushing and bearing in the tail shaft. Ordering new slip yoke Monday.

Tried driveshaft out again and spinning the trans up to 90mph, no vibes.

Adjusted the bands to see if that would make any difference. no change other than maybe getting a little worse.

Just borrowed a buddies driveshaft from a 70 charger that is in the process of being restored. Will give that a go if I can get the slip yoke cleaned up enough to use.

Spoke to a old timer mechanic from the local Ford dealership, really good mechanic even though he worked for the F word guys. He suggested dampner or TC but its not RPM related, its speed related so I don't know how that could be it.....

Anyone have a 8 speed auto from a Hellcat laying around? 

[Slider]

Your question about the axle got me to thinking.....

Checked the carrier casting number and it was 1820657. According to the rear axle page found here

http://members.tripod.com/~Mojo_Page/chry875.htm

That is the 1 3/8" small stem pinion 741. However there is no ratio stamped on the identification boss and the rear axles are not pressed in. The axles come right out after the backing plate is removed. Another weird thing. There is no adjuster on the passenger side axle. The adjustment had been made with shims. I took out the very small play in the passenger side axle by removing  a very thin shim. What is this axle?

[ws23rt]

Your question about the axle got me to thinking.....

Checked the carrier casting number and it was 1820657. According to the rear axle page found here

http://members.tripod.com/~Mojo_Page/chry875.htm

That is the 1 3/8" small stem pinion 741. However there is no ratio stamped on the identification boss and the rear axles are not pressed in. The axles come right out after the backing plate is removed. Another weird thing. There is no adjuster on the passenger side axle. The adjustment had been made with shims. I took out the very small play in the passenger side axle by removing  a very thin shim. What is this axle?

Rear axles are not pressed in? -- Splines are not a press fit.    ---No adjuster plate??  A good question is what do you have?
I'd say get the pinion angle question out of the way before buying a hellcat trans.

[Slider]

Not sure what the rear axle is but I don't think it is the cause of the vibe. It hooks up really good, too good sometimes and feels really smooth rotating by hand.

I thought the angles were suspect but its such a violent vibration now I am wondering if it could be caused just by a driveshaft harmonic. The rear shock are air so I should be able to add some angle pretty easy. Wedges if I have to... I will try that tomorrow and report results. Thanks for your help all.

[1970Moparmann]

On my Coronet, I have always had a slight vibration.  Checked the pinion angle, balanced the drive shaft - helped, but still have it.   Going to keep reading this thread to see if it will help me also.

[Slider]

Update: Jacked up the air pressure in the rear shocks to get the back of the car in the air. Recheck angles. Got me +3 -3 at max air pressure. Best I can get without wedges and messing with the tranny mount. Vibration still just as bad, however, with the snubber on the rear axle off the body of the car is wasn't as pronounced in the back seat as it has been. Gave up on that idea.

Installed my buddies driveshaft which is 1" longer and has original 7260 U joints front and back. No taper at the rear axle end. Slip yoke definitely fits a little better however when I had the yoke on the lathe to clean up the outside of the slip it did have a slight wobble.

Tested the borrowed driveshaft. 1/2 the vibration as with my original. Same frequency as my driveshaft. Now, is my buddies driveshaft slip yoke causing the reduced vibration due to the slip yoke being slightly off? Do I have 2 out of balance driveshafts? Is it the driveshaft at all? The tranny is not kicking down a gear at WOT now either. 2000 rpm in 3rd, floor it and it should kick down to 2nd no?

I don't know if I should start fixing the 727 I have and get a new driveshaft made up for it or dig up an A518 and get a new driveshaft for that one. Very frustrating. 30+ years tinkering with cars and 18 restored cars later and I can't get this figured out. Wish the viration fairy would just fly away!

[ws23rt]

I get your frustration from your vibration problem.   The topic of vibrations and drive shafts seems to go together more often than any other cause I've run into.
I also see your tendency to keep coming back to your transmission as being the source because you have been told the drive shaft you have is fine.  If the trans. is the trouble it is a new one for me and I would like to hear how it could be.

One thing I do know is that a drive shaft that is very close to being perfect from a drive line shop could still be the trouble.  A bit of imbalance combined with flexibility and other bearing clearance issues could cause a harmonic aggravation.

If the vibration comes at a certain final drive rpm of the shaft (or mph) under light load and seems to become less as speed increases and then comes on again (the second one is worse) it is almost certainly the drive shaft that is vibrating.

You mentioned that you know some have had to throw their drive shaft out of balance to get it rid of a vibration.  This sounds like voodoo fixing if I ever heard of it.  How one could come up with an amount of weight and position on the shaft to put it to make it run true and still be out of balance is not rational thinking.

[c00nhunterjoe]

Driveshaft, wobble and lathe should not be in the same sentence. Buy a new shaft.

[1970Moparmann]

This is a good thread to read. 

http://www.dodgecharger.com/forum/index.php/topic,115414.0.html

[mally69]

What flex plate do you have

[ws23rt]

This is a good thread to read. 

http://www.dodgecharger.com/forum/index.php/topic,115414.0.html

That is a good thread to put with this one.

Just for the record---Any drive shaft (or any rotating item) will vibrate when spun up.  The first time it vibrates is called the first critical speed. At a higher speed it will calm down. Additional  increase in speed/rpm will lead to the second critical speed. And so on.

Their are many high rotating speed kinds of machinery such as gas and steam turbines, jet engines, etc.  Some of those operate at a speed/rpm that is past their first critical speed. As they are brought up to speed it is important to get past the first critical rpm as soon as possible to avoid damage that would come from running in that first vibration phase of ramping up.

A good driveline shop knows all about this stuff and should balance a driveshaft (with u joint bearings) to run true at an rpm that is well above what it will see in operation.

[Slider]

Great responses. Thank you everyone.

ws23rt: I am leaning back to the driveshaft as well. The place I had it balanced has a good reputation but everyone can make a mistake. This car has so many mismatched, modified, mickey mouse things on it, the deeper I get into it the more I am amazed it even goes down the road at all. Thank goodness the engine runs like a champ.

c00nhunterjoe: I had my friends borrowed yoke on the lathe only to polish the seal surface. There was some rust on it and with the brand new seal in the tail housing on the tranny I didn't want it torn up. That's when I noticed it didn't run quite true.

1970moparmann: Actually I ddi already read that thread and now with the vibe getting better with a "questionable" yoke, that is why I am leaning back to the driveshaft as the cause.

mally69: I am not sure as to what flex plate is in there right now. I was actually not looking forward of the tranny as the vibration is only there at speed. Engine RPM causes no "unidentifiable vibrations right through to 6000 RPM in park or neutral. Is there an easy way to identify the flex plate without separating the engine from the tranny? I already checked torque on the flex plate to converter bolts. Also the vibration does not go away if I shift it to neutral while at speed.

ws23rt: With MY driveshaft in place the vibration is so bad I don't dare take it over 60 mph right now. When it wasn't this bad it did have stronger vibrations at different speeds. With my buddies driveshaft in place it definitely has good and bad speeds and a much reduced vibration.

Conclusion: I think the best course of action at this point is to get a new driveshaft made up. Exact correct length, new slip yoke, new u joints, new rear diff yoke. Didn't want to spend the $$$ til I was fairly certain it was driveshaft. With help from the members on this board I think that must be the fix.

Anyone have any suggestions on the best place to get a new driveshaft? I would like to add a GV sometime so it would need to be shortened in the future. Or do the A518 upgrade. On the fence on that. 

[suburbanfireman]

I agree with your decision to upgrade the drive shaft.  I've been experiencing the exact same thing - here is what happened Friday night.  My Charger had a slight vibration at 40-50 mph.  I figured it was the drive shaft, and it seemed to go away at higher speeds.  (Keep in mind that it has taken me over 10 years to build the car - and I have less than 60 miles on the odometer.) 

To celebrate our first "family cruise" in the car, we went out to dinner at a local 50's hotrod diner.  You know how it goes - quick little tire-chirp leaving the diner and off we go.  Nothing too silly or abusive to the car.  I decided to hop on the freeway so we can get home before dark.  Accelerated up to 70 mph - no vibration until I stopped accelerating.  Horrible vibration when I lifted my foot off of the accelerator pedal.  I stepped back on the gas - vibration diminished briefly.  Then BAM - and a horrible racket.  I shut off the motor and pulled into the service lane.  (I didn't even make it to the next exit!)  I twisted the u-joints out of both ends of the drive shaft before I could get the car stopped.  I was disgusted with myself when I crawled under the car at home - see my hand pointing to the giant dent that the drive shaft made in the floor pan / muffler?  That is right where my kids were sitting when it happened!   

Spoke with the owner of Henderson's Driveline Solutions (in Westlake, Ohio) on Saturday.  He stated that my drive shaft / u-joints were undersized.  (My car was originally a 318 car.  I guess the previous owner reused the small block drive shaft after he transplanted the big-block??)  I never even thought about it - I just assumed I had the correct drive shaft in the car.  I should have my custom drive shaft (complete with the bigger 1350 u-joints) mid-week.  I thank God that no one got hurt - hopefully I didn't damage the engine, tranny, or rear-end due to my stupidity / haste to start driving the car.  It's going to be a $700+ mistake after I pay my tow fees, Henderson's for the new drive shaft, and upgraded my u-joints / drive shaft yokes.

Sorry about the length of the post - hoping to save you some grief / aggravation.   

[ws23rt]

I agree with your decision to upgrade the drive shaft.  I've been experiencing the exact same thing - here is what happened Friday night.  My Charger had a slight vibration at 40-50 mph.  I figured it was the drive shaft, and it seemed to go away at higher speeds.  (Keep in mind that it has taken me over 10 years to build the car - and I have less than 60 miles on the odometer.) 

To celebrate our first "family cruise" in the car, we went out to dinner at a local 50's hotrod diner.  You know how it goes - quick little tire-chirp leaving the diner and off we go.  Nothing too silly or abusive to the car.  I decided to hop on the freeway so we can get home before dark.  Accelerated up to 70 mph - no vibration until I stopped accelerating.  Horrible vibration when I lifted my foot off of the accelerator pedal.  I stepped back on the gas - vibration diminished briefly.  Then BAM - and a horrible racket.  I shut off the motor and pulled into the service lane.  (I didn't even make it to the next exit!)  I twisted the u-joints out of both ends of the drive shaft before I could get the car stopped.  I was disgusted with myself when I crawled under the car at home - see my hand pointing to the giant dent that the drive shaft made in the floor pan / muffler?  That is right where my kids were sitting when it happened!   

Spoke with the owner of Henderson's Driveline Solutions (in Westlake, Ohio) on Saturday.  He stated that my drive shaft / u-joints were undersized.  (My car was originally a 318 car.  I guess the previous owner reused the small block drive shaft after he transplanted the big-block??)  I never even thought about it - I just assumed I had the correct drive shaft in the car.  I should have my custom drive shaft (complete with the bigger 1350 u-joints) mid-week.  I thank God that no one got hurt - hopefully I didn't damage the engine, tranny, or rear-end due to my stupidity / haste to start driving the car.  It's going to be a $700+ mistake after I pay my tow fees, Henderson's for the new drive shaft, and upgraded my u-joints / drive shaft yokes.

Sorry about the length of the post - hoping to save you some grief / aggravation.   

Very good post   This is the sort of thing everyone needs to hear about. (kinda like a chest pain and left arm numbness). 
You had a near miss.  Their are horror stories of u joints letting go especially the front one.  Glad you and your family missed something that could have been worse.

[GreenMachine]

It sounds like you have an early center section in a B body rear end. I'm not sure, but I thought the splines were different?? Either way, there is some Frankenstein stuff going on. I would suspect the rear end.

[jdscofield]

Check your rear end

[fy469rtse]

? Can I ask if you have rear seal to trans leak ,
Rear slip yoke bush being worn in rear trans extention can have an affect this also,
I had one car where I was trying to eliminate vibration,
By the the time I had eliminated most things , the vibration had flogged this out,
Grab the front of tail shaft and see how much side ways slack do you have , just another idea

[suburbanfireman]

The guy who built my new driveshaft warned me not to torque the u-joint "straps" too tight.  He said that it is pretty common for guys to "over do it" and slightly crush the bearing caps.  I'm not saying that it is what you did - just tossing out another idea for possible solution to the vibration issue.  Keep us informed & good luck.

[myk]

How can you tell if U joints are going bad?  I can imagine that they would LOOK alright before they let go...

[Slider]

Sorry for the late response, it has taken a while to get repairs done as we have been harvesting frantically. Appreciate the response and warning Suburbanfireman. Thank goodness it didn't get that far before I took it off the road.

To sum up what I think has been the issue...... 2 bad (dented) driveshafts (mine and my friends) and a bad balance job caused the greatest part of the confusion. New driveshaft (balanced correctly) with new u joints and slip yoke, new tail housing bushing and bearing, align rear end angle to match transmission angle on driveshaft, install new "homebuilt" cal-tracks and most of the vibrations are now gone. With the driveshaft vibration gone I can now tell I have 2 tires out of balance and one cylinder not firing quite right.

Nice to be able to do the speed limit on the highway and not have my teeth shook outta my head! LOL

I think I'll post a thread on the cal-traks I built. Super cheap and man do they work! Just have to get a pic to post.

Thanks to everyone and all the suggestions Much appreciated!