I have a 91 3.0 lwb monty with the 5 speed. A few questions:

1. Read all I could find on correct manual tranny fluid (gl-4 vs gl-5)my original owners manual states to use the gl-4 but I cant seem to find any. I have 80-90w gl-5 that the label says meets requirements of gl-4..but all I have found to read say that the gl-5 will not work well inside the manual tranny, with the copper or brass material inside.
2. The bottom of the tranny is wet. I seem to burn a quart or two of oil in the engine every 1000 miles. Is this from the rear seal. I have NO spotting in my garage or driveway, is it the rear seal failing when under pressure (driving?).
Or is the wet from my tranny ?
3. Confirming that drain hole is actually horizontal at the bottom of my tranny (not pointing to the ground but on drivers side pointing towards the driver door) and fill hole about 3-4 inches directly above...and if anyone knows offhand, what size are the plugs.

She shifts fine, I have put 10k miles on monty last 8 months and do not know when PO changed or filled tranny fluid last. Shes my DD. Just completed brakes and installed a new rebuilt starter.

Thanks in advance for your help....

Not sure if GL5 will work but in case it doesn't, you should be able to get GL4 fluid from a local Mitsu dealership.

Tranny and tcase have different fill and drain plugs. Tranny fill plug is on the dside of the tranny, roughly halfway up, just behind the bellhousing. The drain plug is below and slightly to the rear of the fill plug.

The tcase drain plug is on the chain housing, low on the dside, pointing to the dside. The fill plug is between the input and output shafts on the rear side of the chain case.

Make sure you can remove the fill plug before you drain the lube. The fill plug level is the fill level on the tranny, but not sure on the tcase.

I've found that the drill powered pumps do a great job of pumping the lube in, much better than the bottle mounted pumps. I use a bent piece of copper line on the fill side and hook it in the fill hole, with the suction side in the bottle. The pumps usually have garden hose fittings (male thread). I buy a washer hose at Home Depot with two female ends and cut it in two to get two hoses to fit the pump.

I have owned my monty for 8 months I don't know if PO put GL-5 or GL-4 in it, as well as the fact as since the monty is 23 years old the odds are great that someone along the way dumped in some GL-5.
Thanks for the info on refilling, will do.
I'm going to replace fluid, and then clean up all the wet underneath. Drive it a bit and see if I can locate leak.

i keep meaning to replace mine with some mtl http://www.redlineoil.com/Products.aspx?pcid=7

i have heard it really helps with worn syncros

NAPA has the GL4 fluid. Our dealer didn't have the GL4.

Replaced fluid. Old fluid was dark, seemed heavier than GL-5 that went in. Test drove about 10 miles thru all gears seems to shift same. Will update if anything changes. Wiped off wet, will attempt to locate the leak now.

Pennzoil Syncromesh is GL4

Do not use GL5 in that transmission. It corrodes the bronze synchros. There is a TSB on this.
Use only Stalube GL4,or Redline MT1. I've mixed Synchro with GL4 before. I run MT1, but as all synthetics it can cause leaks. In my warm localtion GL4 would have been best choice.

its in tranny. I will order GL-4, one of the above name brands. When I get GL-4 can I simply drain out the GL-5 and replace with the GL-4 ? advise.