Defender transmission whine

Hi all,
Sorry for the bombardment of threads lately I'm having a bit of a fad fixing things. I've got everything I wanted to do done all that's left is the one I've been avoiding. The car has a whine. Similar to the noise a reverse gear makes. It's not there in first or second and is barely audible in third. The main noise is in 4th and 5th. It's most pronounced between 35 and 50 in these gears. Above 50 it seems to dissipate but I'd still there a bit. There's no noise when the transfer box is in neutral in any gear. Theres fluid at the required levels in the transfer and gearbox (although I don't know what it is or how old.) I changed the oils in the Diffs which made a very slight difference. There's no issues with the gearbox or transfer box everything works ,there'sno synchro issues and it's not notchhy even when cold.
Oh and the noise goes completely when I put the clutch in.
What on earth could be causing this noise?
Cheers

Which GB? ( R380 ?) - IF so, I'd suggest changing the oil in the GB for good, clean ATF as a flush only. then driving a few tens of miles under light load, and then drain it hot, and re-fill with MTF94 - a good branded MTF94 too ( Carlube seems to get good reviews, and is what I use in SWMBO's R380). And check the level regularly.

LT230 (TB) likes decent gear oil too ... always worth changing it when its history is unknown ..... consider a synthetic like syntrans ... but be aware that it can sometimes find any weak seals and make you some more work .....

IME, the 380 doesn't like old oil, and the bearings in the 5th gear extension housing get somewhat cross about the situation, and start moaning at you

Also IME, the LT77 is similar, but different.

Disco1BFG said:

Which GB? ( R380 ?) - IF so, I'd suggest changing the oil in the GB for good, clean ATF as a flush only. then driving a few tens of miles under light load, and then drain it hot, and re-fill with MTF94 - a good branded MTF94 too ( Carlube seems to get good reviews, and is what I use in SWMBO's R380). And check the level regularly.

LT230 (TB) likes decent gear oil too ... always worth changing it when its history is unknown ..... consider a synthetic like syntrans ... but be aware that it can sometimes find any weak seals and make you some more work .....

IME, the 380 doesn't like old oil, and the bearings in the 5th gear extension housing get somewhat cross about the situation, and start moaning at you

Also IME, the LT77 is similar, but different.

Click to expand...

It's an LT77 in an 86 defender with a 300tdi coupled to it. I think all the oil changes will be my plan for tomorrow then...
Thanks

Disco&Defender said:

It's an LT77 in an 86 defender with a 300tdi coupled to it. I think all the oil changes will be my plan for tomorrow then...
Thanks

Click to expand...

Right, IIRC, LT77 wants ATF in it .... I'd flush it with decent ATF for a 100 miles or so, then change it again with the best stuff you can get your hands on ( IMHO Castrol )...

If it hasn't got a cooler on it, it's worth adding one - its an expense, (sorry), but worth it IMHO - details on the ashcroft site ...

Disco1BFG said:

Right, IIRC, LT77 wants ATF in it .... I'd flush it with decent ATF for a 100 miles or so, then change it again with the best stuff you can get your hands on ( IMHO Castrol )...
If it hasn't got a cooler on it, it's worth adding one - its an expense, (sorry), but worth it IMHO - details on the ashcroft site ...

Click to expand...

Thanks,
Would you say it was a gearbox noise rarther than a transfer box noise then?

Disco&Defender said:

Thanks,
Would you say it was a gearbox noise rarther than a transfer box noise then?

Click to expand...

Yep, almost certainly - assuming the TB has good oil and enough of it , it's probably bearing noise from the extension housing containing 5th and the pump .... change the ATF as mentioned ( flush etc.), and see how it sounds ...

Might be worth a lubricant booster in there at some point ... but an oil change first

Disco1BFG said:

Yep, almost certainly - assuming the TB has good oil and enough of it , it's probably bearing noise from the extension housing containing 5th and the pump .... change the ATF as mentioned ( flush etc.), and see how it sounds ...

Might be worth a lubricant booster in there at some point ... but an oil change first

Click to expand...

theres no bearings in the extension housing in an lt77 box, if its 4th and 5th it needs pulling apart and inspected

jamesmartin said:

theres no bearings in the extension housing in an lt77 box, if its 4th and 5th it needs pulling apart and inspected

Click to expand...

Yeah, I know - I was trying to keep the technical stuff at a low ish level to avoid blinding the OP with science .... IME, which granted, is nowhere near yours, especially with the '77 -( since it is about late 80's since I was last inside one !!), the noise "appears" to come from the extension housing.....

OP:- lots of info here:-

the main GB page:-

https://allbrit.de/select.cfm?CAR=L4&SPRACHE=EN&PAGE=J01

The extension case:-

https://allbrit.de/epc.cfm?PAGE=J01020&CAR=L4&SPRACHE=EN

Disco1BFG said:

Yeah, I know - I was trying to keep the technical stuff at a low ish level to avoid blinding the OP with science .... IME, which granted, is nowhere near yours, especially with the '77 -( since it is about late 80's since I was last inside one !!), the noise "appears" to come from the extension housing.....

OP:- lots of info here:-

the main GB page:-

https://allbrit.de/select.cfm?CAR=L4&SPRACHE=EN&PAGE=J01

The extension case:-

https://allbrit.de/epc.cfm?PAGE=J01020&CAR=L4&SPRACHE=EN

Click to expand...

Thanks for that. I changed the all the oils today. Gearbox level was all good. Clean fluid no shavings. The transfer box was actually very low - about 1 - 1.5l came out. It was very difficult to check before due to the PTO drive in the way. There was also some fine shavings on the magnetic drain. After putting the correct amount of oil in the noise is reduced by at least half. What part is knackered? Is there any other oil (thicker?) I should put in it to quieter it further? Should I be expecting some noise anyway? It is a 32 year old transfer box that's done 200000 miles?
Thanks

Put the right oil in and check change again in a thousand miles or so. If no fileings then keep going.Chance's are because of the pto drive oil has not been changed very much.

tottot said:

Put the right oil in and check change again in a thousand miles or so. If no fileings then keep going.Chance's are because of the pto drive oil has not been changed very much.

Click to expand...

That's probably correct. Was a right game to get the full plug off in the available space. So just ignore the remaining whine?
Thanks

Most older units will make some noise,but only by actualy hearing it the flesh could I make a judgment. Some old units are quite, some whine, some moan but they mostly keep working as long as the have oil in them.

As tottot says above , check the oil frequently, and maybe change it again is a few months to act as a flush .... The thing that "wears" in oils is usually the additive pack, and specifically the friction modifiers ... hence my comment above about adding a lubricant booster, which will increase the qty of additives, and thus extend the "life" of the lubrication...

I used to use Forte SSL in gearboxes and Diffs - it was a military grade booster and gave good results - not used it for years ( like 30+! ), so I am out of touch with the current availability....

There's an american forum, something like bobistheoilguy or similar ... worth a search, and maybe post up on there as required

Disco1BFG said:

As tottot says above , check the oil frequently, and maybe change it again is a few months to act as a flush .... The thing that "wears" in oils is usually the additive pack, and specifically the friction modifiers ... hence my comment above about adding a lubricant booster, which will increase the qty of additives, and thus extend the "life" of the lubrication...

I used to use Forte SSL in gearboxes and Diffs - it was a military grade booster and gave good results - not used it for years ( like 30+! ), so I am out of touch with the current availability....

There's an american forum, something like bobistheoilguy or similar ... worth a search, and maybe post up on there as required

Click to expand...

Thanks for all the advise. Leaving it is what I will do. It's not deafening now and I don't think it sounds like imminent death. In fact unless you had some mechanical knowledge don't think you pick it out from all the rest of the engine/tyre/road noise. I'll take a look at these additional additives etc.