You are correct, solenoid #2 is common to the inoperative gears. The seven speed transmission is the same as an eight speed.
Have you done an oil sample to rule out a fried clutch pack? A sample report showing high concentrations of clutch material or steel means your transmission needs to come apart. Do all these tests to see how far the problems go. You want to go into a repair with your eyes open.
To rule out a solenoid coil with an open circuit (broken wire), put the machine in an even gear with the bowl hard on the ground. For the rear transmission, go to the RH side of the machine (you may have to come in from underneath), and find the second solenoid down from the top (refer to the 10DEC2023 post). Check for magnetism at the end of the solenoid where the nut is with a screwdriver. If no magnetism, unplug the harness from that solenoid and check the DC voltage between the two pins on the harness side. That will tell you whether the solenoid coil is DOA or you have harness issues. It should be 20-25V.
If you have magnetism at the solenoid, next step is to rig up fittings, hose and a 500psi gauge. Remove the SAE plug on the engine side valve body next to the solenoid. I believe it is -4 SAE. I found it easiest to have a 10 foot hose crimped up from -2 thermoplastic hydraulic hose with a female -4 JIC end and a -4 MPT on the other. Gauge will be -4MPT. Use a -4 coupler to connect the two. Purchase a -4 SAE male x -4 JIC male adapter to thread into the transmission valve body. Connect the fitting, hose, and gauge.
With the transmission hot (160 degrees), roughly 2000 rpm, and transmission in an even gear, you should see 245-280 psi. If you see low pressure (10-50 psi), you have a large internal oil leak. It can be the D ring on the clutch pack piston, or there are plastic piston rings on the end of valve body end of each counter shaft.
If your transmission pressure is slightly low (< 220 psi), check your pump pressure. Find the plug called out by "L" in the above post. I believe it's -6 SAE. Pressure with hot oil should be 255-285 psi.
If you find low pressure at your clutch pack, check your pump pressure regardless. Low pump capacity will cause clutch pack failures.
Also check your torque converter (TC) lock-up (L/U) pressure. This will require you to either drive the machine, or have the rear wheels off the ground to spin. You need to either tee a gauge into the hydraulic hose that runs across the non-dipstick side of the transmission from the valve body to the L/U valve group. It is hose #9 in the attached file. Use a gauge tee. I think the hose has -4 or -6 JIC ends. The other way is to chain your ejector up and pull plug #11 in the attached file and connect your gauge there (this valve group is under the round debris cover on the non-driveshaft end of the transmission).
If driving the machine, you will need to be going in 3rd gear on level or down grade at 2200 rpms or better where there is lttle slip in the torque converter. Your torque converter lockup light on the dash will go out and you will feel a kick in the tail if everything is working correctly (the TCU only allows the TC to lock up when the TC slip is under a certain percentage). If checking pressure at the TC lockup supply hose, you should see a drop in pressure at the L/U piston fills, then the pressure should rise back to pre-L/U psi (I.E. the oil is contained in the L/U clutch pack and isn't leaking out).
If checking at the L/U valve casting, you will need to disconnect the harness from the L/U solenoid. With the rear wheels off the ground, put the machine in any gear, 2000 rpm, and apply 24V+ and ground to the solenoid pins hotwiring it. You should see no pressure at pre L/U and normal clutch pack pressure when the L/U is engaged. Again, lower than clutch pack pressure means there is a leak.
The two places for TC leaks are the TC L/U piston o ring and #14 o ring in the front cover group picture. #3 shaft is hollow and carrys oil to the TC. It gets very hot and cooks o ring #14. I've seen either fail. When #14 oring sharts leaking, and the transmission pump starts to get worn and can't keep full pressure to all the components, clutch packs start slipping and burn out. #14 o ring is made from Buna N from Deere. I always replace with Viton.
The #1 and 2 clutch packs are used for every gear with a combination of the A B C clutch packs.
The TC L/U is designed to engage at 2200 rpm and unlock at 1900 rpm in gears 2-7 if the slip in the TC is low enough.
