Knocking under floor while under load up hills (1 Viewer)

[alcheck77]

Got an issue with some knocking, probably better described as thumping, in my landcruiser. It only happens going uphill and under load. It feels like it's under my feet but may not be. I've checked the drive shafts and UJs and there doesn't appear to be play in them. The transfer box appears to running freely when I turn the shaft. I had a mechanic take it for a spin a couple of weeks ago and he couldn't pick it up which was odd cause its friggen bad now. its not steering related, nor suspension, braking etc I feel its either engine or gearbox/txfer box ... I've researched a bot of engine noise and can't find anything similar, its not like plinking or clanging like bearing noise. Much thumpyer than that
Any thoughts of where to start and how to test stuff without pulling the wrong thing apart
Cheers

 

[pithicus]

Gearbox mount?

 

[alcheck77]

Hmmm, it sounds like its rotating eh, but i guess it would if it was out of balance and loose. I haven't tested the mount bolts so might have to hav a look at them. Check engine mounts but they seem sound

 

[pithicus]

What about the exhaust? That would be more of a clunk I suppose.

 

[alcheck77]

It would be bolts rather than the rubber mount itself eh?

 

[alcheck77]

yeh its not clunky enough for exhaust - its a real thump, thump, thump ...like only when under load so climbing up a hill at 100km, then as the old girl slows and I drop it down say from 5th to 4th thats when it starts, and as I drop it into 3rd it really kicks in. So down to 2nd to crawl up the hill. And then it stops. No noise on idol, or flat or sloping down driving eh

 

[pithicus]

It would be bolts rather than the rubber mount itself eh?

The rubber gearbox mounts can break even when securely bolted.

 

[alcheck77]

Right oh, I'll check the mounts in the morning, you could well be right. Thanks for your help

 

[pithicus]

Hope that's all it is. You might have to jack up the gearbox a bit to see the break.
cheers.

 

[oldblue]

Sounds like toque related, as the power of the engine goes up the rotational torque gets greater causing the T/F Case or gearbox to contact the floor.

 

[alcheck77]

Ok so I gave the exhaust a good few heaves and found its knocking, which sounds similar, and theres a small metal wear mark in that place. But it would have to be fair moving around to do this (like an inch) ...why?
Checked the transmission mount - no breaks in seals around bolts, but I did lift the box up very gently and found one of the rubber mounts on one side appears to have come off the plate - but hard to tell without a full removal and inspection but this could be meaning the box is moving around unfixed, so next job is to take the mount out and have a closer look at it.

Decided to take it for a run and before hand we wired up the exhaust so it couldn't move, went for run up hill, I could hear the noise but it didn't have the same knocking sound, did a couple of runs and sound was pretty low. Back down bottom of hill I cut the wire and went back up, knocking returned...so think I have found the noise....BUT why is the exhaust moving around so much.

Maybe its the box mount... but something must be tossing the motor around pretty violently to get the exhaust to move that much...is this the normal torque for 1PZs, or could there other issues?

 

[pithicus]

found one of the rubber mounts on one side appears to have come off the plate

Come unstuck where it's vulcanised on. Fairly common. Will need fixing. I'm surprised the mechanic didn't pick up on this?

 

[alcheck77]

Come unstuck where it's vulcanised on. Fairly common. Will need fixing. I'm surprised the mechanic didn't pick up on this?

yeh me too... I guess he couldn't hear the noise so decided no problem. Do you think that would cause the movement in the exhaust? It would have to mean the engine itself is moving around a lot eh?

 

[pithicus]

Do you think that would cause the movement in the exhaust?

To some extent quite possibly.

Might be wise to double check the engine mounts. Might need to use a jack.

 

[LC100NAM]

yeh me too... I guess he couldn't hear the noise so decided no problem. Do you think that would cause the movement in the exhaust? It would have to mean the engine itself is moving around a lot eh?

Hi alcheck77!

Following-up on this thread as I have the exact same problem, and have been through a lot of troubleshooting with no success so far.
Did you find the source of this clunk / noise in the end?

Thanks

Martin

 

[Omrib]

I have similar issue with a streight flow passenger side outlet exhaust system, it seems to have no room for slight movement between the side steps/sliders mounts and the body, where it is always touching either and resonating the body and/or chassis.
Put a silicone isolating layer for testing and reduced the noise to some extent.
Would have to modify the mounting bracket for the sliders to allow for more clearance for the exhaust sys.

Seems like not exactly what your situation is with OEM exhaust sys, but thought it might be useful info.
Good luck
Omri