What's broken in my front diff?? (2 Viewers)

[Elkwagn]

Long story short...I winched a friends tractor out of the ditch a little while back, in park with the diffs locked. It was a struggle but got the job done. A few weeks later I realized it had busted off the outer hub drive flange on the passenger side. I replaced the entire assembly (bolts had sheared off in hub), and all was good...for a minute. Now it has popped the dust cap off again, and there is a clunk sound in the front diff that increases with speed. I have pulled both axles expecting to find a broken one and they are both good (RCV axles). What else would be clunking in there!!

 

[baldilocks]

It’s quite possible that there is a tooth or two now missing from the ring and pinion gear set. Jack up the front axle, put the transfer case in neutral, then rotate the drive shaft by hand. You’ll know when you come to the broken off teeth if ring gear/axle/wheel stops rotating.

 

[jpoole]

winched a friends tractor out of the ditch a little while back, in park with the diffs locked.

ouch!

As I understand it the front (high pinion) diff is relatively weak(er) when driving in reverse which should match how you loaded it up. I'd try to isolate the front diff with your tests to see if you can confirm that it is or isn't the clunk source and I'd be ready to pull it for inspection/rebuild.

In the future Neutral and brakes/chocks may be a much less risky way to give that winch a workout!

 

[Elkwagn]

ouch!

As I understand it the front (high pinion) diff is relatively weak(er) when driving in reverse which should match how you loaded it up. I'd try to isolate the front diff with your tests to see if you can confirm that it is or isn't the clunk source and I'd be ready to pull it for inspection/rebuild.

In the future Neutral and brakes/chocks may be a much less risky way to give that winch a workout!

It's on the hoist axles out currently, so out comes the front diff!

 

[cruiserdan]

Now it has popped the dust cap off again,

What, exactly are you saying? did the dust cap come off by its self?

 

[jpoole]

Good point by Dan above, you may have mixed later/longer birfs with earlier/narrower drive flanges which can cause the stub axle to knock off the dust cap.

I'm lazy so unless the shafts are already out I'd test more before stripping it down far enough to pull the diff and I'd guess you could narrow down the clunk pretty easily as described above.

Good luck and share pics of whatever carnage you find

 

[cruiserdan]

Put an 8mm bolt in the end of the birf (as a handle) and push-pull the birf to see how much in and out play you have. If it moves much more than the width of the snap ring notch you have a long birf and a short flange. That allows excessive play.

 

[Elkwagn]

Put an 8mm bolt in the end of the birf (as a handle) and push-pull the birf to see how much in and out play you have. If it moves much more than the width of the snap ring notch you have a long birf and a short flange. That allows excessive play.

I've been driving it with these axles for 7 years now, and never had a problem until the tractor incident. Also does not explain the new clunking sound. Something forced the passenger axle outwards hard enough to bust off the drive flange bolts, just not sure what yet

 

[baldilocks]

I've been driving it with these axles for 7 years now, and never had a problem until the tractor incident. Also does not explain the new clunking sound. Something forced the passenger axle outwards hard enough to bust off the drive flange bolts, just not sure what yet

When your ring and pinion broke, there was enough energy released through that axle shaft to sheer off those hub studs. I also run RCV shafts and 37’s and have learned that the front diff is now more vulnerable than it was before.

I blew up a ring and pinion in reverse gear on large rocks 16 months ago. The energy released from the teeth of the gear set breaking was enough to break the yoke of the front driveline DC joint completely off.

 

[80t0ylc]

FYI (for those naive about ring gear teeth). Look at the shape of the gear teeth in the following illustration:

Forward motion of vehicle is powered by the flat or vertical surface. Reverse motion is powered by the sloped surface. In extreme stress situations, which is above and beyond what the drive train is designed for, damage will occur in reverse much more frequently. That's not to say damage won't happen going forward, but the design is significantly weaker in reverse. Using the rig as a free standing anchor for a winch, puts the same stress on these gears as motion in reverse. If you're using winch power for a task, it would be best to secure the frame of the winch rig to an immovable object, or as close as possible, such as another large rig, tree or rock formation. Above illustration was modified from this:

 

[ajordan1975]

I don't thing the ring gear would brake when in park and winching.
Broken teeth don't usually make a clunking sound ether.
At least not in my experiences.....

 

[Elkwagn]

Diff out, problem found. I knew when I pulled the plug it was bad, lots of metal chunks dropping into my drain catch

 

[Broski]

A few things come to mind.
Before I pull or winch anybody, I tell them if anything happens to their rig that’s their fault. If anything happens to my rig that’s their fault too.
If they don’t agree, I don’t pull them out.
Famous words from the late tools, rest in peace, brother!

Second thing if you drove a few weeks with shared bolts at the drive flange, you must have had the center diff locked and if you didn’t hear that noise until you replace the hub and the drive flange, then the damage is new or you would’ve been hearing all the time there’s something else at play Possibly your locker is damaged or something of that nature.

 

[CharlieS]

Wow, that sucks.

In the recovery training classes I've attended, when winching another vehicle, the instruction is winching vehicle in neutral, foot on brake

 

[Mark W]

To be honest, I would have expected the parking pawl to fail first. Obviously it didn't.

The front diff is basically the weak link in the '80 series. This is a classic failure.

In the future, during any heavy winch pull you should use the service brakes to anchor the rig. That takes the strain off of the drivetrain completely.

In my '40 (dedicated trail rig that has moved to tractor tires from the 40 inch boggers) I have line locks on both ends. On good soft but dry tundra, I have actually lifter the tail end to the point that there was only a few pounds of weight on the rear tires during a particularly heavy winch pull. Tires did not even think about rolling as the front end dug in hard.

Hopefully the next time I do any significant work on the '80 I'll be installing linelocks front and back on that rig too.


Mark...

 

[Broski]

Wow, that sucks.

In the recovery training classes I've attended, when winching another vehicle, the instruction is winching vehicle in neutral, foot on brake

This is the correct way, I also set the hand throttle to 1200 RPM and have this installed to make it even easier

 

[80t0ylc]

Diff out, problem found. I knew when I pulled the plug it was bad, lots of metal chunks dropping into my drain catch

View attachment 3592726

Wow, if all this damage was on the tractor pull incident, your rig was dragged for aways to get that many teeth damaged!

Wow, that sucks.

In the recovery training classes I've attended, when winching another vehicle, the instruction is winching vehicle in neutral, foot on brake

And what's the next step when your rig is being dragged? Either secure it to an immovable object or the method @Mark W mentioned.

To be honest, I would have expected the parking pawl to fail first. Obviously it didn't.

The front diff is basically the weak link in the '80 series. This is a classic failure.

In the future, during any heavy winch pull you should use the service brakes to anchor the rig. That takes the strain off of the drivetrain completely.

In my '40 (dedicated trail rig that has moved to tractor tires from the 40 inch boggers) I have line locks on both ends. On good soft but dry tundra, I have actually lifter the tail end to the point that there was only a few pounds of weight on the rear tires during a particularly heavy winch pull. Tires did not even think about rolling as the front end dug in hard.

Hopefully the next time I do any significant work on the '80 I'll be installing linelocks front and back on that rig too.


Mark...

Agreed about the parking pawl and especially burying the front end of the rig if possible. If there's nothing to secure the winch rig to, that's the next best thing. What are line locks?

This is the correct way, I also set the hand throttle to 1200 RPM and have this installed to make it even easier
View attachment 3592893

Love that setup, Richard! Also, I have never regretted installing my hand throttle.

 

[Mark W]

Agreed about the parking pawl and especially burying the front end of the rig if possible. If there's nothing to secure the winch rig to, that's the next best thing.

Slight misundersatanding. I did not dig holes for the front tires or anything like that. Poor wording on my part I guess. The loading of the winch pull trying to drag the rig forward and loading the front axle in a downward direction too as the leverage from the pull point of the PTO winch being above the frame forced the front end downward into the soft terrain. While the tires did not roll due to the engagement of the service brakes, the rig did shift forward as it was dragged, until the downward forces lodges it firmly into the ground (only a few inches IIRC).

I have dug holes for the front tires in the past to anchor a light rig pulling a heavier one during a hard pull. Left the rig in first gear low range with the engine off (electric winch in that rig). Promptly busted a birfield.

Never took that particular approach again.

Mark...

 

[80t0ylc]

Slight misundersatanding. I did not dig holes for the front tires or anything like that. Poor wording on my part I guess. The loading of the winch pull trying to drag the rig forward and loading the front axle in a downward direction too as the leverage from the pull point of the PTO winch being above the frame forced the front end downward into the soft terrain. While the tires did not roll due to the engagement of the service brakes, the rig did shift forward as it was dragged, until the downward forces lodges it firmly into the ground (only a few inches IIRC).

I have dug holes for the front tires in the past to anchor a light rig pulling a heavier one during a hard pull. Left the rig in first gear low range with the engine off (electric winch in that rig). Promptly busted a birfield.

Never took that particular approach again.

Mark...

I kinda understood your 1st description that the front end dug into the "soft tundra". On an outing with another rig, I've purposely stuck (going forwards) my front end for a winch pull. That time I was pulling a Bronco uphill. I was leading rig. Took me 2 winch pulls to get up that hill. Turned around and stuck the front end into the soft surface. We hooked the winch lines together and pulled him up, no problem. Backed out afterwards and we continued on. Ya do what ya have to do.

 

[CharlieS]

What are line locks?

They are a device that closes off the brake line to hold whatever pressure is in them at the caliper.

If you step on the brake pedal, then engage the line lock, the brakes will remain engaged after you take your foot off the pedal, until you release the lock.

I used a line lock for a parking brake in a rally car I used to race. It was very effective.