Bad Day on Trail - likely rear differential stripped and broken CV

[jblinga]

Yep.

You are about the 2000th person to do this to a 4th gen. I even did the exact same thing in the exact same situation. The rear end and a front CV both exploded on the same day on the same obstacle when I was wheeling last year. In my opinion the rear end on the 4th gen is too wimpy to use off road.

A lot of the failures of this type are due to driver error/vehicle capability. If you're open diff, trying to get up a challenging obstacle and the only thing you can do is be the SEND IT KING, something is likely to fail due to the shock load on the drivetrain. Even the strongest axles/drivetrain components will fail.

If you are struggling to get up a difficult section, there is no reason to try and prove something by just mashing the gas pedal. Tire pressure/lockers combined with driver mod are worth their weight in gold haha

 

[Drunner97]

A lot of the failures of this type are due to driver error/vehicle capability. If you're open diff, trying to get up a challenging obstacle and the only thing you can do is be the SEND IT KING, something is likely to fail due to the shock load on the drivetrain. Even the strongest axles/drivetrain components will fail.

If you are struggling to get up a difficult section, there is no reason to try and prove something by just mashing the gas pedal. Tire pressure/lockers combined with driver mod are worth their weight in gold haha

I finally got a chance to put my lockers to use on a trail that I've run 5 or 6 times. Every time prior to lockers I always got hung up halfway up a particular hill because it was so loose/steep and had to rely on ATRAC getting me past it. This past weekend locked front/rear I walked right up it like it didn't even exist. Skinny pedal up an obstacle is just as bad as someone trying to do it in 2wd before engaging 4wd just to see if they can. All it's doing is stressing out components.

 

[CO_Fletch]

I had a shop do it, and yes, they pulled everything off and cleaned the inside of the housing with a rag and compressed air. Since I have a warranty on it, they didn't want to have to do it again if some steel ended up in one of the bearings. Also-- important, you really need to change all the bearings if you want this new diff to last. A single piece of metal on one of the pinion bearings will cause it to heat up and fail and the entire exercise will have to be done again. In my opinion, its just easier to get a complete 3rd from a junkyard and slap it in there and be done with it. In my case I have the Elocker, so it was more work to change the gears.

After researching I ended up sending the complete 3rd member to East Coast Gear. They will take a look at all bearings and replace anything that needs to be replaced and warranty it 5 years - figured is was worth the extra money compared to a junk yard option. I'm just waiting for the rebuild to be sent back. I'm thinking I will do a complete disassembly and clean - my only hesitation was reading how hard it is to reassemble the brake drums.

 

[Bumbo]

I’ve been in situations where this could have happened to me, it probably would have while I was spinning if I got some traction. My friends always warn me about being too aggressive in those types of obstacles. Slow and steady is the obvious answer but without lockers, that doesn’t come easy.

When you guys say the rear end on a 4th gen is too wimpy, what would be the logical upgrade for someone looking for more?

Would this simply be some new gears and a locker, or something else?

 

[Drunner97]

After researching I ended up sending the complete 3rd member to East Coast Gear. They will take a look at all bearings and replace anything that needs to be replaced and warranty it 5 years - figured is was worth the extra money compared to a junk yard option. I'm just waiting for the rebuild to be sent back. I'm thinking I will do a complete disassembly and clean - my only hesitation was reading how hard it is to reassemble the brake drums.

The drums suck, that's why I didn't pull my axles all the way out. Look inside your housing to either side. There's a lip that the axles come out of and there should be a bracket that kinda helps block chunks from getting into the tubes. I shredded more of my ring and part of my pinion gear than you did and I was fairly confident that I didn't get anything in there. 4 gear oil changes later and there's nothing more than the usual shavings.

 

[CO_Fletch]

That does look like a rough day...

I like ur rig, looks like they are brothers.

[MENTION=144483]Bumbo[/MENTION] I like your rig! It looks like you have a CB antenna mounted in the back hatch area, what did you use for the mount?

 

[Billynath1988]

https://www.justdifferentials.com/NPHTFJC-9-5-p/nphtfjc-9.5.htm

this

 

[Bumbo]

[MENTION=144483]Bumbo[/MENTION] I like your rig! It looks like you have a CB antenna mounted in the back hatch area, what did you use for the mount?

Thanks! Its actually a ham radio antenna, but close enough.

It's a generic version of the Diamond truck / hatch mount, I just painted it black...

https://www.amazon.com/gp/product/B00LGNKLXG/ref=oh_aui_search_detailpage?ie=UTF8&psc=1

https://www.dxengineering.com/parts...MI57v06MCw2wIViPhkCh0xbQUAEAQYASABEgJDEPD_BwE

 

[duffdog]

I’ve been in situations where this could have happened to me, it probably would have while I was spinning if I got some traction. My friends always warn me about being too aggressive in those types of obstacles. Slow and steady is the obvious answer but without lockers, that doesn’t come easy.

When you guys say the rear end on a 4th gen is too wimpy, what would be the logical upgrade for someone looking for more?

Would this simply be some new gears and a locker, or something else?

I am seriously considering doing an SAS with a set of axles from an 01+ F350 with ABS. That way you get Dana 60 axles with ABS tone rings and the correct drop for the existing transfer case. Brakes and Atrac will still work normally with no check engine lights.

If no SAS is desired, the newer 5th gen 4runners have a larger ring and pinion on a stronger housing which should be a complete drop in for the 4th gen rigs. Also, the 16+ Tacoma has a great rear axle as well

 

[smallfry]

What trail were you on?

 

[Bumbo]

I am seriously considering doing an SAS with a set of axles from an 01+ F350 with ABS. That way you get Dana 60 axles with ABS tone rings and the correct drop for the existing transfer case. Brakes and Atrac will still work normally with no check engine lights.

If no SAS is desired, the newer 5th gen 4runners have a larger ring and pinion on a stronger housing which should be a complete drop in for the 4th gen rigs. Also, the 16+ Tacoma has a great rear axle as well

SAS = solid axle swap?

I assume this would be the rear axle only, or would you also try and convert the IFS to SA?

Good to know about the 5th Gen housings, ill have to look into this as I get back into exploring gearing and locker options.

 

[duffdog]

SAS = solid axle swap?

I assume this would be the rear axle only, or would you also try and convert the IFS to SA?

Good to know about the 5th Gen housings, ill have to look into this as I get back into exploring gearing and locker options.

I am considering an SAS. I have broken 5 front CV's and the rear end on my rig when wheeling. At some point you just get tired of breaking things all the time and just want your truck to keep working for 1 whole day on the trail. The Rubicon and Fordyce are no joke. All day long you find yourself slamming the frame and skidplates on 3' rock after 3' rock...until you get to an obstacle which is a 5' rock. If the trails near me were way easier I would probably not do it, but it seems like so much fun to be able to wheel without breaking something and getting an alignment afterwards.

 

[Bumbo]

Wheeling at that level is too aggressive for me now. I’m not afraid of breaking something, but I prefer to get home in one piece without a time and cost penalty.

These days I look for leisure, and that generally comes in the form of cruising around off-road on easy to moderate trails or just cruising though sand washed areas and some light dune driving in the deserts.

Personally I like the way IFS drives for my use case... LT and lockers would be my preferred route should I keep throwing money at it.

I like the headroom for saftey and capability, but at heart I am probably a conservative driver that could do without this stuff.

 

[duffdog]

A lot of the failures of this type are due to driver error/vehicle capability. If you're open diff, trying to get up a challenging obstacle and the only thing you can do is be the SEND IT KING, something is likely to fail due to the shock load on the drivetrain. Even the strongest axles/drivetrain components will fail.

If you are struggling to get up a difficult section, there is no reason to try and prove something by just mashing the gas pedal. Tire pressure/lockers combined with driver mod are worth their weight in gold haha

People always say stuff like that when they don't actually wheel. I always hear this from people who who own range rovers or have never been over an obstacle with their truck before. If you do not have to pound your skidplates that you have reinforced with 1/2" thick plate back into shape with a sledgehammer after you get off the trail, you are not really rock crawling, I consider that just "driving". So yeah, if you are "driving" off road over a few pebbles you will never break a differential. I broke a CV axle simply by putting my truck into Drive when I was in 4lo before trying to get off a 5' tall rock. I have no delusions of grandeur when looking at the drivetrain of a 4th gen. The v8 in the 4th gen 4runner has more power than a Ford Super Duty Triton V8 and the ring gear is SMALLER. That combo is a recipe for disaster, so I would rather not hear from someone who wasn't there that its only "driver error" for all the thousands of people who have had the exact same problem with the exact same vehicle in the exact same circumstances. The fact is that the rear differential design for the 4th gen v8 4runner design is horrible, the ring gear from a 90hp truck should not be used on a 270hp truck at any time, yet that is exactly what has happened and every person who attempts to wheel with it is going to break it.

 

[SAC-CA-Runner]

People always say stuff like that when they don't actually wheel. I always hear this from people who who own range rovers or have never been over an obstacle with their truck before. If you do not have to pound your skidplates that you have reinforced with 1/2" thick plate back into shape with a sledgehammer after you get off the trail, you are not really rock crawling, I consider that just "driving". So yeah, if you are "driving" off road over a few pebbles you will never break a differential. I broke a CV axle simply by putting my truck into Drive when I was in 4lo before trying to get off a 5' tall rock. I have no delusions of grandeur when looking at the drivetrain of a 4th gen. The v8 in the 4th gen 4runner has more power than a Ford Super Duty Triton V8 and the ring gear is SMALLER. That combo is a recipe for disaster, so I would rather not hear from someone who wasn't there that its only "driver error" for all the thousands of people who have had the exact same problem with the exact same vehicle in the exact same circumstances. The fact is that the rear differential design for the 4th gen v8 4runner design is horrible, the ring gear from a 90hp truck should not be used on a 270hp truck at any time, yet that is exactly what has happened and every person who attempts to wheel with it is going to break it.

Well damn it...guess I'll blow out my Nitro 4.56 gears and CVJ front axles in style then! I'll try it!

And to the OP...doing the rear brake drums isn't THAT bad. Just make sure you back off the adjustment screw enough so the pads go back in. Then adjust it again. That was my biggest issue. In fact I think I need to go back in and adjust them so they grip a little better!

 

[CO_Fletch]

A lot of the failures of this type are due to driver error/vehicle capability. If you're open diff, trying to get up a challenging obstacle and the only thing you can do is be the SEND IT KING, something is likely to fail due to the shock load on the drivetrain. Even the strongest axles/drivetrain components will fail.

If you are struggling to get up a difficult section, there is no reason to try and prove something by just mashing the gas pedal. Tire pressure/lockers combined with driver mod are worth their weight in gold haha

At the time I knew the obstacle was likely beyond my rigs capabilities - with only 32s (aired down to 18), the obstacle was too tall and I knew I would have challenges. My son had tried it just before me in his 3rd Gen with 32s and got up with a tow. I gave it one try at slow speed and lost traction. I typically don't try to bump up over something out of fear of breaking a CV, but tried that option (beyond my better judgement). Live and learn :doh: I think lockers would have given me a good chance. I thought about adding a rear locker but can't justify the cost and will stick to more mellow trails (this was rated a 7 out of 10 and I try to stick to 5 maybe 6 max or less). Fortunately after wheeling for 4+ years this is my first breakage.

 

[CO_Fletch]

Sorry to hear you're dealing with this man! Let us know how it all works out because I'm sure some of us will have to deal with it one day. I wonder if it would be worth it to invest in some stronger gears/locker while you're in there. Might be a good opportunity for an upgrade!

Thanks man. I explored upgrade options but decided to stick to stock considering the cost was another $1300 for air locker and more for e-locker (part of the problem is the gearing was 3.90 which is not common so I couldn't swap with other used diffs without changing out the front as well). I looked at a Detroit Truetrac but it didn't sound like it would really help as much as what I needed it for (i.e., one wheel off the ground I would need to use brakes to assist the locker and then it's not true 100% locked, plus the daily driving might create issues for my wife). I decided if I wanted to move up to lockers or different gears I would just buy another rig and put the money I save into something newer.

 

[CO_Fletch]

What trail were you on?

Miller Rock just outside of Denver, CO

4X4Explore.com - Miller Rock

 

[DZNUTS]

Sounds about right. The 4th Gen reads are notoriously weak. Throw in a v8 with 330 lb. ft. or torque at the crank and it’s just a matter of time before we grenade our rear diffs.

Check out my thread from last season. Sheared teeth and all.


Sent from my iPhone using Tapatalk

 

[Inv4drZm]

It's not necessarily the torque that is the reason for breaking diffs on our rigs, its the amount of wheel spin and speed due to the lack of an actual low range that a crawlbox or aftermarket tcase can provide. Lower gearing in the t case multiplies torque (think 2x, 3x or more) but allows you more control and time to stop if your tire gets bound in the rocks. I think lockers and lower diff gears help because ATRAC relies on wheel spin to some extent but the next level of durability is a lower t-case or a Diamond w/9.5" LC gears or Currie w/Ford 9", the t-case being the cheapest especially if you've already dumped money into locking/regearing the front and rear.

Edit: and the 5th gen/later FJ "8.2" rear ends (I believe) have the same size gears as our 8" the carrier is just strengthened, which I believe makes the gears just strong enough to outlast the axle shafts in those diffs, so now you'll break axle shafts. How much stronger does that make it? No idea. I wouldn't spend much money on swapping over to one of those when you can get a fully loaded Currie + F9 or D60 with so much more benefits.