Let's hope it's the u-joints. The noise does not show up in city driving, just during highway driving over about 45mph. It's most noticeable while coasting at around 60mph.

 

The noise on coasting is the tip off in my experience. When you get the ujoints out you'll see burned grease and flattened needled bearing in the end caps...

This is not hard to do but you do need a press of some kind. Don't try to hammer out the end caps.

 

OK, so I got the old PTU out. Silverstateford internet listed $650, put then wanted $1100 when I called. Now I want used. Salvage yards all want an ID that looks 8L84-7251-AA or starts with 3L, 4L, ETC. I can't find this on the PTU? Is it on the CVT? Thanks.

 

Check and see if you can order on line from Silverstate at the online price.

There are several websites for Ford Parts that will give you the part number. May take a little digging.

If you take a salvage part look it over carefully for wear patterns. The gear teeth should be worn symmetrically and near the center of the teeth.

 

A local dealer finally parsed my VIN; my PTU part# starts with a 6. Is there any real difference? Can't I just pull a PTU out of a say a 2007 and put it in my 2006? I called silverstate. Once they got my VIN, the price went way up, and they wouldn't / couldn't give me the part # the salvage yards are asking for.

 

As best I know the part number doesn't change unless the design changes.
So, yes you could pull one out of an 07.
You'll find that, I think, the 05-07s were all common parts.
As I recall in 08 they changed things, whether they changed this part of the drive train, I don't know.

 

At some point, they changed from a switchable awd system to completely automatic. But since that probably involved the electronic unit in the rear axle, the PTU may well be the same.

 

The PTU is nothing but a 90° angle drive.

 

OK, I was able to get the part # (6L-847251-AA in my case). A salvage yard within 100 miles of my house has a 2012 with 25K on it that is $260 delivered. They took my part# and said it fits in my 2006 MMH. I will put it in this weekend. I am assuming that it ships dry, so will be adding the 75-140 synthetic. What I was not prepared for (but should have been) was the 2 quart lose of what appears to be ATF when I pulled the bad PTU out.
So, at 94,000 miles should I drain the remaining and refill with all new ATF, or just top off the amount lost? How much ATF is in the CVT? OK, looks like about 5 qts, and I'm close to 100K miles, so upgraded ATF Mercon V is going in.

 

You may need a gasket to go between the PTU & the casing it bolts to. Or it may be gasket maker (the gasket in a tube tube RTV type stuff).

More troubling is the ATF you found. That implies a seal leak between the transmission casing and the PTU. That ATF may have diluted the gear lube in the PTU causing the failure. Doesn't make sense that you found that. Inspect the shaft coming out of the casing and look for indications of a shaft seal failure. May no be obvious...

Yes, drain and refill the transmission with ATF. I change mine periodically (~50,000 miles). You'll see some label this as a "sealed unit" that's a misnomer.

As minimum do the PTU first so you don't pour two qts ATF onto the ground.