steel front diff

Sport · **Posted:** Thu Mar 25, 2010 9:13 am

2mopar_diesels wrote:

Well, I have some actual news to report on this steel diff replacement!!!!! Marlin is about 1 week away from being able to send me his beta unit!!!!! He is in the process (as we sit here and type) of installing one into a gas KJ at his shop and should have about a weeks worth of testing on it before I get mine.

This is actually very cool, it will open alot of doors for the KJ. I wonder if you can still use the factory skid, being LP does that mean that the actual housing will sit lower or just the output part where the shaft hooks up? Excuse my non technical know how. :dizzy:

InCommando · **Posted:** Thu Mar 25, 2010 10:04 am

I still wish that a HP center section would have been usable. The LP D30's rep is only slightly better than the D30A's. Oh well.

If you get in a wreck and hurt someone, you might as well expect to get sued.

If your vehicle is modified any from stock, that might be used against you. As mentioned above, if your bumper is not at stock height and hits another car, well, obviously the damage will be different & therefore actionable in most places.

If your tail lights are moved from the stock location, did that cause the driver who rear-ended you to not see them as well?

If you live in a nanny state more nanny than average, then you may worry about modifications.

ABS, which was proven to increase stopping distances over non-abs and a competent driver decades ago, is not the boon that non-drivers think it is.

If folks are that afraid of living, don't modify anything and hide in your basement all day. Rare indeed is the accident that results in any kind of thorough post-accident de-engineering.

InCommando · **Posted:** Thu Mar 25, 2010 10:37 am

Sport wrote:

2mopar_diesels wrote:

Well, I have some actual news to report on this steel diff replacement!!!!! Marlin is about 1 week away from being able to send me his beta unit!!!!! He is in the process (as we sit here and type) of installing one into a gas KJ at his shop and should have about a weeks worth of testing on it before I get mine.

This is actually very cool, it will open alot of doors for the KJ. I wonder if you can still use the factory skid, being LP does that mean that the actual housing will sit lower or just the output part where the shaft hooks up? Excuse my non technical know how. :dizzy:

Just the part where the shaft connects ( where the pinion exits the housing) is lower. I do not believe there is another difference in the housing size, but I suppose there could be minor differences.

tjkj2002 · **Posted:** Thu Mar 25, 2010 11:28 am

InCommando wrote:

Sport wrote:

2mopar_diesels wrote:

Well, I have some actual news to report on this steel diff replacement!!!!! Marlin is about 1 week away from being able to send me his beta unit!!!!! He is in the process (as we sit here and type) of installing one into a gas KJ at his shop and should have about a weeks worth of testing on it before I get mine.

This is actually very cool, it will open alot of doors for the KJ. I wonder if you can still use the factory skid, being LP does that mean that the actual housing will sit lower or just the output part where the shaft hooks up? Excuse my non technical know how. :dizzy:

Just the part where the shaft connects ( where the pinion exits the housing) is lower. I do not believe there is another difference in the housing size, but I suppose there could be minor differences.

Besides where the pinion sits a LP D30 gear set is far weaker then a HP30 gear set.

USAFCOP · **Posted:** Thu Mar 25, 2010 11:34 am

InCommando wrote:

I still wish that a HP center section would have been usable. The LP D30's rep is only slightly better than the D30A's. Oh well.

If you get in a wreck and hurt someone, you might as well expect to get sued.

If your vehicle is modified any from stock, that might be used against you. As mentioned above, if your bumper is not at stock height and hits another car, well, obviously the damage will be different & therefore actionable in most places.

If your tail lights are moved from the stock location, did that cause the driver who rear-ended you to not see them as well?

If you live in a nanny state more nanny than average, then you may worry about modifications.

ABS, which was proven to increase stopping distances over non-abs and a competent driver decades ago, is not the boon that non-drivers think it is.

If folks are that afraid of living, don't modify anything and hide in your basement all day. Rare indeed is the accident that results in any kind of thorough post-accident de-engineering.

So again the question is raised.... What do you call 100 lawyers at the bottom of the ocean?

dgeist · **Posted:** Thu Mar 25, 2010 12:02 pm

2mopar_diesels wrote:

Take a look below, and you'll see what I'm talking about. I think the only reason you don't see breakage in this point is cause of the weak center section. But with the design and felx, there has to be alot of stress in this area. And now I'm really wondering if maybe you can weld and hard mount the diff and it's related bushing mounts to the cross-member without any consequences???

Interesting thoughts... for those familiar with the breakages that have occurred (as I am not), have any of them been to the center of the pumpkin? It seems like the two mounts that are bushing-attached ought to be forced to move together as they have non-flexing connections to the diff and passenger-side axle tubes, both of which are Al and more subject to shock-load in the stock mounting configuration. a welded stiffener brace between those two would at least force the diff assembly to move as a unit in the steel mounting arms without putting additional stresses on the center section.

If unintended flex between the mounting points is the reason that the case is being stressed in strange directions, then perhaps a simple aftermarket single-piece replacement for those two arms with some decent rigidity would give us some more miles out of our factory diffs. Anyone have a photo of the mounting of a toyota aluminum IFS diff? I have a hard time believing that Dana would make a 30a THAT much weaker than a normal 30HP axle in the directions that one would EXPECT a diff to need strength. Perhaps it's as simple as stresses in directions that DCX built into the system, not Dana...

P.S. What do the two large bolts that come down through the crossmember connect to? I have an off-topic interest.

Dan

tjkj2002 · **Posted:** Thu Mar 25, 2010 12:13 pm

dgeist wrote:

Interesting thoughts... for those familiar with the breakages that have occurred (as I am not), have any of them been to the center of the pumpkin? It seems like the two mounts that are bushing-attached ought to be forced to move together as they have non-flexing connections to the diff and passenger-side axle tubes, both of which are Al and more subject to shock-load in the stock mounting configuration. a welded stiffener brace between those two would at least force the diff assembly to move as a unit in the steel mounting arms without putting additional stresses on the center section.

If unintended flex between the mounting points is the reason that the case is being stressed in strange directions, then perhaps a simple aftermarket single-piece replacement for those two arms with some decent rigidity would give us some more miles out of our factory diffs. Anyone have a photo of the mounting of a toyota aluminum IFS diff? I have a hard time believing that Dana would make a 30a THAT much weaker than a normal 30HP axle in the directions that one would EXPECT a diff to need strength. Perhaps it's as simple as stresses in directions that DCX built into the system, not Dana...

P.S. What do the two large bolts that come down through the crossmember connect to? I have an off-topic interest.

Dan

The KJ uses 3 mounts to mount the D30A.

Passenger side mount(alloy versions on some years,same concept).

Center mount.

Drivers side mount.

Oh and those 2 large bolts are the R&P gear mounting bolts.

InCommando · **Posted:** Thu Mar 25, 2010 12:20 pm

Very interesting. We all believe that the pinion walking up the ring gear is stressing the case beyond what the aluminum can take. But what if we could stop the condition that causes the pinion to walk? Not just the sudden grab of a spinning tire, but the suspension pressures that react to the grab? I wonder if a solid mount might be worse though as sometimes a rigid mount passes on all of the forces while a softer mount would absorb some. Curious.

dgeist · **Posted:** Thu Mar 25, 2010 2:55 pm

tjkj2002 wrote:

The KJ uses 3 mounts to mount the D30A.

Passenger side mount(alloy versions on some years,same concept).

Center mount.

Drivers side mount.

.

Hmm, I guess I haven't taken a good look at those ones on the back side. I suppose with 4 contact points, it's not really designed to move with articulation, but rather just deal with NVH factors of the driveline. Still, I wonder if tying the two sides of the mounting brackets together (at least in the front) would be useful or just an exercise in welding technique...

Anyone know how JBA's system is going to tie into the mounting points? It didn't look like it had all the flanges and such that the mounting arms use (at least not in the prototype pictures).

Dan

2mopar_diesels · **Posted:** Thu Mar 25, 2010 5:12 pm

dgeist wrote:

Hmm, I guess I haven't taken a good look at those ones on the back side. I suppose with 4 contact points, it's not really designed to move with articulation, but rather just deal with NVH factors of the driveline. Still, I wonder if tying the two sides of the mounting brackets together (at least in the front) would be useful or just an exercise in welding technique...

Anyone know how JBA's system is going to tie into the mounting points? It didn't look like it had all the flanges and such that the mounting arms use (at least not in the prototype pictures).

He is having them laser cut and welded to the housing. At least in the BETA version I'm getting. In the full production run, the mounts could very well be cast/machined right on there.........dunno.

tommudd · **Posted:** Thu Mar 25, 2010 5:25 pm

here you can see some of the mounts on the diff for reference
Not sure if it helps to see them on the diff or not when talking about it but........

stumpjumper_09 · **Posted:** Thu Mar 25, 2010 7:41 pm

wow that one is perty!!! send a couple my way tom. I could sell one today. Here is the reference pic I have.

2mopar_diesels · **Posted:** Thu Mar 25, 2010 7:54 pm

That looks just like mine did last year Stump.......this time wasn't nearly as bad, as there's just a single crack running from middle of front bottom diff cover back about halfway to the pinion shaft less than 1/8" wide. Was actually able to drive it home 300mi. with just some minor grinding noises. It is amazing how close to identical the fracture lines are though!!! Wish I had pics of last years bow-up to also compare.

stumpjumper_09 · **Posted:** Thu Mar 25, 2010 8:03 pm

This one was able to be driven 3mi to the STT shop where myself and evil libby removed it and had a 2 x 4 in 1 hour and 15 min. The sad part is that I had the CVs out and both sides put back together in 30 min flat off the floor no air tools. I have ripped these things apart way too many times. The hardest part was figuring out what the best way to get it out. We actually cut the 2 bolts that hold it in the front to avoid removing the lower control arms.

Tokyojoe · **Posted:** Fri Mar 26, 2010 1:03 am

USAFCOP wrote:

InCommando wrote:

I still wish that a HP center section would have been usable. The LP D30's rep is only slightly better than the D30A's. Oh well.

If you get in a wreck and hurt someone, you might as well expect to get sued.

If your vehicle is modified any from stock, that might be used against you. As mentioned above, if your bumper is not at stock height and hits another car, well, obviously the damage will be different & therefore actionable in most places.

If your tail lights are moved from the stock location, did that cause the driver who rear-ended you to not see them as well?

If you live in a nanny state more nanny than average, then you may worry about modifications.

ABS, which was proven to increase stopping distances over non-abs and a competent driver decades ago, is not the boon that non-drivers think it is.

If folks are that afraid of living, don't modify anything and hide in your basement all day. Rare indeed is the accident that results in any kind of thorough post-accident de-engineering.

So again the question is raised.... What do you call 100 lawyers at the bottom of the ocean?

A start.

InCommando · **Posted:** Fri Mar 26, 2010 10:41 am

A GOOD start

Diggerfreek · **Posted:** Fri Mar 26, 2010 3:33 pm

Sea monkeys ???

:ROTFL:

stumpjumper_09 · **Posted:** Fri Mar 26, 2010 4:35 pm

my thoughts exactly

durangotang · **Posted:** Fri Mar 26, 2010 5:20 pm

Here's a question... maybe Troy can jump on this one... how does the pinion assembly hold up on a LPD30? All the ones I've seen never broke anything in the differential... they always broke shafts or bent the axle before that :lol:

I've never seen one break in the diff... anyone know how they hold up?

evil libby · **Joined:** Thu Nov 13, 2008 11:41 am **Posts:** 296

I would like to thank stump for his help and it still fun to run in 2 wheel hop to get a new front still

steel front diff

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