Clunk when starting to move, HZJ78

[janyyc]

I have been trying to chase down a clunk when starting from a stop, which is not entirely consistent. It seems to me that it happens when releasing the clutch, and is a sound which could be compared to putting the transfer into 4HI and then hearing the engagement when moving, but isn’t quite as loud or violent. When outside the vehicle, the noise seems to come from under the front seats, in the transfer case/gearbox area.

Obviously I cannot eliminate every possibility at once, but assistance in formulating a plan of action from easiest to most complicated would be much appreciated.

Base info:

2000 HZJ78
110K km

The most obvious would be the slip yoke. I greased the h*ll out of it (of course later removing the zerk and driving around to let out excess grease). Of course I simultaneously greased the uni-joints and checked for any play (there is none).

I have also checked the suspension components for loose/missing bolts and cracked or deformed bushings. Nothing standing out here. Being a HZJ78 it has springs in the front, but the leafs in the back are fine and cannot be the culprit.

I have verified the transmission mount looks fine with no deformation and is solidly attached.

Where to go next? Potentially I could remove the rear driveshaft and see whether this eliminates the noise when driving in 4HI with only the front driveshaft providing propulsion.

Video (I know, not very helpful…).





Thank you in advance.

 

[prwillard2]

This sounds like something that happens frequently with the 100 series - I used to have it in my LX470.

Culprit is typically the drive shaft, but have also seen it caused by the slop between the hubs and the CV. Are yours manual locking hubs or similar to what is on the 100 series?

 

[janyyc]

This sounds like something that happens frequently with the 100 series - I used to have it in my LX470.

Culprit is typically the drive shaft, but have also seen it caused by the slop between the hubs and the CV. Are yours manual locking hubs or similar to what is on the 100 series?

Yes, searches seemed to give a disproportionate amount of replies in the 100-series section…

Front is manual locking hubs. But as with you Troopy it’s not permanent 4WD, so right now I’m chasing the clunk in RWD.

 

[prwillard2]

Yes, searches seemed to give a disproportionate amount of replies in the 100-series section…

Front is manual locking hubs. But as with you Troopy it’s not permanent 4WD, so right now I’m chasing the clunk in RWD.

My uninformed thoughts are it's probably the drive shaft. I'd take off the front or rear to see if you can isolate as you mentioned. Maybe the u joints?

 

[svsisu]

Obvious check, and one which you have likely looked into are the suspension bushings. My rears are worn as, cracked and crumbling and I get a gentle clunk when backing up and turning. They are soon to be replaced. Similar noise came from the fronts before I replaced those. Can't say if the noise comes from the suspension, or putting funny load on the drive shafts, but I'm glad I know the root cause of my clunk.

 

[janyyc]

Yesterday I removed the rear driveshaft. (NB: wow, there was a lot of grease buildup in the slip yoke).

Unfortunately the clunk remained. It definitely seems to be coming from the transfer/transmission area, and I noted the other day it also occurred when engine braking and then resuming forward power.

This makes me wonder whether it could be a worn transfer input shaft, as for instance documented by @cruiserdan here. Though I do question this slightly as the onset was quite sudden and the noise is pronounced (nobody seems to have mentioned anything about a clunk before fixing it).

Video of clunk with rear driveshaft removed.

 

[janyyc]

Still chasing this clunk, with the goal of diagnosis and in order to decide what to do next…

Upon the suggestion of @cruisermatt I removed the PTO cover to check for play in the shaft/gear interface. Indeed there seems to be a little bit.



That’s with the transfer and transmission in neutral, wiggling on the PTO gear and the input gear.

Then I kept the transfer in neutral and put the transmission in gear. I don’t know if this is within normal backlash…



Finally, I proceeded to clean everything up, put on new gasket, and torqued to spec, no closer to solving my issue…

 

[janyyc]

All right. Some more sleuthing has led me to what I’m almost 100% sure is the culprit.

In 1999, Toyota started the R151F pairing with the split case for the 1HZ 70-series.

Between 1999 & ~2003, the transfer input shaft (separate from the transmission output shaft on the R151F!) was two-piece. The spline/sleeve interface would wear and eventually cause no drive. The Toyota solution was a one-piece shaft from 2003 onwards. Seems that every single transfer of that era had this problem, many under 100K km. Because mine is a 2000 and is still under 120K km (and I bought it around 60K), it’s never had the shaft replaced.

Since this subject is so esoteric (specific model and year range), I hope this helps anyone with a similar issue.

Some forum threads from way back when:

gearbox problems troopy 78 series

I've been following the recent posts about gearbox problems in the troopy 78 series i'm beginning to get worried about my MATE troopy i,ve got a 2002 78 series and i've been hearing a klonk from underneath when i change gears,...

www.exploroz.com

i,ve got a 2002 78 series and i've been hearing a klonk from underneath when i change gears, does that ring a bell with anyone.

From what I gather that is exactly the first signs of trouble---get it checked out as it is better to get it fixed now than in the "sticks"

From a German forum:

HZJ 78 Verteiler Getriebe ... defekt

Hallo Zusammen Brauche Hilfe ... Habe irgendwie kein Verteiler Getriebe mehr. Kann Gänge einlegen und Kupplung loslassen dann rauspert es nur unten im Getriebe.

forum.buschtaxi.org

I'm guessing it's the infamous transfer case input shaft.

It was a weak point in the early years and has since been modified.

From a French forum:

Résolution panne boite vitesse et transfert toyota hzj78 - Casa Trotter

I believe most 7 Series models before 2004 experienced this, often before 100,000 km, and the problem was well known to all users and specialists, except, of course, Toyota, which eventually came up with a solution:
The transfer case sleeve and primary shaft were replaced with a single part, or the (reinforced) sleeve was attached to the primary shaft, which solved the problem.
Indeed, the sleeve was too short on the transfer case side to handle the HZ1's power, and the splines on the shaft and sleeve wore out more or less prematurely depending on the driver's effort!

So I’ve ordered the new shaft, along with all bearings, gaskets, etc., and the improved drive gear which removes the spacer and PTO gear, all from @cruisermatt, and will have it rebuilt. Hope to get a picture of the wear along the way.