The rattling clacking and knocking gearboxes - a strange experience

[biggreen_bcn]

Hi there,
we recently replaced the two gearboxes, the R380 and the LT270T because of horrible grinding and whining of the old boxes. However, since then these boxes still trouble us lot, when changing the gears of the R380 or changing the load just at the moment between acceleration and deceleration there is a loud rather single clacking noise from the gearboxes that could come from either of them. In higher revs there is also some low pitch whine, but that is perhaps not a big deal for the time being.

More importantly, and that is the frightening part, when standing and putting the LT230 in neutral and running the engine from low throttle up with the gears 2-5 there is a loud rattling/knocking/clacking coming from the gearboxes most likely from the LT230 that increases with engine speed. It sounds like a screw banging around in the box.

As we could not hear that when driving, and were actually uncertain, and therefor, we were lifting the vehicle up to free the wheels, and running the LT230 in high and the R380 in the 2nd gear. However, the rattling/knocking/clacking is still there, but not as loud and intensive since the engine speed is kept at low throttle. But it is there.

We were wondering whether there is a lack of load on the gears, so that they cause this noise or even a lack of preload on the bearings of the LT230 input gear or the bearings of the intermediate shaft gears. Or something else we do not even think of yet.
I have attached a small recording of the sound recorded directly 10 cm over the boxes between gear sticks and the frame of the bench

http://earth-traveller.info/local/R380_5th_gear-LT230_Neutral.mp3

The question is also whether you hear something like that when you put your LT230 in neutral and the R380 in the 5th ? We are lost right now.

cheers,
the big green

[BennehBoy]

Check that you've coupled the boxes together with the correct length bolts first of all, the bolt on the front side of the LT230 which goes in through the R380 needs to be the shortest one otherwise it can strike the gears inside....

If you drop the oil and remove the rectangular inspection plate you can see the end of the bolt inside the case.

Are these newly rebuilt boxes, or just ones you've grabbed used? I'd be talking to whoever sold them to you/fitted them if the noise persists and/or there's any bearing whine.

[lo-fi]

What were the splines like on the R380 output and LT230 input? Wear there can cause what you're describing as the backlash is taken up in the worn splines - they can wear significantly before drive is lost.

[biggreen_bcn]

thanks for your comments Benneh,

The boxes are reconditioned and have guarantee, I suppose. Opening the plate without consent may likely violate the guarantee. I have offered to open it and check whatever they tell me, but no consent so far.

The LT230 came with stud bolt at the vulnerable position in the LT230.

I have made the people who reconditioned the boxes aware of the sounds and circumstances, and they argue it is the backlash if the LT230 is in neutral and I should run for 2000 miles to check if anything else is odd.

There was earlier thread about the backlash, the question is did they experience they same scary noise ?

http://forums.lr4x4.com/index.php?showtopic=47332

regards,

biggreen

[biggreen_bcn]

Splines on the R380 output shaft were looking brand new: both boxes reconditioned.