I guess those aluminum gears aren't working out. :jester:

 

I finally got around to opening up the failed diff.

http://austinm.net/titan/diffinternal

As I said on my website, in my opinion, differential failure was caused by weak spider gears (differential pinion gears) alone.

The diff carrier housing is stout, the carrier bearings are fine quality, the ring and pinion are very stout, there are tight tolerances inside the diff carrier including spider gears to side gears, spider gears to spider shaft (cross shaft), spider shaft to carrier housing, etc. The spider gears are simply the weakest link, and they gave out.

Here's a couple pics - many more on the website.


The infamous pin for the spider shaft. This is what Four Wheeler magazine said caused their diff failure - the pin sheared. While I'm too nice 'a guy to throw a BS flag, I will say that this pin is more than adequate for what it does.

New paperweights:

What's wrong with those gears? Looks like the front row at a Willie Nelson concert!:lol: :lol: :lol:

 

I looked at your pics, nice write-up. Weird that they don't use a bearing for the solenoid coil. Auburn has a somewhat similar arrangement in their ECTD and guess what, they have a ball bearing for the solenoid coil. Duh.

 

Austin,

Awesome write up and documentation with pics. So yours failed, did Nissan replace yours, or since you have made some modifications, did you replace it yourself? How did you get to keep your failed diff?
Mine gets replaced Monday.

 

Any chance you can get this documentation off to Nissan somehow?

Are you replacing with a new diff from Nissan or an aftermarket?

 

Ecellent pics & text!
What are your future plans with the diff? Tru-Trac?

 

Yet again, a great photo-essay from Austin. Ive seen alot of broken gears, but never "flatend" teeth like that. Usually the teeth just break off, not really deform like that, could this be a heat-treat issue and the gears are too soft and literally just fold over and then its curtains from there?

 

Yet again, a great photo-essay from Austin. Ive seen alot of broken gears, but never "flatend" teeth like that. Usually the teeth just break off, not really deform like that, could this be a heat-treat issue and the gears are too soft and literally just fold over and then its curtains from there?

Good call. Looks to me like the rear end wasn't properly hardened by proper heat up, cool off break-in. Like I mentioned in another thread, not something the electronics could have foreseen.:cheers:

BTW, if these seem to be the "weakest link", can't they be changed out for harder gears?

 

Looks like everyone is going to have this problem sometime in the future.

 

Looks like everyone is going to have this problem sometime in the future.

Nah. Most don't have this problem, and there are folks with a LOT of miles on their trucks.

 

Good call. Looks to me like the rear end wasn't properly hardened by proper heat up, cool off break-in. Like I mentioned in another thread, not something the electronics could have foreseen.:cheers:

BTW, if these seem to be the "weakest link", can't they be changed out for harder gears?

For whatever it's worth. My dealer had told me that Nissan does not do any sort of break in procedures with the rear diffs before assembling them on the truck. They stated that is why the manual has a strict break in procedure. No towing for the first 500 miles and no speeds over 50 mph when towing for the next 500 miles.

 

Any theories as to why the vast majority of the failures are 4X4's, with the BT gearing, if it's the spiders that are the weak link?

 

Need to floss more.:jester:
For those wondering, Austin had the rear end replaced already through warranty and the service manager say he could keep his old rear end.(that didn't come out right)

 

For whatever it's worth. My dealer had told me that Nissan does not do any sort of break in procedures with the rear diffs before assembling them on the truck. They stated that is why the manual has a strict break in procedure. No towing for the first 500 miles and no speeds over 50 mph when towing for the next 500 miles.

There's also more to it. Don't forget the section explaining just how to properly break in the rear end when you DO start towing....very important! You need to stop every so often and let the rear end COMPLETELY cool before continuing on. This apparently hardens the gears. The owners manual explains this in detail. However, I think the gears should be prehardened before installation because it's a given that some folks don't read their owners manual!

 

Great!Any reason to think abls would stress these spider gears?

Austin-great pictures-thanks.Is there any reason that the ABLS would stress these spider gears-make then "see" forces that a non ABLS equipped vehicle wouldn't?I'm not suggesting that ABLS is the cause, I'm just looking at a 4x4 association(about 80% are 4x4) and all 4X4 have ABLS.Frankly,Im hoping it is a 4x4 "thing" so my 4x2 will be off the hook!!Unfortunately there have been 5 4x2 failures-maybe they just take longer to fail-easier use.The Elock was never a good bet-1/3 of the failures don't have elock.Maybe 20% don't have ABLS-they are 4x2's.
Hudsonvalleytitan-yes most folks don't have this problem,but about 31 folks here have had it(31/5000)-about 1/160.I haven't actually calculated the average miles at failure, but it is in the 10,000 range-pretty low.I would bet the average 2004 Titan has maybe 18000 miles on it-not a lot of miles.I don't think anyone has hit 100,000 miles yet.Very,very few have hit 50,000.
This forum has "sent" Nissan about 45 broken diffs several had multiple failures.Maybe we are harder than average on vehicles-reasonable assumption-but there are only about 5000 of us-and probably not that many have seen the survey-.There are close to 180,000 Titans out there-35 times our numbers.If we are 3.5 time more likely to break our trucks ,then Nissan has had 450 failures so far in a fleet that averages about 1 year old-and maybe 10,000 miles old.
Great stuff Austin.Thanks.Charlie

 

Weird that they don't use a bearing for the solenoid coil.

Yup, I just don't understand that.

I plan on taking pics of the inside of the lock solenoid - try to get a good angle to show the heat scoring.

So yours failed, did Nissan replace yours, or since you have made some modifications, did you replace it yourself?

My service manager believes that the diff in a Titan should hold up to more than what I'm doing to it, and he had no problem replacing it under warranty.

It's about a $2700 part. If I hadn't had it replaced under warranty, I would not have purchased a new OEM axle. Dynatrac makes an awesome D60 axle - I was ready to buy one of those, but at this point no one makes front gears. So, because 14/47 is not an available R/P ratio from anyone except Nissan, I would have had to change the rear ratio - which is fine, except I'd lose 4x4 until I matched the front ratio.

The gear guys I talked to say that it looks like, with a few slight modifications to the OEM front diff housing, a set of high pinion D44 gears could be installed. Hopefully they'll know soon.

How did you get to keep your failed diff?

I asked, and he said yes. The dealerships aren't allowed to sell broken & warrantied parts, and in this case Nissan didn't want it back... so in effect I was doing him a favor by taking something he'd otherwise need to dispose of. He has more broken axles if I want 'em...

Any chance you can get this documentation off to Nissan somehow?

I doubt it.




Meh... I was going to reply to everyone else, but the neighbor stopped over.

 

What are your future plans with the diff? Tru-Trac?

With this diff? Trash can. With my truck, I'll eventually get a Dana 60 with an ARB, and a matching ratio Dana 44 for the front, also hopefully with an ARB.

Yet again, a great photo-essay from Austin. Ive seen alot of broken gears, but never "flatend" teeth like that. Usually the teeth just break off, not really deform like that, could this be a heat-treat issue and the gears are too soft and literally just fold over and then its curtains from there?

Thanks Greg! I'm not a materials engineer, but I've had a few classes in metallurgy. Looking closely at the spiders, there are some brittle failures (quick snaps), and then there are also ductile failures (soft, chewing gum type breaks). I don't know what strengthening processes they went through, but whatever it was it wasn't enough.

Randy's Ring & Pinion is one of the biggest gear places in the US, and lucky for me they're relatively close. I suppose I could take some pieces parts to them and get their opinion on the failure cause and the relative strength of the spiders.

BTW, if these seem to be the "weakest link", can't they be changed out for harder gears?

You can probably change out the spiders, but with what you spend on labor and new bearings & seals to change them, you'd be better off going with a TrueTrac diff carrier.

.Is there any reason that the ABLS would stress these spider gears-make then "see" forces that a non ABLS equipped vehicle wouldn't?I'm not suggesting that ABLS is the cause, I'm just looking at a 4x4 association(about 80% are 4x4) and all 4X4 have ABLS.Frankly,Im hoping it is a 4x4 "thing" so my 4x2 will be off the hook!!Unfortunately there have been 5 4x2 failures-maybe they just take longer to fail-easier use.The Elock was never a good bet-1/3 of the failures don't have elock.Maybe 20% don't have ABLS-they are 4x2's.

Well... All ABLS does is simulate traction on a slipping wheel.

Open differentials transmit equal torque to both sides. The classic example is to imagine one wheel on ice (with zero traction) and one wheel on pavement (with relatively infinite traction). The wheel on ice slips completely - and no torque is able to be generated. Because equal torque is delivered to both sides, the other side also gets zero torque.

When ABLS initiates braking force, that slipping wheel has something to push against - so some torque is generated, and again equal torque is distributed to both sides. In effect, ABLS would cause the same "stress" on the spiders as if that slipping wheel rolled onto a surface with more traction.



In my case, I think that several teeth on the spiders simply sheered off under load. If you look at this picture:

With the diff locked, all the rotational force is transmitted to the side gears via the spider gears (via the spider shaft, mounted in the diff carrier, which is being turned by the input pinion via the ring gear). I think teeth on the spiders which were meshed with the side gears at the time of failure just broke off - too much stress.

 

Wow Austin, awesome pics and post. I suppose I could get the rear diff from my Titan from the dealer as well, they said its sitting out back and asked if I wanted it, lol. The rear diff on my Titan failed at 4800 miles while towing, that was 3 days and 1000 miles after getting it back for a failed front diff........I wasn't too happy to say the least.

I am learning (albeit VERY slowly) about the mechanics of differentials thanks to our skidder (who's ring and pinion make the Titans look like a toy). If I can find it under the snow I'll take pictures of the failed ring and pinion from Kermit, looks like somebody had a snack, never seen anything so chewed up.

 

Austin,

I have a more important question for you, since you know the diff pretty well now and the electronics of it. Looking at the diff lock mechanism, what would need to occur to get the diff light to flash. Is there something (spider gears) that would say, yep if there was so much slop, the diff lock light might think it was locking? I know you have seen my posts, so help me defend my theory, or blow it out of the water, one of the two....

Yomama

PS I have gained new found respect for you after seeing your tear down and documentation. When I first saw you messing with the diff locking in all situations, I thought this guy is asking for trouble. How do I know this? I would have done the same thing a few years ago....You make me proud.....:crying: LOL...

 

Any chance you can get this documentation off to Nissan somehow?

Are you replacing with a new diff from Nissan or an aftermarket?

Nissan has plenty of burn't up diff's for their engineers to look at, they got plenty of documentation, this has been happening of two years now.

 

Those gears are powdered metal gears, they were pressed using a powdered metal mixture with a 700-900 ton press. These types of gears need to go through three heat-treat/anneal processes to make them strong enough to last. The photos show gears that were not put through the heat process. I would guess they were missed by whomever the Tier 1 supplier is to Dana for these parts. I've seen these types of failures at my job, I am a chemist for an industrial lubricant and metalworking supplier, and have seen how the Tier automotive suppliers skimp to save a few dollars to keep thier profits up. These were likely not treated properly, possibly due to a line stoppage, or someone missed a step when moving gears through the processing line. I am beginning to wonder if the failures all come from the same "batch" of parts. The only way to know is by the Dana barcode tag on the rear differential to see when the failed ones were put together. If the numbers of failed ones are sequential, then they could likely all have poorly made parts in them. Just a theory. I pulled my cover at 20,000 when I installed my PML cover, and inspected the gears using a jewelers magnifier, and saw no signs of stress cracks or worn areas on the gears, except the slight tapering of the front face of the gears that occurs from slack in the drive line.

 

Thanks.

Austin,thanks. I'm a bit unclear;are you saying that they broke because the diff was locked-implicating the Elocker?I'm a bit unclear on this?We have about 33 folks(34 actually,but he hasn't posted in the survey yet) who have posted-about 50 failures.Of the 33 about 20 were Elockered,.One of the (CCSI)guys had 5 failures-no Elocker.Another 5 failure guy-Mikey-does have Elocker.
KYDEEPWATER-The failures have happened to 2004 and 2005's-I'm not sure of the build dates,but probably at least a year apart.Could a lot be 100,000 parts big?Maybe the supplier just has intermittent screwups,and they are ongoing-they could be spread over many lots..If this supplier is in China or India etc, it wouldn't be easy for Dana to get to them and correct the problem.I wonder how closely a place that is paying someone 80 cents an hour monitors who makes what.You know,"Jim made your fruit of the looms" sort of thing.Usually employees in those countries are so desperate for the job, that they will conceal any screwups from the higher ups.They just pencil whip the QC paperwork to make sure it is in an acceptable range, and the parts move on.Thanks.Charlie
PS If the employees don't buy into the QC then it is just BS.It is always the upper mgrs fault because they haven't convinced the employees that they won't be "punished" for reporting their own,or their buddies mistakes.I worked in a place where just about everyone faked the QC.The QC persons job became one of correcting paper work so it would appear that everything was done correctly.We had zero errors for a whole year.They were so dumb(the QC and local mgr that was insisting that errors be "corrected") that they didn't realize that their 100% perfect records were an admission that they were faking the records.

 

Good post, KY. I noticed from the photos that the spiders were powdered metal. I would like to see properly heat treated machined steel gears here rather than the molded powdered metal. Maybe Nissan will change the spiders, or perhaps some aftermarket company will produce good steel spider gears.

 

On the topic of Q/C powdered metal parts:

http://www.asnt.org/publications/materialseval/basics/nov02basics/nov02basics.htm

 

Re: Thanks.

Austin,thanks. I'm a bit unclear;are you saying that they broke because the diff was locked-implicating the Elocker?I'm a bit unclear on this?

No, the locker was in no way the cause of the failure.

I think the fact that the diff carrier was locked allowed the stress to be concentrated on a few teeth of the spider gears - but the failure occurred because of weak spiders, not due to any component of the locker.



KY - Thanks! very much for your insight. Can you go more in depth on the treatment processes please? How specifically do you tell if a component is produced from powdered metal? Are the side gears also powdered metal?