5.9L Cummins Front Gear Cover and Rear Main Seal Replacement (2022)

Hey all,

Recently I did some extensive engine work to my 2006 Ram 3500 with the 5.9L Cummins engine. Before I started the work I knew I had an oil leak out of my front main seal on the crankshaft seal and I thought same for the rear. Neither were bad enough to drip on the ground when parked overnight, but there was enough to make things turn oily on the surrounding areas. I hate dirty engines and grease covered parts. Sorry that's my vice. Keep em clean.

FYI: My post is not a 100% how to, but a little reference and maybe some help to someone with similar issues.

I will start with the rear main seal because it was more straight forward. I had my transmission and flex plateout of the vehicle already,so it was a no brainer to replace this seal. Now when I first started on my truck I "thought" I had a rear seal leak. Well after further understanding the Cummins adapter plate and the seal, I don't really think I did. However I had already purchased a Cummins OEM seal before the project started so it was going in lol.

The new seal kit from the dealer was 100$ (give or take a bit). It comes with the new seal and the installation tool. That tool is a must have to properly complete this task. Not sure if auto parts store XY or Z sells one with the tool but it makes the install per the book if you will. I recommend this one.

Removal: You need a little screw in slide hammer. I got one for like 15$ at the local cheapo depot tool shop. You will also need to drill a couple small holes in the lip of the existing seal in order to screw your slide hammer into the seal (holes need to matchthe screw end of your slide hammer). I did three holes into the old seal. One at the 12:00, one at the 4:00, and one at the 8:00. I think you could do 2 holes one at 3 and one at 9 without an issue. Either way the old and new seal both have a metal inner structure that you are drilling into, once you pass through that DON'T drill any deeper, we aren't trying to drill holes in the crank to lighten it..We just want to getunder the outer layer of the rubber and through the metal lip in the seal. Examine your new seal to get an idea of the structure of the old one. Once your small holes are drilled evenly, you can screw in your slide hammer and give it a couple taps out at each location. Work your way around giving a couple taps on each hole. Within one pass around all the different holes the thing will probably pop right out. They are a tight fit but this removal process makes it very simple. Do not try to removethe sealwith a hammer and a screwdriver. This is not going to end well for you...If you knock this seal in there is no way to get it back out easily...

Clean up the seal area both on the crank and the block area (adapter area). It needs to be free of any contaminates like oil, dirt or debris. Check the surfaces for any scratches or wear. It needs to be dry per the instructions.

Install is per the supplied instructions. In a nut shell, it goes in dry. Why?? I don't know but that's what the Cummins package said so that's what I did. The biggest part about the install is using the supplied install tool. It pretty much looks like a metal ring someone cut off of a can. The seal only goes one way (full rubber face out). This install tool does 2 things at once for you. It gives you a surface to hit with your hammer (I used a rubber mallet). This allows you to distribute the force around the seal and not distort it. It also is your install depth gauge for the new seal. Just like any one piece seal you must gently work it from all sides to get it in without damage. Take your time and don't use force. It's rubber and light framed metal. You can bendthe sealif you sink one side infurther than the other. Mess it up and you will have to spend your kids lunch money to buy another one. If your kids are like mine, they won't take kindly to that...

Once the seal starts its way down evenly, continue until the install tool comes in contact with the crankshaft.(The tool has an inner lip that matches the crank diameter, try playing with the tool before you mount the seal to get a feel for how it works.) Trust me it won't let you go any further but you still don't need to beat on it. You will make full contact all the way around the crank with the tool. This way you know the seal is at the proper depth into the engine block,and it is not sitting crooked. Dry is the word and trust me,it will go inwith ease.

Now the skinny, turns out my rear main seal wasn't the cause of the leak. Matter of fact the inside of my bell housing and adapter area was really dry.My leak was coming from between the oil pan, block and rear adapter plate. For those questioning the adapter plate (correct me if I'm wrong), the Cummins engine has a rear adapter plate on the back of the block so it can be easily altered to fit a wide variety of applications. Want to put it on a Ford transmission just get the right adapter and flywheel, want to put it in your offshore power boat? No problem get a different adapter that goes to your drives. Awesome idea in my opinion, however it is another seal and a potential area for a leak, as was my issue. Now the adapter was sealed to the block properly so I didn't have to remove it, but where all three pieces meet there was a leak. Since I was a Cummins novice and well studied in the old SBC motor, I assumed it was a rear main seal leak causing this leak. I had seen thisall to many times in the Chevrolet camp. I was wrong lol. Lesson learned. Experience points gained.. Should you suspect a rear main seal to be at fault, confirm your pan to block is not the culprit first.After seeing the rear main seal and its quality, I would say it's likely not to have issues for many, many miles..

In the end I replaced the oil pan gasket (whole other topic) and no more leaks from the rear. Side note: a leak on the top of your engine (Like valve cover) can drip around and down causing it to look like you may have a rear seal or oil pan leak. Verify that before you go through the trouble of replacing the pan or rear main seal. Nothing worse than all that trouble and it's still leaking lol

Onto the front seal.With the engine work I had goingthe front timing cover was already removed from my truck. Removing the oldseal was pretty easy at this point. I just knocked it out from the back of the timing cover on my work bench. If it were still in place on the engine I would assume the same procedure for the rear seal would work for the front, given you have the space. However I can not confirm that since I did not do mine that way. Maybe someone can add to this post for that.

For this seal I went with a locally purchasedsealfrom store X. I did not install the seal in the cover when I had it off the block. That may have been stupid on my part. This seal was a royal pain in thebutt to get it started into the stamped cover. I'm sure 2 hours of my life was wasted on an unsuccessful attempt with the first seal. The seal I purchased was really kind of flimsy and I ended up bending it trying to get it to level out. They come with a sleeve that helps guide it onto the crank snout but where it seats into the timing cover is another story.So after trashing that seal I went to a different auto parts store for seal number 2. This one was more robust in design. I wish I could remember the brand so I could save you the hassle, but I don't. Sorry. This seal didn't go in any smoother, but it did keep from bending upso itwas able to be installed. What a pain.

Now here is the reason I started this post. I don't know if this problem is local to my truck, my model of Cummins engine or all engines. Upon removing the old front seal I noticed some pretty obvious grooves worn into the crankshaft snout itself. Right where the factory seal was riding. I find it hard to believe that a rubber seal could wear down something as hard as a crankshaft, but I suppose if you add some dirt, oiland thousands of revolutions anything is possible. For arguments sake, when I installed my new seal, I tried moving it a bit further back in the timing cover so it would have a fresh shelf to ride on. Personally I don't think it was enough to help but I didn't feel it was wise to push this seal any further back than what I did. Currently no leaks but it's not really100% dry. I feel a fix will be needed for 100% confidence.

So my question is, is there a fix for this without replacing the crankshaft? Has anybody else seen or had this happen to them? Is there a special seal or kit that address this issue?

Any input would be great. Years ago I thought I read where someone made a repair sleeve that you fitted around the crank but I didn't have any luck finding something like that locally. I really don't recall if it was even for a Cummins engine. The idea seems plausible.Maybe someone here has more insight?

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