New member. 99 mounty questions

[js8330]

Whats up everyone. Names jeff. In the florida keys. I picked up a 99 mounty last year. Its a 5.0 awd truck. Its been amazing. Makes frequent trips from the keys to miami. And it made the drive all the way back from NY state. Anyway, im starting to have trouble with the awd setup. It was popping and the front tires were locking up on me, so i took out the front driveshaft and that was eliminated but the slight grinding still remains. Almost like a bad wheel bearing but i just did the pass and the sound doesnt unload when you turn. Side bearing and half shaft, drivers side bearing is eh i dunno no movementin the wheel and no noises when spinning it by hand. . Gotta check it. But it sounds like its under the truck. Right under where im sitting. Which makes me think T.C or front diff. I checked the oil in there (front diff) amd it was really low so i added some to fill. Also, the joint where the cv axle goes in seems to have excessive backlash. I mean like a half in or more. Is there a pin point dead on way to properly diagnose these so that i dont immediately and impulsively blow my money on a differential? Im thinking its cheap enough ill do the other wheel bearing. Then ill check the backsides of the rotors and see if my ball joints are causing the slight grinding noise i hear. I can get a diff for under 200 and it probably wouldnt he a bad thing to have one on hand.

 

[CDW6212R]

Hi Jeff, welcome.

Your truck sounds like it has a bad AWD TC. What size tires have been on it? Most all AWD issues with these are caused by mismatched tires. When the fronts are a different diameter than the rears, the viscous clutch inside the AWD has to fight the mismatch constantly, and it eventually wears out.

My black 98 truck I bought like that and after about two years of proper tires and care, the AWD finally locked up. I changed the diff fluid three times, it was almost black each time(the black is the color of the viscous clutch wear which are inside a sealed unit with its own fluid). I discovered it going to get an alignment, and found that the front diff, the pinion flange could move side to side a ton, 3/8" or more. I had to replace the diff, but then also had to leave out the front driveshaft, the AWD was still fully locked up.

What does your AWD TC fluid look like? If it really required removing the driveshaft, then either the tires are mismatched now, or the AWD is locked up. If the fluid is black, not red and transparent, it's gone or dying.

Check the front pinion flange, try to move it side to side, there should be very little play. They all have quite a bit of rotational play, that's not a big deal. The biggest weak links are the lower BJ's, and the hubs and axles do fine if they are good brand parts. If the diff fluid was low, that doesn't look good for the likelihood it's okay. But they are not that hard to replace, and a cost under $200 is not bad.

 

[js8330]

Hey how are ya. I havent had a chance to check the TC fluid yet, BUT the tires are all 235/70/16. The car came stock with 15s but from what ive been reading going up an inch in diameter isnt a problem its having different sizes in the front and rear thats the problem.. also, we pulled the shaft out more so because the shaft itself was torn up, it just really helped with the binding. As for the tc fluid i havent yet had a chance to check it. But i will report back as soon as i do. I suspect it probably wont be too good though. As for the diff, yeah i saw its basically unhook the cv axles and then pull the three or four mounting bolts, actually looks pretty straightforward.

 

[410Fortune]

Bang on

Check awd t case fluid
I use Mercon iii / regular atf in there

Front diff should have 1/4 turn or so at the pinion before it grabs, kinda normal. However it should not move in and out or up and down

Your truck has 3.73 gears
That front diff is very common
I can change one in about 45 minutes

Could be cv axle binding/ growling?

How
Many miles?

Low Fluid and growling with no front shaft does point to the t case still or the front diff, hard to decipher but you are on the correct path

You can run 29-33”
Tires it does not matter as long as they are all the same rotation diameter and inflated properly

These awd cases do wear out
You can install another
Or convert to true 4wd but we will get into that later

 

[410Fortune]

Here I recently had to replace my front diff
272k miles it was making growling noise



The play back and forth is pretty much normal but if you could feel it through my hands it was quite obvious the pinion bearing was “dry” and then you can hear the solid Clunk sound…. That part not normal

 

[CDW6212R]

Okay, change the TC fluid, with Mercon V. That AWD TC doesn't have to have special TC fluid like later models which have clutches exposed to the fluid. If the old is black then you might ought to expect the driveshaft will have to be left out. Check for play in the front diff, side to side of the pinion flange is the best way to know if the gears or pinion bearings are bad.