AC model DD grader. I"m a noob! Need some advice

Hi guys,

After a few threads and posts on the subject, I'm still looking to cut in a runway in N NM. I looked at a few cheap options, and now I've come across what should be the ideal tool for the job.

It's a 1950s AC model DD diesel light weight grader. I've been looking at the gas version model D, but have worried that the gas model isn't powerful enough at high altitude.

My research has said it's important to look at the allignment of the wheels to insure they don't tilt in, which indicates a gear box or axle problem. Also the regular stuff like hydraulic leaks, and lack of brakes.

My question is this. Does anyone know other specific items to check on the DD? I believe it's the rather common Perkins NA diesel engine, which I know scant about. I will open the chain boxes and look at the drive, and of course, drive test it. If there's something I need to check specifically, let me know.

The diesel engine should be an AC 262 engine. The DD model was built from 1954-1965.

You may well have done your homework on how much material has to be moved to make your runway...if your concern is about enough power to do the job I would recommend
shopping for a bigger grader. You may find a bigger one for not a whole lot more money. Ideally with any grader you want to know that all the gears are working and not popping
out under load. Take a good look at all the turning mechanisms of the blade. An old grader doesn't have to be perfect and depending on wether you wish to keep it for runway
maintenance purposes or sell when the initial job is done you want to know you can get most of your money back. Sometimes it's better to spend a bit more up front for
something dependable than get into one cheap that becomes a money pit. I have owned three graders over time (not Allis however).

Altitude affects diesels as much as gas, unless you have a
turbocharger.

The old 226 dependable gas should have lots of power and less costly to repair if the engine needs work. There is no differential in the rear end so all four wheels drive at all times which gives it lots of traction. If it has the 12' moldboard I would cut it down to 10' if you are going to move a lot of dirt. I don't remember the transmissions being a weak point. They were made by Clark and were used in the small Galion grader as well. Don't let the rear wheels start to hop if they start to spin or you can take out the pinion shaft. Look in the chain boxes and run a magnet around in the oil to check for filings.

Thanks for the info. As for power at altitude, a gas engine will always suffer from lower internal cyl pressures compared to a diesel of the same size. The pumping losses associated with the carb plate, and also the venturi will have a greater affect than the open intake of the diesel(all other things being equal).

I looked carefully at the model D and all I can say is it has been very neglected. The gas tank is rusty, and they are using a small can with bungees to draw fuel. All three hyd cyl need rebuild, they are all leaking plenty. It doesn't have much hyd pressure either so the pump is in need of some work. Engine runs well, but is caked with oil and crud. Clutch is ok, and gears are ok. I got it to grade a bit, and it'll do the job, but will need a couple tires. Total investment will be $3500 for the unit and maybe $8-900 in parts for restoration.

The DD is in much, much better condition. The owner thinks it has a problem with the inj pump but I didn't have any issues. However, I'll send it off for cleaning and rebuild($375-400) before leaving for the hinterland. Needs one tire. Grades well, the only minor point is the slight curve in the middle of the moldboard blade. The blade has been used plenty, and it's getting an arc to it. I can get the DD for $5000 and also would put $600 in the pump and tire.

Both have leaning wheels, and hyd driven blade rotation. The DD also has a side to side blade shuttle of about 4 feet. I'm thinking I'll put up with the harder starting of the DD and get a better overall unit. I can tow both of them with a buddy's 20 foot lowboy and 1 ton. It'll be about $1000 more for the DD, but I think I'll be better off with a bit more power, and less work needed to get the gas D up to snuff.

Is the mouldboard bent or just the cutting edge worn? If it is the cutting edge and it hasn't been flipped you can flip it over and it will be straight. New cutting edges are also available. The hydraulics are not very high pressure because of the belt driven pump. You should try and have matching tires because they are all locked together to save wear and tear on the drivetrain and the tires..

(quoted from post at 18:42:56 12/23/16) Is the mouldboard bent or just the cutting edge worn? If it is the cutting edge and it hasn't been flipped you can flip it over and it will be straight. New cutting edges are also available. The hydraulics are not very high pressure because of the belt driven pump. You should try and have matching tires because they are all locked together to save wear and tear on the drivetrain and the tires..

Click to expand...

The cutting edge is just worn toward the middle. It is in two 6' sections, so my idea was to swap them left for right. Not sure if the mount holes line up, but that would solve part of that problem. As for the hyd, I'm used to aircraft systems which are much more robust than tractor. My old plane hyd run at 2200PSI, and they are checked once a year to insure it will put out at least that pressure for 10 minutes. If I get the DD, it'll only need one tire, and I would get a matching size. I think they are 9.00x20. also, I could swap fronts for back and insure they all stay real close.

Negotiating with the DD seller now, hope to get it done in early Jan.