Outer Limits 4x4 Board

Hey guys,

I cant work out where its coming from but in any gear, from 2000-3000rpm i get a vibration through the whole car. It doesnt sound like the engine cos i clutch and it goes away (doesnt do it on the driveway in neutral either), although it only ever seems to happen under load (accelerating). it also goes away on coasting in whatever gear.

Most noticeable in 4th 2500rpm and 5th 2000 rpm (60km/hr), you can feel the whole car shake, feels like going over bumpy road even though im not.

Anyone got any ideas? most recent mod is welded rear diff.

uni's?

they look clean as, but wouldnt a uni shake no matter what?

my car did exacty the same thing..it was a uni in the drive shaft between the gbox and tcase. it had worn away and the 2 Ushaped parts of the drive shaver were rubing causing the vibration...gen unsder the car and check all the unis. especialy the uni in the drive shaft between the gbox and tcase.

the tcase to tailshaft uni has a bit of grease coming out of it, the joint itself looks great - the grease is coming from the actual shaft, kind of looks like some grease came out while driving cos its flicked onto the body. not sure if this is a result of the tailshaft being greased or something after the diff was taken out by the mechanic or not though???

how about if i jack up the rear and rev it up - reckon id get the vibrations?

alien wrote:the tcase to tailshaft uni has a bit of grease coming out of it, the joint itself looks great - the grease is coming from the actual shaft, kind of looks like some grease came out while driving cos its flicked onto the body. not sure if this is a result of the tailshaft being greased or something after the diff was taken out by the mechanic or not though???

how about if i jack up the rear and rev it up - reckon id get the vibrations?

did u actually feel the drive shaft ie try to turn it?
there should be no movement


u cant tell buy just looking

sure did - wont move a bit.

ok - jacked up the rear n chucked it in 4th and revved to 2500rpm.. the vibrations are coming from the diff - theres the usual kinda backlash as it receives drive, but it seems to continue shaking back and forward (diff rotating up/down by a few degrees) causing the springs to move a bit - hence the vibration.

now the rears just been welded - could it be incorrect backlash setting on the diff or something? or am i looking at buying a new diff centre cos chances are it buggered?

wen a uni on my zook wore out it would be fine in reverse and when using engine braking as it was only the one side of the uni that was worn. the uni may sit right but wen under drive it may move out taking up the slack.. on flat ground with the car in gear push it back and foward and chec the unis they may have movement in them. not sure what else would cause this vibration unless the bolts in ur drive shaft are loose?

like i said its definitely coming from the diff - it happens minorly just at idle, gets worse to 2300rpm then gets better until disappearing at 3000rpm... all the unis on the shafts are tight as and not looking at all worn. it looks like the diff is delivering the load through the springs into the body, and obviously into the wheels too.

gonna go wheeling today - will see if it gets worse.

If the rear tailshaft was removed, was it put back in the correct phase,
ie, match marks on the spline lined up?
Is the shaft itself straight?
Peter.

Another possibility is that the side gears didn't end up exactly in line when you welded.

The vibration may be when it reaches the resonant frequency of the axleshafts.

The fact that it happens in both 4th and 5th should exclude everything from the engine down to the output flange of the gearbox

i had a customers car come in last week with the same thing happening i checked the inter unis and looked and felt fine but when i pulled it out and removed the caps it was obvious one of the pins had fallen out, replaced the uni and all better now

Did it do it just when u welded the diff?? Could it be the weight of the welds unbalancing everything else??

Check the U bolts are truly tight on the back axle-this has caught me out in the past!!

if your checking unis, the car has to be in neutral, or the uni will be locked and you wont be able to feel any play.

just a thought




Mock

i had similar problem. it was the carrier bearings in diff centre

last time this happened to me the answer was simple, a wheel out of balance. it had thrown a weight and as it got worse it through the rest of them as well. it felt like a badly corrugated raod with the front wheels feeling like they were going airbourne on me.

it cant hurt to check, and it did the job for me.

thanks for all the suggestions!

had another go at rotating the shaft again today after being offroad all day yesterday, and its now moving about 1/32th of a turn, probably about 5-10mm movement.

theres also more grease come out of the uni at the tcase end. seems to be the problem =)

oh and i checked teh wheels when i had it jacked up - they werent outa whack at all (suprising considering the poundings theyve received!)

i hope that includes backlash movement aswell, sounds like a preload problem to me

thats lying under the zuk, grabbing it, and rotating it as hard and fast as i can... about 5mm movement before it stops, then moves 5mm back to where it was.

will keep driving on it till i can get to the mech. doesnt appear to be getting any worse.

I have the sam eproblem atm in 4th and 5th as u say when revving, neutural and coasting are fine, i wil check that shaft you guys mentioned.

It started for me when i put bigger tyres on :/

getting mine checked out tomorrow, let me know what solution to yours is dude...

oh and it does happen in 1st, 2nd and 3rd, its just that you rev past those gears really fast so its only one wobble before you're in the next gear... i tested it today and its any gear under acceleration at 2000-3000rpm. still worse in 4th and 5th though.

im pretty confident its the uni - theres even more grease come out of it now.

I gave gearbox>tranny case shaft a twist and there is a a bit of movement i think thats whats making a clicking noise when i rev or change gears etc, prolly not very good for it, im getting my far looked at tomorrow, need brakes and clutch looking at too :/

ignition leads on mine look to be rooted - another possible cause - will put newies on tomorrow and see what happens!

well, ignition leads have fixed the problem... of course, they only shat it under load... but with new ones on for $48 - thats a dam cheap fix to what looked like a much more serious problem!

so there we go =) another solution to add to the list of causes of driveline vibrations.

Ignition leads o_0

WHere exactly are these on the engine? between the key and battery or starter motor???

I think he means the spark plug wires. LOL

IE: between the plugs and the dizzy

cheers

How do cables cause vibrations through bits with no electrics in them ????

because more voltage goes through them under load, causing the engine to miss and skip etc... however when not under load theres less voltage going in so it wasnt noticeable as an engine problem right away.

ive also replaced air filter on carby, as that was clogged and causing a bit of a lumpy ride too...

but the leads fixed the vibration for sure.