I have a 1987 4runner and think I might be having an issue with my front differential/axle...

1) There's a leak where the front diff and CV axle meet, on the driver's side. I assume this is an easy to replace seal, and I can just following the FSM? Also, I will have to drain the gear oil in the front diff, right?

2) While driving in 4wd, there is a whirring sound that comes from the front end. It only appears when I let my foot off the accelerator. Could this be a loose spindle somewhere, or a bearing? Any recommendations of how I could fix this?

3) I drove (unintentionally) in 2wd with the hubs locked on the highway for a while. There was a lot more vibration than with the hubs unlocked. Could this be the CV axles going bad? Or whatever is causing #2? Or is this normal?

Thanks greatly!

 

When you lock the hubs the cv axles and front dshaft will spin with tires so your vibration could be lots of things. One thing you could do is remove the front dshaft and take it on a short drive with hubs locked. That should at least isolate vibration to cvs or the shaft. If the vibration goes away. Then maybe check the ujoints in shaft. If it doesn't go away then start looking elsewhere.

 

How many miles?
ever do the U-Joint?
front diff have oil?
you can replace both CV axles in about 3 hours and less than $200, do the bearings and inspect your brakes while you are at it
I drove for 4 winters in alaska with my front hubs locked and never had any issues

 

Truck has 320k miles. The CV joints look in pretty decent shape though, so they might have been replaced already.

Have not done the u-joint in the front shaft, I will check it for play.

Front diff definitely has oil, I just replaced all the fluids about a week ago (I think the cv axle leak is not big enough to have drained it so fast)

I'm puzzled by the fact that the noise only appears when I let off the gas. Wouldn't a bad CV joint always make the noise?

 

Assuming wheel bearings are fine. Search "IFS spindle lubricator" usually the symptoms become apparent as weather gets cold but bronze bushing gets dry and sounds terrible. As for the leak at dif flange, you can replace seal. But check seal surfaces on shaft. This is an old truck so seals get old and dry then then wear groves in shafts.

 

A little update --- I tested it with hubs locked and 2wd: no noise. With hub unlocked and 4wd: no noise. And of course no noise with 2wd and hubs unlocked.

So it seems that the whirring sound is only there in 4wd and hubs locked, and I let off the gas.

Does this mean I can eliminate the drive shaft / u-joints / cv-joints / wheel bearings?

Any ideas of what it could be?

Thx a million

 

You might have to open up the 3rd member cover and have a gander at the ring and pinion teeth and any bearing slop.

It is possible to make an estimation of the diffs pinion backlash by careful manipulation of the input flange with the driveshaft disconnected. Check for any looseness or wobble there too.

 

Got the drive shaft off and tightened the pinion nut to 110 ft lbs, didn't really move much past where it was. Not too much slop in the input flange or pinion from what I can tell. Still get a whine on decelerating with hubs locked and 4wd on.

I guess next steps is pinion bearing / ring and pinion teeth / possibly IFS spindle. Is there any DIYs out there? Haven't messed around inside the 3rd member at all, and don't to mess up the meshing of the gears / alignment.

What is the main danger of leaving as-is for now? That front diff locks up in 4wd?

Thanks as always

 

Read www.gearinstalls.com, several 7.5in teardowns and setups on ZUKs site. All the info you could ever need. You could pull the diff, remove cover and check the backlash and do a pattern check without disturbing anything. At least maybe getting a look at the teeth and the pattern might tell you something. If you want to do anymore than that, like change bearings, you're going to need a press and some bearing splitters and pullers and an in lb torque wrench.