This is on my newer El Camino,a non HAMB friendly 78.I asked around on forums but I think there's guys here with more experience...... At about 50 mph you can feel a slight vibration coming on,by 65 MPH it get real serious ,actually causes a resonating sound.The vibration is high frequency,not slower and "softer' like tire balance.This cruck has 3.42 gears and 60 series tires so the driveshaft is spinning 2700 rpm at 60 mph.It's not the front end,the steering wheel is smooth ,but feels like the middle of the vehicle is vibrating.No center bearing,one piece driveshaft. This vibration is not the engine or clutch.Pushing in the clutch ,kicking the tranny in neutral and letting the engine idle has no effect on the vibration.Running up through the gears hard is smooth until the vibration sets in. So far this is what I have done;checked the rear wheel balance,tire and rim runout, twice.Checked the axle flanges for runout,it's all ok.I did check driveshaft runout and it was excessive.Had a new shaft made,but it still vibrated.Took the shaft back ,the shop checked it again on a different balance machine,said it's just fine. The U-joint angles are as stock,no changes to engine angle or pinion angle. With a dial indicator on the rear of the driveshaft,there is maybe.003 runout.Dial indicator on the small section of slip yoke poking out of the tranny,same,about .002-.003 runout.This tells me the tranny output shaft runs true. But move the dial indicator back about sx inches from the front U-joint and there's .020 runout.Supposedly .010 is maxium runout on a driveshaft. The only thing I haven't checked is the rear brake drum balance,but they look good with factory welded on balance in place. Just a little more to read......This cruck was an auto tranny with 2.41 gears,now it's a stick,rear gears changed by me to 3.42,besides a fresh engine and a whole bunch of other stuff replaced.So you might say there's no past history on this shitbox. The tranny and rear end were rebuilt by me,I'm no expert but do have a bit of experience and the rear and tranny went together fine and run quiet.The tranny is an A-833 4 speed with 4th gear being an overdrive. I'm at a loss here.I could have another shaft built at a different shop.But I'm beginning to think it could be something inside the tranny? What about the rear end yoke? My tests show the rear of the driveshaft spins true but could the yoke itself be fucked up and causing the problem? Thanks for any advice.
Is your transmission's rear rubber mount in good shape? Can you put a dial indicator about halfway down the length of the driveshaft and see if it's wobbling a lot down there. Maybe it would be worth sending the driveshaft to get balanced somewhere. Maybe the driveshaft got a dent in the side somewhere sometime between them fixing it and you putting it back in the car? If you just grab the driveshaft with both hands and yank on it up and down and side to side, is there anything that seems loose or any big clunky noises in front or back somewhere? Do they have the u-joints phased correctly? Good luck!
Are you sure you have the correct u-joints with the correct diameter caps? Make sure you don't over-tighten the U-bolts that clamp around the U-joint caps. If you overtighten them, it can crush the caps and make them slightly oval instead of round and severely shorten the lifespan of the bearings. There's a shop called Inland Empire that makes custom driveshafts, and they're really helpful on the phone if you have any questions or you decide to get a new driveshaft made or need a new yoke or something.
Rusty,this is a brand new driveshaft with new U-joints and tranny yoke.It all fits properly,joints move smoothly.This shaft was made by FleetPride,the only shop in the Rochester NY area I know of.In the recent past they made three custom shafts for me that were just fine.But that was then. The motor mount is a new urethane.I'm thinking if the tranny mount was fucked the vibration would rise and fall with engine RPM??? I haven't checked runout in the middle this last time,I probably should check it again. The yoke fits into the tranny ok,no up and down slop and it slides in and out ok.
I had a bad (almost 2 pieces) transmission mount on a '86 Monte Carlo. It didn't look bad but when rpm and torque was applied it would stretch and separate like an accordion. M. McF.
interesting.. im having a similar issue only mine gives a low pitched and evenly paced resonating vibration at around 45 to 50. I never heard of tire balance doing this. might have to check that.
I've felt and heard engine RPM vibrations caused by urethane mounts Was the shaft dynamically balanced in driveshaft balancer? Were u-joints changed after rebalancing. In a El Camino driveshaft, the u-joints are held in with injected nylon from the factory and aren't necessarily installed exactly right. The replacement u-joints are held in with snap rings between the yoke ears, which locate the joint exactly to the center of the shaft. GM rearends of that age sometimes have a wear problem between the yoke ears where the snap rings on the u-joint caps seat in. The snap rings are on the caps, right? The u-joint is held down with straps and bolts, not u-bolts. There's a good starting point for troubleshooting. I have built and installed a few thousand driveshafts.
One more thing, check your tires out. Sometimes like on older radial tires, the steel belts can start to fall apart under the tread, and give you little bulges at the tread of the tire. It can make an awful vibration when you get up to speed, and you can have more than one bulge to make a higher pitch vibration than you would get from just an unbalanced wheel. You can sometimes feel the bulges if you just run your hand around the tread of the tire. The bulges sometimes are bald while the rest of the tire still might look like it's got plenty of tread on it. I had that problem with some older Firestone "performance" radials on a muscle car about 15 years ago. Those lead weights sometimes fly off right after they do the balance if they use the wrong kind for whatever type wheels you have if they don't get a good grip on the edge of the wheel. Those stick on weights sometimes come off too.
Patrick,new u-joints,new yokes,all with snap rings.They built the shaft,gotta assume they know how to balance it.And the rear snap rings are in place,the u-joint fits without play in the rear end yoke.
Yes,preload done with a small torque wrench. There's a place in Buffalo NY called Denny's driveline. I hear they do quality work and have balancing equipment that can spin the shaft to 6000 rpm.Fleetpride does mostly big trucks,maybe their machines don't spin fast enough??? I'm thinking of pulling the shaft,drive the hour and a half,drop off the sahft to them to check.Checked by two shops should pretty much guarantee the shaft is ok.
3 1/2" tubing rules out any RPM capability problems. If the shaft tubing is too small diameter for the length and RPM's, the tubing will start to whip in the middle causing failure known as critical speed failure. What brand of u-joints did they install? Some u-joints just don't fit exactly right in some new weld yokes. If that is the case, you'll have just a touch of play between the ends of the cross and the caps. If the cross doesn't rotate smoothly, vibrations can be caused. My personal preference on a shaft like this is the Spicer OE non-greasable u-joints, part number 5-795x for a GM inside lock on all four caps. Last tidbit, if they didn't get the tubing straight in the middle too, the shaft can be balanced at slower speeds, but not be anywhere close to correct at normal operating speeds.
Spicer joints,supposedly HD,they have a grease nipple .I didn't want greasable joints but that's what they used. I think you're right about the balancing issue.First trip had the shaft with two weights on one end,one weight on the other end.When I took it back for re checking,the guy called said the balancer was broken.Then he sent it to another one of their shops in Syracuse.This time it came back with only one weight on one end.Couldn't tell if if the shaft itself was reworked. I don't have confidence with them right now that's why I think I have to bucks up and have another shop check it out
I left the parts counter yesterday afternoon to pull a shaft from a 99 Dodge van, put back into the balancer, and fine tune myself. The shaft was aluminum and has approx .040" eyeballed wobble toward the rear, about 18" from the rear weld. Didn't try to straighten the tubing, worried about overheating the aluminum and compromising its strength. I fine tuned a little more with a couple of 5 gram weights, but could take out the driveshaft RPM flutter you hear at 65 mph in this vehicle. We'll be building a new steel shaft tomorrow. Have the new shop pull out the good greasable u-joints and install the 5-795x pieces. Save the greasables for a parts getter pickup. Good luck!
I have an O/T 1980's Grand Prix with a 383chevy/a833od/3.42,stock driveshaft with newer u-joints, that does the same thing only more like 75+ mph. I always figured it was pinion angle, because the crossmember I fabbed for dual exhaust changed the height of the rear of the trans. I haven't looked into it much because it's fine at 65, but if you figure it out let me know! My trans is out of a 1984 fullsize pickup, I kept the hydraulic clutch and fabbed a pedal. What's your setup?
Before you pull it out again, try the backyard balance. Put a worm drive hose clamp on the shaft to create an imbalance. Drive it up to speed see what it does. rotate the clamp 90* try it again, and again, and again. See if at some point you reduce the vibration. That will prove it's a balance issue. At no cost, just time.
A833 from an 80's full size Chevy PU,mechanical clutch,82 Camaro clutch housing with the clutch fork hole off center towards the bottoms so the fork doesn't hit the tunnel. I don't like the gears ratios,but The OD is nice. I've redone a few aluminum case GM A833's and every one had the holes in the case for the countershaft worn eggshaped.A few hundred bucks for a machine shop to line bore the holes,fabricate steel bushing and press them into the case. On the backyard balance,I thought of that.This vehicle is lowered a bit,got to jack it up to mess with the driveshaft,and I'm a skinney guy.Seems easier to me to jack it up once and pay the bucks for a shop to mess with it.
A833's are very similar to a GM all synchro 4 spped car tranny when you disassemble them.No surprises,just need a good snap ring pliers and it helps to have a service manual .These tranny's can take a hard pull on the shifter to change gears especially if the lever is short.Even on on good ones you can hear the synchro whine during a down shift.If you're using 90 weight oil,try something llighter like GM Synchromesh oil or 75 weight gear oil used by some foreign cars.Originally they used ATF I believe.
I'm experiencing a very similar thing since swapping a C4 into my '63. My driveline was gone over by Wade King in Mission Viejo, CA (King Drivelines) and it's about as perfect as it can be. My next thing to check is four wheel alignment. Because mine resonates, I believe this could be my problem, might be your too.
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