transmission fluid, leak question

[mb]

I noticed a puddle of oil under the rear end of my tractor last week. After further inspection it seemed as though transmission oil was leaking out of the filler tube. I removed the filler cap to check the fluid level and fluid started back flowing out of the filler cap. I quickly replaced the cap and lifted up the pressure relief valve with my fingers and removed the filler cap again. This time the fluid did not back flow. I bought my 7117 used and it did not have a pressure relief valve installed so I installed a new one last year just to keep debris out of the fitting where the valve was supposed to be. I am wondering if the original owner may have removed the pressure relief valve because he had the same problem. Does anyone know if this is a common problem with hydrostatic transmissions ? Is it a result of a sticking relief valve (it didn't appear to be stuck when I lifted it with my finger) ? Any advice or input would be appreciated. Thanks; Mike

[bigdog46]

The manual states to hold the pressure relief valve up when unscrewing the cap to check the level. The tube should be full of fluid when holding up the pressure relief valve.

[mb]

thanks for the reply but I am still wondering what would cause the transmission fluid to leak out of the tightened filler cap. I am aware that the manual states that the filler cap should not be over tightened however my cap is leaking if it is loose or tightened way to tight. Is there a history of the pressure relief valves failing ??