4x4 strange noise

[ljshein]

All,

my 99 4x4 automatic makes a weird noise in 4wd and I was curious if it's normal.

I tow a small boat that weighs about 2000 pounds. When I put it away in my yard, I need to cross a grassy area so I put the truck in 4wd so I don't slide. Of course, it's a little up hill and I'm backing up the hill.

When I start backing up the hill, I get this very loud noise almost like a fan belt slipping on a cold, wet engine when you start it up. It seems worst when I need to step a little harder on the gas. The noise stops after a few seconds and then it's good to go.

So, the questions are:
What causes the noise?
Is it normal?
if it's not normal, am I doing damage?

Thanks!
Jeff

 

[ljshein]

Just an update:

I used 4 wheel low last night to back it up and no noise. I'll continue to use that mode from here on out but if anyone has any input, I'd still love to hear it!

Thanks!
Jeff

 

[Jim_Chow]

In general I don't think it's a good idea to back your boat uphill since the front diff is reverse cut, meaning they front/rear diffs) are stronger when going forward and weaker in reverse. A number of Landcruiser's (80s and 98-99 100's) have blown apart their front diffs when trying to tow someone out in reverse. This is primarily due to the carrier flexing causing misalignment, then the ring gear teeth break as a result.