The two dual-lip type input shaft seals are installed in specific positions in the case and cover. The IDS output and rear pinion output seals are both designed as a two-piece cassette. The cassette seals must be installed so the inner and outer halves are positioned correctly (relative to each other) to function as designed and to prevent seal damage. All of the PTU seals are different sizes. GM-51834 is designed for double-ended/dual usage to install the rear pinion cassette seal into the rear housing and also to install the RH input seal into the right side cover. To install the two-piece rear pinion seal in the proper position, GM-51834 features an internal counterbore to allow clearance for the pinion shaft and also a raised area/face to position the seal correctly. Incorrect seal installation will result in suboptimal seal performance and reduced seal life.