pressure in gear box?

[Mike k]

I just checked the oil level in gear box ( Hurth ZF 63 A) and when i uncrewed the dip stick and removed it i felt some slight back pressure coming from the box-is this normal or is a pressure relief valve blocked or something??

Any thoughts gratrefully received.

Thanks

Mike

 

[volvopaul]

Hi Mike, its quite normal for that model as there is no breather as far as im aware.

 

[Mike k]

thanks Paul- would it be good practice to release pressure at regular intervals or is it just normsal to have some pressure inside?

 

[volvopaul]

It increases after heat build up and somehow retains it, I serviced a pair of kad 43s on friday, the boat had not been run for quite a while and yet hissed when I checked the oil, so yes id say its quite normal, just check for leaks when you do your daily checks and as you have ATF and its red its usually quite easy to spot.

 

[gravygraham]

Now someone's mentioned it, I always noticed this on my boxes but never gave too much thought to it. Is the panel sure it's excess pressure from within and not negative pressure sucking air back in? Just a thought.

 

[volvopaul]

Now someone's mentioned it, I always noticed this on my boxes but never gave too much thought to it. Is the panel sure it's excess pressure from within and not negative pressure sucking air back in? Just a thought.

I doubt its negative pressure as there are just 2 lip seals on the hs63 one on input and one on output shaft, they are 1 way seals preventing oil leaking outwards so I doubt that very much.