Blown main rear seal - 1991 GMC K1500

not told at all which end leaks (the exact spot matters)
I bet there is lots more wrong !
when did car last run good, or not leak ATF
last week,, last year, last decade? what?clues help.

history matters on all and service done. for 39 years
last owner left the pan loose and 2 bolts left and 5 turns loose, we cant see under any car.
front seal blown on or behind TC
rear seal; blown
pan gasket a wreck
pan hit rocks and cut and leaks
side shifter rod seal blown
or sensors on it leak (VSS)
governor cap seals blown./
more, sure.

Jeep 4.0 Rear Main Seal Part 1 - YouTube

? 9:12
www.youtube.com/watch?v=ft4LhJWOgtk
Mar 11, 2011 - Uploaded by Michael Rogers Jeep 4.0 Rear Main Seal Part 1 .... Should I stay away from buying a used Jeep with a rear main seal .... Jeep Cherokee 4.0LTicking Noise?

If its dark color it is likely rear main seal on engine. If it is red color it is front seal on transmission. check fluid levels, overfilling engine oil or transmission fluid can cause this also. both require major removal of tyranny etc. If you never done this get qualified help. .

several things, the rear main seal is accessable by removing the transmission. if this vehicle is standard transmission, then would recomend new clutch at this time given the amount of labor involved. if automatic, remove drive shafts, transfer case, transmission, and flexplate ....replace rear main. approx 5 hrs.

DW Mylin

engine rear main seal? rear seal of transmission? or rear seal of rear differential? if it is the rear main engine seal, you have to pull the transmission to access this seal.

If you have a shop you need to pull the engine to replace the rear main seal. There is a possibility of a two part seal. If you have a two part seal drop the oil pan and pull the rear main engine cap off and then replace the seal. You may need specialized tools.

The rear seal can be replaced but not without pulling the transmission, then you remove the seal holding case knock out-the seal and find the number on the seal and buy one and replace it and the gasket to the seal holder, also buy a speedy sleeve for the crank or you will find it leaking again.

A leaking rear main seal will not cause your transmission to leak.

The transmission has its own seal and should not leak because of the engine rear main seal.

Due to the labor involved in replacing the rear main seal on the engine, it is best if you replace the front transmission seal at the same time if possible.

Installation varies on different vehicles but the principles are the same.

THE REAR MAIN IS WHAT IS CALLED A FULL CIRCLE SEAL, SO YES THE TRANS AND FLYWHEEL MUST BE REMOVED, U WILL ALSO NEED THE SPECIAL FORD SEAL INSTALLER, WITHOUT IT THE SEAL WILL MOST LIKELY LEAK SOONER AFTER INSTALLATION.

You have to remove the transmission, remove the torque converter to access the seal. Most likely the bushing behind the seal is worn out allowing fluid to leak past the seal. After the trans. is out, take it to a trans. shop. It requires a special tool to change the bushing. Seems like a bunch of work for $10.00 in parts. The rear main seal requires pulling the pan to access it. When the trans. is out, this is the time to replace the rear main seal on the engine.