I have a 2001 Dodge Caravan with the 2.4 engine. After removing the oil pan to change the rings and rod bearings, I noticed a large pump?? It is chain driven under the crankshaft. First I thought it was the oil pump, but that is under the front cover. Has gear driven twin "balance shafts" in the case. Was wondering what this thing does, as it is not on all 2.4 engines. This is the first I have seen one. The sprocket has a timing mark on it. To re-install, does this mark need to point straight up in relation to the index on the crankshaft with the number one piston at top dead center?

 

OK so I found out this is the balance shaft and counters engine vibration. A lot has changed since my small block Chevy days. Does anyone know a link to some good instructions with pictures to lining this thing back up with the crank shaft? Can it be did without pulling the timing belt pulley and front cover?

 

There are people who remove this balance shaft assembly and run it without it. It makes idle rough, but it evens out when driving. it adds horsepower without it, but I don't think it's good for an engine to vibrate like that continuously. Anyhow, I have the factory service manual for a 1998 that discusses removal and installation of the balance shafts. 4 page file with pictures, but cannot upload on the site. email me with your email address and I will send it to you via email. private message me your email address..