99 expedition loud engine roar??
 

Hey guys,
I have had my 99 expedition EB 2wd 4.6l now for 10 years and it actually has been a great vehicle......I have 197,000 miles on it,but just this year I'm getting a loud roar at startup and will go away once I start driving and disappear at around 20 miles an hour(basically after first tranny shift)......This does happen more frequently on hot days here in Florida and the roar lasts alot longer, like when I'm taking off at a light and will continue doing this til I get home........My service engine light came on the other day and the code has something to do with the EGR.....My boyfriend did an induction service and cleaned out the throttle body....We also cleaned the K&N air filter and Mass Air flow sensor......The shifting has been alittle rough,around the third shift.....Sometimes I have to let up on the gas so it will shift into 3rd....This morning I got it up to 50mph and my RPM's raised and lowered without me giving it more gas??......I was just wondering if anyone else has had this issue and may know what causes it??......In fact my boyfriend just changed the tranny fluid and filter and added some type of conditioner..........He seems to thing it is in the valve body??.......I thought maybe from the loud engine roar it could be the fan clutch,but we just replaced that last year......Temp gauges are normal......Is there something called a thermal bypass in the transmission??......I read a post about an explorer having this loud roar sound and they said it was the thermal bypass.

Thanks and any info would be greatly appreciated,
jblake6197