95 150, 4.9 2wd, 5-speed, all stock

I have notice a vibration while I am driving down the highway.
kinda like hitting a rumble strip about every 30 ft. usually around 70 mph

I also have noticed if I am sitting still and rev up the motor @ 3000 the motor starts shaking pretty bad. this happens in a very narrow RPM window any ideas

thanks
Chris

 

I would take a look at the motor mounts first. Check to make sure they are intact with good rubber. Don't forget to look at the tranny mount as well. Oil, grease, & salt all tear down rubber & eventually will rot it out.

Walter

 

In addition to the above, I would check the carrier bearing mount. This is the rubber-mounted bearing under the truck where the two halves of the driveshaft meet, i.e., the front half coming from the tranny joins w/ universals to the rear half coming forward from the rearend.

While I don't think this is it, as when mine was bad it was a constant, heavy vibration at highway speeds, rather than intermittent, as your is, if I read you right, I would still check it. Mine was bad when I bought the truck, so I don't know what they're like when they first start failing.

BTW--the bearing itself was not the problem in mine--the rubber doghnut itself "packs down," so not round but slightly oval inside the mounting strap, so that the shafts get to dancing up and down. It should be round, tight, etc...

Let us know and good luck!

BigSix

 

the mounts look good no cracks, would a clogged injector do this?

I do not have a carrier bearing?

 

Check all the engine accesories like the water pump , alternator , air pump etc for a bearing that has failed in them . Since it occurs when the engine is running that would be a good place to start . Does the vibration change any when the truck is moving ? Either or both the driveshaft U joints will cause a vibration if they are failing .

 

[font size="1" color="#FF0000"]LAST EDITED ON 22-Feb-01 AT 02:02 AM (EST)[/font][p]I don't see it being a clogged injector, as it only happens at one RPM.

But as far as that goes, okay, it does it at @ 3,000 RPM when in neutral, but you didn't say what RPM it occurs at when you are going 70 mph. Please clarify.

Also, when it happens at 70 mph, see if you can get it to do it at 70 mph while in neutral (one big hill needed) and also (if you can) run in a different gear at 70 and see if it does it.

BTW--no carrier bearing? My shortbox '81 has none either, b/c it's a one-piece driveshaft. What box length do you have? If 8' box, and you've verified you have a one piece driveshaft, then I guess the '95's are different from the '88's in this regard, which I find kind of surprising.

Let us know.

 

How about wheel bearings. Maybe check your tires as well for damage. Is the rumbling there when the truck is still & at 3000 rpm or is that just engine shacking? If no rumbling, then it must be something along the drivetrain. Otherwise you would rumble while sitting.

Walter

 

For the vibration, my hunch says its the U-joints like Paul said. Have them checked out at a brake shop or tire store.

As for the engine missing at 3 grand....how's your tune-up package looking? Plugs,wires,rotor,filters,fuel quality...etc.

Lets us know what you find!


1981 F-150 2WD STYLESIDE P/U
4.9L 1 BBL CARB
C6 AUTO
2.73:1 LIMITED SLIP REAR AXLE
STABILIZER BARS FRONT & REAR
6100 LB GVWR PACKAGE
ORIGINAL OWNER
193,000 PLUS MILES
100% STOCK & UNREBUILT
BUILT FORD TOUGH!!!

 

thanks for the great ideas, this is what I was hoping to get,

ok let me see if I can address all of you...

I checked my pulleys and all of them turn smoothly and straight, but ... the power steering pump turns kinda hard, it will not free spin like my Trans am on does. is this normal?


1995 f-150 xlt 5 speed(Mazda=junk) 4.9l 8' bed single part drive shaft "BIGSIX' if this is strange then that is just how this truck is. everything is STRANGE on it. the wiring colors are all different, confirmed by the alarm installation expert, the clutch is a 11" that came from the factory, confirmed by the ford dealer when he replace that back in august, my serpt belt is even longer than the normal application. it seems I have an extra smog pump. NOBODY CAN EXPLAIN THIS. I was thinking California emissions? somebody also told me the truck was built in Canada FOR Canada! but I am not sure...

I have no tach so my rpm @ 70 is strictly a guess. I just went by the sound of the engine!?... if I push in the clutch @ 70 the vibes are still there.

my ujoints as well as the tires were replace back in November (had the problem before then and thought that would fix it)
I did however craw under and look... the joint are tight and I shot some grease in for good measure

I gave it a full tune up: cap rotor wires, but I do not know what to unplug to set/adjust the timing. my other cars you have to unplug something like a spark advance unit. any descriptive help in this area would be greatly appreciative.


whew... keep the ideas coming,
and thanks

 

[font size="1" color="#FF0000"]LAST EDITED ON 23-Feb-01 AT 05:11 AM (EST)[/font][p]Wenger:

Okay, I'm running out of ideas--I think more description of the problem may help. My initial reading may have been too hasty. I assumed the shaking at an estimated 3,000 RPM and the rhythmic vibe at 70 mph, were, in your opinion, the same situation. That was an error on my part. Just confirm--they don't sound the same, right?

So--the timing would not cause a vibe at 3,000 RPM, IMHO, UNLESS perhaps it's "walking" around on you, i.e., randomly changing, and no I haven't heard of this in non-mechanical ignition systems. One of the guys w/ a newer truck can advise you re: how to check it, as on my '88 there is a "SPOUT" connector your pull apart, in the wiring harness near the distributor, to check timing. I know there's more to it b/c I've done it, and I would review it for you but who knows if a '95 is different (when aren't they?).

You can probably call Ford and have them tell you if your VIN was made for the Canadian market. This could mean a number of subtle differences, potentially (I beleive this varies by mfr.)

Don't laugh, but have you checked your lug bolts? I didn't once, (another one for the "Blunders" thread!) and it'll vibrate all right, but I could feel it at 20-30mph. Just a thought.

Make "motor noises" for us or something, to describe it more, so we're "right there with you." I need more info, otherwise, I'm outa ideas.

 

There should be a vacuum line going to the distributor base. Unplug the vac hose and plug it with a golf tee or a piece of tape. Then check your timing.

Missing @ 3 grand: I doubt that it's your timing but check it anyway. Try using some "dry gas" in the tank to absorb any moisture that may be in there lingering. In the DARK pop your hood, run the engine, and look for any signs of spark arching in your wires. Even though you said they are new...you could have a bad wire. Look where any wire cross another wire for signs of melting. Try running some quality fuel injector cleaner also.

Vibration: Could your vibration be coming from a bent wheel rim? You said you replaced your tires in november....Did they high speed balance your tires at the same time?

You might want to check your brakes for warped rotors or out of round rear drums. How is your driveshaft? Are the balance weights still welded on it?

Keep us up to date on your progress when you can.

1981 F-150 2WD STYLESIDE P/U
4.9L 1 BBL CARB
C6 AUTO
2.73:1 LIMITED SLIP REAR AXLE
STABILIZER BARS FRONT & REAR
6100 LB GVWR PACKAGE
ORIGINAL OWNER
193,000 PLUS MILES
100% STOCK & UNREBUILT
BUILT FORD TOUGH!!!