My 97 dodge ram 5.9L does not shift into od it

no engine told. size, this tells what transmission sites behind it.
1999 Dodge RAM 1500????? not VAN. 1500
2wd or 4wd'/
5 engines. then.
check all fuses, some have stand alone TCM brain (tranny)
scan the PCM for P07xx error (tranny)
check ATF levels hot, park ,idle, only do not overfill it ever.
ATF+3 (not sure but do check)
they used 3 transmission then
4-speed 42RH-RE automatic
4-speed 46RH-RE automatic
4-speed 47RH-RE automatic

42RE , is electronic shifted,
OD gear is dead or just the TCC lockup deaD
best is count the gears more carefully to see truth.
yes 4th gear is OD Geared. 3rd gear is 1:1 lockup.
.74-to-1 for first, 1.54-to-1 for second, direct 1.00-to-1 for third and 0.69-to-1 for fourth.(OD)
scab the PCM
to see if errors from the transmission show up.
I bet they do.
the 3>4 shift solenoid must work, .and no pressure errors.
the schematics show an OD switch if not closed OD does not happen, forget about that switch>
if car is 4wd and is in 4wd, many cars/ and truck all shut off
OD in 4wd, by logic inside the PCM (pure) my not be true on the biggest engine not told.

The linkage needs to be adjusted. It should be the one from throttle to transmission. They have to be set properly or vehicle will not shift correctly.

what led up to the no start

WAY TO GO !!! another "great idea" from vehicle manufactures

Hey, I also have a 98 ram with the cummins and what you are talking about is when you are pullin hard in overdrive the trans is working to hard causing the shudder, when this happens back off the throttle and get back on the throttle to allow the trans to downshift. If you dont it will break the overdrive gear. There is nothing wrong with the trans it is just that it is shifting to early and bogging down causing the shudder.

should be inside the trans have to drop the pan

inline of air duct (plenum) after air filter

ckeck linkage they might have undone iy and not put back in right place

sound like a tork converter problem or the shift solinoids are faulty or internal damage have it scanned hope this helps