You have a 4R70W Transmission.
First: You need to change the speedo gear. 3.53 is not a ratio I've ever heard of, so I'd look into that. If you really have an actual 38" tire, with 3.53 gears, the computer will not read this properly and will not be able to shift accordingly.
This thread has links to good tire size a speedo gear calculators:
97 speedo gear 255/70/16-285/75/16?
I'd suggest that you first change to an accurate speedo gear and then consider flushing the trasnmission and replacing the fluid with Mercon V.
The speedo gear is only a few dollars and may save you from a transmission rebuild. I don't know how optimistic you should be about this though. A 38" tire is HUGE!!! Your transmission may be worn out from this.