Transmission Crossmember Removal Questions

[Justinj360]

I have a 2004 Yukon 5.3L and I'm going to be replacing most of the exhaust soon. I've read that in order to replace the catalytic converter section of the exhaust you need to remove the transmission crossmember to have enough room. How hard is it to remove? What do you do exactly? Thanks.

 

[MadDogDelpho]

I haven't done it on a GMT800, but I did a GMT400 and it wasn't too bad, I just supported the transmission with a jack and remove all of the bolts connecting the crossmember to the transmission, then the nuts and bolts connecting it to the frame rails.

 

[Justinj360]

I was thinking it would be something like that but I wanted to be sure. Will the transmission actually fall out if it's not supported? Either way I'll still support it.

 

[MadDogDelpho]

It shouldn't, but it'll definitely tilt the engine back.

 

[rockola1971]

Yep. You must support the transmission. You could crack the bellhousing of the tranny or bust off the tailshaft of the tranny if you do not support it. Do NOT put a jack under the transmission pan. It will crush the pan into the valve body of the tranny. Lay a scrap 2x4 across the bottom of the tranny pan and put jack under the 2x4.

 

[MrBalll]

Only issue I had with the cross member when moving it was one of the O2 sensors got in the way of removing one of the bolts. So you may have to take out the O2 sensor to get that bolt out.
But you should be removing those anyways.

 

[Justinj360]

Yep. You must support the transmission. You could crack the bellhousing of the tranny or bust off the tailshaft of the tranny if you do not support it. Do NOT put a jack under the transmission pan. It will crush the pan into the valve body of the tranny. Lay a scrap 2x4 across the bottom of the tranny pan and put jack under the 2x4.

Noted, thank you.

Only issue I had with the cross member when moving it was one of the O2 sensors got in the way of removing one of the bolts. So you may have to take out the O2 sensor to get that bolt out.
But you should be removing those anyways.

Yes I am sure I will have to remove the O2 sensors. How stuck should I expect them to be? Mine are the original 13 year old sensors.

 

[rockola1971]

THey arent too bad to removed. Easier with the oxygen sensor socket made specifically for the job. Fire truck up and let exhaust heat up or use a torch lightly and that will make it even easier to get out.

 

[MrBalll]

Yeah, definitely heat it up before attempting.
I live in Texas so we have no real rust or salt issues so my sensors and pipes were pretty clean. But I was not able to get the sensor off just normally with a wrench. I heated it with a torch, since the truck was six feet in the air I couldn't really turn it on. I then got my wrench with a six foot cheater pole attached. Probably overkill, but the pole was nearby so why not. With that is was cake.

 

[Justinj360]

So I'm in the process of removing the crossmember now and I have all 6 nuts off but two of the long bolts on one side won't budge. You can spin them but they must have too much weight on them still? Should I just jack the jack up some more? How far should I jack it up in the first place? I'm scared to move the jack at this point..