KZN185 driveline clunk on and off the gas.

[floatingkiwi]

Hi All

99 surf in v good condition with 220Kkm on the clock. Always been well serviced by me.

So in normal driving (in 2wd), there is the usual amount of slight slack in the drivetrain between throttle on and off as you would expect. Now, when in 4wd (4wd button pushed in, Central diff lock not yet engaged - so basically "AWD" mode), there is a LOT of slack between throttle on and off e.g around a windy road, that quite obviously "thuds" somewhere in the drive train when I'm on and off the throttle.
It's a softish thud but quite noticeably a slack thud as if something is taking up a lot of movement between throttle on and off, and most noticeable as mentioned in the push button 4wd mode.

This is quite different from the slip joint thunk when stopping at lights (and I have a bit of that too!).

All unis excellent, Both driveshafts well lubricated. Rear diff has just been done with a locker and backlash is fine (and always was). Front diff dunno but seems all tight and good when in "proper" 4wd with the center diff locked in.
Engine mounts? I've check them and they seem fine. Pulled the rear transfercase mount completely out and it looked fine. Checked all bolts etc.
I'm an engineer and very aware of any issues in my truck - my mates in the 4wd club would probably say anal... However what I'm getting at is that I'm more aware than the average bear about maintenance and failures etc.

Are these transfers known for something like this? It really makes it impossible to drive on the road in mountain conditions where you would really like to have it in AWD mode. So much so that I'm wincing every time I get back on the throttle.

Ta all.

Matt

[sirLachlan]

Is it a auto locker or air locker in the back ? They have a lot of play in them to allow one side to disengage . Get under there and you can prolly turn the drive shaft a quarter turn with both wheels on the ground if youve been driving straight

[floatingkiwi]

E-locker, but its not that. It has been doin it well before the elocker, in fact since I got the truck at 100KKm ex japan. This is one nice surf, been very well maintained ever since I got it, and before that too by the looks. I think one rare surf that was actually looked after in Japan as well. She's a beauty. And a keeper....

[churchill]

I've noticed that Toyota full time 4wd systems in their trucks always have a clunk between power and coast. I suspect that is due to combined backlash of the 3 differentials as all 3 need to take up the backlash on reverse loading as opposed to just 1 diff in 2wd.
My 80 does it, my father in laws 80 does it and my mother in laws KZJ95 does it. All these vehicles are full time 4wd with 3 differentials so the same as yours when in 4wd mode by the sound of it.
As you say it's not a bad clunk but it is more noticeable on sudden throttle changes. If this is the clunk you are talking about I wouldn't worry about it as all the above vehicles have traveled a combined 800,000km and will probably do another 500,000km more.

[floatingkiwi]

Maybe - I don't seem to have noticed it getting any worse over the years...

[wjw]

I've noticed that Toyota full time 4wd systems in their trucks always have a clunk between power and coast. I suspect that is due to combined backlash of the 3 differentials as all 3 need to take up the backlash on reverse loading as opposed to just 1 diff in 2wd.
My 80 does it, my father in laws 80 does it and my mother in laws KZJ95 does it. All these vehicles are full time 4wd with 3 differentials so the same as yours when in 4wd mode by the sound of it.
As you say it's not a bad clunk but it is more noticeable on sudden throttle changes. If this is the clunk you are talking about I wouldn't worry about it as all the above vehicles have traveled a combined 800,000km and will probably do another 500,000km more.

had the same in my 80 too, doesnt happen since I modded to 2wd though

[jonossiksilvia]

Hi All

99 surf in v good condition with 220Kkm on the clock. Always been well serviced by me.

So in normal driving (in 2wd), there is the usual amount of slight slack in the drivetrain between throttle on and off as you would expect. Now, when in 4wd (4wd button pushed in, Central diff lock not yet engaged - so basically "AWD" mode), there is a LOT of slack between throttle on and off e.g around a windy road, that quite obviously "thuds" somewhere in the drive train when I'm on and off the throttle.
It's a softish thud but quite noticeably a slack thud as if something is taking up a lot of movement between throttle on and off, and most noticeable as mentioned in the push button 4wd mode.

This is quite different from the slip joint thunk when stopping at lights (and I have a bit of that too!).

All unis excellent, Both driveshafts well lubricated. Rear diff has just been done with a locker and backlash is fine (and always was). Front diff dunno but seems all tight and good when in "proper" 4wd with the center diff locked in.
Engine mounts? I've check them and they seem fine. Pulled the rear transfercase mount completely out and it looked fine. Checked all bolts etc.
I'm an engineer and very aware of any issues in my truck - my mates in the 4wd club would probably say anal... However what I'm getting at is that I'm more aware than the average bear about maintenance and failures etc.

Are these transfers known for something like this? It really makes it impossible to drive on the road in mountain conditions where you would really like to have it in AWD mode. So much so that I'm wincing every time I get back on the throttle.

Ta all.

Matt

I think im having the same issue as you. mine kzn185 auto 170xxxkm. i tend to notice it more when come up to a hard stop and once fully stopped ease up on the brake pedal to normal force and i feel a clunk. i also have a werid vibration sometimes (various speeds and random) that shakes the whole car. wonder if its related? Tires are balanced. kkeen to find out aswell

[floatingkiwi]

I think im having the same issue as you. mine kzn185 auto 170xxxkm. i tend to notice it more when come up to a hard stop and once fully stopped ease up on the brake pedal to normal force and i feel a clunk. i also have a werid vibration sometimes (various speeds and random) that shakes the whole car. wonder if its related? Tires are balanced. kkeen to find out aswell

Your issue sounds like the infamous spline thunk, plus possibly some stuffed unis. Greased your splines lately? All unis taking grease?

[spanky]

my work prado has the same clunk,spose at 531000km on all original running gear you gotta expect it,we have 5 prados all nz new and all are over 400km,all auto and no major trouble,mine is an intercooled one,must be bloody good vehicles as they tow trailers up and down a mongrel windy road all day,

[jonossiksilvia]

yeah unis are all taking grease and grease also getting into splines as i can see it coming out. (assuming ur talking about the splines in drive drive?) are the double carden joints serviceable on these? i greased the drive shafts tonight so ill see if makes a difference