Low speed vibration
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Low speed vibration
Hi folks,
I have a 1977 F-150 4X4 short box, 351M, 205 transfer case, C6 tranny.
I have a bad vibration at about 25mph. If I let off the gas it calms down quite a bit, touch the fuel and its back again. This thing is really kicking my butt as I can't figure out what is wrong.
Here is what I have done. I rebuilt both front and rear driveshafts. If I remove the rear driveshaft and run the truck off of the front, the vibration is totally gone. As soon as I put the rear shaft back on, the truck vibrates like crazy 25mph. If I take it up to 30 to 35mph its okay but if I apply the brakes to take a turn it vibrates.
Could a bad torque converter cause this?
Thanks, Gary
I have a 1977 F-150 4X4 short box, 351M, 205 transfer case, C6 tranny.
I have a bad vibration at about 25mph. If I let off the gas it calms down quite a bit, touch the fuel and its back again. This thing is really kicking my butt as I can't figure out what is wrong.
Here is what I have done. I rebuilt both front and rear driveshafts. If I remove the rear driveshaft and run the truck off of the front, the vibration is totally gone. As soon as I put the rear shaft back on, the truck vibrates like crazy 25mph. If I take it up to 30 to 35mph its okay but if I apply the brakes to take a turn it vibrates.
Could a bad torque converter cause this?
Thanks, Gary
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Is the rear shaft in "phase?"
Probably not in the trans or the converter. Not the harmonic balancer either if the truck does not vibrate with the rear shaft removed.
Anything odd like the rear driveline angle or something?
Probably not in the trans or the converter. Not the harmonic balancer either if the truck does not vibrate with the rear shaft removed.
Anything odd like the rear driveline angle or something?
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hmmmmmm!!
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Good call, the rear shaft had washers welded to it so it was balanced......This is what led me to believe I needed the CV joint/ball rebuilt. The old shaft had a slight bend to it. The shop took the bend out and took the washers off as they were no longer needed. The vibration stayed exactly the same after the rebuild.
hmmmm!!
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Yes, that was replaced about 10,000 miles ago and is kept well lubed.
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Post Fiend
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U joints are good correct? You did not over tighten any u joint fasteners right?
A u joint strap that is too tight will turn a bearing into a bushing, and this would not be good.
You mentioned a driveshaft repair,,,,,,,,,has this shaft ever been in use sucesfully? IS this a new condition that is new to this shaft?
A u joint strap that is too tight will turn a bearing into a bushing, and this would not be good.
You mentioned a driveshaft repair,,,,,,,,,has this shaft ever been in use sucesfully? IS this a new condition that is new to this shaft?
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From: Big Sky Country
So if i'm reading you correctly the bend in the shaft was the original cause of the vibration, the shop took the bend out and removed the balancing weights (washers) stating they were no longer needed, are you positive the shop re-balanced the shaft afterwards?
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U joints are good correct? You did not over tighten any u joint fasteners right?
A u joint strap that is too tight will turn a bearing into a bushing, and this would not be good.
You mentioned a driveshaft repair,,,,,,,,,has this shaft ever been in use sucesfully? IS this a new condition that is new to this shaft?
A u joint strap that is too tight will turn a bearing into a bushing, and this would not be good.
You mentioned a driveshaft repair,,,,,,,,,has this shaft ever been in use sucesfully? IS this a new condition that is new to this shaft?
Nope, never over tightened fasteners, for some reason this truck has always eaten the single rear joint at the diff end.
This shaft has worked great for years even with a slight bend and well balanced. One day it just decided to make this vibration. The new rebuilt shaft has never worked for me yet.
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Note: I did phone the shop and told them the rebuilt shaft never made a slight difference nor did it make it any worse. I asked if they rebalanced it and the answer was no!
My heavy duty mechanic friend is also confused and still blames the driveshaft as the problem. He mentioned I don't need the CV-joint and it should be cut out?......Yikes, it worked fine before so I don't want to cut anything off.
I'm going to remove the shaft and take it back to the shop and have it balanced.
This thing is so crazy already.....
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From: Big Sky Country
It may not help (though i suspect it will) but it certainly won't hurt either, especially since the shop acknowledges they didn't rebalance the shaft after the work.
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Okay, I got the driveshaft balanced when I picked it up it was out of phase.
I said that don't look right to me......His reponse was as long as it's at a 90 degree its good to go. Although its a double joint/CV on one end, I always thought to be in phase was both volks lining up?
Anyways, the truck still vibrates.
Something to ponder: The reason I decided to rebuild the shaft in the first place was because it started to vibrate for no reason one day.......I checked for bent axles and replaced axle bearings and seals. I just can't figure out when I take the rear shaft off, it stops vibrating. What other thing(s) could cause this condition?......Tranfer case or the rear diff ain't slopped out?
I said that don't look right to me......His reponse was as long as it's at a 90 degree its good to go. Although its a double joint/CV on one end, I always thought to be in phase was both volks lining up?
Anyways, the truck still vibrates.
Something to ponder: The reason I decided to rebuild the shaft in the first place was because it started to vibrate for no reason one day.......I checked for bent axles and replaced axle bearings and seals. I just can't figure out when I take the rear shaft off, it stops vibrating. What other thing(s) could cause this condition?......Tranfer case or the rear diff ain't slopped out?
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From: Big Sky Country
Okay, I got the driveshaft balanced when I picked it up it was out of phase.
I said that don't look right to me......His reponse was as long as it's at a 90 degree its good to go. Although its a double joint/CV on one end, I always thought to be in phase was both volks lining up?
Anyways, the truck still vibrates.
I said that don't look right to me......His reponse was as long as it's at a 90 degree its good to go. Although its a double joint/CV on one end, I always thought to be in phase was both volks lining up?
Anyways, the truck still vibrates.
Pirate4x4.Com - Extreme Four Wheel Drive
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I'd highly recommend you find another shop, 90 degrees out of phase is NOT ok.
Pirate4x4.Com - Extreme Four Wheel Drive
Pirate4x4.Com - Extreme Four Wheel Drive
That is what I thought........
One more question, my truck is a 1977 but the transfercase and tranny came out of a 1979 Bronco. Was this CV joint only a Bronco thing? My truck is stock with no lift kit. I'm thinking of destroying this shaft and cutting out the CV joint. I've talked to a few mechanics and they see no reason why its even there?
I'm taking it to another shop tomorrow.
Thanks!!