Drive Line Vibration
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Drive Line Vibration
My 94 F150 5.0 4R70W has a fairly mild but annoying driveline vibration. It can be felt off and on at any speed. It is usually worse under moderate acceleration or load. It is present most of the time while driving.
Every item from behind the transmission to the tires is new. The U joints are Spicer. The center support bearing is Ford (Spicer). The rear end was completely rebuilt with a 3.73 LSD change. Those were used but in good shape. The bearings, seals, and clutch pack are all new, most of this is Ford Racing. We double and triple checked everything such as backlash, wear pattern, and pinion preload during the rebuild.
I am puzzled as to what the issue is. There is also no noise that can be heard. Does anyone have a clue here?
Every item from behind the transmission to the tires is new. The U joints are Spicer. The center support bearing is Ford (Spicer). The rear end was completely rebuilt with a 3.73 LSD change. Those were used but in good shape. The bearings, seals, and clutch pack are all new, most of this is Ford Racing. We double and triple checked everything such as backlash, wear pattern, and pinion preload during the rebuild.
I am puzzled as to what the issue is. There is also no noise that can be heard. Does anyone have a clue here?
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I don't see how the pinion angle could have changed, since everything is in the original stock position. The slip joint was keyed if I remember correctly. I'll look to see if everything is in phase or not.
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From: Foothills of NC
You could have a bad tail shaft bushing in the transmission, the rear axle could have been removed, lifted or lowered with blocks, throwing the pinion angle off, the center carrier bearing may be taller or shorter than what came on it, throwing the pinion angles off in the center, the slip yoke could be a spline or two off, or if lined up, it could be 90 deg out of phase, which will definitely cause some nasty vibes. Make sure on the slip yoke that both yokes have the u-joint receiving ends lined up with each other.
You could also have a bent or twisted drive shaft.
You could also have a bent or twisted drive shaft.
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While it worsens under moderate load, it does sometimes apear to get even more obvious the more the engine is lugging for lack of a better word. I guess that would be increased load. Also, it sometimes seems to get better when giving more throttle so that it downshifts. I've also not really noticed the issue much under hard acceleration from a stop.
I do not believe it is torque converter shudder. I had that years ago on my old 95. It is definitely coming from the rear.
Everything was replaced as maintenance due to age. I was also doing the gear change and LSD swap. I did not have any vibrations before this. However, there were also no noticeable vibrations for a while after everything was done.
I do not believe it is torque converter shudder. I had that years ago on my old 95. It is definitely coming from the rear.
Everything was replaced as maintenance due to age. I was also doing the gear change and LSD swap. I did not have any vibrations before this. However, there were also no noticeable vibrations for a while after everything was done.
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If it was smooth for some period after all the work was complete, then the vibration started at some point after, then I think I'd put the rear end up in the air and get under there and start checking if things like u-joint straps, center bearing support, and driveshaft yokes are tight. It would give you an opportunity to run it up to speed too to eliminate front wheels. Obviously this kind of experiment is only conducted with the truck firmly supported on level hard ground on jack stands.
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The center support bearing was replaced twice. The first time with an inexpensive Timken and the second time with a Ford one. This was after the vibration started. The aftermarket one did not seem nearly as well made. Also the drive shafts are in phase.
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We ran the truck on jack stands. The vibration was present at all speeds. There was a light clunking or tapping noise each time it shifted gears. The noise can be heard very softly under the back of the truck when in a gear. Using a stethoscope it sounds like it is inside the diff housing. What's strange is that the rear end does not vibrate at all.
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Not sure about the noise inside the rear, but for no cost/sheets & giggles regarding vibration, unbolt companion flange from driveshaft. Then rotate to next matching set of bolt holes. Know the flange is double drilled & tapped. Don't know if you can go 90* or just 180*.
Won't cost anything but time.
Won't cost anything but time.
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From: Ohio
That clunking/tapping noise when it shifted is likely just lash in the gears and since it has no real load with the tires off the ground it might just be gears clanking til it settles in with the new speed.
Since the rear end does not vibrate, then it can't be the tires. I've had belts separate and give a vibration while driving. Couldn't figure it out til I let the air out and it had a big flat spot on the tread. New tires and NO shaking.
My '95 has a similar vibration, around 30-40 mph is the worse. New u joints and it didn't help. It is a one piece shaft, so no carrier to worry about. The tail housing bushing is not that loose with only 75K miles on the truck. Get up to speed and put in neutral and still vibrates so it is not motor/trans related.
I've wondered if it is just a bad driveshaft from the get go. I've wanted to either get it checked or just buy a used one and see if it anything changes.
Since the rear end does not vibrate, then it can't be the tires. I've had belts separate and give a vibration while driving. Couldn't figure it out til I let the air out and it had a big flat spot on the tread. New tires and NO shaking.
My '95 has a similar vibration, around 30-40 mph is the worse. New u joints and it didn't help. It is a one piece shaft, so no carrier to worry about. The tail housing bushing is not that loose with only 75K miles on the truck. Get up to speed and put in neutral and still vibrates so it is not motor/trans related.
I've wondered if it is just a bad driveshaft from the get go. I've wanted to either get it checked or just buy a used one and see if it anything changes.
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We did mark everything with paint, in order to keep the same orientation. I may try rotating the pinion yoke 180 degrees. I may also pull the cover and check wear pattern and backlash again.
I do not remember there being any vibration prior to doing this project. I remember things being fairly smooth.
I do not remember there being any vibration prior to doing this project. I remember things being fairly smooth.