My 4.4 v8 L322 is going in for a rear crank seal replacement as it is leaking.

Question: While the gearbox is off should I change the oil? How much can you get out but tipping it up? Or Is it better to do a mega flush?

What is the likelihood of disturbing any sediment and sloshing it around the box by tipping it up?

Any thoughts?

Might be a good time to ensure the oil cooler is all clear, you are going to have to disconnect it to get the box out (?)

Surely best to drain before removing the box? (you can get the oil nice and hot then before doing do) .
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You can also drain all the oil out of the torque convertor which is where the oil gets stuck when normally draining it out, it's a pain to do as you can't just pour it out, you have to keep tipping it back and forth...

Personally I'd put in a new TC while you have the gearbox out, they don't last forever... get near 100,000 and you are on borrowed time for it anyway....  Pete
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How sure are you, that the rear seal is indeed leaking.
Obviously, you must be seeing oil at the gearbox to engine joint...but, If your rocker covers are leaking, they can weep onto the valley pan, and drain out the rear of that area, down the rear of the engine, and drip out the join to the gearbox. Which looks to a typical mechanic, like the rear seal is leaking. If you search for a thread I've commented on, regarding resealing the coolant leak, on my valley pan, you will see the area, that leaks any fluid, either oil/coolant/both, from the rear of the valley, it's worth, checking this area, with small torch, and confirming all is dry there, before committing the gearbox out job.
Look at this guy,

he's doing the coolant leak, but at at 6minutes 20 secs, he points out this hole, where his coolant was running out. Your rocker cover, can weep oil to that area, and it will find it way down the rear of the block. There's a hole on each side.

You don't need to do all the work he's doing, just the rockers covers. 1 hrs work....(His stay on on this YouTube job) But I would recommend you put new spark plugs in whilst you have them off. The gaskets will cost you about £50, plugs a bit more.
over time, the gaskets go rock hard, and leak, especially if disturbed. Had your plugs changed recently? I say do them, because if your covers are indeed leaking, you plug wells will fill up with oil too. This does not help matters, and changing the plugs, though messy, will remove the oil, though it's best to have the oil soaked up with rag first.
Mine were like this, and were leaking just like the symptoms you are describing.

Hi all

Thanks for the replies - definitely a rear seal as all the rest is good and done.

Apologies if I didn't make it clear but the point of my question is - which is considered best - a mega flush or tipping the oil out??

Thanks

If you are splitting the box off and can get the TC out then there is no benefit in power flushing the box, the idea of which is to make sure all the oil is changed.

if you can manually drain all the fluid out wile the box is off and as said make sure that the TC and cooler are drained too then you should be able to achieve a total fluid swap in one go, which is the aim of a flush :thumbs:

you should get pretty much all of the fluid out of the box part of the system as a matter of course during a normal fluid change, its the TC and cooler which hold on to their oil. There is nothing that can't be fixed with a hammer😜😜
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I would change TC like Pete says. It is considered as wearing part. I did change it on mine when engine was off. -08 3.6 Vogue
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