Rear Main Oil Seal Replacement

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Larryjb

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Okay, you guys have helped me out tons with stuff. Maybe this will help newbies.

As others have said before, removing a transmission is just LOT of work. None of it is particularly hard. This comes with a couple of caveats though:

1) Get a good low profile transmission jack and test it out fully before using:

-Make sure it is properly filled with hydraulic fluid.
-Check to see how much tilt slack it has. Will the deck of the jack suddenly tip forwards once you pull the transmission off the back of the engine? Remember that the transmission is front heavy.
-Make sure any lock nuts on the ends of the bolts are secure. If necessary, remove and apply some threadlock.

2) Check out some youtube videos. Tahoe Steve has a good series:

3) Have a service manual, preferably a FSM. They're not that expensive if you are willing to wait.

4) Although I have written many torque specs and sizes, check those for yourself in case I made a mistake.

5) If you are doing this for the first time, get the right tools. Some extra tools that I found useful:
-high torque cordless impact
-long 3/8 extension (24 inches at least)
-torque wrench (remember that for accurate torques, you make sure the torques are not near the ends of ranges on the torque wrench. For example, do not use a 15-150 ft-lb torque wrench to torque a 20 ft-lb bolt. 20 ft-lbs is an awkward torque, but I found a torque wrench with a range of 10-100.)
-A decent creeper.

6) One of the reasons this job took me 3x as long as anyone else is that I wrote everything down that I took apart. This was very helpful as I didn't forget to do anything when putting it back together. This guide is just that, a guide. You may find you prefer to do a few things differently.
 

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Larryjb

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Here was my timeline: 10 days, not as bad as I thought. It felt like more. I wasn't working 8 hour days, but it did take me much longer than most guys. I'm guessing about 50 hours for me. If I had a thread chaser to clean the rear cover bolts, that would have saved 3 hours at least. Not messing with the transmission pan in the beginning like I did would have saved another 3 hours. Fixing the transmission jack (lock nut came free) and dealing with a tilting transmission as I removed it lost me another couple of ours. Installing the transfer case took me about 3 hours longer than it should have.
  1. May 25: start date. (4 hours) Attempted to remove transmission pan. Don't bother with drain plug if you have one. GM uses a thread sealant making this really difficult. Just do it the old way fashioned way. It's not that bad. Difficulties with bracket. Either bend as other have suggested or remove front drive shaft to gain better access to Torx-40 bolts. Or wait until more stuff is off.
  2. May 26: (4 hours) Got up to removing all electrical wires from transfer case.
  3. May 27: Remove transfer case. Remove electrical connectors from transmission. (use heat gun or remove bracket for Driver side connectors) See https://www.tahoeyukonforum.com/threads/rear-main-oil-seal.117639/page-14#post-1450368
  4. May 28: Transmission removed.
  5. May 29: Cleaned gasket surfaces, bolt threads etc. Installed rear main seal. Installed transmission back to engine with connections.
  6. May 30: Install transfer case.
  7. May 31: Drained transmission, replaced filter.
  8. June 1-3: Finished installing odds and ends. Filled fluids. I used a tiny bit of pipe dope on the last few threads of the transfer case plug threads. Then, I torqued to only 10 ft-lbs. This pipe dope is non-hardening, so I can torque a little more if necessary.
 

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