Drivetrain whine - FG434 + Entertaining Pics

[Spoony]

My old FG434 (340,000km) has a constant drivetrain whine, increases with speed so not that noticeable at lower speeds but is apparent in 4th and 5th, occurs during both on decel and acceleration, will shut up for a period in between that load, stops completely with the clutch in but will start back up with only a little bit of clutch take up (seemingly no load though, ie can still rev engine). I can notice it window down past barriers too. It had a whine since I got it last year, the old owner (in both regards) recons it had a whine since he bout it 9 years prior.

I changed the fluids when I got it and they looked good, I rechecked recently and still look good + the levels are good both box and transfer.
I did do some heat/sound insulation work and it's been turboed so noises are reduced elsewhere, so it may still be the same it always has been and I've just noticed it now as the more/most predominant sound. What is heard cannot be un-heard haha.

Do these older trucks have fairly whine drivetrains?

A few inside pics and some of me have a play the other day, deciding to see what it felt like leaning over and if the fibreglass body can take the weight of the truck on a bank haha. It did fine. I could have driven out but opted to winch backwards with a side pull to save damage. It litterally just scratched the paint

 

[DzlToy]

Being an 'older' model FG, it is possible that transfer case gears are straight cut. In the states, it is common for older cases, such as the venerable NP205, to use straight cut gears right from the, now shuttered, factory. Straight cut gears are stronger than helical cut gears, but significantly louder.

If you have a safe place to do so, get the truck rolling down a hill, with the transfer case in neutral and the transmission in neutral. If the whining goes away, try one or the other independently. If the gears are straight cut, a heavy synthetic lube such as one from Amsoil or Redline may help, but they are just noisy gears. A rebuild on an older piece may help, but again if the gears are straight cut, even a rebuilt case is going to be loud.

 

[Spoony]

Being an 'older' model FG, it is possible that transfer case gears are straight cut. In the states, it is common for older cases, such as the venerable NP205, to use straight cut gears right from the, now shuttered, factory. Straight cut gears are stronger than helical cut gears, but significantly louder.

If you have a safe place to do so, get the truck rolling down a hill, with the transfer case in neutral and the transmission in neutral. If the whining goes away, try one or the other independently. If the gears are straight cut, a heavy synthetic lube such as one from Amsoil or Redline may help, but they are just noisy gears. A rebuild on an older piece may help, but again if the gears are straight cut, even a rebuilt case is going to be loud.

Cheers, while it stops with no load (clutch in) I'll certainly try neutral on the box and transfer and see.

 

[PKDreamers]

Also try put the transfer case in neutral while the engine is running and go though the gears in the gearbox .
Have a look at the center bearing too.
Any different with the Free wheeling hub in or out?

 

[toylandcruiser]

Being an 'older' model FG, it is possible that transfer case gears are straight cut. In the states, it is common for older cases, such as the venerable NP205, to use straight cut gears right from the, now shuttered, factory. Straight cut gears are stronger than helical cut gears, but significantly louder.

If you have a safe place to do so, get the truck rolling down a hill, with the transfer case in neutral and the transmission in neutral. If the whining goes away, try one or the other independently. If the gears are straight cut, a heavy synthetic lube such as one from Amsoil or Redline may help, but they are just noisy gears. A rebuild on an older piece may help, but again if the gears are straight cut, even a rebuilt case is going to be loud.

Helical cuts gears are stronger as there are more teeth contact

 

[Spoony]

Thanks for the input guys. I'm hoping it's just helical cut gears in the transfer that I now notice more.

I did a bit of testing and it's only apparent with load against the motor, either in acceleration or deceleration.
So clutch in it does nothing, Clutch out and in in Netural does nothing. Putting the transfer in netural again nothing.
My guess in any of these cases there's very minimal load on any gears or bearings as they are just free spinning.
I forgot to check the hubs in, transfer in 2wd though (oops).

Interestingly though in 4h hubs unlocked there's a vibration that starts at higher(ish) speeds so maybe tight uni joints I'm guessing. Probably not an issue as wouldn't use 4h on the highway.

I've been in performance cars with helical cut dog boxes and It's sort of like that but sounds higher pitch (at highway speeds 95km/hr). That could just be gearing though, so short in the FG434 everything spins faster.
It also has similar behaviour as in that 'waaaa waaa waaaaaaaaaaaaaaaaaaa' loading whine sound as the vehicle load rocks a little against the drive train if that makes sense.

I'm going to try get to a transmission shop today and see if they have some ideas, mainly for piece of mind as hopefully next year this thing will be on the road full time around Australia.

Cheers
Dan

 

[Aussie Iron]

Why don't you crawl under and remove the side plate of the transfer case ( big flat plate 300 x 160mm and 11 bolts) and look inside your self. Grab yourself a largish screwdriver and you can lever the gears side ways and up and down and see what is going on. You will also be able to see if the gears are badly worn and check gear backlash. I'd be very surprised if the gears aren't helical cut as that is what they should be. I haven't seen any different in Canter transfer cases.
In 4WD the transfer case will certainly make more noise as you increase load so this would be only undertaken on non-hard surfaces.

Dan.

 

[Spoony]

That's not a bad idea, I've seen that big inspection plate. Will I need to drop the fluid before taking that plate off?.
I talked to a gearbox/diff shop today and the bloke said that it won't be the gearbox if it's the exact same in 4th and 5th and thought it would be most likely the diff. Suggested putting it on stands and having a listen.
So I did, while a bit scary spinning up 70kg wheels and a 4.5t truck to 90km/hr on stands but seemed stable. I wasn't game to crawl under the middle but the sound clearly came from mid truck and not the diff, seemingly the transfer case.

It's on it's side but this is a video of it.

New video by Dan Poole

photos.app.goo.gl

Sounds much like fun times in a mates old modded WRX with a Dog Box in it. Guessing it's just noisy helical gears in the transfer.

 

[Aussie Iron]

Yes you will need to drain the oil first. Okay if I am hearing it right from that short video - it certainly does sound like gear whine. This could be from a few different causes. The noise is from the meshing of the gears and could be from excess play in the bearings. It could have been run dry and the gears have worn some. Look for excess play, see if the gears in the bottom set have any wobble in them ( the bearings in them are fine needle rollers), backlash between the gears, look how much side shift you get in the centre cluster gears as they are known to wear the side load washers. Check for metal on the magnetic plug and for metal in the bottom when you have the plate off.
If all looks good close up and refill with good quality oil in grade 85/140 High pressure. Being not new you could even go straight 140 oil, but this may be hard to find/get in the "City".

Pull the plate off and have a look. Let us know what you find.

Dan.

 

[Spoony]

Thanks for the guide, I'll inspect on the weekend. When I changed the fluids after purchasing all were pretty clean and nothing on the magnets. I put in Penrite 75w-90 Trans Gear in it (Gearbox too, I went of what guides indicated to put in). This sounds like it is probably too thin. It's easy to find quality hi-pressure 85-140w LSD gear oil , straight 140w will need more searching as you've mentioned.
The Diffs have Penrite 80w-90w LSD Gear oil in them

 

[Spoony]

A bit of an update on this. I pulled the inspection plate and to me it all looked really good, almost new. No bits came out on drain, the year old oil looked really good, and magnet had only a small amount of filings, hardly noticable. I couldn't pick up any side load play or any wiggle play at all. There's minor play rocking back the gears on each other but I figure that is normal. I re-filled it with 85-140. Given then visual condition I figured straight 140 wasn't warranted.

I took it for a short drive up the highway, and while it may be placebo it seemed a bit less pronounced, but the real test will be after driving for an hour or so when temps come up properly. Before it was louder once hot vs cold. If it's not changed at all maybe it's the diff and somehow the sound, even on stands is being transferred up the tail shaft? I would have though on stand with a ridged path to ground if it was the rear diff it would be amplified at the back?

A boring video of me stabbing it

https://youtu.be/MnrhHH09rIM

Cheers

 

[Aussie Iron]

From what is visible to me it all looks good. Teeth meshing surfaces are what would be expected.
Lets go to the diff. At what speed are we having the most pronounced noise on acceleration and deceleration. If it not too fast, "" I MAY "" remove rear tail shaft and rear axles an just drive on front axle (4 high) to try and track noise. This could possibly be done on stands (wouldn't need to remove rear axles) as we had the noise earlier when on stands. Don't be too radical on the accelerator, smooth increase and decrease (we don't want a lot of torque load to build up). The front drive system is not as robust as the rear.

Dan.

 

[Spoony]

Yes I thought it looks pretty good. Now I've got 85-140 in it, is that a problem if it's good? Spec is SAE90.

On stands I got under the back and the noise was so pronounced in the middle of the truck, it just didn't seem to be from the diff. The gearbox bloke recons once on stands with the axle ridge to the ground it usually amplifies such noise and makes them more noticeable. Though sound can do strange travel things, maybe down the tail shaft, who knows :/ . I need to do the rear uni's too, but they wouldn't whine.

As far as speed, the faster one goes the more noticeable. I cruise at about 90 odd (gps) and it's most noticed hear but still apparent at about 60, then it largely shuts up.
Given it's load related just removing the tailshaft would be enough, as coasting there isn't any noise, there needs to be load against the motor power or decel to create the noise.

I could try this when doing the uni joints soon............ish.

I might give it a good 40min run on the highway tomorrow and see if it's actually really less noisy, if it is once hot then it's the transfer. Which is fine, given all seems well inside I can leave with it, just dont' want to start travelling Oz next year and have the drivetrain fail.

 

[PKDreamers]

Mate I would be checking the center bearing , spray sum inox , wd40 what ever on it see if the noise goes away.

 

[Spoony]

It's a SWB so not centre bearing, transfer straight to diff. ?