Excessive play in transfer box KZJ90

[Shayne]

Sorry Rich i hadn't seen your post as you can see from my last post i'm still searching for possibilities . I will mess about with the camera but hopes of a cheap fix have pretty much died . Whats doing my head in is the bang only happens when i release the clutch -

open or closed centre diff makes no odds . Freewheel and jump on the brakes no bang . Tickover to floor it no bang .

But its not the clutch , it can't be if removing the front prop cures the problem surely ?

I will never get my head around how the transfer box works unless i take it apart but Bob's kind warning against using the centre difflock to hold the the flange while undoing the stake nut with a power bar makes me think the force of this bang would almost certainly trash the box in short order if the fault lay within .

 

[StarCruiser]

I've watched your first video of the transfer box and I have gained two things from it.

1, it's not in the transfer box because even before you start the engine, as you check for neutral, the slightest movement is observed ON BOTH FLANGES. If there were any backlash within the T box this would not happen.
2, the clunk is far too low down in the sound spectrum to be something in the drive train and is from somewhere remote from that video.
3, you have a Sony stereo fitted.


Therefore the problem is a large lump hitting another large lump. For my money, that rules out the lions share of the drive train.

Your initial thoughts on a rubber being the problem were closer to the scent IMHO.

I'm off to look again and see what I think is doing it.

 

[StarCruiser]

Take similar videos of front and rear axles. In board of each wheel, so you can see the suspension above =4 plus one each of the doffs with clear views of the flanges entering the diff casings.

I would come and lay under your truck myself while you did it. I'll bet it would soon be located by sound.

Vids should be a close second. Make sure we can identify where each was taken. Speak each ones location before you get in the truck and try and replicate what you do to be constant across each of the tests.

 

[BobMurphy]

I'm off to look again and see what I think is doing it.

It might be worth checking the engine mounts, in particular the N/S one.

I once had a mounting become 'unbonded' on a Volvo 240 Estate, while towing horses. There was a loud bang when taking up the drive but inspection showed nothing - because the engine was happily keeping the two halves pinned together when not under load.

On that motor the cam box was hitting the clutch master cylinder when torque reaction caused it to pivot over the intact O/S mount.

Bob.

 

[Shayne]

Everything is telling me it has to be the front diff , all is well in rwd only .

What does not figure is this truck has to my mind lived its life as a glorified ford fiesta and these diffs are strong or else i would have had about 10 replacements in my own truck by now .

I am back to thinking about the crush sleeve (front diff pinion spacer) i believe it is imperative that this be torqued to the absolute correct setting as it will crush to set the pinion on the crown wheel at an exact specification .

I'm just struggling to picture what would happen if it were reused following a change of oil seal resulting in either it shortening beyond what it should or not being torqued up tight ?

 

[Shayne]

Can i jack the engine up on the oil pan Bob ? inspection without spanners is proving pointless ?

 

[diggerdave]

I'm just struggling to picture what would happen if it were reused following a change of oil seal resulting in either it shortening beyond what it should or not being torqued up tight ?

That would cause excessive backlash between the pinion and the ring gear, resulting in a clunk. However, I think you would feel in-out movement/end float at the pinion flange wouldn't you? And the diff would be noisy, although distinguishing it from tyre noise is probably difficult unless it's really bad.

 

[Shayne]

I think you would feel in-out movement/end float at the pinion flange wouldn't you?

Good question ?

 

[StarCruiser]

Good question ?

Something I was going to suggest you look for. As the crown wheel and pinion are helically cut, the torque of the shaft would likely cause longitudinal movement and a clunk.

I also thought of engine mounts but have discounted that as there is no movement in the engine in your first video. Worth ruling out by putting a jack under the sump with a block of wood in between.

If I'm right in thinking, the clunk happens in both forwards and reverse doesn't it?

 

[BobMurphy]

Can i jack the engine up on the oil pan Bob ? inspection without spanners is proving pointless ?

Yes, but you need to be careful. As StarCruiser says - spread the load with a block of wood and don't try to raise it very far - you don't want to burst a perfectly good engine mount .

Bob.

 

[Shayne]

Yes clunks when clutch is released in reverse but you wouldn't notice unless you were looking for it

 

[StarCruiser]

Yes, but you need to be careful. As StarCruiser says - spread the load with a block of wood and don't try to raise it very far - you don't want to burst a perfectly good engine mount .

Bob.

It doesn't take much to see in actual fact. If the whole truck starts lifting on its springs while you watch the engine stay level, they are all ok. A couple of pumps will cant it over to one side or up at the back a fair bit very quickly.

 

[StarCruiser]

Question for you Shayne, think I know the answer to it, but is the clunk louder inside the car than what we can hear on that first video of yours? I reckon you're going to say it's far more noticible.

 

[Shayne]

I'm deaf to 50% of tones so can't trust my own words here but while driving its a muted but solid thud and the dash rattles . I didn't get at it today as there was somebody busy in the lane out back .

I imagine i could replicate the noise in my own or any other truck by slipping my foot off the clutch while in gear and stood hard on the brakes . Might need to add a little throttle to up the volume ..... but i'm deaf

 

[Shayne]

That said i could drive you around town in it without you noticing anything amiss i just need to match revs with speed .

 

[Shayne]

Well the mrs just reported the dreaded diff rumble so the investigation is at an end .

The truck will be sold whatever route i take (repair or replace) and what i spend now is simply a gift to the next owner .

I could have it rebuilt and put it in my truck i suppose and swap mine into hers as both are R16 (4.100 i believe) so i would be grateful for opinions .

Aggro + time + cost - what are my options ?

 

[Shayne]

£350 delivered from a crashed truck and a guy i've used before , its a no brainer really isn't it .

 

[clivehorridge]

£350 delivered from a crashed truck and a guy i've used before , its a no brainer really isn't it .

It could be worse Shayne, are you really convinced it is the diff? I've re-read the posts on this thread and I don't have any comments on your conclusions. But it's been a long saga of maybe this and maybe that, I'm just hoping (as you must be) that this is it.

 

[StarCruiser]

Thou shat not replace what thou hast not proven to be at fault.

One of the sacred rules of troubleshooting.
I have been know to break this one, many times in fact when it comes to the Smart as sometimes you just cannot tell until it's replaced.

 

[Shayne]

It was was the singular aspect of the clunk that baffled me Clive i felt a dodgy diff with cogs spinning every which way should surely result in a continuous noise of some sort , whine-squeal-rumble-clatter something but there was nothing .