Only three more Jiros to go to after this one, since they just added a new one in Tachikawa. The Mejirodai Jiro is in Hachioji City, a fair distance from the loop. You have to take the Keio Honsen (the Takaosanguchi branch) and then get off at Mejirodai. To do this you can take whatever the next express is to Kitano, then switch to the local to Takaosanguchi, or they do have a Special Express (no change of trains) that goes from Shinjuku to Takaosanguchi, and Mejirodai is the stop before Takaosanguchi. After you get to Mejirodai you can take the 05 (グリーンヒル寺田) or 06 (法政大学) bus, you will see the yellow sign on the right after about 10 minutes, the closest bus stop is Harunabashi (榛名橋はるなばし), there is a small river and bridge right next to the shop. If it looks like you are going into a forested mountain area then you have gone too far. Each bus line in Tokyo seems to do things a bit differently, but with this bus line you get on in the back and swipe your Suica card, then when you get off you swipe your Suica card again. At 1 PM on a Saturday there were about 10 people on line. The service is very fast at this Jiro as there were three people behind the counter. In order to get the tsukemen you have to buy the correct chip for the base ramen size/style that you want, and then add a 150yen chip for the tsukemen. This is a lot of food. When it comes you may be a bit scared by the amount of noodles but there will be a bamboo support under it to suspend it about 1/2" off the bottom of the bowl, I believe this is done to allow the water to drain underneath. Presumably you get more noodles and broth for that extra price. The broth is quite similar to the Nishi Shinjuku Ramen Jiro except with a significantly higher percentage of onions and much less suspended fat and surface oil. The pork was very good cuts, not too fatty, and some of the thickest that I have had recently (3/4" or so). The noodles were the size of thick linguine, but you have to ask for them to be katame. The veggies were about 50/50 between moyashis and cabbage and the cabbage had quite a large amount of the larger greener leaves in it. Not too convenient unless you live in the area but definitely one of my top Jiro experiences.
OTaqe's Blog page
Tabelog page (more pictures)
Local directions once you get to Mejirodai
Diddlefinger Map (English labels)