???? about changing hyd/tranny fluid on a 790

kebo · Jul 6, 2009

I'm about to change the hyd/tranny fluid on my 790 for the first time. I already have the filter, but still need to get the cheap & inexpensive JD Hy-Gard fluid at my local JD dealer this week. My manual says I need 4 gal's, that's fair enough. But, will I need some extra with the loader on it? The manual mentions nothing about the loader. Or, is that irrelevant cause the loader won't lose much (if any) when I do drain the tranny? Also, any tips on removing the internal mesh wire screen, or the vent tube on top of the axle housing?
Thanks!

kennyd · Jul 6, 2009

You will only be draining oil from the sump, not the loader. But. OTOH, extra fluid is always good to have around.

dirt ditch · Jul 6, 2009

Just changed fluid 10 tractor hours ago.

5gal. bucket will not fit under 790 with R4s while setting on ground.

Make sure JD fluid is Low Viscosity HY-Gard.

Filter has to be partially filled before it is installed and I bought the 5gal. bucket so can't tell if exact 4gal. but looks like it. Loader did not matter. Filled 3 3/4 gal. then topped off.

Used 2 funnels. 1 to fill 1gal. jug and 1 large hole funnel that set tight in fill hole. (got at walmart.) (I had help filling jug.)

Had to disconnect break linkage rod from pedal to remove screen. Messed up cotter pin removing linkage so had to replace with new one.

kebo · Jul 6, 2009

dirt ditch, you read my mind! I was planning to use a 5gal bucket to catch the old fluid in too, but will have to come up with something else. That's another good tip about the brake linkage being in the way of removing the screen too. I'll look that over before I get started to see if it's gonna be a problem for me as well. Thanks for the info!

dirt ditch · Jul 6, 2009

The screen is too long to be pulled out of the housing with out disconnecting the brake linkage and swinging it back out of the way.

You may want a pan and brush with gas or solvent to clean the screen. It is a very fine screen.

Good luck

Phineas7 · Jul 9, 2009

I'm not sure if it helped or not, but I raised the loader all the way up, drained the fluid, then lowered it. Figuring it would push fluid out of the cylinders on the pressure side and only suck air on the return side.