I have recently purchased a d8 dozer. I don’t know much about the machine, not even the year. I had some trouble finding serial numbers in the normal locations described in posts on this forum due to the tags being removed. But I did find a few around the machine. 1E2528 is on the left side of the engine block. 9F8092 is on the side of the pony. 6F6066 is on the cable unit on the back. 
   The machine sat for 6 months before I purchased it but was used regularly when the previously owner  parked it. When I started the machine, the blade would go up normally but would slowly fall down. Once I got the machine home I ran it for an hour or so and this issue got worse, had to hold the blade control all the way in to keep the blade off the
ground. There’s an oil leak around the back of the dozer running through the cable Unit and the drum and pads are slightly wet from oil.

Could that E be and "F"? 1Fxxxx would make it a D8 13A model and the 9Fxxxx would be the matching pony block.

1E2528 would be a #25 Cable Control.

Hi, bnjhnsn.
Try looking for the serial numbers stamped into the parent metal under where the serial # tags would have been located.

Photos would also help.

Just my 0.02.

you may need to scrape of layers of crud and paint to find them.

The part number on starting engine 9f8092 refer 9f8135 and fitt on D8 SERIE 13A AND D8 2U and you should have a serie tag on big blok rear the starting engine transmission

Here’s some pictures I’ve taken of the d8 and the serial numbers I’ve found.

holding the cable control lever in to keep the blade up will just overheat the clutch plates and cause excessive wear. if the clutch is slipping that bad you need to adjust it now and probably add a few discs to take out the slack. since the blade sinks probably the brake needs adjusting only.   very different from hydraulics.  think friction and heat. make your control movements quick and deliberate and don't slip the clutch.

Does anyone have the proper procedures for adjusting the clutch? 

first identify your control and if it is a front or rear control. make all adjustments with the blade on the ground and keep fingers clear of cable.

try this www.tractorparts.com/PDFs/CAT_25_23_CCU_OPERATIONS.pdf