If you don't have a lift and the engine could use a re-seal I'd suggest pulling the engine and transmission as an assembly. You probably already know this but the hood can stay in place.

__________________
"Rudeness is a weak man's imitation of strength" - Eric Hoffer

Even though you disconnected the kick down, is there any possibility of the wires being fouled? Does your shifter allow you to select 1st gear?

Yes, i can go through all of the shifter positions.

The symptoms, as described, point to a fault in the valve body, or in the governor pressure.
The statement "shifted into 2nd very late (25mph)" is understood to be an automatic upshift (selector in D). Is that correct?
Then "and there was no shifting past 2nd. 3500 rpm+ and no more upshift." Did the trans attempt to shift into 3rd, with the result that there was a "neutral" and engine speed broke-away?
If there was no break-away of engine speed there is probably no failure of clutch K1.


Again, if there is no break-away of engine speed, clutch K1 is probably OK.
An examination of the valve body and the governor is in order prior to pulling the trans.
It should be understood that transmission shops do not remove engines from the W123 chassis when rebuilding the trans!

Thanks! There is indeed no "false neutral" the transmission just fails to shift. Although, i have been doing some calculations and i believe i have been wrong this entire time. I believe i may have only lost 4th gear and my transmission is starting only in 2nd gear. My 1-2 shift that is occurring at 20-25 mph i believe is actually 2-3. The car will travel 45mph at ~3500 RPM, which i believe places it in 3rd gear, not 2nd.

Looking at the clutch/band application chart, it appears the issue would be somewhere in the K2 clutch circuit?

You can force a 1st gear start by placing the selector in "L".
The trans will remain in 1st much longer than your nerves, so move the selector to "2" as the engine approaches 4000.
You will then know if a shift to 3rd is failing, or a shift to 4th.

Is there any chance that the 1st gear forced is stuck and behaving like a kickdown? Might need some lube or a look at that switch. Do a bunch of snappy shifts down there - even with the engine off, just move the shifter a bunch - and see if it gets that unstuck. This sounds like the situation with a gasser that has that slide plate sideways to get from first to second. You can slide that plate over when in the higher gears and acts like kickdown is pressed, but you don't have to have your foot in the injectors. ( I call that sport mode) inspecting that wiring & switch might be in order. A test could be redlining in 3rd and see if it shifts up to 4. But what speed does that happen at?

Got pressure gauge connected to modulating test port, 40-42 psi at 31mph and vacuum disconnected. Next will be the governor test port, i am hopeful there is a smoking gun with the governor.

Governor pressure was good 1/2-3/4 vehicle speed, which should rule out a governor issue.

I can do 55mph at ~3500 RPM, which i think means i am certainly in 3rd gear. 2nd gear at a 2.41 ratio should max out at 40MPH at 4500 RPM. However, i am only getting 1 shift. I am either starting in 2nd, or skipping 2nd, along with no 4th gear.

What was the result of forcing a 1st gear start?

Behavior starting in in (L) is the same as starting in (D).
Shifter in (L) - Drive up to 15 mph
Shift into (S) - transmission shifts and goes up to 55 mph at 3500 RPM
Shift into (D) - No further shifting

Start in (D) - accelerate to 15mph, shifts once, goes to 55mph at 3500 RPM

I have gone as high at 60-62mph to get close to redline but still no shift.

Modulator pressure: right on the money
Governor Pressure: approx. 2/3 of road speed
No "False Neutral", just a failure to shift.

The Reason I think i am starting in 2nd is per the transmission and final drive gear ratios:
1st gear (3.68): engine would be turning over 3500 RPM at 20mph shift, which it is not shifting that high
2nd gear (2.41): engine would be turning a bit under 2500 RPM at 20mph shift, which is pretty close to what i am seeing in both a (D) start and a (L) start.

May try one more time to drop the valve body, disassemble and clean before throwing in towel and pulling the trans.

The results described above suggest that brake B1 is not applying (no 2nd gear), and that clutch K2 is also not applying (no 4th gear).
Inspection of the valve body for sticking command valves seems in order, and an inspection of the servo for brake B1.

Thanks Frank! Do you have any thoughts on why i think i am starting in 2nd (even with Shifter in "L")?

1st gear (3.68 ratio): engine would be turning over 3500 RPM at 20mph shift, which it is not shifting that high
2nd gear (2.41 ratio): engine would be turning a bit under 2500 RPM at 20mph shift, which is pretty close to what i am seeing in both a (D) start and a (L) start.

If, in fact, there has been a 2nd gear start throughout this episode, without the ability to select 1st, have a look at the shift linkage bushings and the linkage adjustment. This would not be the first instance of the arm on the trans not being moved quite far enough to move the internal selector sleeve into 1st (B1 release).

Quick Update!, I made it worse .

Took out valve body again for cleaning, Found a few valves that were very stiff and got them cleaned up. I was very careful with disassembly, labeling and reassembly, but somehow I have made it worse. Now i only have one forward gear (2nd) no matter which position the shifter is in. Despite my care, i made something worse.

Any idea a good place to get a good used VB?

Thanks!
Alex