Aloha, I could use a little input please before I just go and buy more parts. I have a 1986 Silverado with a TH400 Transmission to a 6.2 Detroit Diesel. The issue I am having is upshifting,(apparently.) So... I have opened up the trans and replaced Kick Down Solenoid, Not It... Replaced the Governor, Not It. Replaced Vacuum Modulator, Not It. Chased down the vacuum line and then finally ran into what I should have checked first, (the vacuum lines.) Duh... So I found a hose that was from Vacuum Modulator to a port that then splits to the Vacuum Pump? (behind air filter.) I replaced the cracked rubber lines and noticed that there is no vacuum at Transmission Vacuum Modulator. There is not at all to hardly any vacuum at Vacuum Pump. I pulled it and blew it out. Still, Not It. Any help would be appreciated. Does the Vacuum pump have to sit correctly, adjusted to, when reinstalled? Is the port that I earlier explained where the two hoses meet in the middle of the run need/mean much to anything? Much Mahalo to whoever takes this post... Cheers!!!