D10 Tranny Gears

I have found that 3rd gear is just a hair thicker than the original gear, but reverse is MUCH thicker and I am thinking this will not work.  I notice now after the fact that all the gears on the vendor websites that I normally buy from say they are for a much later tractor than mine, which is an earlier D10, S/N 1731.

Looking for thoughts or advice, where to source the gears for my tractor because all of the ones I see online from restoration vendors seem to be for later model D series tractors.

Is it possible there could be an issue with shift forks or detent?  I've read some on this site about replacing or even modifying the forks or detent locations to get the gears to engage further.  Just not sure what the steps are involved to do so.  I am not looking forward to tearing the tractor completely down again.

When I go through a D10-D15 transmission, I always move the detents to get a full engagement of the cogs. Sometimes I modify the collars to get even more engagement.

Here is a test you can do: With tractor off, sit in the seat and shift into 3rd gear. take your hand off the shifter. Now take the palm of your hand and push the shifter hard and try to push even further into gear. If shifter moves more, that means there is more area of the cogs that could be meshed. To take advantage of this further mesh of the gears, the detent must be moved.

The problem from the factory was the gear cogs are only set to mesh 1/8" maybe 3/16". That is not enough when you get operators who are in a hurry and force the gears in. When the cogs get rounded off, say 1/8", then there is nothing left to hold gears engaged and the rounded off cogs act as a wedge and push the gears apart. Engineering fail from the factory.

To remedy this, we learn not to grind gears, but also to make the transmssion better, one can move the detents so the gear coggs engage fully, up to 1/4". The problem is to determine how much the detent groove in the shift rail can be moved, because with the shift cover installed, there is no way to physically see the gap between gears. In a perfect world, with the shift cover off, one would use playdough-like material about 1/4" bead and put it on 3rd gear in line with the top of the shift cogs. Then install the shift cover with gears in Neutral and shift into 3rd, being careful not to go further into gear than the detent allows. Shift back into Neutral and remove shift cover. Now the playdough will have compressed when you shifted the 3rd/2nd collar to engage 3rd gear. Since you didn't push the shifter past the detent to engage 3rd gear fully, the thickness of the compressed playdough (X), will be the exact measurement to move the 3rd gear detent.

To functionally move the detent groove, remove the 2nd/3rd shifting rail from the cover. Get a measurement from the center of the detent groove to the end of the the rail. Weld groove closed. Now take your old measurement (X) and add it to the thickness of the playdough (Y) and machine new detent groove with the center of the groove according to the sum of the measurements (Z). X+Y=Z That will get the detent as close to spot on as possible with full engagement of the gear cogs. Same procedure with any other gear.

A note about the aftermarket gears vs new OEM gears. During a D10 trans job last week, I noticed the customers supplied aftermarket gears were not machined as precisely and seemed to have more of the cog machined off at a taper than the OEM gears.