CAT 938G, transmission

ok nige so i tested the prssures again P2 AND P1 look identical when shifting into foward reverse vise versa. also ohmd out all coils 29.5-31 ohm 2 and 4 do power up together when shifted into REVERSE 1. it seems odd to me that when i engage the machine to reverse it lunges foward but does not move after the initial lunge

What voltages did you measure on the 3 solenoids.?

and yes i did back probe the solenoids.. also forgot that when p2 pressure drops for either forward or reverse the guage goes to zero then returns for both gears

Pressure drop to zero is a bit surprising. Uusally it only drops 100psi or so.

Did you confirm that the correct solenoids energized simultaneously when selecting 1st FWD or 1st REV.?
What voltage did you measure on each solenoid when they were energized.?

the solenoid had 23.4 volts and yes the coreect solenoids were energized simutanously

I think that "clunk" you hear when engaging reverse is nothing to do with the torque converter, because if it was you would hear it when you engage forward speeds also. The torque converter is working all the time the engine is running.

I'm still not happy about the fact that you apparently have to jiggle the transmission control more than once to get any gear to enage, but despite that voltages at the solenoids and correct coil resistances seem to indicate that power is getting to the transmission clutch control valves.

Have you tried switching the #2 reverse solenoid valve with one of the others, maybe #5 or #6.?
If that doesn't work then my opinion is that something is likely broken inside the transmission on the reverse clutch countershaft. The power flow down through the transmisison goes via two totally different paths depending on whather the FWD low clutch (Ref #4) or the REV clutch (Ref #23) is engaged.

I know that the above is probably not what you want to hear, but in the absence of actually being there with the machine it seems as though a process of elimination has brought you to this point. As I said above, I'm still not happy with the operation of the cab control, but there seems to be nothing else left as an option but an internal transmission problem. Rather you than me take the decision to pull it though.

im gonna pull it bud .. ive built a lot of zf / funk style transmissions .. what exactly will i be looking for with the reverse pack?

I'll be honest I think you will find a mechanical failure somewhere either on that shaft or in the gear train that drives the reverse clutch basket. I think that's what the bang or noise or whateve rit ius when you select reverse is related to.

The fact you have P2 at specified pressure when you select reverse means that the reverse direction clutch is engaging fine.

Just FYI "The Book" procedure is to remove the engine & transmission/converter as a unit, then split them once you have them on the floor. I'll send it to you.

An update. The OP pulled the transmission and on disassembly it was discovered that the fwd high clutch basket was in two pieces and the discs/plates of the clutch itself were welded together - probably what broke the basket.

The broken clutch basket was probably also related to the "clunk" he stated that he could hear when selecting reverse.