Strange Caterpillar transmission knock

" Hi

I hope some body can

" Hi

I hope some body can throw some light on this for me - many have tried.

I have a 36 tiara and recently the transmission on the starboard engine (Cat 3208) has started to make a loud knocking noise (like you were banging on the hul with a bit of 2*4). The knock is only when cold and in gear under load, a 10 minute run and then she runs like silk. The next day (2 days later after a hard run) the transmission is cool again and the knock is back.
I have noticed that on the port unit (which is running fine) the transmission oil presure runs @250 when engaging gear the presure drops instantly to 80 and straight back to 250 (why do they do that?). On the knocking starboard unit the presure is 250 also - but on engaging gear the presure drop to 80 takes a second or two and and rise back to 250 takes another second or two.

any bright ideas much apreciated. I have been told to take it out and rebuild but would like to have an idea what was wrong first.


thanks


Steve. "

" The knocking sounds like a b

" The knocking sounds like a bearing or planet gear that moves better when warm, you definitely need to isolate the knock or you may find out what it is in a more surprising manner. When you engage the drive the pressure is routed to the clutch piston, if you are not recovering the pressure quickly there is a leak or possibly a valve sticking. "