790 Hydr. Oil Survey

[neilw]

I'm interested in determining what kinds of hydraulic oil you use and what your opinion is of its performance in high ambient temp. situations.

My 790 operators manual , copyright 1998, tells me the low viscosity hydraulic JDM J20D is good -22 f to 122 f. However, the technical manual, copyright 1999, tells me the low-viscosity hydraulic oil, no JDM number given, is good -22 f to 68 f.

For the past few weeks I've noticed a gear whine noise from the transmission once it gets good and warm. And here we exceed the Tech Manual's maximum limit as a low for the night. In fact come August a 68 f morning will be nothing more than a fond memory.

I need your input a 790 would be a terrible thing to waste.

 

[smilingreen]

Neil,
The whine you are hearing is normal in the 790. Mine does the same thing, especially when loading it down or pushing or pulling something heavy. I asked my dealer about it last year and he said it was normal mechanical noise. As for the hydraulic oil, I am still running the factory original. No problems, so far.

 

[joecdeere]

Neil,
low viscosity hydraulic oil was mainly produced to be used in the various hydo transmissins Deere has, it was adapted to help them from straining when the oil was cold, and to handle the heat these trannys produce, Your OK with either. I would't mix them if possible, and if it was mine I'd run the regular Deere Hyguard

 

[Anonymous Poster]

Neil

We retail 100+ 790's a year through our dealership...

Largest 790 dealer in the country.....Deere HyGuard is the oil to use....Slight noise from Transmission is normal. To eliminate transmission noise you would need to have a syncro, trans or Hydro...More $$$$$.

The 790 is by- far the best mid size no frills compact money can buy.

Have fun working with the 790.

Ed. V.