I have a new clutch to install in my truck, so with 200k on it, I figure I should replace the rear main seal. I checked the service manual, and it says to put it in dry........is this correct? I've always put a little oil on seals when replacing them, although I've never done one in a Cummins.

As an aside, I've read in the past about a cooling system mod that installs on the back of the head. If it's going to be done, it seems it would be a good time to do it while the trans is out. Is that mod actually beneficial?

 

Follow the FSM directions. Make sure its clean in dry if you change it. Personally, if its not leaking, I'd leave it alone. It could go a long way without leaking. You may look into putting a speedi-sleeve in if your crank has a groove worn into it.

 

Thanks Tate.....just seemed odd not to lube it for the install, but I'll go with it. It is seeping a bit, and since I'll be in there anyway it seems like replacement is a good idea. FSM says if it's grooved, the seal can go in another 1/8", but if it's bad I'll sleeve it.