Rear main info

[Byoung1330]

What’s up y’all. Just had some info about my rear main. I developed a leak at around 230k. I ran castrol bout the whole time I had it. Someone told me to switch to Mobil 1. Never again. After about 2 oil changes it started leaking like crazy. Switched back to castrol an the leak never went away. Tried every stop leak on the market with no success. I had oil on bell housing. Down starter bolts. All that. Couldn’t see oil on fly wheel through inspection cover. Changed valve cover gaskets. Oil pressure sensor. Crank sensor. Oil pan gasket. Everything. So by then I knew it was rear main. Never done a job that big. Biggest I ever done was install my lowering kit an changed every piece of suspension on my Tahoe u can change. It’s all new. Also did a new timing chain an oil pump. But didn’t wanna drop tranny especially with it being so low. Well I said screw it an went for it. Bought me 2 long extensions off Amazon an 15mm and 13mm deep well swivel sockets. Bought tranny Jack from harbor freight. Took it back when I was done lol. The cover. The gasket an a barbell while I was in there. At the end of my y pipe I don’t have a flange to unbolt so had to cut it. Clean cut welded back up after I was done. Anyway if u guys have this problem don’t be scared if I can do it u can do it. Took me about 12 hours. That’s cleaning all bolts an crossmember an taking my time not to mess anything up. I haven’t had a drop of oil since. Been 4 days now.

 

[Byoung1330]

Forgot to add I even pulled intake. Even tho I had it off a year prior. Just to take the valley pan gasket out the equation. Didn’t stop the leak.

 

[Rocket Man]

Awesome job. I have done everything to my truck including the trans (3 times lol) and rear main while I was in there. It’s just turning bolts like everything else except you’re on your back unless you have a lift. Which I don’t.

 

[Erickk120]

Its quite the job to take the tranny out, I hate when its the time to pull it out.

 

[corvette744]

Nice job on the project-i think mobil 1 is one of the best oils out their-its my oil of choice but to each his own.

 

[iamdub]

What’s up y’all. Just had some info about my rear main. I developed a leak at around 230k. I ran castrol bout the whole time I had it. Someone told me to switch to Mobil 1. Never again. After about 2 oil changes it started leaking like crazy. Switched back to castrol an the leak never went away.

I'm reading this as the detergent additives package in Mobil1 being very effective at dissolving and removing buildup. This is how the rumors spread that "synthetic will make your engine leak oil" as if it's an inherent negative factor of using synthetic oil. Technically, it can make an older engine leak, but it's not because it's synthetic. It's because the conventional oil and/or the lack of timely oil changes allowed sludge/gunk to build up, even if just a thin film, on the internal surfaces of the engine, mostly in the finer creases. Also, the molecules of conventional aren't as "fine" as those of synthetic. It could also be that the conventional oil doesn't have as robust of a detergents package as that in the more expensive synthetic oil.

The buildup and "coarser" molecules of the conventional oil masked the worn seal(s), preventing leak(s). Running the Mobil1, with its powerful detergents, cleaned away the buildup. The Mobil1, with its finer molecules and now lack of buildup to dam it, leaked past the seal(s).

 

[drakon543]

well above argument about mobil 1 aside when a rear main is ready to start leaking its all or nothing and will only progressively get worse. nothing you add to it will help much if at all because its a rotational seal. making it to 230k is more suprising for some as a rear main can start as early as 150k on older rigs.

 

[Rocket Man]

Agreed, once your rear main starts to go it’s only a matter of time regardless of what oil you’re running. I always figure if I have to rely on stop leak, I wonder where else it’s it’s gumming things up. I would never run it unless it’s a last desperate measure and the engine is at the end of its life. Pulling the trans is a bear of a job for the average backyard mechanic but it’s not technical, just physically difficult. And while it’s out you should consider replacing the torque converter just because it’s the other component that could fail down the road that requires pulling the transmission. For me, it would be worth the peace of mind. When I did mine I was replacing the transmission with a heavy duty built unit so the TC was a new billet one anyway but if it wasn’t I would have bought a new stocker. Also inspect the flexplate for cracking or just replace it too. You don’t want to pull that trans again, believe me. Be sure to read up on the alignment of the new rear main as it’s critical, and misalignment will cause the new seal to wear prematurely. There’s a tool made for it or better yet, buy the AC Delco rear cover with rear main already installed in it and follow the instructions. It’s pretty foolproof that way and you get a new rear cover seal in the deal.

 

[Byoung1330]

Awesome job. I have done everything to my truck including the trans (3 times lol) and rear main while I was in there. It’s just turning bolts like everything else except you’re on your back unless you have a lift. Which I don’t.

No the next day I couldn’t move being on my back that long. My neck felt broke lol

 

[Byoung1330]

An yes I was afraid of the Mobil 1 cleaning out gunk an cleaning out spots holding the seals together an it did lol