Why huge differentials on trucks?

[ovrszd]

ruffdog mentioned larger axles requiring larger cases to hold more oil. Actually the case size is to be strong enough to not distort under load. Secondary benefit of holding more oil.

A properly set up differential, properly maintained, not abused, can potentially run hundreds of thousands of miles without failure. Most common failures are bearings which allow distortion which in response destroys the gears.

Setting up a differential from a pile of parts laying on a bench is very technical. Very Technical.

 

[ovrszd]

I see some "pieces parts" (teeth) chipped on the ring gear of that Dana 44

Good catch James!!!

I'm guessing shock failure from the abuse our buggies withstand. Came out of my front differential. I noticed under slow hard load I would hear a "thunk" at times. I finished wheeling that day and then tore it apart. A tooth had failed on the ring gear. I'm guessing the adjacent teeth could no longer carry the load and started failing. The single chipped tooth on the opposite side was probably caused by a piece of tooth pickup by the oil.

 

[k0ua]

Setting up a differential from a pile of parts laying on a bench is very technical. Very Technical.

And when they are not set up right, and the teeth don't mesh in the right spot, they whine. We had a Explorer from that bunch of Ford Explorers that came thru the line and the setup of the differentials for about a week was not done right. Known problem, but they made it out to the public. And we had one.

 

[k0ua]

Good catch James!!!

I'm guessing shock failure from the abuse our buggies withstand. Came out of my front differential. I noticed under slow hard load I would hear a "thunk" at times. I finished wheeling that day and then tore it apart. A tooth had failed on the ring gear. I'm guessing the adjacent teeth could no longer carry the load and started failing. The single chipped tooth on the opposite side was probably caused by a piece of tooth pickup by the oil.

I had a lawn mower the chipped a tooth and that piece got caught between the ring gear and the case at a low spot without enough clearance and it pushed out of the aluminum case. Big trail of oil on the ground as the wife drove it to the barn. Not pretty..

 

[4570Man]

If you think pickup differentials are huge go look at medium and heavy duty trucks. As for the size look how much more weight and toque the trucks have over a Subaru.

 

[ovrszd]

How do tire diameters and tow ratings compare between the Miata, the Benz, and our HD or Super Duty pickups, even half ton models?

Like James says, everything proportional and darned little is 'overbuilt' these days ..

In my modified world here's an example of tire diameter differences. The more stress applied to the differential, the bigger and stronger the differential needs to be.

The larger buggy is on 48" tires and Dana 60 axles. The smaller is on 33" tires and Dana 30 front, Dana 44 rear.

 

[ovrszd]

I had a lawn mower the chipped a tooth and that piece got caught between the ring gear and the case at a low spot without enough clearance and it pushed out of the aluminum case. Big trail of oil on the ground as the wife drove it to the barn. Not pretty..

Saw a friend's Blazer do that one day. He got in to back out of the shop and it wouldn't move. He mashed on the gas and puked the tooth out the bottom of the case.....

 

[ovrszd]

And when they are not set up right, and the teeth don't mesh in the right spot, they whine. We had a Explorer from that bunch of Ford Explorers that came thru the line and the setup of the differentials for about a week was not done right. Known problem, but they made it out to the public. And we had one.

My street Jeep whines. I added an electronic locker to the rear. Tore it apart four times to reshim. Gave up and live with it. I'm the only one that hears the whine when you let off the throttle. Everyone thinks I'm being picky. Maybe so, but it didn't do that before I swapped the carrier.

 

[ovrszd]

If you think pickup differentials are huge go look at medium and heavy duty trucks. As for the size look how much more weight and toque the trucks have over a Subaru.

Yep. It's a handful to pick up a ring gear from a heavy truck diff.

And they have the torque to explode the driveline if trying to move an immovable load in low gear.

 

[k0ua]

Saw a friend's Blazer do that one day. He got in to back out of the shop and it wouldn't move. He mashed on the gas and puked the tooth out the bottom of the case.....

I bet he said a word or two that you can't print!..