Transmission noisy in 5th gear

[Hugues]

My manual 710M gearbox is making noise in 5th gear. It's been like this since I bought my Pinz 2 years ago. Not getting worse, just looking for my options.
The other gears don't make noise, maybe a little in 4th.
Can this be fixed by changing some components ?
I'd like to do the job myself this summer, during a 2 week vacation.
Do I need special tools to replace the problematic components?
Can I "risk" buying the parts I need before actually opening my gearbox? (to reduce downtime)
Should I take the opportunity to replace more parts of the gearbox?

It's not entirely clear from the picture below which parts are involved in 5th gear.
Taken from here:
https://www.puch.at/en/products-&-spare ... ive-shaft/

Or is it here instead?
https://www.puch.at/en/products-&-spare ... ntershaft/

This is all new to me, but willing to learn.

pic_Pinzgauer_710-712_(Benzin)_071.02.01_Antriebswelle.jpeg (25 KiB) Viewed 2189 times

[ChickenPinz]

How is the 5th gear noise different than the other gears? Can you post an audio clip?

[Hugues]

Not easy to capture it, but here it is:

https://youtu.be/XUgm7bZZojE

It's more noisy at lower rpm, starting 1600 or lower...too low for 5th gear ?

[Hugues]

i went out and tested it again today, different road,
first tested in normal gear
then tested the same road in low gear
on my dashboard we can see the engine rpm and the vehicle's GPS speed
in normal range we hear more noise in 5th gear than 3rd and 4th:
https://youtu.be/n5qimYW5oBI

in low range there is no more noise from 5th gear than 3rd and 4th:
https://youtu.be/AYp6aTTqX1g

Could it be coming from the driveshaft instead ?
https://youtu.be/nT1JwUDPk4s

[Stumbler]

Although Pinzgauer gears are noisy, you might be sure of a couple things. I'm not sure you have a real issue there and it could be engine or gears, depending on whether you are accelerating or slowing down.

1. Make sure your oil is right enough for your climate. You don't mention weather or temperature. In the Midwest US we have weather from 110 degrees F to -10. usually a 20W50 for engine oil (Quaker state makes one specifically for older engines), and regular SAE 90 for all the gears/trans/transfer case/portals. Some guys swear by Redline MT-90 for the trans. Be sure you fill them up to the appropriate levels. No synthetic oils. The old gaskets are not made for the synthetic stuff.

2. Use a zinc additive made for older engines. I get one at Autozone. I think it's about $10 or $15.

Might help. Might not. It's a cheap and easy way to check.

[ChickenPinz]

I listened to the video, and it's not clear that 5th is especially noisey.
You noted you don't hear the sound in low-range. The transmission doesn't know anything about high or low range, other than the change in torque applied to being notably less at the same RPM when in low range. If you were driving up a hill in low-range, you could simulate the transmission load of flat ground in high-range.

What I do hear, a bit, is the low-frequency "rumble" that can come from imbalance in the center tube driveshaft.

Do you hear a difference in the sound when you engage the front axle? If it goes away, that points to the center tube driveshaft.

[Hugues]

...

Do you hear a difference in the sound when you engage the front axle? If it goes away, that points to the center tube driveshaft.

Engaged the front axle today on my way up, a couple of times, could not say that it makes a difference on the 5th gear noise.

I'm told in the german forum to disconnect my driveshaft from my transmission and check for play.

[ChickenPinz]

Rotational play (in the gears in the transmission), or radial play in the output bearing?

I don't see any reason to drop the driveshaft to do that -- just put the two-speed gearbox (AKA transfer case) in Neutral.

[eric82000]

Google translate :
Hello Hugues
don't you have a pinzgauer owner near you to compare sound volumes?
if you're like me: when I hear a noise I can't forget it!
Eric

Original
Bonjour Hugues
tu n'as pas un propriétaire de pinzgauer à coté de chez toi pour comparer le volumes sonores
si tu est comme moi : quand j' entend un bruit je n'arrive pas à l'oublier!
Eric

[Hugues]

Google translate :
Hello Hugues
don't you have a pinzgauer owner near you to compare sound volumes?
if you're like me: when I hear a noise I can't forget it!
Eric

Original
Bonjour Hugues
tu n'as pas un propriétaire de pinzgauer à coté de chez toi pour comparer le volumes sonores
si tu est comme moi : quand j' entend un bruit je n'arrive pas à l'oublier!
Eric

unfortunately not

[Hugues]

...- just put the two-speed gearbox (AKA transfer case) in Neutral.

How to do this ?
you mean the lever to switch to low range ?
sorry, i don't understand what I should test here...

[ChickenPinz]

Yes. The two-speed gearbox is controlled by the tall stick above the accelerator pedal, with a red knob IIRC. It has three positions: forward, neutral, and backward. The middle position is neutral, and will allow the driveshaft to be disconnected from the center tube driveline. The other two positions are High and Low ranges.

[Hugues]

Yes. The two-speed gearbox is controlled by the tall stick above the accelerator pedal, with a red knob IIRC. It has three positions: forward, neutral, and backward. The middle position is neutral, and will allow the driveshaft to be disconnected from the center tube driveline. The other two positions are High and Low ranges.

OK clear
How do I test this?
Drive in 5th gear and switch to neutral and see if noise disappears?
I know noise stops when I press the clutch, wouldn't this test result in the same?

[eric82000]

Google translate

Hello Hugues
This is an additional test without pressure on the bearings and sprockets
By putting the transfer case in neutral (short/neutral/fast)
you supply torque to the gearbox and output shaft
you will operate the gears and the 5+r gears of the gearbox without the vehicle moving.
It allows you to listen to the gearbox noise without load, without transfer case, without axles, without wheel reducers.
Eric


original

Bonjour Hugues
C'est un test complémentaire sans pression sur les roulement et pignons
En mettant la boite de transfert au neutre (courte/neutre/rapide)
tu alimente en couple la boite de vitesse et l'arbre de sortie
tu fera fonctionner les engrenages et les 5+r rapports de la boite de vitesse sans que le véhicule se déplace
Il te permet d'écouter les bruit de boite hors charge, hors boite de transfert, hors ponts, hors réducteurs de roue.
Eric

[Hugues]

Google translate

Hello Hugues
This is an additional test without pressure on the bearings and sprockets
By putting the transfer case in neutral (short/neutral/fast)
you supply torque to the gearbox and output shaft
you will operate the gears and the 5+r gears of the gearbox without the vehicle moving.
It allows you to listen to the gearbox noise without load, without transfer case, without axles, without wheel reducers.
Eric
...

Interesting.
So vehicle not moving.
Just shifting gears, 1,2,3,4,5, R.
And what do i need to look for ?