Help me figure out what broke in my rear diff

[Stuntman Mike]

I broke something while spinning on ice/pavement.
It made lots of clanging and it was on and off catching(felt like jamming it into gear) and spinning freely(like slapping into neutral at throttle) for a short time after this happened. Now it won't catch with enough force to even move the truck on a level surface.

I removed the differential cover and I'll describe everything as best I can:

Driveshaft turns the main gear and carrier.
Rotating the rear wheels rotates the side gears in the differential.
Spider gears aren't turning, as in teeth not meshing.
I can put it in gear and then get out and watch the gears go round and round...

It makes a sort of "zzdtzzdtzzdtzzdt" like it's not catching more than the tips of the spiders. You can kind of feel it catch with very light clutch, but more engagement makes it give up and spin around aimlessly.

7.5 Trac Loc.
Fluid was slightly silvery-silky in color when I started to drain it but mostly black after.

Only visible damage I have seen inside was the eaten pieces of half a tooth from the main gear. The debris added up to just that much, so I assume there's not any more carnage besides that.


If anyone could give me some idea of what's going wrong, I'd appreciate it.
I don't really have money to replace 'costly' parts...
If it comes down to it I can weld it solid. I don't want to, but it's the cheapest option.

 

[tpking]

sounds to me you broke a tooth of a gear and when it gets to that point nothing to grab to till the next one so it might have a slipping feeling

 

[Stuntman Mike]

It's not a 'slipping feeling' and the missing half-tooth isn't causing slippage.
The ring turns fine. The spiders in the carrier aren't turning the side gears. At all.

The catch/release behavior I mentioned got progressively worse for a minute or two before it finally couldn't move the truck on level ground.

The parts that move with input from trans side:
Driveshaft > Pinion > Ring > Carrier

The parts that move with input from the wheels:
Wheels > Driveshafts > Side axle gears

I can put the truck in gear with the engine running and all 4 wheels on the ground, and get out of the cab, lay on the ground under the truck and watch the ring + carrier go round and round. The truck cannot move on it's own.

 

[AllanD]

I think when you disassemble it further you'll find more of the spiders broken up.

YEARS ago I ran one of the Borg Warner(Auburn) cone type differentials
in my 2.9wd truck, when that diff finally broke it was a total catastrophic failure

the "good" spider gear was in FOUR pieces and the biggest piece had three teeth

Which is damned impressive failure for a gear that only had
seven teeth to begin with.

the other gear had two-pieces with two-pieces each I never
found all the pieces in the mess because some of them got
sucked through the ring & pinion and pieces of each of
those added greatly to the carnage.

In any event you had a major event and the easiest fix
involves removing the nuts from the U-bolts, disconnecting
the shocks etc... in short replace the entire axle as an assembly

AD

 

[Stuntman Mike]

I don't believe there are any other broken apart pieces other than the half-tooth from the ring gear. I scraped out the bottom of the diff housing and only raked up enough metal shards to match the visible damage. I drained slowly into a shallow pan when I opened it up.
I have rotated everything that can rotate in the entire rear end. I can see all of the teeth are still attatched to the spiders.

I would just like to know what could cause the two axles to still turn but not engage the spiders. That's a lot of gear clearance to suddenly appear without any real outward sign of damage, if you ask me.
I don't want to tear into it more than I have to because I can't afford to fix it 'properly' right now if it's going to cost more than like $50. I can live with a welded rear (free), but I wouldn't mind keeping the thing servicable to rebuild the trac-loc later. I'll probably put in a dana 35 with a locker after I save up enough cash.

 

[Hahnsb2]

It took me a while but I think I get what you're saying. The spider gears don't need to turn when both wheels are traveling at the same speed, what you're seeing is normal, chock one of the tires and rotate the pinion by hand, you will then observe the open diff doing it's thing.
Check out these animations.
http://auto.howstuffworks.com/differential2.htm

 

[LittleHorse]

if it's a trac loc you may have burned up the LSD clutches.

LSD's dont like being spun at high speed with zero or near zero traction. It's even worse on a viscous type, but either way they can overheat and stop working.

 

[Stuntman Mike]

I'm going to make this as clear as I possibly can...

My driveshaft going into the differential turns the ring gear (f)
(f) is attached to (e) and turns
(c) and (d) are attached to (e)
(c) and (d) are NOT in mesh with (a) or (b)
---this is as far as the action goes from my driveline---

I can turn my axle (g) and it turns (a);
I can turn my axle (h) and it turns (b);
---this is as far as the action goes from each wheel---

I know a burned out trac loc will act like an open diff, but I also know that an open diff will move at least one axle. This is not the case.

I can put it in 4 low 1st gear with the engine running and step out (truck completely motionless, just sitting on all 4 wheels unchocked) lay under the bed and watch as (c) (d) (e) and (f) turn around and around and around..
(a) and (b) are not being turned.



``````````````|| <-g
``````````````||
`````____________________
````/````````````````````\
```|``````````````````````|
```\/\/\/\/\/\/\/\/\/\/\/\/ <-f
```````|.------------.|
```````||````_||_````||
```````||```/````\<-a||
```````|| /\\/\/\//\ ||
```````||/ /``````\ \||
```````||[ \<-c```/ ]||
```````||[ /```d->\ ]||
```````||\ \``````/ /||
```````|| \//\/\/\\/ ||
```````||```\____/<-b||
```e-> ||`````||`````||
```````\'------------'/
````````""""""""""""""
``````````````||
``````````````|| <-h


I hope this clears up any confusion as to what I'm describing. I left out the 'S' spring and the pin so it wouldn't be too cluttered in the picture.

 

[86ford]

Take real pictures.

86

 

[Stuntman Mike]

Helpful.
What would be the point? The actions of the gears is what's important. (FYI: I don't have a digital camera.)

If you're still having a hard time understanding what's what from the ascii drawing:

a,b,c,d = spiders.
e = carrier.
f = ring gear.
g = left axle.
h = right axle.

 

[Bent Bolt]

Sounds like the clutches are worn out thin and the side gears ( A and B ) have moved outward ( towards the tires ), thus the side gears won't engage the spider gears ( C and D ).

Do the axle shafts move in and out alot ????? They shouldn't.

 

[Stuntman Mike]

Yes, I will check the side-to-side play soon, that sounds like a logical cause. Thanks.

If all I need is to replace the clutches + plates, where would be the cheapest place to get them? Hell, I'll take used ones if these are ground that thin!

 

[4x4junkie]

Sounds like spider gears with sheared teeth to me too.

Without taking actual pics, I can't really offer much beyond that either, as it is physically impossible for what you say to happen unless the spider gears (C & D) are stripped or are no longer engaging the side gears.

If you don't have a cell-phone camera, then maybe you can find one of those little cheapie key-chain ones at a drugstore for $15 or whatever they sell for.

I do have to comment that's pretty good with the text art though lol

 

[Stuntman Mike]

Okay, it took me a while to see but the spiders are worn out in a strange oval-kind-of-way.
If I rotate them, the good teeth would engage the side gears. It wouldn't take much to move them back to where they slip though.
I'm tempted to weld. Should I try to replace them instead if it's not a major PITA?

 

[85_Ranger4x4]

Only visible damage I have seen inside was the eaten pieces of half a tooth from the main gear. The debris added up to just that much, so I assume there's not any more carnage besides that.

If you broke half a tooth off of the ring gear this axle isn't worth throwing any money at or welding IMO. By the time you buy a ring and pinion and spiders and get them set up you could have gotten another 7.5 a couple times over, or an 8.8 or two if you shop right.

Remove axle, insert a new one.