A Thud when dropping the Clutch

[Richard Lorand]

After eight years and 120k of 4Runner ownership I now have a 98 Collie 3.o manual. The first two years of it's life it did 82k and then the last owner did 28k in 17 years. It has never had a tow bar and the engine sounds and runs very well. My problem is when setting off, when the clutch bites if I let it off quickly there is a bit of a thud and this continues in all gears, certainly lesser when getting into higher gears but presume there is less torque higher up. If I release the clutch slowly and gently it is fine. No noise on acceleration or deceleration. No problem on gear selection or slippage and the clutch travel is in the middle of the pedal. The local garage says let it develop but would like any ideas from the Cruiser Club Experts.

 

[Shayne]

I have replaced all balls joints , bushes , suspension etc and swapped the front diff to no avail leaving what was the most likely culprit from the start - the transfer box as odds on favourite to be the cause .

While typing this i have reminded myself that i never did get around to jacking up the engine to check its mounts though i think its improbable that one is broken .

 

[diggerdave]

It's hard to compare 'shunts' over the internet. But I second what Shayne has said.

I spent many fruitless hours (not as many as Shayne) chasing down the driveline slack on mine, also coming to the tentative conclusion that in my case it's slight wear in the transfer case. I now just change gear gently, although this is often not enough to avoid a shunt especially in traffic or accelerating hard. Plenty of Defender or Disco 1 owners live with driveline shunt - to some extent its the nature of permanent 4wd vehicles...

Mine's been present throughout my ownership (30,000ish miles?) and has never got any worse so I got over my initial fear that something was about to break! I've not been particularly gentle with the clutch either with UK greenlaning trips at least every month, continental greenlaning trips and it's my daily (city) driver too.

There are some simple things to check that can cause the symptoms: propshaft UJs being a favourite, the flanges on the diffs and the t/box and is it just clutch wear? Worn bushes in the suspension are rumoured to cause similar but I've never quite believed they could be enough. If you want to try to track it down beyond the simple stuff, a first step is to get a handle on how the transfer box works and remove each propshaft in turn to get an idea of whether it's likely to be the front or rear diff, etc.

 

[Shayne]

Its not actually a common problem , not to a troubling degree anyway , but slack in the chain is what i've always thought . I have a suspicion that some have suffered owners that assume the transfer stick is for engaging 4x4 and so use it while towing or maybe winter driving ?
I lent someone my truck to tow something very heavy and caught them at it which is where the idea was born .

I have 2 90's by the way mines 1998 and no shunt the mrs drives the 2001 d4d 90 that was bought with a terrible shunt in the assumption that an LC can always be fixed .

Locking the centre won't stop the shunt which is what leads me to think its the chain , front wheels take off and rear wheels catch up when the chain goes taught is what i think .

I think it was the front prop i removed and there was no shunt at all .

 

[Richard Lorand]

Many thanks for your ideas and will try and check them out.

 

[Bob]

As others have said, it's something that can come into permanent 4x4 set ups. Replacing the UJs made a difference for me, and also upper control arm bushes on the rear axle helped reduce the thunk. There's still a bit there if I'm a bit speedy with the clutch, but not excessive or anything I'd be worried about.

 

[RL12]

I had a similar thing a few yeas ago with a RRC and it was a broken engine mount so check those and the gearbox mounts.

Would also suggest jacking up the wheel(s) and trying to establish if the driveline has excessive play in diffs/uj's/transfer box.