grove cutting tool

[Frank S]

this is another of those sometimes I hate it when I am always right things.
The whole reason I made my transmission jack was to change a rear main seal on a friends Mack truck
I had been telling him for a year or more that he had an iol leack between the flywheel housing and the engine block.
Every Mack service center in country that he has had some repairs done on his truck while out on the road has said the rear main seal was leaking.
Finally he took it to a shop to get another related issue taken care of on the transmission they kept the truck for 2 weeks then claimed the only thing wrong was the throw out bearing was dry and greased it. The issue was the clutch arm bushings were worn They were supposed to pull the transmission and replace them but they didn't Saying OH they are not bad enough to need replacing at this time
Anyway I told him that if I was to drop the tranny I wanted to replace the clutch since he had 400,000 miles on it already. and I was not going to do a job twice.
He said he wanted the rear main seal replaced anyway OF COARSE YOU DO I thought. And I'm going to have the flywheel ground as well and pull the housing off to FIX the leak
In all the years that truck manufactures have been in business they still haven't learned that when they assemble the flywheel housing to the engine the only thing that keeps the oil from leaking is a microscopically thin layer of RTV sealant. and when the housing is tightened to the block most of that is squeezed out and over time what little that is still there will deteriorate Either the bolts will become loosened slightly from the constant pounding form the torque of the engine or heat and cooling what ever, eventually it is going to leak. because the main sealing is not between the mated surfaces but the tiny little bead of sealant that forms along the edges
The solution that I have done to every housing I have installed for the past 45 or 50 years I learned from my dad long before that. Back when the housings were made of cast iron before RTV was ever invented
You cut a very small grove all the way around the housing on the mating surface.
Note the evidence of oil leaking to the outside of the housing

First I cut a small grove using a ball file with a baby hobby tool
then I made the grooving tool to deepen the cut

This is a poor quality video since my friend nor I am are video graphics engineers
but is explains the process