Thread: Gearbox clatter on overrun/coasting

No the noise is unlikely to be the transfer case , given the overrun clatter was not there before gearbox rebuild , and is there after the gearbox, plus the fact that you eliminated front and rear axles by removing drive shafts in turn , I would suggested old mate that rebuilt your gearbox maybe fell asleep at the wheel.

Drain the gearbox oil and see if it's got any evidence of metal in it.

Seconded the idea of draining the oil and checking for metal.

You mention it only happens on overrun - is that only in third/fourth? If so I'd start suspecting the piece of crap bronze bushing for third/fourth. It splits quite easily, and it's only held in place by a tiny little pin. If you're using GL5 gearbox oil that's apparently not good for it either. My gearbox did the same thing before I rebuilt it - the bushing had split but there were also a pile of other issues, so hard to narrow it down further. Land Rover Restoration Part 2 - Gearbox 1/2 - YouTube is worth a watch if you haven't seen it, along with part 2.

You can get over run noise from the transfer case if there is too much play or end float in the bearings that carry the main shaft in the transfer box.

End float is set by the speedo housing, has that been taken off?

I rebuilt box gear box and transfer case and had bad over run rattle and that was the cause.

Adelaide based as well if I can be of any help.

Before getting into the internals of the gearbox/tc, you need to make certain it is a real issue.

When on the overrun, compared to driving, because the engine/gearbox/tc is on rubber mounts, they move, since the torque is in the opposite direction. There is a very good chance that this brings some part of the assembly closer to the body/chassis so that it touches and transmits the normal vibration to the body panels so that it acts as a sounding board. This sort of effect can give exactly the symptoms described.

The most likely points of contact are somewhere on the exhaust system or the overdrive lever linkage, but there are other possibilities as well. Landrovers are very good at this sort of thing because there is no sound deadening and the bolt together body means that clearances vary substantially from car to car.

G'day All,

Just a comment on Roamerdrive. The oil you should be using in Transfer case and Roamerdrive is a GL4 fully synthetic 75W/85 oil. Go the Roamerdrive website to read all about why you have to use a GL4 oil.

Chris

Thanks for the suggestions folks.

Originally Posted by goingbush

No the noise is unlikely to be the transfer case , given the overrun clatter was not there before gearbox rebuild , and is there after the gearbox, plus the fact that you eliminated front and rear axles by removing drive shafts in turn , I would suggested old mate that rebuilt your gearbox maybe fell asleep at the wheel.

Drain the gearbox oil and see if it's got any evidence of metal in it.

I should clarify - I'd never driven the gearbox before rebuild (car was a non-running project)
I have checked the oil twice over the 1000 or so km since rebuild. No metal apart from the expected slight silveryness that comes with new internals.

Originally Posted by JDNSW

Before getting into the internals of the gearbox/tc, you need to make certain it is a real issue.

When on the overrun, compared to driving, because the engine/gearbox/tc is on rubber mounts, they move, since the torque is in the opposite direction. There is a very good chance that this brings some part of the assembly closer to the body/chassis so that it touches and transmits the normal vibration to the body panels so that it acts as a sounding board. This sort of effect can give exactly the symptoms described.

The most likely points of contact are somewhere on the exhaust system or the overdrive lever linkage, but there are other possibilities as well. Landrovers are very good at this sort of thing because there is no sound deadening and the bolt together body means that clearances vary substantially from car to car.

I have checked this too. Its not close enough to the exhaust to touch. I did think maybe something like the overdrive lever, but it still made the noise without the overdrive and associated attachments removed.

Its bound to be something internal. I did supply a new one piece bronze bush.
I suspect its something like you've mentioned Cadas:

Originally Posted by Cadas

You can get over run noise from the transfer case if there is too much play or end float in the bearings that carry the main shaft in the transfer box.
End float is set by the speedo housing, has that been taken off?
I rebuilt box gear box and transfer case and had bad over run rattle and that was the cause.
Adelaide based as well if I can be of any help.

We'll see if he finds anything this week and I might chat more with you given you're local.

Originally Posted by Busted Syncro

Just a comment on Roamerdrive. The oil you should be using in Transfer case and Roamerdrive is a GL4 fully synthetic 75/85 oil. Go the Roamerdrive website to read all about why you have to use a GL4 oil.
Chris

I'll definitely have a read. Thanks.

Just a thought you stated you had not driven the vehicle until completion of refurbishment, if you replace components in a drive train they may not match the existing parts exactly and as such you may get some unusual noises until such parts either become meshed/ mated to the existing components or the high spots wear off. Harmonic vibrations are common in engines and gear trains and can appear under different load conditions.
For example Cummins 855 inline six engines harmonic critical revs is 1450 rpm if the harmonic balancer fails when the engine is at 1450 rpm under load it sounds like it is about to fail when driven at those revolutions. Change the failed component and the engine will run smooth. Drive trains are the same all the rotating components must be balanced and the mating surfaces in the same condition or you will get abnormal noises.
My thoughts are if there is no metal particles in the oil drive it for a few thousand kilometers and see if it quietens down things take time to settle in.

Gippy

Originally Posted by Gippslander

Just a thought you stated you had not driven the vehicle until completion of refurbishment, if you replace components in a drive train they may not match the existing parts exactly and as such you may get some unusual noises until such parts either become meshed/ mated to the existing components or the high spots wear off. Harmonic vibrations are common in engines and gear trains and can appear under different load conditions.
For example Cummins 855 inline six engines harmonic critical revs is 1450 rpm if the harmonic balancer fails when the engine is at 1450 rpm under load it sounds like it is about to fail when driven at those revolutions. Change the failed component and the engine will run smooth. Drive trains are the same all the rotating components must be balanced and the mating surfaces in the same condition or you will get abnormal noises.
My thoughts are if there is no metal particles in the oil drive it for a few thousand kilometers and see if it quietens down things take time to settle in.

Gippy

I frogot to return adn give an update, and Gippslander you are correct 100%
I took it back to the gearbox guy. He was still reasonably sure its purely gear chatter. We went for a lenghty drive without the middle seat and plate in (open to the box) and he could clearly hear what I was talking about. Emptied the oil, nothing in it.
He was very thorough and took the gearbox out, and completely stripped in down again. I visited a couple of times during this process for updates. We repalced a few more internal parts we didn't last time, and put it back together. Resintalled and the nosie is still there. Slightly reduced, but there. Only on overrun - a little noticeable in 4th (maybe 3rd if you listen really hard) but as soon as the Roamer engages its very apparent again. Car drives amazing and generally quiet apart from this sound.

Anyway, Landy life, done a thousand km since then with no issue.