Transmission noise, any thoughts?

Brown · Dec 23, 2020

I'm getting some transmission noise and I wonder if anyone has any ideas. It's a 2006 TD5 model Defender with the R380 gearbox that appears to be original to the machine and has done around 140,000 miles. There's a whiny, scrapy noise that is gradually getting more obtrusive.

I'm thinking gearbox because it can't be heard at all in 4th gear. In the other gears it can be heard on acceleration, and especially on the overrun if you release the accelerator suddenly.

Has anyone any thoughts?

I don't believe it's anything in the axles because I gave these a good going over back in September (and posted pictures on here). Propshafts are fairly new. The fact that it can't be heard at all in 4th when the input and output shafts are locked together is making me think it's gearbox related. But I'm open to suggestions . . .

payydg · Dec 23, 2020

I don't know that box but if its the same as the LT77 sounds like Layshaft bearings.

Brown · Dec 24, 2020

payydg said:
I don't know that box but if its the same as the LT77 sounds like Layshaft bearings.

Yes, I'm increasingly thinking about gearbox bearings. A bit of internet browsing suggests that gearbox noise that is absent on 4th may be wear in the bearings in the 5th gear area (the alloy extension case on the back of the box).

Anybody else got any thoughts?

lynall · Dec 24, 2020

Change the oil and stop worrying.
The syn difflock stuff is very very good in the 380.

Brown · Dec 24, 2020

lynall said:
Change the oil and stop worrying.
The syn difflock stuff is very very good in the 380.

I've got a nearly full container of MTF 94. I'll give it an oil change for now and see what happens. I might invest in some of that Difflock stuff in a few weeks.
There was a lovely passage in the old Haynes manual we had for the Series 2 years ago, which said that in considering whether to rebuild a gearbox you should take into account the amount of noise and inconvenience the driver is prepared to put up with. Which implies they'll rattle along for ages before terminal failure. That was for the Series gearbox of course but I wouldn't be surprised if the R380 has inherited some of the same tendencies.

payydg · Dec 24, 2020

Brown said:
Yes, I'm increasingly thinking about gearbox bearings. A bit of internet browsing suggests that gearbox noise that is absent on 4th may be wear in the bearings in the 5th gear area (the alloy extension case on the back of the box).

Anybody else got any thoughts?

As in it makes the noise in all gears apart from 4th? If it’s like the LT77 then 4 gear doesn’t use the lay shaft (which all the other gears are on) and a noise present in all gears apart from 4th is classic for lay shaft bearing failing.

resto_d1 · Dec 24, 2020

I had noise on overrun however I also had noise in top gears. It is a vibration, bearingy noise. My point is I identified it by getting it up on the ramp, accelerating up to 40 then letting off and finding where the noise is. Was so easy to pin it when on the ramp. Turned out the front diff was a potato sack as was the transfer box.
Yes, I did give my Christmas bonus to Ashcroft....

Brown · Dec 24, 2020

payydg said:
As in it makes the noise in all gears apart from 4th? If it’s like the LT77 then 4 gear doesn’t use the lay shaft (which all the other gears are on) and a noise present in all gears apart from 4th is classic for lay shaft bearing failing.

Yes, nice and quiet in 4th. The gears are all going round, of course, with synchromesh, but they're not taking any load, either when I'm accelerating, or conversely, when the propshaft is trying to turn the engine over, when I lift off the accelerator. According to Mr Ashcroft's website it's the bearings in the 5th gear section of the box that are the most likely culprits.

resto_d1 said:
I had noise on overrun however I also had noise in top gears. It is a vibration, bearingy noise. My point is I identified it by getting it up on the ramp, accelerating up to 40 then letting off and finding where the noise is. Was so easy to pin it when on the ramp. Turned out the front diff was a potato sack as was the transfer box.
Yes, I did give my Christmas bonus to Ashcroft....

I'm reasonably happy with the axles, because I had a look inside when I was doing the steering swivels, brakes and wheel bearings back in September. Likewise I had a look inside the transfer box in the late summer, and changed the output bearings. The rest of the bearings were changed when I fitted a limited slip centre diff in 2016. The gears all look nice - no signs of pitting or steps being worn in the faces of the teeth, so they're unlikely to have gone so far downhill in the last few weeks. The only thing that I've not refurbished internally in any way is the main R380 box itself.

jamesmartin · Dec 24, 2020

Brown said:
Yes, I'm increasingly thinking about gearbox bearings. A bit of internet browsing suggests that gearbox noise that is absent on 4th may be wear in the bearings in the 5th gear area (the alloy extension case on the back of the box).

Anybody else got any thoughts?

layshaft bearings

Ratae · Dec 24, 2020

Had 5-speed box go on a Mk2 Granada 2.8 years ago.
Lots of noise & vibration in all but 4th - which took drive straight through the box.
Did around 300 miles in 4th over a long weekend.
Turned out to be input shaft bearing had failed allowing it to wobble around. Had done a lot of damage to the layshaft gear as a result.

Brown · Dec 24, 2020

jamesmartin said:
layshaft bearings

Yup, that seems like where the finger of suspicion is increasingly pointing.

Ratae said:
Had 5-speed box go on a Mk2 Granada 2.8 years ago.
Lots of noise & vibration in all but 4th - which took drive straight through the box.
Did around 300 miles in 4th over a long weekend.
Turned out to be input shaft bearing had failed allowing it to wobble around. Had done a lot of damage to the layshaft gear as a result.

Some years ago a friend had one of those 'wedge' Leyland Princesses with the 2200 transverse straight six engine. What at first appeared to be a slight whine and a minor oil leak turned out to be one of the larger cogs responsible for first gear milling its way out through the casting. The clearances in there must have been quite tight because it wore right through the outer wall, yet the teeth must still have been engaged with the corresponding gear because the car was still driveable, if rather noisily. Eventually a good deal of the car was built into a stone wall. Cylinder heads and various engine castings make quite good corner stones because they've got some nice square faces, whereas diff mechanisms make good finials or embellishments for pillars and archways. Last time I passed the place a lot of it was still there.

Brown · Dec 31, 2020

I haven't been out in the Land Rover for a few days but I've given it an oil change (with generic MTF 94, Smith and Allan brand I believe) and whilst driving around this morning it's been much quieter. I'd hardly have noticed the transmission noise if I wasn't looking out for it.

Once again, this points to the R380 as being responsible, rather than anywhere else in the transmission. Whilst I've quietened it down I'm sure this is only temporary and I'll need to keep it on my list of jobs to be done in the next few months. I regularly travel between where I live and Wales along the M6 through the Midlands, which has no hard shoulder most of the way. So I don't want to be left without any drive on the so-called 'smart motorway'.

Transmission noise, any thoughts?

Brown

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Brown

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lynall

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Brown

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payydg

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