Vibration In Coast
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Junior User
Joined: Dec 2000
Posts: 80
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From: Lakewood, CO
Vibration In Coast
Hello all,
I have a vibration when my '78 F250 4X4 is coasting at highway speeds. It occurs right when the gas is exactly matching the speed of the Truck (not accelerating, or decelerating). If I then press on the gas to accelerate, the vibration stops, and when I let off the gas to decelerate, the vibration stops as well.
What could this be, and how do I fix it?
The truck is a 4sp, 4.11, 33" tires. I recently inherited it from my brother, so I don't know what it has done before. He just put in a new clutch. Could it be something in the clutch? The same vibration occurs when coasting and the clutch is depressed.
I also have the same problem, only a little less major in my '70 Bronco.
Help!?
I have a vibration when my '78 F250 4X4 is coasting at highway speeds. It occurs right when the gas is exactly matching the speed of the Truck (not accelerating, or decelerating). If I then press on the gas to accelerate, the vibration stops, and when I let off the gas to decelerate, the vibration stops as well.
What could this be, and how do I fix it?
The truck is a 4sp, 4.11, 33" tires. I recently inherited it from my brother, so I don't know what it has done before. He just put in a new clutch. Could it be something in the clutch? The same vibration occurs when coasting and the clutch is depressed.
I also have the same problem, only a little less major in my '70 Bronco.
Help!?
Senior User
Joined: Oct 2000
Posts: 227
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From: arkansas
Vibration In Coast
sounds like a driveline vibration to me. I had the same problem, and the culprit was worn rear wheel bearings in my 8.8" rear, as well as loose pinion bearing. Check for worn u-joints, loose bearings, slack in the rear end, things like that.
Moderator
Joined: Jan 2001
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From: Virginia
Vibration In Coast
I had this vibration in several vehicles and in one case it was
the splines were worn on the slip yoke on the driveshaft. The
other case was the pinion shaft had play where it comes out of
the rear and hooks to the driveshaft. Block the wheels so the
truck will not roll and with the truck off take it out of gear
to take any pressure off the driveline. Get under there and grab
hold of the driveshaft and shake it back and forth. Any side
play is bad.
the splines were worn on the slip yoke on the driveshaft. The
other case was the pinion shaft had play where it comes out of
the rear and hooks to the driveshaft. Block the wheels so the
truck will not roll and with the truck off take it out of gear
to take any pressure off the driveline. Get under there and grab
hold of the driveshaft and shake it back and forth. Any side
play is bad.
Thread Starter
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Junior User
Joined: Dec 2000
Posts: 80
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From: Lakewood, CO
Vibration In Coast
Thanks for the response. I searched through some previous posts, and one person had this type of vibration, and it turned out to be the U-Joints. I checked them for play, and they seemed pretty tight, but the driveline was connected and in gear, so it might have been wound up. More tests are in order I guess. I hope it's not more major than this.
Senior User
Joined: Jul 1999
Posts: 472
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From: USA
Vibration In Coast
[font size="3" color="#191979"]
It's best to test the u-joints with the trans in Neutral. Gear wind-up will hide a sloppy u-joint.
I have seen this condition caused by a worn driveshaft slip-spline. Check it with the transmission in Neutral as well.
"You mean I'm supposed to grease those things?"
Art
It's best to test the u-joints with the trans in Neutral. Gear wind-up will hide a sloppy u-joint.
I have seen this condition caused by a worn driveshaft slip-spline. Check it with the transmission in Neutral as well.
"You mean I'm supposed to grease those things?"
Art
Senior User
Joined: Oct 2000
Posts: 219
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From: Richmond USA
Vibration In Coast
You also might have to check those clutch to Flywheel bolts.
To make sure they are torqued to spec.
Dre'
1978 F-150, 460ci(750cfm,Edelbrock Performer,Dynomax Ceramic Coated headers,etc.)Auto-C6,3:70.1 - 9" Posi.
To make sure they are torqued to spec.
Dre'
1978 F-150, 460ci(750cfm,Edelbrock Performer,Dynomax Ceramic Coated headers,etc.)Auto-C6,3:70.1 - 9" Posi.
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Senior User
Joined: Jul 1999
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From: USA
Vibration In Coast
[font size="1" color="#FF0000"]LAST EDITED ON 21-Feb-01 AT 06:15 PM (EST)[/font][p][font size="3" color="#191979"]
The only way to solve loose slip-splines is to replace the worn parts. Could be the internal splines of the yoke, the external splines of the shaft, or both. Be sure to mark the shaft parts before disassembling it to ensure the u-joints are in-phase when re-assembled. I'd look in the boneyards first for parts if you can. Check the easy things first... like the u-joints.
When the clutch is depressed, more load is put on the flywheel-pressure plate screws, since the clamping springs are compressed more. Loose screws is probably not the cause.
Was the vibration present before the clutch change?
Art
The only way to solve loose slip-splines is to replace the worn parts. Could be the internal splines of the yoke, the external splines of the shaft, or both. Be sure to mark the shaft parts before disassembling it to ensure the u-joints are in-phase when re-assembled. I'd look in the boneyards first for parts if you can. Check the easy things first... like the u-joints.
When the clutch is depressed, more load is put on the flywheel-pressure plate screws, since the clamping springs are compressed more. Loose screws is probably not the cause.
Was the vibration present before the clutch change?
Art
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Moderator
Joined: Jan 2001
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From: Virginia
Vibration In Coast
If you find your spline coupling is worn, you can buy new.
You should replace both as a set. You will get a new yoke
which you just install with a new u-joint. Take the male spline
piece you buy, along with the old driveshaft down to the
local machine shop or somebody that does driveshaft work.
They will put the old driveshaft in a lathe and cut the weld
so the old spline can be taken out. Then they will slip your
new spline in place and weld it. Then they will balance the
whole shaft. If I remember correctly all this is still cheaper
than buying a new yoke and complete driveshaft.
You should replace both as a set. You will get a new yoke
which you just install with a new u-joint. Take the male spline
piece you buy, along with the old driveshaft down to the
local machine shop or somebody that does driveshaft work.
They will put the old driveshaft in a lathe and cut the weld
so the old spline can be taken out. Then they will slip your
new spline in place and weld it. Then they will balance the
whole shaft. If I remember correctly all this is still cheaper
than buying a new yoke and complete driveshaft.
Thread Starter
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Junior User
Joined: Dec 2000
Posts: 80
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From: Lakewood, CO
Vibration In Coast
Art,
I don't know if it was present before the clutch change. I've only driven it with the new clutch.
I will try all the suggestions and investigate more between now and Monday. I will post back with results.
I'm hoping it's U-Joints
Jeff
I don't know if it was present before the clutch change. I've only driven it with the new clutch.
I will try all the suggestions and investigate more between now and Monday. I will post back with results.
I'm hoping it's U-Joints
Jeff
Senior User
Joined: Jun 1999
Posts: 265
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From: Greenville USA
Vibration In Coast
Mine was the result of a loose pinion bearing in the rear axle. When I replaced it, the vibration went away.
fordmando
70 F-100 Ranger XLT 400 C6
78 F-150 4x4 400 4 on floor
86 Nissan 300ZX
92 Scooby Doo (Subaru Legacy Wagon)
George
fordmando
70 F-100 Ranger XLT 400 C6
78 F-150 4x4 400 4 on floor
86 Nissan 300ZX
92 Scooby Doo (Subaru Legacy Wagon)
George
Senior User
Joined: Feb 2001
Posts: 146
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Vibration In Coast
well well well this is a stinky problem with old fords but all the answers are correct but i did not see any carrier bearing repairs. this is the part that is holding up the drive line after the transmission. it has a rubber all around the drive line .it takes a 11/16 to remove it. then get a new one pressed on. not very costly but its a place to check.when you accelerate it would put this in kinda a bind so it wont vibrate then when you let it coast it would take the pressure off the drive line;thus leaving it to vibrate. i hope this helps ya. to check it is quick and simple you will need a lond screw driver and put it near this area then pry up on it if it moves alot its bad.good luck.https://www.ford-trucks.com/dcforum/User_files/3a98299615e4afbe.gif
Senior User
Joined: Jul 1999
Posts: 472
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From: USA
Vibration In Coast
[font size="3" color="#191979"]
ford4604x4,
You are correct in that the carrier bearing and/or its support could cause driveline vibration problems. However, we are talking about a 4x4 here which won't have a carrier bearing - otherwise I'd have suggested it. I had to repair the carrier bearing's rubber support on my 1969 F100 2WD.
Art
ford4604x4,
You are correct in that the carrier bearing and/or its support could cause driveline vibration problems. However, we are talking about a 4x4 here which won't have a carrier bearing - otherwise I'd have suggested it. I had to repair the carrier bearing's rubber support on my 1969 F100 2WD.
Art
Senior User
Joined: Jul 1999
Posts: 472
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From: USA
Vibration In Coast
[font size="3" color="#191979"]
Well, I learn something every day. My 4x4's don't have one (1969s, 1973, 1976, 1978/1979s), but they are all either standard cab with an 8'box or shortbox. Is yours a supercab or a 4door (longer wheelbase)?
Art
Well, I learn something every day. My 4x4's don't have one (1969s, 1973, 1976, 1978/1979s), but they are all either standard cab with an 8'box or shortbox. Is yours a supercab or a 4door (longer wheelbase)?
Art