Hydramatic or hydrostatic? former is a trade name for automotive transmissions; latter is a transmission type used in lawn/garden tractors, among other things. Pls advise.
If it IS a L&G tractor app we are talking about here, would also help if you would supply the make and FULL model number from off it's ID plate so that we may be able to chase down detailed specs.....

Thanks for clarification. It is a hydrostatic in a 38" gravely lawn tractor. Although the tractor bears the gravely name, I think it was built by Ariens. I will try to find the ID plate. The Gravely manual does not cover changing the fluid. It mentions to keep the fluid at a certain level in the expansion tank. The Eaton 750 was superceded by a 751 model. I cannot find any info on the Eaton site. I know for sure the 750 and any parts is no longer available.

Try this... http://www.google.com/url?q=http://sonnys_bolens.tripod.com/manuals/images/ST-Series/1765963A-ST-SERIES.pdf&sa=U&ei=xa_sUaSIL4SgyAGC2oGgBg&ved=0CBsQFjAB&usg=AFQjCNEGnUb8u2nrJnTDZDLfTmzxtIBVUg

Section 5

All I could find on the Eaton 750

I just did this on my Simplicity which shares the chassis and transmission with yours. Here is what I posted to Simplicity forum I frequent.

I found an easy way to change the hydro fluid on my 12.5LTH. Here is what I did over the weekend:

1 - warm up the fluid by driving around a bit
2 - open front hood for access to the reservoir
3 - there are 2 hoses connected to the reservoir, hose A at the bottom, hose B connected to side of the reservoir
4 - disconnect both and place hose B to the bottom nipple of reservoir
5 - connect hose A to a vacuum source - MityVac(used for auto brake bleeding) is what I used
6 - keep reservoir filled with fresh oil and draw out old fluid through the vacuum device

In normal operation hose A is connected to a port at the bottom side of the transmission. Hose B to the top side. What I did was used that circuit to draw out the old fluid from bottom and let the new fluid fill in from the top. Using this method there is no need to burp the transmission as there is no air introduced during the fluid change.

I did the fluid change with 30W oil twice, once before and once after hauling 4000lbs of mulch. I plan to do this once a year as it's so simple to do.

tonyx
Very clever . . . that's how they change out transmission fluid in cars. Very good tip