Harmonic vibration at 110km/h

[Jayce]

Hi all

I was wondering if anyone could be able to shed some light on the following problem. when cruisng at high speeds (landy relative) the following happens to me.

1. 95 kms/hr small vibration felt (sound almost like a drone), frequecy low
2. 100 kms/hr vibration louder, frquency medium
3. 110 kms/hr vibration, through entire body, seat and my teeth, frequency high, to the point that is almost becomes a constant pitch.

It almost feels like something is not balanced, but then I am guessing hense me asking the guys in the know.

Regards

[Bogatyr]

Jayce,
Wow, my Series truck doesn't get much over 55mph, so under 100kph at all times...

Now, I don't recall if you have another engine in there, but sheesh, you've got to be really close to redline (4250 right?) at those speeds especially without an overdrive...

Anyway, tires would be my first thing to check. Then tie rod ends, then suspension bolts (ubolts and shackle bolts). I'm assuming you don't really feel this through the steering wheel though right? You could also check your swivel pin preload...but since you didn't mention the wheel, I'd assume it's tire or suspension related.

[Moeras]

And the winner for the fastest Series truck on the Forum is.......





Jayce!!!!

[Jayce]

Okay, it looks like I might be getting close to max revs........ I dont know, I dont have a rev counter. I was wondering if it could not be propshaft related?

But seeing that Moeras reackons I have the fasted series truck in the forum, let me raise the bar.

I am getting to 110 km/hr without overdrive. This however should be rectified as I have an overdrive sitting in my garage waiting to be fitted. If I remember correctly from the brochure, an overdrive should give me a 27.8% increase in speed. If I add this onto my 110km/hr, it looks like I will be able to get to 140km /hr.

Moving from the sublime to the ridiculous and now for the interesting bit, lets say the vibration is being caused by my crankshaft, to increase speed I should take it in so that it can be knife edge balanced, let me through in the camshaft as well at this point.
Secondly I think I must whip off the weber 36dcd I have on there an replace them with twin weber 40dcoe's, an stick this on top of a tuned outlet manifold these I also have in my garage.

Then I need to look at my roadholding, i think i will swop my 7.50 R16 for a set of low profiles like pirellis and fit some stellar mags, and fit adjustable shocks.

So what will the ultimate result be, a series 3 109 that can do 0 to 100 in just under 12 secs, over rocky terrain, and have the same fuel consumption in the region of 2.5kms per litre. I think I better fit some parabolics springs to help with the articulation and fit air suspension under my sit, so that I dont loose any teeth in the process.

cheers

[Moeras]

How about dropping the roof by a couple inches to improve the airodynamics??