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Discussion Starter #1
The Auto-Turn differential fitted to my Platinum is Ariens part # 04584100 (Differential, Automatic) and appears to be the same part used for all Auto-Turn differentials up to now. It is made by General Transmission as model DI 300 (marked on nylon cover).

Last year I noticed the machine veer to right on starting forward motion, and this spring there was grease coming out the sides of the differential. Looking at it this spring I see the right side hollow short axle is cracked beside the woodruff key way for 4 inches or so and a second crack farther around the tube for 2 inches. So that is the cause of machine veering to right and not a differential problem. But I had ordered a new differential anyway since the loss of dirty grease seemed problematic, by what others have said.

Removal of the differential is straight forward once the rusted 3/16" roll pin is removed. C clamps to hold the case together are not necessary for separating the cases, but would help reassembly. There are 8 screws to be removed using a flat blade screwdriver and they are easy to remove. The internal spring is not strong so you can hold the case closed with one hand.

With the top cover removed the assembly consists of:
- Two nylon covers, each with thin O rings on outer edge and a typical "grease/oil" seal at the center,
- Cogged Drive outer ring (that meshes with the pinion gear) and on the inside there are 8 projections (with the holes for the screws) to drive internal gear tabs;
- Old hardened grease covering most components but not all;
- Two sets of gears, each comprising two parts, smooth surface next to the nylon cover then on other side a drive half with the 8 half rounded (but flat topped) cast in separators. The outer edge has 8 tabs that are driven by the outer ring. These two halves pull apart to reveal the fine teeth gear set on each part that allows clutch to drive and to separate when automatic turning is exercised.
- Between these two separate gear sets is a slightly cone shaped spring, a thick O ring mounted in the center and a washer that fits inside the O ring to prevent each axle stub from engaging the opposite drive.

So there are 5 rubber grease seals, a drive ring, 2 nylon covers, a spring, a washer and 4 gearsets (2 pairs), grease to lubricate parts, and 8 screws. Disassembly and cleaning and greasing and reassembly was easy and took about 1/2 day, working slowly. One issue that I encountered was a half circle cut into the smooth side of each gearset (2 notches) perhaps for alignment but I don't know, I did not try to align mine.

I re-installed the differential and it appears to be working properly (with just hand power) just like the old one with the machine in maintenance position. Since I lubricated with grease between the two sets of gears (fine teeth separate for Auto-Turn to operate), the clicking noise is a lot softer (not previously greased from factory). I will run a power test once the new short axle (with bushings) arrives from my dealer.

I have lots of pics but am out of storage space on this site, so I expect this is "useless without pics".
 

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This hands-on teardown detailed description is a great read. The only thing better would be photos.
Thanks for your time and effort to document it.
 

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Town--

Your above post caused me to shudder by thinking of my old Bolens. After too many times (years) taking too many hours repairing that machine, I finally realized there were better things in life to do. My solution, I replaced it with a new 28 Ariens Pro
 

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Discussion Starter #4
The new Auto-Turn differential arrived Tuesday afternoon and the short axle with bushings arrived Thursday, so all put together this Friday morning. The new differential has T20 torx head screws instead of the straight blade screw heads. Otherwise it looks the same as the old one. It is much quieter in operation with muted clicks that are hardly noticeable and much like my repaired differential with grease used between the clutching gears.
 

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Nice job! I like taking things apart too :) I wonder if there's room for a small grease fitting on the new one. I put a flush one on my Deere (ariens) differential last year so I can make sure it's always lubed.
 

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Nice job! I like taking things apart too :) I wonder if there's room for a small grease fitting on the new one. I put a flush one on my Deere (ariens) differential last year so I can make sure it's always lubed.
In the 3rd pic of my earlier post you can see what lies under the nylon cover on each side of the differential so there appears limited access to the internals of the differential. If you look at the outer edge that is the drive ring that takes power from the pinion shaft and applies it to the 8 tabs on each side that drive the gearsets. It may be possible to mount a grease fitting to inject grease into the opening between drive tabs and the gear, but the drive tabs will move in that drive ring depending on forward or reverse or drive disengaged on both gearsets. So it is possible the tabs may affect the grease injection to the interior of the differential. The other issue is the nylon cover has a large O ring at the outside edge touching the ring gear so not much space for the grease fitting. You may want to put grease fitting on the other nylon cover too, but while lots of access to the left side cover the right side is more restricted by the chassis.

For me it is way too risky using grease fittings when every 6 years you can remove the differential. Removing the differential is easy although removing the rusted 3/16" roll pin needed @Jackmels advice to cut the pin to the shaft on both sides and remove right side short axle then remove the axle after pulling it out a few inches on left side to clear the differential and right side spacer and washer. Knocking out the pin on a solid surface was easy.

Since the original differential was used for 6 seasons and still worked properly except for some grease leakage at the seals in the center of nylon covers. I bought the new one as a precaution and greased the old one as a spare. It can be taken apart and cleaned and greased and reassembled in probably a couple of hours (only took 4 hours originally) in the warmth of my basement. The differential may not have replaceable parts but it is surprisingly simple mechanism and very strong and well built so I don't think any parts may be required except for the 5 grease seals perhaps.
 
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