A couple years ago I posted about replacing the ring gear and starter drive on my Farmall 656 Hydro because they were badly worn. They were that way when I bought it and there was some confusion about what starter drive to use. Well this week the starter started grinding again and I looked in the inspection hole only to find the ring gear torn all to hell again. That means splitting the tractor again. Damn!!
I used a 396421R1 ring gear with 133 teeth along with a 10 tooth starter drive # 1877355. I believed those to be correct. I sure wish I could see in there and tell what the problem is but seeing anything through that lousy little hole is next to impossible. Not sure if the gear isn’t extending all the way or if the clearance is too much or too little. It appears that the rear part of the teeth on the ring gear is ground away, all the way around, and the entire tooth is almost missing in at least a 6” section.
Any suggestions are welcome at this point! As you can tell I’m PO’ed!
Tim

In those hard to see/get to places I try to use the camera off my smart phone. Other than that there might be some type shims to keep the gear from going too far into the flywheel.

Even the parts books are confusing on which starter drive to use with which ring gear. If you could get your dealer to pull up the old original service bulletin where they changed the number of teeth on the ring gear and drive to go with that I think you could figure out if you have correct one. You did not say gas or diesel but I know they changed on the gas engines. Not sure on diesel. I had another mechanic mix them up at the shop but the starter did not sound right so I caught it. Now, on the 706, there are two different drive gears also, HOWEVER they did not change the ring gear on those tractors. They changed the starter nose cone, so either starter will work but you have to have correct drive gear for that starter. More confusion. A good dealer can go way back and find the bulletin and it will be dated during the active production period of the 656 tractor. I have a lot of bulletins but not that one.

I did forget to mention that it is a diesel. Ill go up and pick the dealers mind again. Seems like I questioned him a couple years ago about it though.
Tim

The ring gear number 396421R1 should be correct. The Hydro tractor uses the same flywheel and ring gear for both gas and diesel.

The number you posted for the drive, 1877355, must be in error. That number comes up as a CW drive with a 36 mm gear rather than a 32 mm gear. A CW drive will not go on a CCW armature.

The diesel starter number should be 1113201. That starter used drive number 1970544. It has the physical dimensions as drive number 1851427 which is uses for the gasoline starter. It s also the drive used on later gas gear drive transmissions. The difference between the two drives is the diesel drive uses a spragg type clutch while the gas drive is a roller clutch.

You're right Owen. I typed too many 5's in there.
The drive I used is 1877350 not 1877355.
1877350 should be 10 tooth CCW rotation but it lists it as 39.4 mm not 32mm like your saying it should have. I cant find any # on the starter itself. 1877347 drive looks physically different than mine however and I dont think it would work in this starter. Is there a drive similar to 1877350 with a 32mm gear?

Any ideas as to how I could physically check the clearance or alignment of the teeth once I have the starter in place.

This first picture is of a 1851427 drive used with the gas engines. It has a roller style clutch that can be identifies by the crimped steel band around the clutch.



This picture is a 1970544 drive used with the diesel engines. It has a spragg type drive that can be identified by the machined housing for the clutch. Both of these drives are the same physical size, 10 tooth, 32 mm gear OD, and will interchange. The spragg clutch is a heavier clutch for use with the diesel engine.



This next drive is number 1965788 used on the diesel gear drive tractors. It is a roller type clutch, 12 tooth, 36 mm gear OD.




This last picture is an 1877350. It may not be the same as the one you said you used since this drive has a ratchet style clutch. It is quite similar to the spragg type. If you turn the gear you will hear it click like a ratchet. It is a stronger clutch than the spragg. This drive is a 10 tooth with a 40 mm gear OD. It is used on diesel tractors from the 706 on up.




The drive you want is the second one, number 1970544. That would be the preferred drive. Drive number 1851427 will also work but may suffer a clutch sooner than the other drive. On the other hand drive 1851427 will probably be easier to find since it is also used on the gear drive gas tractors up through the 766.

To check for the mating of the gears you can spray a bit of paint on the teeth and spin the engine over. You should then be able to see the pattern

How would the tractor start at all with the wrong starter drive?

~8mm is a lot. Enough that the gear would not mesh at all or grind against the ring gear instead of engaging it. The noise from such grinding would be immediately obvious on the first startup, wouldn't it?

IMHO you probably had the right parts, just poor materials.