my opinion: 656 draft control leaks repair

I did some research...in the book and inside the tractor.
Thanks for the input from everyone a few days ago.

Those with concerns about affecting the tractor like I had, do not worry about it because: a)the differential is lubed from the oil cooler circuit, which will not be affected from this procedure b) there will be a good dousing of oil inside the lift cover while the engine runs, and the remaining oil film coating shoud be sufficient to keep parts lubed while sitting over time. c) there is an added benefit of knowing you have drained ALL of the oil when you drain the transmission housing--otherwise you have to remove the seat, and the draft control cover and take the tall plug out, then put it back, and repeat at the next oil change.

There are 2 ways to do this. The first is remove the front plug as Allen and a few others have talked about. The second is to remove the actual drain pipe in the rear of the lift housing--I opted to do this but also replaced the pipe with a shorter one that will keep the oil about an inch deep, same as the front plug when removed. If you need to remove the cylinder assembly, you may as well remove the rear drain pipe. I decided this route mainly because it can drain off faster than the 1/4" pipe hole the front plug covers and because i had the cylinder out. bc had mentioned observing his cavity filling faster than the small front hole could keep up, and since the cquadrant leaks are from too high oil level, I think the larger drain out the back is the way to go since the oil will be less likely to bottleneck and rise. The rear drain pipe is only threaded on tractors with draft control. For those like bc, without draft control, you could maybe unbolt the plate from underneath and just let it dump out the 5x5 hole, or cut the tube short.

Now that I know how the thing works, I am not scared of this method and I will help recommend this modification to anyone with the 656 666 686 models.

-karl f
ps might be good info for 504 and 544 too, YMMV
my first post on this topic

I"m considering replacing the tall plug with a shorter pipe.

Sounds good to me. I've already removed the long bull plug. My recollection is that the drain tube in the rear may allow oil to run right on top of the rear end gear but I'd have to go look again. Since my 2606 doesn't do any heavy long term field work, I probably can't hurt the rear end.

I didn't see a way to unbolt that plate with the drain tube unless the rear end housing was opened up or I believe the draft control housing is removable from the top of the rear end but more of a job than it is worth. If I felt the necessity, I would cut the tube. I did have about an inch worth of sludge I cleaned out of the bottom though. My drain tube had a bead that made it look like it was welded and no thread on it that you would see since tapered pipe thread usually doesn't screw all the way into a nipple. I'm not sure why they would change that particular part with some welded and some threaded though. I just know I put a pipe wrench on it and all I could do was start bending the tube.

On the 2606, my recollection on tracing out the oil cooler line is that it comes back to a block on the side of the draft control housing. I don't see it going to the rear end housing. However the draft control housing itself has some internal passageways in the housing and maybe one of them run down to the rear end and spray oil.

When i looked at my 656, the rear drain pipe drops straight down to nothing. The oil stream pretty much goes down between the bull gears and behind the differential--a wide open space!
removing the bull plug in the front of the housing would be slightly more beneficial to the left side of the differential but not enough to really matter.

i looked at the caseih parts site on the 2606 and can tell you that the only way you could remove the drain pipe plate would be either through the pto opening or by removing the draft housing. at least the lower link sensing models give you an access hole above the pto because of the 3rd link mount. But, for you a sawzall sounds easier!

tomorrow night will be the beginning of running my tractor with the modification. soon as i install the hyd pump gear (pto driven shaft bearing went out taking the gears with it...was a good time to do all the little things while waiting for major parts). Between new gaskets, seals, and o-rings; along with the standpipe modification, the top end of the tractor should be leak free for a good time.

karl f