Hello Mopar experts!! I need help please.
I have a new to me 1970 Dodge Challenger with a 440 and a 727 automatic transmission. I bought this car and the engine was all done by the guy that owned it before. This car did not leave the garage very much is what I am guessing as there were belt issues that I had to fix so no way he could have ran it that way without a tow truck following him.
I have a harmonic pulsing vibration in the seat of my pants at 2700-3000 rpm. It does not vibrate or pulse at any other RPM. Its not a violent pulse but it is there and I want to fix it. I have done all the basics like driveline angle (now perfect), new driveline, new transmission mount and also rebuilt the rear end. Engine mounts are brand new and nothing touching anywhere to cause vibration. I also ensured there were proper shims in the gear vendor which now its perfect. The transmission was also supposedly rebuilt by the restore place and the engine was not touched besides new Performer RPM intake for the FAST fuel injection I wanted on the car. Nothing to date has fixed my issue yet and i'm still in the hunt for this vibration. I was under the car the other day looking around even in more detail and I pulled the transmission inspection plate and found a chunk of steel welded to the flex plate? I was kinda in shock to see this.
The weight weights 3.7 ozs. There was 2 out of 3 welds that were cracked so I tacked them back up hoping this was possibly the vibration I was feeling. No luck and still vibrated after I ran the car again at that RPM. So I pulled this steel weight hoping that it wasn't supposed to be there and then car really vibrated bad so I stopped immediately.
My question is - How do I fix this properly and the right way? What do I need to do? To me, welding a chunk of steel seems like not the right way to me as obviously it isn't the right weight or in the wrong spot as my car still vibrates with it on. My data sheet for the engine says that it was balanced but it does not say anything about being internally balanced or externally balanced. I do not see anymore weights on my torque converted welded on either. This motor looks like its a 74 year vintage from the block stamp so it should be a cast crank which would mean externally balanced unless the engine rebuilder balanced internally which I do not know? The harmonic balancer mounted on my engine looks like an internal balancer as it is fully round and no cups or grooves or divits on the back side towards engine for mounting external weights? I believe my torque converter is a 3000 stall.
What do you guys think is my issue for this vibration felt?
Thanks for your help.
It sounds like an internally balanced or externally balanced issue to me. If your engine is internally balanced and your torque converter is not correct you might feel something like this. :notsure:
Being a '74, my guess is you need an harmonic balancer for an externally balanced engine AND the weight kit for your torque converter. The weight kit comes with a template for where to position the weights and you weld them on.
This guess is based on when you removed the homemade weight from the torque converter, the vibes got worse. So I think you have an externally balanced motor.
Have you tried running it up the the RPM and then put it in neutral? This will tell you if it's the engine or trans back.
Thanks everyone for your replies! Really appreciate it!
I haven't tried shifting it from drive to neutral which is a good test but have ran in up to rpm in neutral and car doesn't vibrate like a pulsing like it does when it's in drive. It's different or not existent in neutral - maybe just a hint of vibration but minimal if any. Definitely way different than when its in drive. Also if I pull driveshaft and run it up to rpm in drive it doesn't pulse either which lead me to all the driveshaft and rear troubleshooting I done previous.
With the steel piece removed if I run motor up in neutral it vibrates bad. It almost seems to me that the steel piece was close to proper weight but just out a bit and that bit shows itself at 2700-3000 rpm. I'm not sure.
:iagree:
Welcome to the site , as well
Try shifting into neutral & coasting when it is vibrating if it continues it is in the driveline , if it stops it has to be the engine & converter .
If it is the engine it should also vibrate the given rpm while sitting still .
Once you determine where the vibration is we can narrow it down , you need to know if you have a steel crank or cast & what damper you have , steel crank is approx 1" thick cast is thicker with an offset plate on the front of the damper . Even if the damper is correct if the engine has been rebuilt with lighter pistons using the correct parts will not fix the vibration .
My guess is the engine is out of balance if removing the converter weight changed it that much
worst case you may have to pull the engine , disassemble it & have the rotating assy properly balanced , anything else is a guessing game at this point .
I have learned if you feel vibration in the seat of your pants it is not an engine or transmission issue. The vibration is caused by the driveshaft back. Believe in trying process of deduction. Rotate wheels and tires and take up to fwy speeds. If that doesn't help tow car up to 70 mph without drive shaft. If that doesn't eliminate vibration check for bent axle flange. Inspect pinion yoke for distortion. Check transmission output shaft angle...should face up 2*, check pinion angle.....should be 2* downward. These angles are a general rule of thumb. Has the car been lowered? Also, the driveshaft should be precision balanced at 3000 rpm or higher when there is a vibration issue. Good luck!
I would also have your Tires checked for Balance, especially the Rear tires, out of balance or separated (if they're radials) tires can cause vibrations and shimmies.... :alan2cents:
If you have BFGoodrich tires that is very likely your problem but generally they will not be vibrating in such a limited rpm range
Bad pinion angle will cause a vibration at certain speeds. :alan2cents: Does the vibration happen at a certain speed?
Had a vibration like that in my 73 challenger and never resolved it. It had an Art Carr torque converter. Pulled the converter and sold the car. A few years later I built my current Barracuda to drag race in the street brackets and installed the Art Carr converter. Yep the vibration was back in a different car. Sent the converter to a shop where they cut it open and found some broken parts inside.
Thanks Everyone!!
When I am running my car I am doing it on jack stands in my shop as it is still winter where I live. I always run the car without tires to ensure its not a tire issue and have ran the car without axles in either and did not help. The only time it goes away is with driveline out?
Im guessing and will try this tonight by running it in my shop is that the vibration will go away when I shift it from Drive at 2700-3000 RPM to Neutral as this should be the same as just reving the motor in neutral to 2700-3000 RPM? I will try it and post back here tonight.
Please see attached pictures for Harmonic balancer. I think it is an internally balanced harmonic balancer but hoping you guys can tell me fursure please. Also can anyone tell me from picture possibly if this is a cast or forged crank? It would be awesome if they just had the wrong balancer on the motor but like Chryco Psycho said - it still may not fix issue as may have lighter internal components in engine. Isn't there a way to balance with a B&E flex plate that allows external weights to fine tune if I did have lighter engine parts or bad balanced torque converter?
Iron Man/Shane Kelley - I have my pinion perfect now. I adjusted transmission and Rear-end. Transmission is 2.5 degrees down and Rear-end pointed 2.4 degrees up. Both Diff and Transmission have a running operating angle of 1.1 degrees. Brand new drive shaft from Bears performance that came with new greaseless U joints. Vibration only happens at 2700-3000 RPM which is 60 MPH with Gear vendor Overdrive off or 70 MPH with gear vendor overdrive on. Both these speeds are at same RPM.
Chryco Psycho/Jim AAR - only run car with tires off to reduce rotating mass and also remove as many variables as possible. Have even ran car without axles to ensure they are ok too with no help. I have pulled Diff apart and put a new master kit in and clutch packs for my positraction.
"I have my pinion perfect now. I adjusted transmission and Rear-end. Transmission is 2.5 degrees down and Rear-end pointed 2.4 degrees up. Both Diff and Transmission have a running operating angle of 1.1 degrees."
Pinion angle needs to be down not up. So you have your pinion already up 2.4 degrees and when you accelerate that pushes it even higher. Could be as much as 4-6 degrees and that can play havoc with the u joints. I'm not saying this is your vibration problem but it is definitely a problem.
Below is from Dr. Diff.
Well your flexplate is for an internal balanced engine, so lets hope the crank and balancer is too!
Please post what you find. I have almost the same exact problem.
Car only vibrates between 75-85 mph or about 2800 rpm.
Little different combo, 340 with 518 OD transmission.
I suspect a TC or driveshaft problem
303 mopar - I tried the drive to neutral trick. Once the mph dropped a bit the vibration went away but my rpms did go up a bit too so was hard to keep exact rpms. The pulsing did go away.
Shane Kelley - isn't the diff supposed to point to the frame of car and transmission point to ground? So if diff points 2 degrees up and transmission 2 degrees down they are parallel?
Quote from: 303 Mopar on February 13, 2018, 12:46:02 PM
Well your flexplate is for an internal balanced engine, so lets hope the crank and balancer is too!
Flex plate is the same on internal or external balanced motors. The weights are on the converter.
The back of your converter looks to have an extra hole in the mounting pad. I would pull the 4 bolts from the flex to converter and make sure that the flex plate doesn't have any out of round or enlarged holes. The flex plate and converter are indexed and proper alignment is critical. The flex plate should not need any balance so that weight is wrong.
Quote from: 440SMOKE on February 13, 2018, 05:49:06 PM
303 mopar - I tried the drive to neutral trick. Once the mph dropped a bit the vibration went away but my rpms did go up a bit too so was hard to keep exact rpms. The pulsing did go away.
Shane Kelley - isn't the diff supposed to point to the frame of car and transmission point to ground? So if diff points 2 degrees up and transmission 2 degrees down they are parallel?
No, pinion also points to the ground . Here is a pic of -7 degree pinion angle. You want -4 degrees same principal applies.
Thanks 750-h2 - wow I have done it all wrong and I thought it was perfect? I researched and researched.
Question - so how do I get the transmission shaft to parallel the pinion yoke shaft if pinion yoke is pointed down to ground? I doubt I can get transmission to point up especially with gear vendor installed without hitting frame or tunnel. I would have to drop engine mounts to get transmission to point up but that makes oil pan clearance and issue?
The balancer is for a steel crank , no way to tell what the crank is though
Quote from: Chryco Psycho on February 13, 2018, 06:40:33 PM
The balancer is for a steel crank , no way to tell what the crank is though
I think if it was a forged crank, it would not vibrate when he took the homemade converter weight off. I think he has an internal balance damper, a cast crank and a Magyver'd torque converter.
IMO, buy an external balance damper, external balance weight kit for the converter. Install and you will likely be good.
It seems if the rpm stayed the same but the driveline slowed in neutral & the vibe went away that the vibration is Not in the engine but behind it instead
Years ago, I had this exact problem with my old 340 'Cuda. Turned out the driveshaft needed to be balanced. Once I had that done, all of the vibrations went away. At this point, a relatively easy and not-too-expensive way to check an item off of your list of possible causes.
I hope you find the fix soon, as I know this problem is very frustrating.
MIKE/fantum
Thanks Fantum - it is very frustrating and would like to get this resolved!! :headbang:
This is my second drive shaft and the one in my car now is built from Bears Performance so im guessing it should be good?
Chryco Psycho - I am finally putting this cars history together and talked to the engine builder that did engine for the guy that owned the car before me and he says it is externally balanced so we do know that fursure now. He did say that on some engines that they left the internally balanced harmonic balancer as it wasn't a big difference so they left it. Also he said that if it was a harmonic balancer issue it would vibrate all the time? I do have the balance card now for future reference and can get things weighed up properly now without a full teardown of the engine. The Engine shop was the ones that welded that chunk of steel on the flexplate to balance engine. What im guessing is when the restore shop installed a new higher stall converter the flexplate needed to be replaced too and they took the steel off of the old flexplate and welded onto the new flexplate by just eye balling it? That's what it sounds like anyway. But if it is a engine vibration issue like it sure seems with an incorrectly balanced flex plate why doesn't it vibrate all the time?
Question - So when I drop car into neutral and vibration goes away, what does it mean its now behind engine? Where could it be, where should I start looking? Could it be a balance issue in torque converter?
Thanks
440SMOKE
Quote from: dodj on February 13, 2018, 07:07:28 PM
Quote from: Chryco Psycho on February 13, 2018, 06:40:33 PM
The balancer is for a steel crank , no way to tell what the crank is though
I think if it was a forged crank, it would not vibrate when he took the homemade converter weight off. I think he has an internal balance damper, a cast crank and a Magyver'd torque converter.
IMO, buy an external balance damper, external balance weight kit for the converter. Install and you will likely be good.
Dodj - I totally feel the same as you and I feel that will fix us up too but just one item still concerns me still. Its a harmonic pulse rather than a continuous vibration so would fixing those components remove the pulsing feel that I feel in the seat of my pants at a certain RPM/MPH in Drive only? Or am I not diagnosing the felt vibration properly in neutral and a harmonic pulse is a part of a continuous vibration? Its a brain stumper fursure. Thanks
if the engine rpm is maintained but the driveline rpm drops down & the vibration stops , it should not be the engine ,
There is a drive line video on this site somewhere that I posted
Here it si https://www.youtube.com/watch?v=gmV4qwLfOMY
It's the engine. Get the proper weights on it for an externally balanced motor. I mean it only makes sense to get the proper parts on it. You have found out it is an externally balanced motor, so leaving an harmonic balancer meant for an internally balanced motor makes no sense at all. If they could effectively balance a motor with weights just on the torque converter, Mopar would have only made one style of harmonic balancer. :alan2cents: