4x4 experts chime in- diff question/possibly trans
 

It may be common sense to some of you guys but I've never had a 4x4 ranger. This current one I have has 4 wheel drive. I've never known what was wrong with it (it has never worked) and I've been using it as a 2wd. I've been hearing a ever so slightly friction noise from the front end when I put it in gear. If it's in park or neutral and rev it I hear no noise whatsoever. When I drive up to around 60mph it starts to howl. Ive checked the driveshaft from the trans to the rear diff and im not getting any play whatsoever. Someone told me I should take a look at my diff fluid. I looked and stuck my finger in the front diff and it feels low. There's is oil staining around the cover plate so I assume it's been leaking out.

Here's where you guys can chime in. I was under the impression that the front differential wasn't in use until I select 4wd? Obviously my next plan is to reseal and top it off but does that mean my 4wd system is engaged even when it's off? I can spin the shaft going back to the transfer case and it starts feeling stiff. Is it supposed to be freely rotating? Reading about the gear oil also gives me conflicting info. Do I just follow the owners manual and go with 80-90 or do I need friction modifier? I have an lsd in the rear and I know that uses the friction additive but I'm unsure about the front.

Stock front differentials are not limited slip.

1983 to 2000 Rangers used auto or manual locking hubs on the front axles.
2001 to 2012 had "live axle", always locked front axles, some 1999 and 2000 did as well, but all 2001 and up had it

So it would be good to post the year of your Ranger when you post a question, also engine size

If you can spin the front driveshaft by hand then you probably have a 2000 or older Ranger, so not "live axle".

But because the front differential is OPEN type you could have one failed hub that has locked which will cause a noise when driving, and still allow you to turn drive shaft when parked.

Tell us the year and I can direct you to which Auto Hubs you have and how to check them
But if you jack up both the front wheels and spin them you can tell if one hub is locked

It is an 02 4.0. It looks like iihave the live axle from your description. What I meant to say is I could turn the front driveshaft and it would "lock up" if I tried to spin it. Seems like that's normal. I filled the front diff back up with 80-90. I don't know if it's just a placeabo but it seems to have baffled the noise down by a little bit. I still get a howl around 60 though. Idk how long the diff has been low as I put abut 3/4 of a quart in there. My take is it's been too long and it's damaged something already. Since I found the front low I completely forgot to check the rear. I'll have to take a look at the rear later to see how that one is doing and if it's causing the noise.

Yes, 2002 would for sure be Live Axle

I have a 1997 Ford Ranger XLT manual transmission 4x4 im trying to find a really cheap transmission or A rebuild kit

4.0 motor

You have an M5OD-R1 transmission, 4x4 version, which is different from 2WD version.

M5OD-R1 is also called M5R1
M5R2 is a larger version and won't work for you, used in full size trucks

These transmission are engine specific, bell housing does NOT come off
So if you have a 4.0l engine then you need a 4.0l M5R1 for 4x4 transmission

2001 and up Rangers got the 4.0l SOHC engines, these had same bell housing as your 4.0l OHV engine(1990-2000), so can be used on your 1997 4.0L
They are called the M5OD-R1HD, or M5R1-HD, but must come complete WITH shifter, the shifter inside trans is different, so yours won't fit
Same clutch and other parts as M5R1

So your range is 1990 to 2012 4.0l M5R1(HD) for 4x4

Rebuilt M5R1s and kits are available on ebay or local parts store

So ive had a few test drives. Now that the front diff is full the noise felt like it was coming from the rear. I checked the rear diff and found the fluid in there to be rather grungy. The magnetic plug had a few small shavings stuck to it. How should i proceed?

Should i try to service the fluid or do you guys thing that will make it worse?

I looked at the owners manual and it also says 80-90 with xl3 friction modifier since my axle code indicates i have a LSD. But i also remember reading somewhere that the owners manual is outdated and there was a TSB for another type of fluid.

As bad as it sounds you will usually find some metal in front and rear fluid, also manual trans fluid.

Yes, drain and refill, heat up the oil bottles to make filling easier
You can use any matching viscosity oil and add friction modifier to it(it comes in small bottles), or use the oil with it already added