Front differential slipping in 4 low under strain. (1 Viewer)

[NickMazzenga]

This past weekend I did some light off-roading here in Virginia in my new to me 87' FJ60. It is bone stock which is the way I like it. So whenever I was going up a steep incline where I needed 4 low once the vehicle came under strain the front dif sounded like it was slipping and not sending any power to the front wheels. It would make a clanking sounds similar to slipping gears perhaps. I couldn't 'recreate' this problem in 4 high, it was only when I was in 4 low going up something steep. Creeping down hill in 4 low didn't give me any problems.

So does anyone have any initial guestimates as to what might be causing this? I will most likely have to take this in to have it looked at but before I do that I want to do a bit of research to better understand the problem. Also anyone know of any good TLC shops in Richmond, Virginia?

 

[Elbert]

assume you have the front hubs locked when this happening?

 

[NickMazzenga]

assume you have the front hubs locked when this happening?

Yes, you are correct front hubs are locked when this occurs.

 

[roadstr6]

Hubs may not be engaging. There is a spring in there that forces the mech to lock when you turn the dial. They can get crusty and fail to engage. It would be worth pulling the dials and looking inside. Clean / lube and reinstall. If that doesn't do fix it (I'd wager that it will) then look at the transfer case linkage to see that the front is engaging at the TC.

 

[mongoose2231]

What he said^^

 

[woytovich]

What they said...

 

[Landpimp]

I bet it was your t-case and not your front axle and I'd bet if you replaced the low range shift detent spring that would take care of the issue. could also be the shift boot putting pressure on the lever and allowing it to slip partially out of low

if you hold the hold the t-case lever in low range when(or before) it happens, does it stop making grinding noise?

 

[2mbb]

You can check pretty easily whether the front hubs are locking up by locking both hubs, putting the truck in 2WD and seeing if you can turn the front drive shaft by hand. You shouldn't get to far rotating the shaft before the hubs lock in. Conversely, you can unlock the hubs and put the transfer case in 4wd. The front drive shaft should also lock up if the transfer case is going into 4WD properly. Landpimp's theory that it is popping out during driving would have to be checked under power.

Their are two different shift rods for the transfer case. One is for high/neutral/low and the other for 2wd/4wd. theoretically shifting between high and low shouldn't effect whether it is in 4WD. You can check the shift rods from under the truck to make sure they are moving properly throughout their fully stroke.

If what you are experiencing is mostly noise, as in a grinding noise under heavy load (and you are not absolutely sure you lost 4WD capability), this could also indicate a broken motor mount. The motor lifts off the mount enough for the fan to rub against the fan shroud. You can inspect the tips of the fan blade to see if they are worn or shredded.

 

[NickMazzenga]

I bet it was your t-case and not your front axle and I'd bet if you replaced the low range shift detent spring that would take care of the issue. could also be the shift boot putting pressure on the lever and allowing it to slip partially out of low

if you hold the hold the t-case lever in low range when(or before) it happens, does it stop making grinding noise?

I thought that might be the problem, so I had my buddy in the passenger seat next to me hold it in 4 low and it still made the noise when we went up hill.

 

[NickMazzenga]

You can check pretty easily whether the front hubs are locking up by locking both hubs, putting the truck in 2WD and seeing if you can turn the front drive shaft by hand. You shouldn't get to far rotating the shaft before the hubs lock in. Conversely, you can unlock the hubs and put the transfer case in 4wd. The front drive shaft should also lock up if the transfer case is going into 4WD properly. Landpimp's theory that it is popping out during driving would have to be checked under power.

Their are two different shift rods for the transfer case. One is for high/neutral/low and the other for 2wd/4wd. theoretically shifting between high and low shouldn't effect whether it is in 4WD. You can check the shift rods from under the truck to make sure they are moving properly throughout their fully stroke.

If what you are experiencing is mostly noise, as in a grinding noise under heavy load (and you are not absolutely sure you lost 4WD capability), this could also indicate a broken motor mount. The motor lifts off the mount enough for the fan to rub against the fan shroud. You can inspect the tips of the fan blade to see if they are worn or shredded.

Great suggestion, I will try and test this tonight. I tried to 'recreate' the problem under 4 high but it stalled out on a hill before any clanking sounds occurred. I'm fairly certain that it was not just noise because the front wheels were spinning but there was no real power going to them. It's like they were stalling out. The rear was definitely working hard to push me up the obstacles. I'm also going to check the fan, really appreciate the help!