Jeep grand cheroke jumps when you put it in gear

Sometimes I take the starter motor off the vehicle. Lay it on the ground, hook up jumper cables properly from battery to starter motor, it should do two things, kick out the drive gear and spin. Do you have a flywheel cover that you can remove and watch the starter drive gear engage the flywheel? Also, check the flywheel teeth.

this is an automatic transmission question?
the question needs to be stated as to a gear or if the A./T TCC lockup clutch is dropping out.
to learn that is hard. to explain, it is felt, get any mech
to tell you. he must drive and it feel it.
dropping out of Overdrive from 4 to 3 gear
or the clutch unlocking,
2 different parts sections of the box do that.

alternator , kicked the bucket

a Fiat Grand cherokee? i know fiat bought jeep but?
is this a motor swap?
jumping, is this a stick shift. do tell?
do tell real car make , year, model and number of gears in trans.
(and if A/T or M/T)

check fuses and relays might have popped one when switching battery

check the trans fluid smell it to see if it smells burnt the goveror may be bad or it may need serviced

1998 Jeep Grand Cherokee Service Manual
http://rapidshare.com/files/138412864/ServiceManual.Jeep.Grand.Cherokee.1998_by_Parasico.rar
see ezg_8w.pdf, PDF page 46 of 448 for the junction box

SEE ALSO
http://www.scribd.com/doc/4790640/93ZJ-Secc-8W-Wiring-Diagrams
look for diagrams for fuse block, and relay center and power distribution center

fuse location is on front passenger side's side of dash (open door) OR underneath the dash, kick panel
the power distribution center is under hood.

headgasket failiure

I would check your linkage for proper adjustment.If that is ok check for bad trany mounts creating to much movement making it pop out.

They told me it is becouse the front tires are new and the back tires bad. I put new tires on the back the same as the front and hope this workes.