1997 Jeep Cherokee Generic error code #37, Also known as PO

Connect scan tool. Connect pressure gauge. Attach it to the overdrive pressure port on the driver's side rear of the case, where the overdrive bolts on. If it's being commanded on, there should be pressure here (like line pressure), but off it will be less than 5. Now drive it. Watch for the command for Fourth, and observe the gauge reading. If you get any reading,in excess of 15 PSI, at the time of command the solenoid is functional. If the pressure does not rise to 70 PSI and higher, and no fourth is detected, you have a LARGE leak in the Fourth circuit. Piston seals fail at a very high rate in this location, and there are two items in the clutch piston housing that can cause you grief. In view of the mileage, internal problems cannot be ruled out.

If you do not have a scan tool or pressure gauge for testing, then plan on spending some diagnostic time ($) to have this checked. A shop spends crazy money to purchase, learn how to use and interpret results. A shop that can do this will charge a good dollar for this and justly so.