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Vibration..... for 2 years.

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Discussion starter · #21 ·
Alanrw,

I haven't tried running the engine in neutral with the vehicle stationary. But, I have tried blipping the throttle in neutral at highway speeds and even turning off the engine (neutral with the clutch engaged and disengaged) and they don't affect the vibration.

It feels like the entire vehicle is shaking. Can't tell if it's the front or the back. I have had 3 different sets of axles, 2 different carriers and 2 different housing.... and many different combinations. Nothing changes the vibration.

I might try pulling the driveshaft at the top of a hill....coast up to 50-60 and see what happens on the way down the hill. Or, maybe find a friend with a pick-up and rent a tow dolly.
 
Discussion starter · #23 ·
I haven't been able to isolate the source of the vibration. I am using Del-A-Lum bushings front and rear which dont' offer any damping / isolation. I have had someone else drive while I 'felt' for vibrations in the drivetrain by reaching through an oversized shifter hole. I didn't appreciate any excessive transmission vibrations. I let the slip yoke slide past my fingers at 60mph (that's not exactly in teh owners manual, but I"m desperate) and didn't feel or see any vibration.

I have had all 4 wheel / tires rebalanced. The shop didn't add, take away or move any weights, but they said they were OK.

How could I check for a bent spindle?
 
#24 ·
As you stated, find a tow bar or a hill and remove the driveshaft and coast.
I have seen shocks being too soft allow an imbalance.
Bent spindle would be seen by one wheel not parallel with the other side.
Bent axle flange cna be measured with a dial indicator, total runout less than 0.006" right on the flange.
Vibration moreso in the back seat than front seat(s)?
 
#25 ·
What about a tow dolly for two wheels. then you could test front/rear with and without the driveshaft installed to isolate it further?

It sounds like a bent spindle is the only thing really unaccounted for. Although, Have you inspected the tie rod and sway bar bushings and their mounting hardware?
 
#26 ·
I'm watching to see where this one goes. My 68, all new front end (Moog)torqued to spec,new wheel bearings,spindles are good,all new bushings on frame and rear end,alignment is right( checked and rechecked),bellhousing alignment is OK,new bronze pilot bushing,new clutch,new pressure plate,surfaced and balanced flywheel,new tailshaft bushing in trans,new driveshaft(balanced and rebalanced)new u-joints,driveline angles all check out OK over and over,new tires (balanced and rebalanced),basically everything except axles,so guess where I'm going to check next.Have run it up to speed on stands and it doesn't seem as bad with the tires off the ground.It has a good shake at 60,not a buzz but a shake that you feel in the seat.Don't ask if it always did it ,when I bought it the suspension was junk and it wasn't driven over 40.
 
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#29 ·
scblucam said:
This may sound simplistic, but is the rear U-joint seated properly in the yoke?
Click to expand...
Very good point and look closely at the caps on the joints to make sure there isn't any spacing between the cap and joint. Could just be a bad/sticky needles in the cap, they don't need allot of torque on these just until the lock washer is full compressed otherwise you will oblong/egg shape the caps.
 
Discussion starter · #31 ·
Thanks for all the input:

I've run the car on the highway without rear brakes (rotors removed) and with a different set of tires / wheels on the back.... no change.

I have the correct hybrid u-joint in the back to allow me to use a new yoke (for a late model 10 bolt). There is nearly zero clearance between teh end caps on the u-joint. I have replaced the u-joint several times since it's cheap / easy.

I haven't had much luck running the car at speed on jackstands. Without the vehicle weight loading the wheel bearings, the axles can float around and excite other vibrations. I think I will need to rent a tow dolly, but I sold my pickup when I got laid-off last year. boohoo

I will inspect the exhaust and engine / drivetrain for clearance to the body and other parts. A lot of things are 'close' since the car is lowered and I don't have extra room.
 
#32 ·
When the motor is running in neutral and the hood open, can you see if the balancer is wobbling at any rpm's. I take that back, i see you have tested with the motor off. Its gotta be the differential gears sticking locking in and out, dump the fluid and if a posi add the posi additive with new oil.
 
#33 ·
Reading through the post it looks like you’ve tried everything. My money would still be on drive train alignment, specifically pinion angle, if the driveshaft (tried 3) are straight and balanced. I would try the plumb bulb, but I would go from the spring perch to the lower control arm bolts to check for equal distance between left and right sides. If that checks good (1/16-1/8”) I would the do the same but from a point on the rearend housing.
Then I would go after correct pinion angle, as many have stated above.

Back in the mid 80’s GM sent me to a vibration course, we used a Reed Tachometer to calculate where vibrations were being generated. The one we used sat on the dash, and once you felt the vibes you wrote down the info on the tach and used some simple known formulas to calculate what rotating item would be causing the vibes. All rotating items on the cars have a known rate at a specific RPM or speed, you just need to find the baseline numbers/ratio to go from. Most shops never bought the tachs due to how expensive they were and most of us could find a vibe pretty quick anyway, so it wasn’t worth the high dollar amount for the tool.
Might be worth a try, if your out of options.

Google “reed tachometer” there are a few sites that list info on using them.
I checked ebay and found a couple of listed. Back in the 80’s it was close to $5000-$7000 for our shop, now they’re on ebay for $80.
 
#34 ·
Here is a very long shot...what kind of clutch? I had a vibration like yours, could not figure it out and was reading something on clutches. I had a centerforce and the weights open at 3500 rpm...guess where my vibration began? So, one day I bought a Hays clutch, vibration is gone!
 
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Discussion starter · #35 ·
Skeeter..... I have had 3 sets of gears installed on a new Auburn posi.... no change between different gears sets. And, I installed an open differential carrier on the current set of gears.... no change.

Paul..... checking if the axle is 90° to the driveline is a great idea.... never tried that. I have a leaf spring car so, hopefully it's square cuz it's a pain to adjust.

Trex.... the vibration doesn't change even if I shut the motor off and coast (clutched engaged in neutral or clutch disengaged in any gear). So, hopefully, it's not a clutch thing......I vowed to never pull a T56 out without a lift. I end up bruised and bloody everytime.

Thanks for all the ideas guys..... I put 70 lbs of Dynomat in it this weekend....maybe that will make it more tolerable so I can finally drive this thing.
 
#36 ·
Been following this post and hope you find the issue.
\
The only thing that you should have to live with for two years that pisses you off is........yep ..the old lady.
Too much time & money invested in them to.
 
#37 ·
If the 70 LBs of dynomat dont help it might help to put 70 Lbs of dynomite in it next an maybe the vib will show up!!! LOL I hate when the plan dont come together. I had a 55 chevy that done somthing similar to what your car is doing. At 45 mph it was like you turned on a switch that started the vib and it vibrated until I went back under 45 mph then it was like you turned it back off. It ended up being the mainshaft in the muncie that was bent. I found it after changing several driveshafts and posi units. I found my problem by accident after starting the car with the driveshaft out tranny in gear I got under the car and looked at the mainshaft and it was running way out. It looked like a wobbler shaft or somthing. Good luck with yours. By the way the removing of the driveshaft and rolling the car down a hill or toeing it would be a good way to eliminate a lot of things.
 
Discussion starter · #38 ·
Dynomat / dynomite....... either way I wouldn't really care right now. It's a good thing Chevy parts are relatively cheap. I have thrown a lot of parts at this thing.

I can't find a towing service that will allow me to be in the car while towing, but I've been looking for a back-woods road with a big hill.
If that doesn't work, I'll be looking for a back-woods road with a big hill AND a deep lake at the bottom.
 
#39 · (Edited)
I don't know how far you've gotten with this thing but let me bring something up.

How are you checking your pinion angle? I ask because I put the Moser in with my old engine and M20. I checked it the way everyone said to.....I used a digital angle meter and checked the slip yoke and then the rear end. It looked two degrees off so I shimmed the rear.

I put the new engine and TKO in and spent way too long trying to get the pinion angle. It looked like the trans needed to come up two degrees but I didn't want to have shims in it AND the rear. So even though it was a big pain, I took the rear shims out which would be the same as taking the trans up.

I remeasured by putting just the slip yoke in the trans and leaving enough out so I could stick the digital meter on the shaft. Then I put the meter on the pinion tube of the rear (the yoke is not flat). It kept changing every friggin' time I checked it. I was getting pretty worried.

I noticed that the pinion shaft in the rear was machined perfectly flat on the end. So, I put the meter on it and zeroed it out. Then I put it against the back edge of the tailshaft (just like you would put the slip yoke in) of the TKO figuring it should be machined flat and that the output shaft should be parallel to it. I got 0.5 degrees difference so I went ahead and installed the driveshaft.

So, today I got to take it out and put some miles on it. Ran up to 100 on the freeway and all speeds in between on secondary roads. The thing is like butter.

Try checking like I did....on the pinion shaft itself and on the tailshaft and see what you get. Basically instead of trying to get the meter parallel with the output shaft and pinion it seems easier to get it perpendicular to them.


This is the meter I used. With a digital meter, you can put it on one surface, zero it, then check the other surface to see what it is with respect to the other. Like when I zeroed it on the pinion and checked the trans and it read 0.5 degrees.

http://cgi.ebay.com/Wixey-WR300-Dig...auge-Level-/120531962124?cmd=ViewItem&pt=LH_DefaultDomain_0&hash=item1c1043c90c
Image
 
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#40 · (Edited)
T56 swap
Click to expand...
I haven't read through the whole thread but it's possible the Bell Housing isn't aligning the Transmission causing the manual transmission Input Spline to Wobble. - NOT Good for the Tranny Bearings. A good indication of this is to note a looseness of the Spline Cylinder in the Clutch Disc and Input Spline of the Transmission.

This is usually noticeable when letting the Clutch out relatively fast from a stop under load and does cause Vibration at Speed.
 
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