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So I just found out that my rear main is leaking. I'm trying to figure out if I want to do the replacmeent myself and use the money I would save in labor to upgrade the tranny while its out, or if its going to be too much work, just give it to a shop to do.

I've replaced transmissions in a few cars, both early and late model, never in a newer chevrolet though, mostly muscle cars and a couple of newer Mazda cars. So, Im not too familar with this particular tranny and application, but I am familar with the inner workings of a transmission in general and have most of the tools needed. I have a nice location to do this out on some property we have. We have a fresh 150' x 100' concrete slab that our horse barn use to be on that is now covered for storing motorhome/boat/toys/etc. I have a ton of jacks, pnumatic tools, ramps, etc. and some help from my 2 brothers.

All that said, what kind of work is involved in getting the tranny out and back in? I have a '02 2500HD with a 6.0 gas engine. Im assuming along with the drivetrain and cross member the exhaust has to come all the way, or part way out? Also, since the tranny is controlled electronically, is there anything to worry about there?

Lastly, if I decide to do this myself I was thinking of upgrading it a bit. This is something I know nothing about. I've put shift kits in older ford muscle car trannys but thats about the extent of my knowlege when it comes to opening up a transmission. I have a 6" RCD lift and am running 35" tires, so what would you all reccomend as far as beefing it up goes? And any direction in term of online sources for these upgrades would be appreciated. Thanks!!!
 

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HOT AIR BALLOON OWNER
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14,932 Posts
Rear main is like any other... shaft, cooler lines, x-member, trans itself, flexplate, etc, etc, etc all come out to gain access. Not hard, just time consuming as all hell and a pain in the ass without a lift.

Easiest thing to do is a valve body build up... aka shift kit. TransGo are usually the most indepth, Superior as well as Sonnax make quality stuff too. Just set them up for HD/Tow use.

PS be damned well sure the rear main is leaking. Check the PCV system out. Inspect valve covers for leaks, etc.
 

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haz 12"s!
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Getting to the seal is no biggie.. remove tranny, exhaust, etc.. The seal is a one piece that may be a PITA to get out and will usually take a special tool to put back in as even a small scratch on the lip of the seal and you have a big leak. Its a HUGE PITA if you dont have it. If you take the rear cover off, youll need a special tool to put it back as it has to align perfectly with the bottom rails of the block and centered on the rear of the crank.
 
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