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67 289 engine vibration

6569 Views 16 Replies 6 Participants Last post by  Dboxman7
On the freeway most noticeably above 60 mph, when on even flat road if I let off the gas, no problem, but when I give just enough to maintain speed I get a heavy vibration/shaking feel from the engine. Not violent like something is breaking, just too heavy to feel right. Doesn't do it when accelerating or when I let off the gas. I haven't started to try to diagnose yet... maybe vacuum advance? or ignition/timing?

Any thoughts or help appreciated!
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Vibrations are sometimes hard to find, any in the drivetrain (engine, trans, driveshaft, u-joints, diff) can feel like it is coming from a different spot. So I will give you some things to check starting at the engine:

1: Check the PCV and the hose
2: If you have an autolite carb, check the power valve, you have to remove the carb, do not turn it over, remove the 4 screws on the cover on the bottom between the idle mixture screws, remove the cover, if fuel comes out the power valve is bad, you can get one at your local autoparts store.
3: Check the torque convertor nuts if you have an automatic trans, remove the inspection cover, rotate the engine with a 13/16" socket, 6" extension, and ratchet or breakover bar, until one is visible, check it and then turn the engine 1/4 turn and check the next one, until you have done all 4.
4: Check the front u-joint on the drive shaft, if there is any play in the joint it is bad, then check the rear u-joint, the same applies.
5: It doesn't hurt to check your ignition timing and vacuum advance.

Post your results. Good Luck.
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If you've installed a harmonic balancer and/or a flexplate/flywheel designed for a later model engine such as the 1982 and up 5.0/302 HO, there is a chance that this is your problem.
The balance factor, (Referring to the crankshaft counterweight), for all Ford V8 engines is 28 ounces with the exception of the engine listed above which has a balance factor of 50 oz. The parts will interchange, but the counterweights are different. The difference can be checked by comparison, as obviously, the counterweight is larger on the 50 oz. example.
All factory 50 oz. balancers will have 4 bolt holes for the crankshaft pulley, the factory 289 balancer will have 3 bolt holes. (There are aftermarket 50 oz., 3 bolt hole balancers available, FYI, but never factory issued). If you have a C4 automatic transmission, the only way to get a 157 tooth flexplate with the 50 oz. balance factor is through an aftermarket source, again the factory only issued the 28 oz type. The 157 tooth is the only size flexplate that will work on the Mustang with the C4. There are no factory C4 flexplates that are 50 oz. they are all 28 oz. There are factory 4 bolt balancers with the correct 28 oz. factor, but they were installed on 302's starting in 1970. The 289 ceased production in 1968.
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Thanks for the suggestions. The engine is stock, vibrations just became noticeable last week. I have had the car over a year with no problems. Both u-joints are solid and the pcv valve seems fine. Still need to check the torque converter bolts and ignition.
Vibration that appears/disappears or changes when lifting off the throttle or applying throttle is usually attributed to a bad u-joint. Sometimes a bad joint cannot be detected by simply shaking the driveshaft. Pull back the rubber seals on the joint and look inside with a flashlight.
A little better inspection...rear u joint is toast. Not sure if that's the problem, but I will start there.
Wheel balance (shake)? Bad pinion angle will cause a vibration under load. Also check slip yoke bushing in the tail shaft. Move the slip yoke up & down to check for excessive play. I've seen a bad bushing cause a vibration under load. Oh yea prop balance too.
Rear U Joint

Got the driveshaft off and the U-joint out. One of the 4 bearings was cracked and a piece fell off when it came out. no bearings inside, just dust and the inner part was obviously worn to a taper. The grease port to that bearing was clogged with what I presume was the remains of the needle bearings.
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Thanks for the suggestions. The engine is stock, vibrations just became noticeable last week. I have had the car over a year with no problems. Both u-joints are solid and the pcv valve seems fine. Still need to check the torque converter bolts and ignition.
Are the motor mounts in good shape? A loose/worn mount (driver side) would not show up during acceleration.
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Noticed the vibration still there after a week or so. Driving home from work yesterday it became terrible. Looked this AM and the rear U-joint is hosed on one of the 4 bearings - will need replaced again. Differential causing it to eat u-joints? Appreciate any suggestions.
If you are replacing the u-joints yourself, then you are missing something in the procedure. Here are some tips, when installing them the zerk fitting should be to the inside meaning it is closer to the driveshaft itself, after the u-joints are installed they should move freely, if they are tight you need to take a blunt chisel and a hammer and place the chisel on a V in the u-joint in the direction of the cup you want more clearance to loosen it up (i do all 4 and then check it for freeness) and tap it with the hammer with the u-joint holder resting on something solid (if it sounds confusing, maybe this helps, pressing or pounding in the cups on the u-joints makes them tight against each other, I use the blunt chisel and hammer to tap the u-joint X shape to push out each cup against its clip, so to release the tension on it. Also the u-joints need to be greased, the easiest way is to grease it before you install the driveshaft is to use a c-clamp or vise to hold the 2 cups on the rear joint that would go in the diff yoke, while you grease the rear one. The only way the diff can be eating up the u-joints is maybe if the pinion bearings are bad causing it to wobble, but I have never seen this, it is just a thought. Good Luck.
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Yes, as Rex1965 mentioned, the joint cups need to be "relaxed" after the "cir-clip" is installed.
Happy Motoring.....
Thanks for the suggestions, didn't know about the "relaxing" part. I figured if the differential was causing it it would be the pinion bearing. My concern about the pinion is because the old U-joint was fine for a year and a half that I had the car until it started to degrade and vibrate. The one I replaced has only lasted a few months.
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Maybe a dumb question, but how much slop is acceptable between the pinion and the ring gear teeth. I haven't pulled the differential, but when the driveshaft was disconnected, I could rotate it a little between the teeth. 1/4" OK but 1/2" too much??? Foreign territory here and just wondering if it needs rebuilt or replaced. 8" stock rear end, 2.79 ratio. My 2004 F-150 has virtually none, but it is a lot newer.
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On a used differential, if you are referring to the flange as being able to rotate a 1/2" that should be okay. If it is a conventional rear axle the wear and clearance in the spider gears also affects the amount the flange can move, in essence it is the total clearance of everything from one direction to the other, not just the ring and pinion. What is important is that the pinion bearings are not worn so much as to allow the pinion to move like up and down or side to side, as this will cause the alignment to change on the pinion to ring gear, and in severe cases will cause the teeth to get broken off. My 2 cts. Good Luck.
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As far as I know it is the original differential. Flange rotation is what I was referring to. Still have some vibration. Don't understand how the driveshaft can just get unbalanced if that is the problem. I'll keep at it. Thanks for the help.
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