Komatsu D21A-6 powershift hesitation

[chuckbuck]

Hi, I'm new to the forum.

I just purchased a 1992 Komatsu D21A-6 with the two speed powershift. The machine is in nice condition with 3150 hours (suppose to be correct).

When I shift from first to second, there is a hesitation of a couple seconds. The hesitation is enough that the machine comes to a stop if going up hill or has any load on it. I serviced the transmission oil and cleaned the strainer. Found some clutch disk material in the strainer, not a lot but about 30 pieces about ¼ in by 3/8 inch. No metal what so ever in the strainer.

I check the pressure at the top of the transmission control valve and in neutral there is zero pressure and when I shift to first gear the pressure goes up to 350 psi. When I shift to second, the pressure drops to zero for a second of two (tracks stop) then goes up to 350 psi.

Does any one have any ideas what is going on with my dozer? Is 350 psi the correct pressure? Why is the pressure dropping to zero between first and second.

Any help will be appreciated. I need to get a service manual but don’t have one as of yet.

Regards,
Chuck

 

[MadReferee]

If you get no help here on TBN try asking over on the Heavy Equipment Forums, specifically the Excavating Equipment forum. Somebody over there will have experience with the Komatsu.

 

[chuckbuck]

For future reference, the problem was dirt in the modulating or quick return valve in the valve body in the front of the transmission, not the valve body on the top of the transmission. I cleaned the valves and everything works fine.
Regards, ChuckBuck