driveline vibration
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driveline vibration
My truck is a '68 long box F100.i keep running into this and wonder if anyone else might have a solution. I replaced my 6cyl 3spd with 5.0 ho and aod trans. had the driveshaft shortened at a reputable driveline shop. It is a 2 piece shaft. It never had any vibration before i did the swap. Now it shudders around 30-40mph and is worse under load, either on acceleration or deceleration. it seems to be getting worse and is driving me nuts. All ujoints are new and the balance has been checked on the shaft twice and appears ok. If i'm deceleration and shift to neutral it totally goes away. i would go to a one piece shaft but they tell me it would be to long and may not work properly. I have noticed this in other trucks of this vintage but less pronounced. My last '68 had it but i was told the front shaft was bent so i left it. Any ideas out there? Thanks
Hotshot
Joined: Oct 2002
Posts: 18,488
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From: The Big, Oregon
Also make sure all the u-joints are in line. If they are out of phase, it will vibrate as they pivot around at different spots. Check to make sure the tranny output and pinion bearing don't have any play to them as well.
Elder User
Joined: Jul 2004
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From: Westminster, Colorado
Well, you said you had a new driveshaft....but check it and double check it....my truck behaved in the same manner at 45 MPH and up....due to a dent in the rear Driveshaft....the shaft still "looked" true...but the slight bend at the u-joint caused by the dent would send it a shuddering at speed.
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thanks for the advice. the carrier(steady) bearing feels perfect in both my opinion and the driveline shops as well. Its certainly not to do with the engine, all that is ok. The shaft is in correct phase and i sure can't see any dents or anything and i have checked it very closely repeatedly. I am thinking of going through the diff thoroughly next but boy it sure doesn't feel like a diff bearing issue to me. Process of elimination leaves it as my next step though. Its not a tire issue that has been checked and it feels different than a tire balance issue. So i guess diff it is for now and see from there.
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Logistics Pro
Joined: Jun 2003
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If a diff bearing was out enough to make a vibration it would be making a hell of a lot of noise plus you would be smelling burnt hypoid gear oil.
I have never seen a diff cause a vibration.
I have never seen a diff cause a vibration.
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Thanks instig8r and everyone. i'm with you on the diff thing thats why i am hesitant to go down that route. But the diff does make a bit of noise and the pinion seal is leaking so it needs attention. It was a used diff so i don't know its history. I am not expecting to locate my vibration issue there but it has to be done so nows the time. A customer left a truck at the shop i work at and he did a similar swap but he built a one piece shaft that i think would be the right length so i thought i would swap it temporarily just to narrow it down to driveshaft or not. i will let everyone know what i find(assuming i find it!!!)
