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Curtis B.
Curtis B., Technician
Category: Construction and Road Equipment
Satisfied Customers: 1177
Experience:  Technican turned service manager with multiple lines of equipment and rental units.
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D8H 46A trans has delayed engagement into reverse when warm

Customer Question

D8H 46A trans has delayed engagement into reverse when warm after light use of an hour or two, then later it will delay into drive also but not as bad. When cold works fine into all gears. Gets gradually worse and shift lever moves itself into neutral, cannot hold lever in gear. When this problem first starts the delay will be 1 to 2 seconds into gear, eventually 10 to 15 seconds and then the shift lever moves itself into neutral. All other functions seem fine including brakes and steering, fluid levels are clean and correct. Has been doing this for many years with no change. Thank you.
Submitted: 2 years ago.
Category: Construction and Road Equipment
Expert:  catmastertech replied 2 years ago.
Hello,If your pump pressure is correct, then the issue is in the transmission valve.You can try removing the valve and cleaning it to see if an orifice is plugged but, often this is due to worn out valve bodies.
Customer: replied 2 years ago.
Valve and valve bore are perfect, no wear and no dirt, adjustment is correct. In my opinion the 'Safety Valve' is pushing the lever back to neutral, however, per the manual it should only do this due to low line pressure and my pressures are good in neutral and all gears. Again, it takes about an hour of use for the problem to present itself and then it is only in reverse at first and then an hour later it starts happening in forward, though not as bad. I only use it in first gear but pulling it into 2nd or 3rd gives the same result. Since the same valve controls the gear you are in it would not seem that that would be the problem; also the 'Forward - Reverse' valve is good, too. FYI, I am a professional mechanic but not an equipment guy, I use this dozer only on my own property for what I would call very light duty. I have owned it for over 15 years and the problem has not changed, it probably has less than 200 hours on it since I bought it. I also have a 416B and a Deere 772A grader. In my opinion the 'Safety Valve' must be sensing low pressure, I'm just not sure why since readings are good. Thank you.
Expert:  catmastertech replied 2 years ago.
I have not repaired a valve that had this problem. The ones I have worked on needed parts and the customer took it back but, did not tell me how much they put into it to fix it. I agree the issue is the safety valve but, since I don't have real experience on this repair I can only pass on what I was told. This could be the orifices in the valves or in the plates. It must be debris trapped in one of them to get the valve to keep kicking it back to neutral. Since I cannot answer your question completely, I will OPT-OUT so others can help.

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