looking at a D-7..dont have year...late 50's ...early 60's..its at a farm sale tommorrow...it has a left final drive seal leaking ...they unloaded it yesterday...and looking at it today the left track was covered with oil pretty good...looks like to be leaking just sitting static..how difficult is it to replace the seal..???. also notice oil or oil residue coming from out of the top of the exhaust pipe running down the side of the pipe to the exhaust manifold...almost looks like unburned diesel fuel...have a older Farmall 806 that leaks unburnt fuel around the exhaust manifold joints after long periods at idle..then clears up under load...is this kinda the same thing.. thanks

The earlier Cats (up to the late 1950's) used a bellows-style final drive with cork faces, each side of the sprocket. The later Cats use a metal-to-metal polished face type seal, called a duo-cone seal.

The pressure is kept on the seal faces by the bellows, or by large diameter rubber toric rings, behind the duo-cone metal sections. Both types of seals can be damaged by wire or other stringy-type material being picked up by the track and wrapped around the seal.

The most common cause of seal leakage is failing, or failed taper-roller bearings on the sprocket shaft. There is a large taper roller bearing each end of the (hollow) sprocket shaft (which shaft is slid over the solid dead axle, and the sprocket shaft rotates around the dead axle).

The taper roller bearings need to have substantial preload on them, and this is applied by tightening the nut that is adjacent to the sprocket. This nut needs to be adjusted every 1000 hrs to keep the preload on the taper rollers. Many owners and operators fail to do this, and the preload goes off, due to wear, and the bearings accumulate clearance. Once there is clearance between the taper rollers, they commence to hammer under working conditions, and quickly destroy themselves.

You can find out if the bearings are loose by inserting a large crowbar between the sprocket and housing (after ensuring the track isn't too tight) and prying the sprocket. If it moves at all, or worse, goes, "clunk, clunk" .. you have excessive bearing clearance and the bearings are at best, extremely loose .. and at worst, starting to collapse.

With a high degree of luck, the tractor may only have extremely loose sprocket bearings, allowing the pressure to come off the seal faces. In 95% of cases, in my experience, a leaking final drive seal indicates failing bearings, or severe seal damage caused by wire or other foreign objects .. and your only option is full final drive dis-assembly and repair.

You can do a quick check of the oil by unscrewing the filler plug and seeing if the oil has metal particles in it. If the oil looks like silver paint, the tractors got big problems.
An even better check, is to unscrew the drain plug and release half a gallon of oil and let it settle, and check for metal particles that look like chunks of taper rollers.
You often get small chunks of metal that have broken off the gear teeth .. that's common, and shows normal wear .. but if the chunks comprise rounded sections that definitely represent taper rollers, the tractors most certainly got sprocket bearings that are shot, or on their way out ..


The oil running down the exhaust pipe is the identical problem to your 806, and is known as "wet stacking". The engine has been running for short periods, and is not reaching adequate operating load or operating temperature, to burn off the oil getting past the rings .. so it get pumped out the exhaust and dribbles and sprays everywhere. A few hours of hard work generally fixes the problem.

thanks ozdozer..I am going to draw alot of attention if I use a huge pry bar.. ..during or before the sale..I will at least take the fill cap off and look at the oil..again..I really appreicate your help...I am a novice dozer buyer..and your input will not be taken lightly..