Dresser TD8G powershift transmisson aerated oil

[Unimog406]

Hello I have a new to me TD8G with about 4k hours. I changed the transmission fluid and both filters ( the pressure filter is a baldwin and the scavenge filter was a aftermarket but the micron rating was the same and it looked identical to the one that came out) , since that time when the machine is running there is a considerable cavitation noise coming from the pressure filter. The old oil was clean with minimal debris. The scavenge filer had some debris but nothing i would think out of the ordinary for an older machine. The oil in the sump is full of air. The oil level is full when running. I added a extra gallon thinking the dipstick could be off or something with the pick up. I have had both filters out several times and do not see any issues. I have tried cranking it over several times to bleed the filters out and let it idle for different periods of time. I do not see any leaks on the suction hoses or filter bodies. When first starting the machine after sitting you can hear what sounds like a large slug of air coming through the lines by the filter housing. I used a universal trans/hydraulic oil which has a viscosity of 10w30. The machine is inside in a heated shop. It drives and moves in all gears and the clutch pressure seems ok.
Any Ideas on what could be the cause. I don't think the machine had this issue prior to the oil and filter change.
Thanks for any advice

 

[Welder Dave]

What oil does it spec. in the manual? Some oils have anti-foaming properties but if it makes a noticeable noise wondering if a seal or o-ring on the filter is not quite right?

 

[Unimog406]

Hello welder Dave Thank you for your response. The manual calls for a 10W oil. The oil I used I have used previously in various types of equipment that have combined hydraulic wet clutch transmission with out issues the oil does have anti-foaming properties. I have replaced and checked the filter seals A few times and not found anything that would indicate a leak. But I do think the air is being pulled into the system possibly due to a pump seal ?

 

[John C.]

Those used automatic transmission fluid when they came out as I recall. I've had customers that used engine oils and then had heating problems. The last I heard was the tractor hydraulic fluid was being used. You might ask your question over on Red Power.

 

[balls2go]

It probably uses Hy-Tran. Will definitely have problems if you switch to something else.