Transmission chatter 2001 HSE.

[PeterH]

I've noticed a subtle mechanical chatter sound coming from what seems to be the auto transmission.
It only occurs under load, but not while coasting.
It is not very loud, but it's there every time I accelerate.
I have replaced the transmission fluid and filter a couple of times since I've had it, made no difference.
The auto shifts smoothly and quietly, with no problems.
Has anyone come across this before?

[Hoges]

Peter, it may be a slipping chain in the transfer case...jumping sprockets under tension when accelerating. There's a couple of detailed descriptions with pics on how to replace the chain in rangerovers.net. A big job in DIY terms but quite doable in a day ...apparently!

[benji]

Worth checking the transmission mounts. Im thinking if they are shot it may be banging against the catch strap.
Also the tailshaft bolts.

Apparently a chain skipping is quite loud, but hope its not.

[PeterH]

You might just be onto something there Hoges, it does sound like it could possibly be a loose chain.
It is certainly not loud though, but may have stretched enough to cause a noise.
I don't think it's to the point of slipping teeth, I imagine that would cause vibration and a more jarring noise.
I just changed a timing chain on a Delica diesel 4x4, that was causing a 'chuff chuff' noise in the motor, it was not slipping but was causing a worrying noise. New chain fixed it.

Thanks Benji, I'll get under there today and check the transmission mounts, tailshaft bolts...I wonder if a uni joint on the way out would cause such a noise? Might grease those while I'm there and see if that helps.

[PeterH]

I had a look at others experiences with TC chain, and I do not think it is that.
I don't have the loud machine gun noise they talk about on acceleration.
The noise is present at idle, also while driving, so probably not a uni joint.
I'm thinking it may be something inside the auto or possibly the TC.

[mtb_gary]

Just a thought, items close by to the transmission are the catalytic converters. It's not one of the converters starting to rattle is it?

Gary

[PeterH]

Good point mtb_gary, my cats are a bit rattly, I notice it mostly when I start up in the mornings.
They are probably due for replacement, might have to look into prices for some new ones.
It does still sound like something inside the tranny or TC, though...it's so hard to tell, sometimes it's hard to hear unusual noises from inside the cabin as P38's are so well sound proofed.

[PeterH]

So after a bit of searching around different forums, I came a cross some others that have had the same chatter sound coming from the transmission, also described as a grinding sound.
The noise has always been there since I did my first atf and filter change, even through a couple of filter and atf changes.
As it turns out, dexron 4 or 5 is not always compatible with dexron 3, which is the recommended atf for P38's.
I drained the old atf (dexron 4 or 5 from memory), out this morning (did not do the full flush), and put in good old Penrite dexron 3 mineral atf.
What do you know, noise gone instantly!
I drove it for about 50km and then drained and refilled again to flush a bit more of the old stuff out.
The filter is only about 12 months old, so I left that as is.
It was my understanding that dexron atf's were backwards compatible, but as I have found that is not the case.
Hope that helps someone else experiencing the same transmission noises.
Cheers, Pete.

[FANTOM P38]

Good pick up Pete,
Was thinking possibly uni joints as i recently done mine due to similar noise.
found one to be much worse than i would ever have thought, so did all four to give some piece of mind.
now am having a smoking issue, not sure if its oil im using or possible rings bypassing. going to run some engine conditioner through it and take for a bit of a run to see if that cleans out any gunk!

[PeterH]

FANTOM P38, just out of interest, which uni joint was the bad one?