Rear Main Seal replacement

[AlanS]

I've removed the rear filler block and as I was trying to remove the upper half of the seal, the upper filler block guard also wants to rotate out. Will that work, or do I need to make sure the upper filler block stays in place. I'm doing this with the motor in the truck.
Thanks again for everyone's help.

[brute4c]

My guess...its been a while, is that you do not want that upper filler block guard to come out.
I found this in the manuals about rebuilding the the motor in that area:

h. Install Oil Pan.
(1) Apply a thin coat of non-hardening Permatex, or equal, over engine surfaces of the oil pan gaskets. Install gaskets on cylinder block.
(2) Make sure new oil pan seals are installed on front and rear filler blocks. Install lower rear seal in rear filler block. Position gasket inserts in recesses of filler block.
(3) Position assembled filler block on the cylinder block, making sure the dowels in the filler block squarely engage holes in the filler block guard. Secure filler block to the cylinder block with two screws. Torque screws 15 to 20 lbs-ft.
(4) Position front filler block on the crankcase. Secure with two bolts. Torque screws 8 to 15 lbs-ft.
(5) Apply a liberal coating of nondrying Permatex, or equal, to front and rear filler block seal grooves in the oil pan. Position oil pan on cylinder block. Install cap screws, flat washers, cap screw assemblies and spacers.
(6) Tighten cap screws alternately to prevent movement of oil pan. Torque cap screws 10 to 17 lbs-ft.

Since line 3 there says the upper part should be installed already, i think it needs to be left in there for what you are doing. I dont remember removing it myself when i did it...just a pain getting the old seal out of there...

heres the oil pan installation with engine in vehicle instructions from the manuals as you will be doing that:

1. Oil Pan Gasket Replacement - Engine in Vehicle.
(1) Remove oil pan from engine.
(2) Pull ends of oil pan seal gasket from front and rear filler blocks.
(3) Insert gasket alining dowels W-285 in the oil pan front attaching holes on each side of cylinder block. Place new gasket on top of old gasket.
(4) With gaskets held in position by the dowels, make a cut through both gaskets, 3/32-inch from edge of front filler block or 5/16-inch from edge of the nearest hole. The cut must be so the triangular end of the oil pan seal will cover the splice.
(5) Remove both old and new gaskets. Discard old gasket.
(6) Clean the surface of the cylinder block. Apply thin coat of non-hardening Permatex, or equal, on the new oil pan gaskets and the splice near the front filler block. With dowels in the holes, position gaskets on the cylinder block. Replace ends of the oil pan seal at both front and rear filler blocks.
(7) Clean and inspect oil pan gasket grooves and bolt flanges.
(8) Lubricate filler block oil pan seals with engine oil.
(9) Loosely install oil pan. Hand tighten screws, being careful not to change position of oil pan in respect to the filler blocks.
(10) Working from the center screws outward and alternating from side to side, torque screws 10 to 17 lbs-ft.

[AlanS]

Thanks for the information. After researching some more posts here about others experience, I may just leave it alone. Mine didn't leak bad. This all started because of a bad oil pump drive gear. I dropped the oil pan to clean it out and while it was off I thought about replacing the rear main seal. I might just need to leave it be.