Post Lift Noises Isuzu MU

[Jimmu]

I have done a 2.5" suspension lift front and rear and am now having what I assume to be tailshaft issues.

I am guessing that being a SWB the lift has changed the tailshaft angle more than it would on a LWB vehicle.

Under load it is fine but when you back off a sound that could only be described as 'graunching' comes out from underneath the vehicle.

I noticed after the lift that the shaft had moved a fair way back of the slip joint so I fitted a spacer which brought that back to where it was pre lift.
But that did not fix the noise.

Do I need to get a new shaft with a DC on it? Or maybe spacers on the gearbox mount (To bring the angle back a bit) as was suggested to me last weekend?

Who in Brisbane would you suggest for the driveshaft work if it is required?

Thanks

Jimmy

[Beastmavster]

Ok.

First thing I can think of is to check your uni joints. They may still be within angle tolerance but the poor old (probably 15 year old) uni is pretty worn out.

You can get single unis (as opposed to the expense of DC's) that can run higher angles than stock too.

You would then consider using gearbox spacers etc before double cardan joints.

[DamTriton]

One option would be to lengthen the upper link(s) in the rear to tilt the pinion up. It's usually the pinion end of the driveshaft that causes the most grief as it not only rotates with vertical axle movement, but also rotates due to compression of the bushes under accelleration/decelleration.

If you do this make sure you have clearance to other items such as the shockers against the axle. You will find it will not take much of a lengthening to have the desired effect. I had similar vibes when I did a 2.5" lift and found that all it took was an extra 8mm on 330mm original length.

Tough Dog make a Hilux rear diff locator (part number: TDDL-001) which may be about the right length. You can get the correct sized bushes (I.D. bolt diameter) made up to fit at most suspension places.

[vorno_18]

as said before check your uni joints as they have been turning at a particular angle for the last 15 or so years and they have worn into that spot and changing the angle will cause them to move differently and cause a noise

the day i lifted my cruiser i had a pinion seal leak replaceed the seal and its been fine since

suggest you remove the shaft and turn it over by hand off the car

[Jimmu]

I am not exactly sure how to tell if the uni is worn. But being a 93 model and being that the uni looks original I would guess they have seen better days.

Who is Brisbane would you reccomend to replace them with new units?

Damkia I cannot work out what you mean sorry.

Jimmy

[-Scott-]

Under acceleration the rear axle is trying to rotate in one direction, and on deceleration it tries to rotate in the opposite direction. If your bushes are shagged, it will rotate further between load/no load conditions, which may be just enough difference for the unis to complain, or not.

DAMKIA is suggesting a minor geometry change to slightly alter the angle at which your rear uni runs. It may fix the noise problem, but if you move it too far you risk introducing vibration problems as front and rear unis fight each other.

Essentially, take it to a reputable suspension place for assessment. NOT Pedders - you'll walk away with a four figure quote. For initial assessment, Fulcrum at Moorooka would be my first stop.

Cheers,

Scott

[rOd]

Damkia I cannot work out what you mean sorry.

Jimmy

He may not be aware that MUs have leaf sprung rears.
What he suggested is a remedy for coilsprung 4x4s.

[Jimmu]

Thanks for the extra explanation. By 'Links' do you mean the leaf spring shackles or were you referring to a coil sprung vehicle?

I have seen some wedges advertised that adjust the rear diff angle maybe that is the go.

I had a good look at it again today. The angle of the shaft does not seem extreme, so I pulled out the shaft and checked the Unis for play. They seem to be tight. There does seem to be a bit of play on the spline / slip joint where the shaft joins the gearbox though. Which is also where the noise appears to be coming from.

I will head into Fulcrum on your suggestion tommorow and see what they have to say about it.

Thanks

Jimmy

Edit: Started post before above post. Re Coil / Leaf