Excessive play in transfer box KZJ90

[Shayne]

One for Bob Murphy i reckon as i found this which removes the need for me to explain symptoms http://www.tlocuk.co.uk/forums/viewtopic.php?t=12037&sid=7e2c35a28a53a58f1afcc75260183b3c

and this http://www.tlocuk.co.uk/forums/viewtopic.php?t=7848&highlight=stripping+transfer+box

My own test was to park the truck facing a wall leaving a 2" gap then i climbed under the truck telling the mrs to leave the handbrake on , foot brake to the floor , engage first gear and lift the clutch until it bites a couple of times .

My diagnosis without having a clue how the transfer box works is that the chain is slack ???

So where do i go from here ?

Title is wrong its Helen's KDJ90 i'm talking about though i imagine they are identical on both trucks , can't edit titles

 

[Bob]

Hard to see how one of those chains would go slack Shayne, but I could be wrong. If its a clunky shift, and not UJ's then perhaps it's wear in the front or rear diff. If it is in the transfer box, then I'm out!!! Me no touch unless to change oil

 

[Shayne]

I don't suspect the diffs because the test i devised results from a bang that had me thinking the gearbox is being lifted off its mount and dropped back down . Only changing up in 1st 2nd and 3rd hard bang to soft in that order .

While under the truck it reminded me of an old 5 speed pushbike i had as a kid the chain tensioner was crap so if i rested freewheeling then stood up to pedal again my foot would find no resistance until the chain pulled tight .

Stretched maybe ??? i've been searching the web most of the night and its seems unlikely but not impossible if someone has unwittingly been driving around with the centre locked . UJ's are all good and even the rear diff lock works .

 

[Shayne]

Drained the box through a sieve and nothing sinister to report .

 

[BobMurphy]

Shayne,

Is this the "Knock when up-shifting that rattles the dash" problem or something else (we never did get to the bottom of that one) ??

If you think (whatever it is) is caused by a slack chain in the Transfer Box, remove the front propshaft and try driving the truck in 'HL' to see if its still there.

I have a 2000 auto Colorado coming on Monday - the owner thinks the front prop output bearings are shot. That would produce slack in the output shaft that would make the chain slack. Is there any sign of sideways movement in the output flange on Helen's ??

Nasty noises, slack and play in the drive can come from the Centre Diff Planet Carrier. Even if it isn't broken the needle bearings in the planet gears wear and get very thin with sharp points meaning that the connection between the front and rear propshafts is slack (like having a slack chain).

The Centre Diff isn't very strong whereas the front drive chain is enormously strong. I find it difficult to believe that the chain is worn (unless the Transfer Box has been run without oil).

Let's hear the symptoms .

Bob.

 

[BobMurphy]

Drained the box through a sieve and nothing sinister to report .

That's 'cos there's a big magnet in there - the steel bits don't drain out, the box has to be stripped .

There has been a bit of activity while I was pondering this one so the symptoms are a bit clearer. Driving with the Centre Diff locked shouldn't bother the chain much, its the Centre Diff Planet Carrier that breaks.

The Centre Diff is effectively a sealed drum so if something breaks in there the bits can't fall out. They lie in the teeth in the outer drum and the planet gears have to run over them. Problems then multiply.

In a straight line, the Planet Gears aren't moving relative to the outer drum - that happens when the front and rear axles take different paths (as in cornering). Do you hear any noises when cornering ??

Bob.

 

[Shayne]

Yep the dash rattle thread is pretty much right on the money but any dash will rattle with a knock that powerful going through the chassis .

Will remove front shaft tomorrow and report back . I did give everything a good rattle while under the truck but i wouldn't have expected nor looked for sideways movement at the output flange so again i will have to report back .

There's a box on ebay ending tomorrow for 200 odd quid and i've found breakers asking more for just the chain , should i jump the gun or hope he relists ? are all manual 90 transfers the same ?

 

[Shayne]

It runs perfect apart from what i first named clutch bang

 

[BobMurphy]

Shayne,

To my knowledge, all Manual Transfer Boxes are the same in the 90-Series. The Autos are a bit different as they have longer Selector Shafts with the blocks on the outside. The gear lever turret is on the Gearbox Extension - not on the top of the Transfer Box as it is on a Manual.

Thinking about it, If the Centre Diff Planet Carrier is bust, having the box in 'HL' with the front prop removed will still produce a bang. You'll be as well driving it as it is in a straight line with the box in 'HL'.

When the Centre Diff is locked, the outer drum (the annulus) is locked to the central shaft (the Sun Gear) that drives the rear propshaft. As these two parts now rotate together the planet gears can't rotate either as their outer track (Annulus) has about four times as many teeth as the inner track (Sun Gear). The Planet Carrier then locks up.

The problem with that is that there is a lot of strain on the Planet Gears while the front wheels are being driven at the same speed as the rear ones. Any slack in the Planet Gears will show up as 'shunt' when the Centre Diff is locked.

For £200 I would buy the box - I'll buy it from you if you don't end up using it .

I could do with a couple of spares that I can rebuild. Swapping them over is a lot quicker than me having someone's car in bits for a couple of weeks while I strip everything down and order parts .

And I thought retirement would be relaxing .

Bob.

 

[Shayne]

Been out for a bit of a play and it still bangs in HL , also in reverse which i hadn't noted before . Foot off the throttle for a pause during changes eliminates the bang yet i can get the bang parked as per the test i described earlier .

No sideways play in the front shaft and perhaps a little in the rear . About 10mm rotational play in the rear with transfer in H and gearbox in neutral with the handbrake on , the front has less .

Seems quite a few have had similar problems and most blame the clutch , curiously i'm sure the previous owner said a new clutch was recently fitted but i can find no evidence in the paperwork , maybe he like others expected a new clutch to cure the problem ?

Its also odd that neither of us is alarmed by the bang its just a bloody nuisance is all i am trying to think of a better way to explain it ..........

It's a solid thump not metallic sounding at all , its more like ... like a clutch engaging with too much force so there is no slip at all

 

[StarCruiser]

It sounds to me Shayne, like it's taking up some backlash in the whole transmission, probably in everything from the gearbox to the wheels. If you don't get any movement on driveshafts then this will be internal and could possibly be slightly slack bearings. Does it do it when it's been for a good run and is nice 'n' warm? Another test could be if the transfer gear lever has a neutral position, pop it in that and see what noises come from what gearbox (that's if you can tell with the engine running). I would have thought a new clutch would show little or no difference TBH.

 

[Shayne]

Sat there this morning staring out into the rain wondering what would cause a bang so powerful it rattles the whole chassis , dropping the gearbox from a 6 inch height onto a thin rubber chassis mount might do it but that isn't the cause . There is no indication at all there is anything wrong with the drive train and no single component failure could replicate the chassis being hit by King Kong with a bloody great rubber hammer . Which leads me to think it might be everything rather than a thing .

I almost regret you said it before me Starcruiser the web is full of people describing a similar problem if you swap and change search criteria clutch or drivetrain - noise - clunk - bang - thump and god knows how many other variations from chevys to vauxhalls but nobody not a single person offers an explanation or cure .

I changed the gearbox oil today and with the truck perfectly level left to right and very slightly nose down i got an oil shower removing the filler cap , way to much oil in there

 

[StarCruiser]

You've looked at engine and gearbox mounts? Put a jack under to see if anything moves?

 

[AndyCook]

Have you checked the prop UJ's for slack : wear ?


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[Shayne]

I can't move the engine by hand at all but with the engine started it rattles away quite comfortably without vibrating anything it shouldn't . Props and joints all seem good , trailing arm and panhard bushes do need changing but the axle doesn't move when clutch bites . I was going to video the parked test today but i couldn't get the bang while parked which why i decided to change all the oils .

The parked test yesterday showed both prop shafts turned when the clutch was released from 12 oclock to about 12.15 before engaging with a bang .

 

[StarCruiser]

Automatic freewheel hubs?

 

[Shayne]

Its a manual but i am still thinking about the chain , the muted thud sound fits and would be amplified by a synchronized meshing of the whole drivetrain . If the chain was slack would it drop like this https://www.youtube.com/watch?v=QSwJxCnOOXc when freewheeling with the clutch pedal down ?

The faster the engine speed the harder the clutch bites which makes sense if it encounters very little resistance for a fraction of a second before the chain pulls tight .

 

[Trevor]

Buggered flywheel? I know dual mass when seized can give a thump. Yours will be single mass but I don't know what symptoms you'd get if it's cracking or got high points on it.

 

[Sag]

Hi Shayne,the automatic free wheeling hub i think starcruiser is on about is at the front hubs,they used to be manual years ago where if you wanted 4wheel drive you had to turn the hub from free to lock for it to engage,now though they are all automatic,it was meant to give you more mpg but used to seize up if not used,hope you get to the bottom of it buddy.

 

[steve allard]

I had one car that had been driving forever (about 1000km) with the centre diff locked and everything had been hot and horrible. The box was discoloured and the chain was stretched. The cost for a chain was about $250 and time was about 5 hours. sorted it out nicely