Making a screetching/ rubbing noise while on. still working but very noisy.

Sounds like you need to replace the bearings supporting the shaft. Not an easy job without the proper tools and if you haven't done it before.

Hi martyski39...

ALWAYS UNPLUG YOUR DRYER BEFORE STARTING ANY REPAIRS
Your dryer drum is mounted in the rear with a bearing, most likely the bearing is faulty and making the grinding noise, or maybe two conditions exist.
1...Bad drum bearing noisy
2...Bad drum bearing noisy, and with play in the bearing allowing the drum to rub the felt seal away at the door making metal to metal contact.Check your door for obvious rub signs...
I will include a parts house webpage link where you can look at you "exploded" view of your dryer and order parts also.
Please take time to rate me
http://www.partselect.com/MultiModels.aspx?ModelNum=de7400p&searchTerm=&RefineSearch=0

No you sound like you know what your doing, there is nothing to be aware of when compressing the piston back in except make sure there is enough room in your reservoir for the extra fluid that will come back up (you may need to empty some out).
The problem with the noisy pads may be a little more tricky,
is it a squeeling noise you hear when brake?
is it a grinding noise (like metal on metal) when you brake?
or is it a constant noise?

if it is a squeeling noise the most likely senario is dust on the pads and disc's. this is normally a problem with cheap brake pads and may be solved by buying a more expensive brand.
if it is a grinding noise it may mean there is something else rubbing on the disc. once the wheel is off check for any rubbing marks from any part of the wheel or guards that are on the disc.

if the blades are metal they may have been bent during installation. try to straighten them. make sure blades are not rubbing anything.

Does the a/c work (get cool)? Sounds like a belt,but you have to find out why. Even an old belt shouldn't make a noise. Check out the belt tensioner

ive heard that these pulleys have bearing mechanism in them that ware out check your dealer ask them

Sounds Like the drum is scraping. You can remove the drum and inspect the felt bearing/gasket for damage or a coin or screw that got lodged in it. You will need to remove Top and front in order to remove drum Carefully note the routing of the belt near the moter.

possibly bearings gone on drum shaft

Its an inherent problem with any Dynammite model = the fact that the motor is at the front means that it is extremely noisy.