Grinding in front, gets worse higher speed while accelerating - AWD

[stang99gtv8]

On my 97 AWD 5.0 Ex that I just picked up, I notice that it has a somewhat of a grinding-ish feel when accelerating, starts around 40-45mph. Don't feel it up to 40 mph. Also acts like it doesn't really want to go when starting off in reverse or turning at very low speeds. I see that while it has the same set of tires front and back, the front ones have more tread depth than the rear ones. Front ones probably have 20k miles on it while the rear have close to 100k miles on them.

My question is, would a difference in tread depth on an all time AWD like this cause it to have issues because of the difference in rotating speed from the lower tread depth in the rear? Could it be mismatching the speed that should be there and causing it to have problems adjusting, making it feel like it's trying too hard some times or kind of vibrating when going higher speeds?

I'm trying to determine if it's something in the drive line that's causing this or something such as the tire size being enough off to cause it to rotate faster in the rear, or if it's an axle or transfer case issue.

 

[G-96XLT]

I highly doubt you would be able to hear tire depth differences while driving the ex. On my old 96 I couldn't afford 4 tires at once so I had 2 of the old tires in the front and 2 news ones in the back and there was no noise or difference in driving.

Grinding while driving for me has been the following..

front wheel bearings - grinding and humming - during turns it stops for a second when the pressure is on the right bearing, this is how you know its the wheel bearings

front drive shaft - not really grinding but wobble wooble woosh, seems to be common in 4WD models

lower ball joints - cracking

 

[stang99gtv8]

front wheel bearings - grinding and humming - during turns it stops for a second when the pressure is on the right bearing, this is how you know its the wheel bearings

This sounds closer to what it's doing.

when back up it almost acts like it doesn't really want to at usual idle speed, and turning at slow speed clanks around. higher speeds it starts to vibrate above 40 and gets worse as it goes higher.

I'm thinking a combination of things, maybe the bearings, CV join, and ball joints.

 

[stang99gtv8]

I'm noticing some specific chattering the more I really listen to it. Almost sounds like a chain if there was no oil on it. Would this be possible with tire differences or sound more like the actual transfer case having a problem?

 

[stang99gtv8]

Alright after reading many posts here on different issues i figured I would post up exactly what I'm hearing in an attempt to narrow down what sounds like ti could be a few different possibilities.

What my exp is doing:

When at idol and letting off the gas for it to roll a little bit, I hear a chatter/ticking sound. as the wheels turn it gets faster. only hear it when I'm just barely rolling, don't hear it when I start driving off so it doesn't get any louder if it's still happening as I'm driving, or at least not loud enough to be heard over the general exhaust tone of the 5.0.

When I take a sharp turn at low speeds or turn the wheel all the way when at a stop and then attempt to go at low speeds, the tires will chirp a little bit like they are wanting to jump around on 4x4. It's most pronounced when turning from a dead stop or backing up and having to cut the wheel sharp. Feels like it's having to "push" a little bit more than normal to get it done. If i don't cut the wheel all the way, this doesn't happen.

While driving, I don't notice any strange vibrations until i get up around 70-75mph. At that speed, it starts vibrating pretty decently. Stops doing so if I let off the gas and coast at those speeds or return to under 70.

I've narrowed this down I think to a few possible things. First thing I'm going to check is the front drive axle. Other possibilities I'm seeing after some searching are the front CV joints or the transfer case itself.

What I'm hoping to get in some replies is advice on the steps to diagnose this correctly without spending a ton on just replacing every part I can think of. I'm starting off by this weekend throwing some tires on that are verified as matching tread depth and seeing what happens. I assume the next step if this doesn't fix the problem is to remove the front drive axle and take it out for a drive to see what happens. I'm praying I don't go through all of this to find out the TC is bad, but hopefully I find the issue before something major breaks.

 

[expl0rer98]

my front axel was ####ed up as well and it didnt do that... and im pretty sure my bearings on my right are shot as well in the front because of the humming sound it makes, and yet mine never shook like that..

 

[expl0rer98]

yea dude that could be the tires, you aren't suppose to mismatch em like that. and i know for a fact on certain vehicles the wrong tires make it sound weird and wobble a bit.

 

[Joe Dirt]

I suspect you're having some transfer case issues, especially if you hear chatter/ticking when letting your foot off the gas. If the mismatched tires have been on that way for a while, it is a very real possibility that the transfer case is indeed hurt.