05 Yukon XL 4x4 Rattling in bellhousing area with AC on

[Tonyrodz]

Just got everything repaired. The rattling noise was the flex plate, and the starter solenoid was going out due to the flexplate being cracked. And the sluggishness when giving gas turned out to be the rear knock knock sensor being corroded with water. The knock sensor being corroded fouled out cylinder 7 spark plugs so I got new spark plugs as well. $600 in labor for a shop to replace the flexplate/flywheel and starter as I didn't have the tools necessary to drop a transmission out to change that, not including the cost for the parts for it, I bought them myself. Parts included new battery, new starter, new knock sensors and harness, new intake gasket, total for parts was around $700. So $1,300 later it seems to be running fine now. And just in time for my birthday tomorrow. Good birthday gift for myself. Thanks for the tips on the flex plate.

She was holding on by a hair! Happy early birthday!

 

[HighestStorm]

I have the EXACT same symptom....noise is very random, usually only occurs when first start/drive, then goes away quickly although I sometimes immediately turn AC off... the other day it did it and then I notices AC not blowing cold, took a look no AC belt! So I just ordered and received and tensioner/belt kit for Gates.. It has a TSB sheet with it.. explains the "Slugging" issues with GM AC Compressors... hoping my tensioner/belt kit is THE problem!!

If the tensioner and new pulley doesn't fix the issue I would say take it to somebody who can drop the transmission if you can't or drop the transmission out yourself and have them check the flex plate/flywheel. If you look at the pictures I just posted you'll see what the cracked flywheel/flex plate looks like and that's what was rattling on mine.

 

[Fless]

So I'm wondering, are the replacement flexplates beefed up at all, or are they the same as OE?

 

[Tonyrodz]

So I'm wondering, are the replacement flexplates beefed up at all, or are they the same as OE?

Funny, flexplates in my Tahoe, 01 and 05 Express Van's all cracked and had to be replaced. Went aftermarket on those.