Gravely 408 deck questions.

wvpolekat · May 20, 2009

I recently picked up a Gravely 408 rider. After adjusting the points, I got the old Kohler running pretty good.

Now that it is running good, it is obvious after mowing with it that the deck and blades need some attention.

Yesterday, I took the deck off to have a look. The blades were about as sharp as a 2x4. I went ahead and put a quick edge on them.

Now, for my questions.

1) The deck has 2 adjustments. One is the large lever that obviously controls the overall deck height. The other is close to the rear of the deck and appears to adjust the rollers at the rear of the deck. I have no idea how to adjust that one. Thoughts? Is this to adjust deck "angle"?

2) The blades are 2 different lengths. There is a sizable gap between them that leaves a strip down the middle. Each blade is connected to a 90 degree gearbox with a common shaft connecting them that the belt pully is attached to.

After looking at the blades, it seems to me that there should be some overlap in their coverage. Since they are mounted on gearboxes that are connected via a shaft, timing them should not be much of a problem and it would not slip and cause the blades to hit each other.

I can take pictures if needed. But, would welcome anyone's input and thoughts.

MMagis · May 20, 2009

If it's anything like the deck on my 8123, if the blades overlap, they will touch. Ask me how I know.

I had the same thinking as you when I built some blades for mine. I don't remember the particulars, but I know I set the blades three times before I finally accepted that they couldn't overlap. It's not a pleasant sound when you turn on the PTO. I'm not sure my deck is set up the same, but I'm thinking that there are two adjustments for deck height, front and rear. Adjusting the wheels would be the rear adjustment.

wvpolekat · May 20, 2009

I think my saving grace on them colliding is that they are gear driven off of a common shaft. Unless the ratio in the 2 gear boxes are not the same, they should remain synced.

Unless the mowhawk yard look was in style, I can't imagine that this was by design. But, I have no idea.

dex3361 · May 20, 2009

WVpolecat you are right the blades should be the same length with overlap.I had a 408 about 10 years ago and I had to rebuild the deck and gearboxes. It is just as you suspect that the gear boxes keep them from hitting. The gear boxes are Peerless brand.

wvpolekat · May 20, 2009

Great! I will have to see if I can track down what the right length is. I suspect the longer one is correct, mainly based on the distance from the edge of the deck to the tip of the blade.

The blades that are on there are similar in design, but obviously 2 different sizes.

Is there anything to know about timing them, or just make sure that they do not collide in the center? The way it is right now, they are probably 15 degrees out of sync. Meaning if one blade is at 12 o'clock, the other would be at about 1:30. I can't imagine that anyone has taken things far enough apart to get them out of time, but you never know.

I traded a carton of generic cigarettes for this because "Nobody could get it running". It had sat for at least 5 years that I know of. Took me and my father in law about 15 min to get it running. The points had slipped far enough out that they were never opening. After getting them set, it fired right up.

Right now, the old Kohler runs good, but is a bit tired. It belches blue/grey smoke (oil) under heavy load or throttle changes. Right now the exhaust consists of about a foot of 1" pipe with no muffler. I will pick a muffler up when I get the blades.

All things considered, for a tired 8 hp mower, it's a fine little machine. It pulls my ample butt around without complaint even when cutting pretty heavy grass with blades as sharp as a 2x4.

I am debating a repower with one of the 10hp diesels. They can be had for about $500, and I would be the only diesel 408 around, I am sure! It would take a bit of math on the pulley, since there is about a 1000 RPM difference between the Kohler and the diesel. But since it's all belt driven, that should be easy enough to do. Maybe over the winter..........

dex3361 · May 21, 2009

If I remember correct the blades are 90ｺ out of sync. I cut cut heavy wet grass with that little machine and I run the kohler motor wide open when I cut with it. I retro fit a chevy alternator on it when the charging system went south and it worked just fine.

JohnD · Dec 28, 2009

Congratulations on a wise purchase! The Gravely 408 is a really solidly built machine - they are nearing 40 years old, and many are still going strong, and with a little care will continue to function well, long after anything made today. They were quite expensive back in the early 70's but today can be found at bargain prices. The fine and even cut the deck makes really shows off your lawn.

First, if you haven't found it already, there's a GREAT Yahoo group dedicated to the 408. You can find it at: Gravely408 : Gravely 408 Lawn Tractor Group

That site has photos, specs, manuals, service tips, etc - anything and everything you want to know about the Gravely 408, and a whole lot of experienced and knowledgeable 408 owners.

Now to your questions:

1. Deck height and levers. The large lever on the left side of the tractor is used to lift the deck and set it down on the lawn. It will "float" as needed when set in the down position - always "level" to the surface. The small lever on the right side of the mower deck controls the grass cutting height, by raising or lowering the gage roller height setting. This design is responsible for the superb quality of cut these mowers are known for.

2. Blades. The blades should be the same length, and they do "cross" each other. The proper setting is to have them at 90 degrees, for maximum clearance. The two (Peerless)gear boxes are connected with a splined shaft that has to be removed to replace the drive belt attached to the deck. Care must be taken to adjust the blades to their 90 degree positions when replacing the connecting shaft. Check to be sure the woodruff keys on the output shafts (where blades mount) are not sheared off - a common problem after "contacting" a rock, stump or other obstruction. They are important to hold the blades in proper 90 degree timing. The Peerless boxes are expensive, but parts are readily available. Typical rebuild cost is $60 parts plus labor (I rebuilt one in Sept 2009).

Blades are GRAVELY part number 11234 / 88616. Specifications: Length :17 Width :2 Center Hole Diameter :5/8 Thickness :0.204