Bell grader 770c fault code F 736 got only 1 gear forward and 1 gear revers

Question edited for a lot more clarity.

Transmission oil level? It takes 47.6 gallons! Transmission pump?

https://www.google.com/search?q=NEW+HOLLAND+RG170+Grader+will+not+engage+transmission

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The transmission has failed.

run the fault codes and check for faulty TCM or reverse servo/solenoid

run the fault codes as it may be a servo/solenoid problem or a TCM problem.

DISCONNECT BATTERY ,WAIT 3 MINS RECONNECT. SHOULD BE GOOD UNLESS A HARD FAULT, THEN REPLACE PART THAT IS BROKEN

valvebody or soleniod not aplying revers band in trans 1st gear is the same clutch pac as revers only diferenc is in revers a holding band is aplied causing revers rotation

you have a 6 speed gearbox and you are missing reverse,push DOWN on the stick.check your manual PLEASE..........

check the gear selectors

sounds like sticking EGR valve to me but ned more info