This same problem came up about a year ago on another woodworking forum. It seems that there is a conflict between the internal fan and the dust collector. I'll cut and paste what one of the guys had to say.
From Rennie Heuer on Family Woodworking
I have a Dewalt planer (DW735) with which I am rather pleased. It is a work horse that has never failed me in over 10 years of use. The only issue I have with it is that debris keeps building up inside the case fouling the gears that raise and lower the cutters. It was bad with the original knives, it seems much worse with the Shelix head I just installed. It requires really removing the cover, vacuuming out the bulk of it and then alternating between a dental pick, vacuum, and small advances of the mechanism to get it all dislodged and cleaned out.
I did some research on line and found many people have the same problem but few had any luck in correcting it - except one fellow. His solution was to remove the fan on the motor shaft. He reports that the problem has completely disappeared and the machine runs quieter. I believe his theory is that the fan blows the chips out at a very high velocity, a higher velocity than the dust collector moves the air out thus compressing the chip flow and causing it to back up into the machine.
I'm no engineer, but I do think I possess a modicum of common sense and this made sense to me. So, after the clean up (the third one in a month!) I removed the fan shroud and took out the fan. The machine is indeed quieter. I will be running some white oak and poplar through the planer in a day or so. I'll give you all an update then.
Rennie removed the impeller and ran a bunch of oak and walnut through with no build up and the motor was just warm as the fan is just to remove chips not cool the motor. His was an older model DW 735
Here is a link to the whole thread if that is allowed.Pictures are not available unless you are a member. https://familywoodworking.org/forums...er+plugging+up