It happens right around 60-65mph. Tires have been balanced and rotated and the vibration feels the exact same. I know its coming from the *** end somewhere. Pinion angle is correct on the vertical plane but I had to shift the engine over to the p***enger side about 1 1/2" and did my best to measure it. I also had the driveshaft shortened and balanced. My fear is that the driveshaft is out of balance and I'll have to pull it and get it checked. Is there anything else you guys can think of before I do this? Also, is there a trick to check the engine to rear end angle from side to side? I just used an angle finder on the tailshaft and the pinion for the vertical. Thanks all, NAES
Are you running bias or radials? I have bias and had to have all four tires shaved and balanced, like a new set of tires which they are weth about 3ooo miles on them. Might jack the rear up and see how the runout is on the tires. Vergil
Centreline of engine / transmission must be parallel to or on centreline of car, Corvettes and Mustangs from memory were slightly offset to drivers side for clearance and not exactly in the centre. As long as pinion angles match up and down as stated everything should be right. Might pay to check wheelbase in case differential isn't square in frame?
Engine and trans were shifter over together. Rear end is Ford so im not sure how square it is at all. Engine was shifted over for steering linkage clearance purposes. Its a common thing to do for early Mopar engine conversions.
Find out how the balance was done, most spin balances go to 60-65 mph and that's good for most tires. I agree if you drive in and out of a vibration most of time it is tire balance. Try different tires for a test, rotate would show one or a pair out, but if all are balanced the same it will be the same result. For piece of mind, Double chech the crank-tailshaft center line is square to the rearend and that those u joint angles are equal - equal like a pinion angle. Chech the phase of the drive shaft yokes.
I would tend to agree. In some problem cases on-the-car balancing works if you can find someone who still does it. I'd be interested to see the run out though. Also switch the tires, back to front and see if it gets better or worse. A driveshaft related vibration comes in at around 2500 RPM and just gets worse as speed increases. I've driven the most screwed up old cars and trucks on the planet, but the majority of them drove as smooth as silk, no vibrations. Figures you fix something up nice and it rides... not so well. You'll get it sorted out. Bob
I dont agree with that. After I installed a T5 in my 57 I ended up with a vibration around 65-70 that I could drive out of. Had to be driveline because it wasnt there before. Problem ended up being a worn extension housing bushing. I can recall when I first started in the late 60s a vibration problem that would come in at 30mph then go away. Being a dumb kid I asked one of the old guys for help. He drove it & said "ujoint" . After inspection it ended up being a frozen frt ujoint. Then he har***ed me for months about it. I learned over the years that just when you think you know it all something will jump up and bite you in the ***.
Try running to the vibration point,kick it into neutral..see what happens to the vibration..if it immediately quits,this helps to rule out engine ,trans, induced vibrations...if it continues ,while in neutral and goes away as speed falls ,its probably the tires/wheels,etc...This does not totally rule out driveshaft vibrations, however...Then the route would be to remove the drive shaft,have the balance checked ,to rule out that source... This problem can be solved by ruling out .." what it isn't.." if you know what I'm getting at. And,also don't "***ume " anything , have each area checked by a different shop.. I've chased tire vibrations that were checked by the company I bought the tires from..and then had them checked/rebalanced at a different store ...problem went away.... Same with driveshaft,if you had it made at one shop ...have another check it... Stan
Try rotating you drivr shaft 180 degrees in relatioin to the differential. Disconect the u joint from the diff, spin the shaft 180 and re attach it. Hve seen this work in a lot of situations.
You can also cheat the balance on the driveshaft with hose clamps. Tighten till they are just less then snug and if its out of balance, the clamp will self locate and then you just tighten it down. It takes a little trial and error but I've heard it works great.
Have you tried the neutral test yet? How about driving in different gears at that speed? Is the frequency of vibration so low you can almost count the individual vibrations? Is it something you only feel, or can you see the seat back or other stuff interior shaking, too? Is there a deep booming sound audible when you can feel the vibration?
I went through this exact same **** ,a vibration at about 65 ,getting worse with speed,after having a new driveshaft made.Took it back twice,shop said it was perfect.Messed around with tire balance,wheels out of round,brake drums,everything was reasonable.Finally called a specialty drive shaft shop out of town and had a new one shipped to me.End of vibration problems.
Went through this with a 65 Mustang that had a 9" rear. balance drive shaft,new u joints,checked tailshaft bushing, checked the pinion yoke [kind of]. Ended up that I could slide the u joint from stp to stop in the pinion[not much] but after centering the joint in the pinion vibration was gone.
You say pinion angle is correct on the vertical plane, I suspect not. Not doubting you know how to set up driveline, but most don't, its easily misunderstood. If the tailshaft on the ****** faces down 3 degrees, the pinion angle must face up three degrees, meaning that the two angles are paralell, lots of builders will say that this isn't the case, but in my experience, the mystery vibration on a custom built ch***is usually boils down to this. The vibration comes from one u joint has to turn further thru its rotation than the other, meaning its gotta make the turn faster, both should turn the same speed thru the driveshaft rotation, I've fixed a lot of these over my career, its a common mistake. Hoping this helps, hoping you find it, sometimes hard to find, easy to fix. Good luck.
And here again the explanation is misleading and partial. Repeated over and over on the internet. The angles must be equal - parallel or intersecting doesn't matter. If building off center those must be equal also. You can account for torque as needed for application. Parallel- If the trans is down 3 to the back then the pinion is also down 3 to the back. Call it up 3 if you need to but make sure to add " to the front" Both ends of a ujoint only turn at the same speed 2 times for a small fraction of 360*. The other end of the drive shaft needs to be phased so it cancels this out. It's tricky to understand, study and understanding of a constant velocity joint first helps. If the angles are different so will the speeds be different. If using weighted angle finders and bubble levels the car must be on a level surface, sitting on the tires it will run and at ride height.
Here's another thought...I worked at a dealership and got stuck several times fixing vibration complaints.. At first, they had this harmonica-looking device with different length metal reeds.( They later on bought this highzoot electrical sensor device) On a test drive with the Reed device on the dash, when the vibration occured,you would read the frequency of the reed that was vibrating (sympathetic vibration) . After that ,you could calculate what on the car was rotating at that speed/frequency...Crank -pulley,alt pulley,engine, driveline,etc I think I still have the workbook stashed around here somewhere.. Don't know if you could find/borrow/beg one of those devices..but ,it sure helped to pinpoint the area to check... Here's a link to some really helpful info: http://www.vibratesoftware.com/vibsoft/diagnose.htm Stan
Well I rotated the tires again and rotated the driveshaft 180* with the same results. The U joints are new ****er units, no slop in them at all. I rechecked pinion angle in the vertical plane and have 1 1/2* down at the tailshaft of the trans and 1 1/2* up at the rear end. This is with the vehicle level and weight on the tires simulating ride height. I have an appointment next week to get the wheels rebalanced, checked for bent or out of round rims and runout of the tires (radials). Otherwise I'm going to have to safely ***ume it's the driveshaft and go through that mess removing it and getting it rechecked. Thanks all for the help. It's very much appreciated. Again, if anyone knows how I can check my tailshaft to the pinion in the horizontal plane, please help me out. I cannot wrap my head around how to square it all up. Thanks a million, NAES
Took the wagon to Nate Jones tires in Long Beach. They shaved all the tires and then balanced them on the car and indexed them so I can't rotate them from side to side and have to put them back on the car the same way when I take them off. The worst of the vibration is gone but there is still a subtle one at high speeds that doesn't shake the car nearly like it used to. Nate said the driveshaft looks to be a little wonky so I'll delve into that soon enough. THanks all for the replies and advice, NAES
Have the driveshaft checked for concentricity (out of round). Particularly if it's ever been shortened like mine was in our 50 Convert. No problems until a lower geared R&P installed then a vibration that you could drive out of between 60-65. New driveshaft fixed it. Also noted a washer balance weight was coming loose on the old shaft. Couldn't be moved by hand but could see rust under it on one side where it was working loose.
Try putting a radiator hose clamp on rear of the drive shaft and mark it's location. Test drive it and see what happens. Crawl back under(please stop the car first) and change the location of the head of the clamp.Drive the car again see how it feels.Keep doing this until you have walked the clamp around the shaft. If the shaft it is out of balance you should feel a difference some where during this.The Head of the clamp weighs about 1/2 oz. You can also use two clamps and split them rotating one in one direction that other one in the opposite
The Jalopy Journal
