Make sure you have the mechanism that opens the brake shoes to engage the parking brake installed correctly. If that little piece is not installed correctly, it will lead to the problems that you mentioned.
1986 300E (3/2002) Rear ended and totaled (10/2009)
2000 Xterra (5/2000)
1992 400E (11/2009) -Sold
1986 300E (12/2009)
2004 E500 Wagon (6/2013)