</font><font color="blue" class="small">( Does anybody know what is done to install the optional creeper gears? Does it reguire splitting the tractor? About how much time, half a day, full day? Also approx. cost of parts (gears)? )</font>
Derek, I suspect you can install the Creeper Gear option but I just looked it up in my 2120 service manual. It was a factory installed option and there is no mention of field installation. This is a service manual for an early 2120 so that could have changed.
It does require separating the tractor between the transmission and rear axle center housing. According to the manual "The creeper gear consists of a sliding gear on the drive pinion shaft and a fixed gear and main shaft. When the creeper control lever is moved to the standard gear position (up), the shifter fork is moved forward and couples the sliding gear directly to the transmission output shaft. This couples the output shaft to the drive pinion to provide standard drive.
When the the creeper control lever is moved to the creeper engaged position (down), the sliding gear is moved rearward engaging the gear of the main shaft.
Power then flows from the transmission output shaft to the fixed gear and main shaft to the sliding gear which is splined to the drive pinion, thus reducing speed at the final drive."
From what I can see to assemble it you pull the PTO shaft and then do most of your work from the top of the rear end assembly. I think it is doable and it actually doesn't look that bad if the current tractor is 4WD since some of the shifting rails are shared.
I have no idea of the price for parts. It looks like a day job to me. Spencer200 should be able to give you more info.
Let me know how it turns out.
Andy