JD 670/770/790/870... maintenance items over the years

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bczoom

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Please add any tidbits, suggested or preventative maintenance items as well as what you've had to fix.

I have a 770 and it's been a great tractor but over the years, it's needed a few little things to keep it going properly.

Engine
Has been bulletproof and has required nothing but oil changes & filters

Hydraulics
Blew a hose or 2 on the FEL. No big deal. I think I now keep a spare on the shelf.

It's been leaking towards the front of the transaxle over the years but got pretty bad lately (like almost a pint per day). After a good cleaning of all the oily crud, I found and fixed the issue. In this diagram, part #7, those brass gaskets needed replaced. All 8 of them cost about $13. Remove the right fender and you'll see the large (22mm?) bolts. Pull them, replace the inner and outer gaskets, tighten them up TIGHT and reinstall the fender. Takes about an hour to do the whole thing.

Electrical
Turn key on, good dash lights but no start. EVERY TIME this happened to me, it was a bad battery cable. Happens about once every 10 years.

No headlights, no dash lights - Check the 5 amp fuse in the panel near your left knee. If the fuse is good and the taillights work, check for loose wire connection at that fuse box.

Body, Tires...
Yea, except for some minor dents/scratches, the body/frame is good. I use Fluid Film on the couple spots where paint is gone and is susceptible to rust.

Tires/rims - A few important things. If your rims look like they're going to need replacing, start shopping soon as they're hard to come by and pretty darn pricey. IIRC, it took me months to find replacement rims.
Another thing about front tires. The numbers are NOT the same in terms of diameter. E.g. on my tractor, I have 6.00x12 front tires. 6x12 tires are not the same diameter and can mess things up.
 
My 2001 790 was a great machine.Batterys oil and filters a hose from a vent on the rear diff.Two valve adjustments clutch adjustment.I had a right rear brake i had to keep up on the lube or it would get sticky.Top of steering shaft needed lubed from time to time.Turn the key it would always go.Looking back i think a 955 with ag tires and a front loader would of been hard to beat.But i dont think the hydros were built by yanmar.
 
The 8 or so years I had a 770 it required very little more than routine service. When I purchased it from the original owner it had a slow fluid leak on one of the hoses, he parked it on cardboard and added a little fluid every so often. I did the same for a year or so. I finally was smart enough to source the leak. A slightly loose connection, that I tightened with a crows foot wrench. Problem solved, felt silly for not addressing it sooner. I put about 100 hours a year mowing with a belly mower and a little with a brush hog. It was a great machine and I still have sellers remorse!
Neighbor had a 970 for years and he was hard on it, but had very few issues. I used it regularly for the FEL and brush hog, before I got mine. He had some problems with the dual stage clutch, probably self inflicted by not keeping it properly adjusted over time.
 
I had a 790 for about 10 years. Engine was bullet proof. Frame ground from battery was always an issue. Finally put a new longer ground lead on it and moved it out of the battery compartment to the frame.

It was easy to adjust the hydraulic bypass pressure with a cheap shim kit installed under the seat. You could then make your 790 dance on it's front axle when you lifted something heavy with the FEL and it pulled the rear end off the ground with the box blade attached to the 3 point.

The only thing I hated about it was the location of the tie rod for the steering. They should have placed it behind the front axle instead in front of it and low. I must have replaced at least 5 tie rods in 10 years. Oh....and front grilles. Replaced that a few times.
 
Smilingreen said:
The only thing I hated about it was the location of the tie rod for the steering. They should have placed it behind the front axle instead in front of it and low. I must have replaced at least 5 tie rods in 10 years. Oh....and front grilles. Replaced that a few times.
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Forgot about the tie rod. I'm on #2. I too have front grill damage (a hole about the size of... a 2" branch ;) ) I have a new grill sitting on a shelf but saving that for if/when I ever decide to sell so the tractor looks fresh.
 
hondajoe said:
I think the only ones that tore them tractors up should not of had a tractor to start with.
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They were used as a tractor on a farm with lots of woods. They weren't garage kept and waxed every week. They worked in mud, dirt, snow, trees, fields, fence rows and rocks. If you are bush hogging an over severely grown field that doesn't belong to you and you catch a stump left 14" off the ground.........the tie rod was the first thing to make contact on the tractor....kind of like curb feelers.....so your bush hog didn't catch that 14" tall hidden stumps. Moving piles of brush with the FEL and the tractor didn't have a full blown brush guard on it. The tree branch easily penetrates that flimsy perforated, spring loaded metal, used only to keep chaff out of the radiator. What kind of environment does your tractor operate in?
 
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