I have a '98 4X4 SC auto with 100k (60,000M) it has developed a shutter above 50mph the trans and transfer case fluids have never been changed I plan to soon. My question is what transmission do I have I don't seem to be able to find the code any where except the window sticker says 4-speed auto. Where can the code be located?

 

There's a sticker inside the driver's side door jamb. Among other information, you'll find the transmission code. Most likely, you'll find a "U" to denote the 4R70W transmission.