I need to check my transfer case level and change the transfer case oil - 95 Isuzu Trooper. Can anyone tell me how and what oil to use?

USA car yes/no??
2002 Isuzu trooper.
2wd or 4wd?
check engine lamp on means scan the OBD2 scan port
and it tells you of VSS sensors are bad, some car have 2.
fuses farst
scan it next./
C10 and C15 fuse must not be blown out. dash box.
marked as Meter and Audio, ignore names, 10 and 15 fuses both good.
electronic, speedo it is. and same for VSS
vss for 2wd not same as 4wd,
2wd is on rear of transmission , manual stick or autmatic
4wd is on rear of transfer case.
not telling your drivetrain makes for long answers
engine>>>trans>>>transfer case.
non of that told at all

VSS is the speed of the far rear , prop drive shaft.
it converts, RPM of said shaft to MPH, (speed) and then sends said speed directly to Speed and to the PCM and TCM if there is a TCM

what tranny you got>>>>>???? in front of XFR case>???? automatic?
what is the question.
does it have it, yes on 4wd option
what type,
what viscosity.
how to do it, ?
how often.?
it holds 3 pints
the early cars used 5w-30 engine oil in tranny m/t box and transfer case and was shared oil.
http://www.pirate4x4.com/forum/attachments/isuzu/345441d1199634929-mua5-transfer-case-fluids-chapter8_16.jpg

MSG-5ETC, MSG-5FTC, ISUZU Transfer Case

The Isuzu 3.5's all burn about 1 quart between oil changes. It was an engineering flaw with that model engine. Some people have said that running full synthetic oil will correct the problem over time. Either way, it is extremely important that you check your oil regularly.

As for you second question: Torque on demand has at its heart wheel speed sensors which typically are the issue. Having a wheel speed sensor replaced will set you back about $300.

I hope I was helpful.

sounds like a sensor - when did it start - if just cranked up one day and bam it is there - sounds like either a brake wear indicator issue - if they are connected in those - or a fluid level change in the rear end or transfer case - look for leaks and check the brake pads or shoes

There may be a dirty or corroded terminal connection inside one of the plugs that go to the transfer case or the solenoid that actuates and engages the FWD is faulty or weak.

You can remove the dash urself.Its quite simple.4 screws.Then you can check the wire plugs at the back.And you can change the bulbs by twisting the plasic ends,
for your brakes change the pads..

trans =2.95 gal.
transfer case =1.45 gal.

drivers side right above the oil pan

Just have your auto - locking hub cleaned and use your 4wd more often, it get stock usually for non usage. dont use grease after cleaning, use oil or thick silicone oil.

after changing the fly wheel did you re instal the torque converter before you hooked up the transfer case? 2 have you checked the trans fluid ??