If it is the original drain plug it should take a 15mm.
19 MM
spark plug gap for 1994 gmc jimmy
It would be found at the lowest point of the oil pan. It should take a 15mm wrench to remove it.
It should take a 15mm box wrench to do the job.
.60
.096 is the spark plug gap
per vehicle specs on a 1998 gmc jimmy 4x4, the correct size tires are 235/70/15
0.060
stubby 18mm wrench and a hammer
The differential fluid on a GMC Jimmy is changed by removing the drain plug, draining the fluid, and re-installing the drain plug. The filler plug can then be taken out, fluid added until it reaches the bottom of the filler hole, and the plug re-installed.
Stock size 235/75 R15
P235/75/R15