How hard is it to replace the rear main seal in a '87 Samurai?

depends of still is stock, still 1.3Liters engine?
many are not. after 26 years. still have a carb ?
on the stock motor the pump is driven off the cam shaft.
look at head, see valve cover, ? the FP is mechanical on carb cars.
unless modified.
here are the free books.
all is here if not modifed, if modified post a link to your engine photos. (show carb fuel lines)

http://www.acksfaq.com/sitemap.htm

leak in intake manifold sea, at the rear of intake manifold. have to remove intake manifold and replace gasket.l

could be tranny mounts or engine mounts

ait fuel not being adjusted correctly is usual cause.

ITS NOT A HARD JOB. BUT YOU HAVE TO BE CAREFUL.YOU ARE WORKING UNDER A CAR. BESURE TO USE JACK STANDS .YOU NEED A REPAIR MANUAL.IT SHOW YOU HOW TO REMOVE TRANSMISSION.YOU HAVE TO SUPPORT ENGINE WHEN MOVING TRANNY.REBUILT KITS.WILL HAVE ALL GASKETS SEALS AND BEARINGS.BUT MAJOR PARTS YOU HAVE TO BUY THEM SEPERATE.LIKE SHIFT FORK COUNTERSHAFT AND SYNCHRONIZERS.NOW THE CLUTCH KIT IT WILL HAVE CLUTCH PRESSURE PLATE AND CLUTCH RELEASE BEARING.BESURE WHEN YOU BUY KIT MAKE SURE CHECK IT.MAKE SURE IT HAS EVERYTHING YOU NEED.

Remove the shifter from inside, two connectors to the sensorson the trans at the firewall, remove 4 bolts holding front driveshaft to the front diff, slide rear section of front driveshaft out of the splines, remove 4 bolts holding rear driveshaft to transfer case and slide the driveshaft out of the transmission tailshaft, remove the two starter bolts ( hardest part of the job), leave the starter in the engine bay with the wires still attached, remove the clutch ARM from the transmission, remove the rear transmission mount (4 12mm bolts) support the transmission on a jack, put another jack in from of the engine to pitch the engine so the rear is sagging down slightly (this is so you have enough clearance to remove the transmission), remove the four 14 mm bellhousing bolts (remember the longer one goes onto the passenger side top) tip the tailshaft up to the floor of the Sammy and slide it to the rear as far as possible, let the front come down slowly ( it will barley rub the pressure plate but not enough to hurt anything) presto its out, replace the clutch assembly and grease throwout and transmission splines the reverse these steps. I have done 3 of these and accomplished my last one in 4 hours total. No need to remove the exhaust, transfer case or engine as others have stated on numerous write ups. You will need two 12mm combo wrenches, one 14mm combo wrench, one 3/8 drive ratchet with 12mm shortwell socket, a couple extensions for said ratchet, one small pair of pliers (to hold the clutch cable while adjusting) and a hammer to gently tap the clutch arm onto the splines.

check your gear oil if that is fine then its your shifter guides they are more then likley wore out i had the same problem in my 87 zuk you can buy a rebuild kit for around 75 bucks

Check the metal vent tube on the fuel pump. When the diaphram goes out, oil will leak from the vent tube. If that is the problem, get it fixed pronto. Not always but there are some times when fuel gets mixed into the oil when the pump is going out and that thins the oil out. Keep on driving with this problem and you can kiss your engine good bye.

When/if you change the fuel pump out, make sure not to lose the push rod that is behind it. It goes between the camshaft and fuel pump.

Have you tried the dealer, they should have this seal, if not let us know the measurements and we can help

buy gas.