Outer Limits 4x4 Board

Folks,

Have failed to get the paj through low volume vehicle compliance here in NZ. I wonder if anyone else has encountered the same problem?

The inspector is unsatisfied with the pinion angle of the rear diff as a result of about 55 mm of lift on the rear (firmer cobra springs). His feeling is that it introduces excessive driveline vibration. Strikes me that this is a fairly run-of-the-mill modification...

Is this likely to be the cause of the vibration? Could it just be worn out transmission mounts or the like? Vibration is worst when vigorously accellerating from rest and results in a knocking sound from the transmission tunnel and a lot of transfer case lever wobbling.

Has anyone done pinion angle correction on a paj? I'd love to be able to just get a set of offset nolathane bushes for the control arms and be done with it.

sounds like flogged out bushes\mount of some description to me.

or maybe a stuffed uni joint

check your rear driveshaft uj. i failed my wof on that a few years back. it was vibrating on acceleration. also check the transfur case side mount. seemd to go through them on mine also.

good luck.

Sam

I've had a look around under the truck at the drivetrain mounts and I think I found something that _might_ have something to do with it...



This appears to control the drivetrain torsion, well, used to anyway. I guess it's just clonking around in there and making a lot of noise.

I've read that those mounts are designed to flog, that the inner ring is normally loose like that. If you decide to replace it before the next inspection, don't do it a long time before - as it may not last long.

Excessive pinion angle will increase vibrations, as the inspector said. I have a similar problem.

Apparently there's a brass bush in the output of the transfer case which wears and contributes to vibration. I don't remember all the details, but it's described somewhere here - try your luck with the search function.

The other option is a CV joint on the transfer end of the prop shaft. I believe NL shorties came with this, but they won't fit the smaller transfer in 3.0/2.5 models. You could try a custom shaft?

Mine has a CV on the front end, they are standard with the 3.5 shorties.

The paj does have an odd pinion angle with the driff end pointing straight at the transfer case and as you lift it, it just amplifies the problem at the T/C end.

I was mine on here that I had a new bush machined, made it out of brass, somewere here is a thread

edit* Found it
http://www.outerlimits4x4.com/phpBB2/ft ... =vibration

The 3.5's also don't have that bush that is worn out. To see if it is that bush, before you replace it, jam a piece of wood into it (shaped like a wedge so its hodl tight) and see if it stops.

yip thats the bush i was meaning! but im on my second and the only vibrations that ive had that remind me of what you describe were caused by the uni joint on the rear drive shaft.

so are you going for a WOF or getting cert? either of them the inspector should have been able to at least point you in the correct dirrection of the problem.

I replaced the whole extension housing in mine. Vibration became better but was still there. I have about 4" of lift in the rear, so i fit a re bushed GQ panhard rod to centre the diff and the vibration went away. I still have a fair bit of play in the extension housing which causes the seal to leak more frequently than normal and also gives me a slight harmonic vibration at 100kmph. The stabilizer mount you have shown does bugger all. I replaced mine chasing the vibration and it did bugger all. It is a very flimsy mount and is more of an anti harmonic than anything. I also replaced the main trans mount which helped as well as it had sagged.

Since I got the bush manufactured for mine the play in the extension housing is non existant.

NJV6 wrote:Since I got the bush manufactured for mine the play in the extension housing is non existant.

You run a tailshaft spacer?

that gearbox mount is not faulty if you look at a new bush it will be thin enough to put your finger through and tear it.within a week it will look like the old one.

hudson44 wrote:

NJV6 wrote:Since I got the bush manufactured for mine the play in the extension housing is non existant.

You run a tailshaft spacer?

No

Wacko, I'm shooting for certification at the moment. All the inspector really said was the pinion angle of the diff is not exactly ideal, and that he's concerned that it's causing excessive driveline vibration.

I'm only running 2" lift in the rear, so that's only about 4 degrees increase in prop shaft angle, plus it sounds like there are plenty of pajeros out there with plenty more lift that that...

NJ, you sure are right about the strange pinion angle; Looks pretty much by eye that the pinion is pointing directly at the T/C output. This would make sense if there was a CV at the T/C end like yours. From what I've heard, with u-joints at both ends, it's important that the output shaft and the pinion shaft remain parallel to avoid vibration - this is one of the downsides of 3-link suspension I guess.

So, just so that I know we are talking about the same kind of vibration here:
On hard(ish) accelleration from stationary or very low speeds, the transmission gets a pretty good wobble on and make a decent clonking sound. Never a problem at normal road speeds, even when accellerating hard. Seems worse when also corning. Imagine for example pulling out across traffic results in good ol' rattle.

Does this mesh with the symptoms of the worn output shaft bushing? I have given the prop shaft a decent shake and I can't feel any play.

How would I go about investigating the state of the uni joints?

Had an email conversation with someone from Redranger who do the nolathane bushes. I have a set of these at the ends of my trailing arms at the moment. They make offset bushes for all kinds of vehicles to modify suspension geometry. Of course they don't do this for mitsi's, but if they did it sure would be an easy way to adjust the angle of the diff slightly.

I guess there's no way for me to tell if this is going to help, but I'm tempted to see if I can find someone who can machine polyurethane who could then just copy the one's I have and bore them off-centre by about 6mm. I can reuse the crush tubes from my existing set.

Rather than offset nolathane bushes could you have some castor correction plates made up?

Yes, I realise castor is a steering thing - but if it's about rotating the axle to alter the pinion angle, the principle should be the same. A laser cutter should knock them up pretty easily - just need somebody to draw them up.

The issue could be the minimum rotation you can achieve - it may be too much rotation, and over-compensate for a small lift.

If you are going to play around with things like that (plates/bushes) then the panhard will need modifications also otherwise it'll be sitting in the wrong twist angle.

I'd try new U/J's 1st. Then realise there will always be some vibration - there is a big weight hanging off the rear of the transfer case beside the output housing from standard so Mitsi knew there was an issue.

Mine vibrates under acceleration also. Get you certifier to look under a normal Pajero and see that the pinion angle is also not the best on them either.

Glen

Okay, so I had another look under the truck, this time without any load on the driveline from being in park (oops ). Sure enough, there is some movement in the T/C output.

Sounds like I might need to look into solving this extension housing thing. Starting to get a little out of my depth...

I might try reindexing the tailshaft connection to the diff as some have suggested, but I don't have much confidence that it'll make any difference. Worth a try tho!

NJ, do you think it would be possible to retrofit a CV joint from a 3.5 paj in place of the u joint from an older tailshaft? Wonder if the shaft into the T/C is the same...

No they are different.

It is normal to have some movement in the output housing, don't replace that until last resort. Were the vibes there before the lift?

To be honest, I can't really remember. I didn't _notice_ anything in particular, which leads me to thinking that perhaps it's worse now...
I'm half tempted to put the old springs back in to see.

I am waiting on a quote from dotmar, who can supply machined polyurethane, for offset control arm bushes. I'm anticipating they will be prohibitivly expensive.

Alright, Dotmar want $400 for a set of 4 half bushes. Ouch. Maybe not.

Spun the driveshaft around 180 on the diff and couldn't tell any difference at all. Perhaps I'll try the other two positions. I'm also going to try loading the back with as many heavy friends as I can , see if that has any effect.

Well, I put rent-a-crowd in the back of the paj, plus a pile of dive gear, must have loaded the axle a good 300 kg. This dropped the ride height by 45 mm, nearly back to pre-lift height.

No appreciable improvement in vibration, plus after flogging the poor truck around with the brakes on, I've now got oil coming out the back of the transfer case. So I guess with the slop in the output shaft and the resulting vibration, the oil seal must be getting a beating.

Supposing I get a complete new extension housing, is it much of a job for the hobby mechanic to do the swap? Any special procedures/tools?

hey man.. before you go to all these troubles of new extension housing and the replaceing entire driveshafts..... have you replaced the drive shaft ujs yet? simple job if you have a vice and a socket set and maybe an extra set of hands.

and come to think of it, why did you decide to get cert? did you fail a WOF or is it a do it now rather than fail later? i never had any trouble with wofs when i was getting them and had the mods you sound like you have. ball flip, springs and 33s...

Hey Wacko, well, I've had the shaft out, and the u-joints feel really smooth and I can't feel any looseness in them. I don't know whether this is any indication of their condition or not, but I thought maybe they are okay.

The puddle of oil out of the T/C is what's really prompting me to do the extension housing. Good news is they're only $300+gst from mitsi.

As for the WoF, yeah, definitely a case of making it ligit so the wof guy can't have a grizzle at me. I've had it through the wof with the ball joint flip and springs, but I thought I'd be pushing my luck with a body lift and 33s.

Anyhow, get my shiny new housing on Monday. Fingers crossed.

hope the housing comes with new seals.

WACKO wrote:hope the housing comes with new seals.

Will need to be purchased separately.

Indeed the seal is a separate item.
Installed, no more leak or play in the output shaft.
However, no improvements in vibration.

Time to replace the u-joints I guess.

Update: driveshaft is at the driveshaft shop getting new joints and a balance. The guy said there was some nitching going on, so might as well get it done while it's out.

Further investigation reveals that the engine mounts look stuffed: http://www.outerlimits4x4.com/ftopic195899.php. So this is my next task.

Looks like I'll be swinging a spanner for christmas!