vibration under acceleration?

[gregamorton]

Guys I have got a new crewcab 71 and have the engine running super smooth and when I take off and start gaining rpm it starts vibrating. I thought at first it could be the clutch but it is suppose to be new and new throwout bearing. I took it this morning to a real good mechanic we have in our town look at it and he got in and played with the rpm a little and the clutch and he said it felt like it had the wrong balanced flywheel in it. My question to yall is the a difference in the 360 or 390 flywheel? I dont know what it is. The factory engine showed to be a 390 but the previous owner said they put a 360 in it. Just trying to figure out if I need to pull it down as the vibration is bothering me.

[Brokenarrow]

All the 352-360-390 are internally balanced, they use the same flywheel and harmonic balancer. The 410 & 428 are externally balanced and have a weight on the flywheel & balancer. Could be the pilot bushing is worn or was left out Just a guess, (i've ran into it before).

[Racer Z]

Does it vibrate only while you drive?
If so then start checking the driveshaft, U-Joints, the middle driveshaft support. If that all seems good check the tires for separation, balance and check the wheel bearings. Oh, yeah, check the rear tranny mount too. Might as well check the motor mounts while your at it, but those don't usually cause a vibration.

[gregamorton]

yes it vibrates while going down the road but if I throw it out of gear and coast it doesnt. But when I add gas again it starts vibrating or if sitting still and I blip the throttle it vibrates. It makes the most sense that it would be something to do with the clutch or like brokenarrow said pilot bearing. Are the pilots in these engines just brass bushings or are they roller style bearings?

[Brokenarrow]

You can get roller-style pilot bearings, but bronze bushings are the norm. If it's not the pilot bushing it could be a clutch problem. Or possibly the wrong flywheel and/or balancer.

[70_F100]

Since you can get it to exhibit the vibration while sitting still, I would start with ignition.

Any ignition component can break down under a load, emulating a vibration, when it's actually a misfire.

[gregamorton]

sitting still idling it is as smooth as can be, but when you give it some throttle it vibrates.

[Brokenarrow]

sitting still idling it is as smooth as can be, but when you give it some throttle it vibrates.

70-F100 is right, It could be a miss causing it. If it's bad enough to cause a vibration you should be able to tell by listening to the exhaust. Had a friend years ago that had a 302 with the same problem as you're describing. Turned out it had two piston skirts in the oilpan.

[Crazymike187]

Not wanting to hijack your thread but I am also having the same vibration during acceleration but it only happens when I hit 45 through 55 mph but then when I reach 60 mph plus then it stops. My motor mounts are ok I had my cousin that is mechanic to take a look at but other than that I don't know what else it could be?

[gregamorton]

usually when it is at a certain speed it is a tire or the drive train out of balance. I had a not on a tire not to long ago and it only seem to make a noticable vibration at lower speeds.

[fordman]

Not wanting to hijack your thread but I am also having the same vibration during acceleration but it only happens when I hit 45 through 55 mph but then when I reach 60 mph plus then it stops. My motor mounts are ok I had my cousin that is mechanic to take a look at but other than that I don't know what else it could be?

yours could be a tire. but it could also be in the steering system tie rod ends king pins so forth. or it could be a spark thing liek said about. my 94 F250 does about the same thing. either the trans or motor vibrates badly when the truck is going down the road. i was told to change the spark plug i didnt i put trans shake fluid in it and that stopped the problem for about 2 weeks. i did the fluid thing again and i got another 2 weeks. finally i changed the fluid and added the extra vibe fix fluid and that didnt work at all this time. i have not worked on the truck since.

Guys I have got a new crewcab 71 and have the engine running super smooth and when I take off and start gaining rpm it starts vibrating. I thought at first it could be the clutch but it is suppose to be new and new throwout bearing. I took it this morning to a real good mechanic we have in our town look at it and he got in and played with the rpm a little and the clutch and he said it felt like it had the wrong balanced flywheel in it. My question to yall is the a difference in the 360 or 390 flywheel? I dont know what it is. The factory engine showed to be a 390 but the previous owner said they put a 360 in it. Just trying to figure out if I need to pull it down as the vibration is bothering me.

i would check the spark. that is the way i am leaning. the wrong damper or flywheel should do it all the time the engine is running.

[gregamorton]

I put new wires on the truck today and it runs even better but still has the vibration with rising rpm. I did notice when I took the coil wire off the end had clear fluid on it. I dont know if it is something that helps with conductivity or if the coil is leaking something from inside the plug area. Any body ever seen this before?

[fordman]

replace the coil it is bad.

[gregamorton]

you think that could be the issue? So when the coil leaks it is going bad or could be getting hot? I know that the duraspark thing usually goes bad soon after it starts draining out on the inner fender of the dent model trucks.

[fordman]

when the coil is leaking the fluid it is going bad.