RB20/25/26/30 Rear Main Seal - 12279-5L310

RB20/25/26/30 Rear Main Seal - 12279-5L310

RB20/25/26/30 Rear Main Seal - 12279-5L310

bash out the old, gently tap in the new

Easy enough while you have the transmission out to replace this. A huge pain to make sure it's warm enough and there is no oil touching the RTV stuff while it's curing, otherwise you'll likely have a permanent small leak.