I hope you can help. This has stumped two mechanics so far.

This is the first winter with my '99 2.0 Tracker (4 door auto w/ 79k). On the first snow packed roads this winter, I put it in 4wd, light came on and over 35 mph the truck growls like an angry cat and it didn't appear that the 4wd was engaged. I put it into 2wd with the hubs still locked and the growling sounds were reduced but the truck swayed from left to right with a mind of its own. I unlocked the hubs and the truck was happy again.

I had the front differential replaced-had some metal flake, checked the transfer case oil and did an alignment. Next snowstorm, the growling came right back so I went right back to rwd and have driven on the roads that way since. When I go to my boyfriend's house which can only be accessed in the winter with 4wd, the 4wd will work there every time and without the growling (I'm going 5pm uphill).

This is my 3rd Tracker ('90 & '95 both with auto-locking hubs that were claimed by rust or they would still be here) and I have never had this problem. Does anyone know what it might be?

(One other unsolved issue: When under moderate to heavy acceleration in rwd, you can feel a 'thump' in the rear of the vehicle. This will only occur when going from 1st to 2nd gear. The entire rear end has been replace, exhaust tightened, transmission mount bolts are tight, spare tire bolts and mount checked/tightened, u-joints replaced, mechanics stumped again. Possibly related?)

Any suggestions are appreciated. Thanks!

I would say to check your CV joints, but the garage SHOULD have noticed a broken CV.  Look for a torn boot, shake the axle shafts for play, with the front up on jack stands and transmission in park turn a wheel listen/feel for grinding noise.  Also if your stub axle (right side) isn't all the way in, that will happen.  You could see that when it is up on the jack stands, and the end of the stub shaft will be buggered up.  Clean it up with a file.

Find a better mechanic. I think your auto hubs are sticking, probably not engageing all the way.

Maybe I'm missing something - but - a '99, 2.0 Tracker would not normally have locking front hubs, either auto or manual, it should have the air operated freewheel differential setup - which the '90 & '95 would not.

I have assume you know what you're talking about when you say ...

I put it into 2wd with the hubs still locked and the growling sounds were reduced but the truck swayed from left to right with a mind of its own. I unlocked the hubs and the truck was happy again.

Let's assume for the sake of discussion, that manual freewheeling hubs have been fitted - the next question would be was the air operated freewheel removed, or is it still there?

If the air operated freewheel is still in place - this would mean with hubs locked the axles are still turning the differential, and with the hubs unlocked the axles don't turn, so the differential doesn't (the freewheel locks the differential to the ring gear), and that (the freewheel differential setup) is most likely the source of your growl.

That's what got me too, the " hubs " thing. I think I'm confused.

Thank you very much for your help! I apologize, I wasn't really clear. It does not have manual freewheeling hubs. Nothing was altered. On my '90 & '95, to unlock the hubs I put it into 2wd and reversed for 6-7 feet to return to rwd. There was no mention of doing so in the '99's manual however the times I had it in 4wd/2wd and I "unlocked" like I did for my other 2 Trackers, the noise went away.

I know the basics of 4wd but I obviously need to should learn more about my '99 system.

On a 99 when you shift from 4HI to 2HI the air operated freewheel should disconnect pretty much immediately, without the need to reverse - you mentioned replacing the front differential, did you replace the differential itself or the oil?

sounds like the air vacuum for the hubs arent working right 

There's no "air vacuum" hubs on a '99 - the hubs attach to the axle shafts with a flange - they're connected 100% of the time.

The entire differential was replaced with a used one with 60k. Didn't make any noticeable difference. 

There's no "air vacuum" hubs on a '99 - the hubs attach to the axle shafts with a flange - they're connected 100% of the time.

I used to have a 99 Tracker and it did use a air compressor to lock the hubs.  I know because when my hubs wouldn't engage, the line going to the diff had gotten disconnected.  Mine was a 99 2 door with the 1.6. 

I used to have a 99 Tracker and it did use a air compressor to lock the hubs.  I know because when my hubs wouldn't engage, the line going to the diff had gotten disconnected.  Mine was a 99 2 door with the 1.6.  

Whatever makes you happy bro.

It's just unfortunate that you no longer have that 99 Tracker - so I can't send you outside to take a front wheel off and see if you can find the locking hub that you think is there.

For any one else who want's to discuss this - can we please start by examining our Tracker's so we know what we're talking about.

By the way - if you check my first post (fourth from the top), you'll find that I do state exactly how the air operated freewheel mechanism in the front differential operates, by locking the differential to the ring gear.

Jokaz - you can add me to the list of stumped folks.

It only happens in 4WD - the options are front axle, front drive shaft and transfer case - almost all of my suspicions point to the front differential and it's air opeated freewhell setup, but if you swapped the entire front diff, you've swapped all of that stuff already.