[Hotrodguru]

w0ot, w00t! Rear Diff exploded on the FJ...

Alright to bring everybody up to speed. Back in late December my rear diff locker light came on before my road trip to Colorado. Took it into the dealer and they said it was ok to drive but ordered me a new rear diff lock actuator.

Since then, haven't had the time to take it in. Light went away and figured I would drop it off when work slowed. Fast forward two months...rear diff explodes. This is the update and what I posted on the FJ Forums.

http://www.fjcruiserforums.com/forums/general-discussion/17688-urgent-rear-locker-light-stuck-dashboard-2wd.html

Rear Diff exploded yesterday on the way back to work from lunch. Since I arrived back from Colorado I hadn't had a chance to drop off the truck at the dealer. The light had went away and I figured I woud leave it once a month long project I'm working on was done. This past weekend did like 4 hours of knarly wheelin and no issues. After the wheelin though the rear locker light did come back on.

Long story short, on the way back from lunch I heard a loud clunking. Would quite down when coasting but anytime I gave it gas it would start back up. Figured the diff or something went. Phillip my service rep called me today...said the mechanic came up to his desk and laid a big chunk of broken metal on top. Later in the day I spoke to him and he said the shop foreman was taking a look at it. At this point I was a bit worried, figuring they might say the 285's did it or the 3" ToyTec lift. Called me back later in the day and said they were going to have to order the rear diff. They are on back order here in the states and it'll more than likely come from Japan. Looks like it'll be there 10 days to 2 weeks.

Ohh well, at least I got a nice loaner Porsche

 

[CUCUY]

pics of porsche?

 

[Interex]

Loaner Porsche? What dealership was this?!?

 

[purity]

Loaner Porsche? What dealership was this?!?

ya no shit. i got a corolla last time.

 

[Hotrodguru]

Loaner Porsche? What dealership was this?!?

Haha...my co-worker Kelly let me borrow her Boxster. Even though she said I could use it as long as I want, I'll more than likely go up to the Toyota dealer today and pick up a Yaris or something.

So how will a Yaris perform at a Autocross??? haha

 

[FlipSideUp]

Note to self: Call Kelly next time my rig needs to go to the shop.

 

[purity]

So how will a Yaris perform at a Autocross??? haha

like its on rails!

 

[hossmaster]

Note to self: Call Kelly next time my rig needs to go to the shop.

No Shit!

 

[AK98Taco]

You are going to mention the "A-TRAC + Rear Locker Mod" to your service manager, aren't you?

You changed the way the locking diff system operates and Toyota does not have to warranty the item.

 

[Hotrodguru]

Well AK if they ask I'll be honest with them, but haven't mentioned to them. Actually ever since I went with the ToyTec lift I seem like I have better articulation in the back and rarely run the locker and A-TRAC. Mainly A-TRAC if anything and the locker alone when running thru some soft sandy areas.

I did consult with the service manager before getting some bigger tires and the lift though. I do know the new TRD SE edition FJ does come with a factory A-TRAC + Locker functionality and it's been released that ALL future FJ's will have it. Valkyrie did mention this on the FJ board which is interesting. Wondering if they changed something on the diffs 4 months ago.

I'd be interested to find out exactly what broke.

The problems with Toyota rear diffs has been strictly with the smaller ring gears used on the e-locker models (Tacoma and FJC), and generally, they have all failed under stress.

Note: This shouldn't affect models produced within the last 4 months or so...

 

[Valkyrie]

Well AK if they ask I'll be honest with them, but haven't mentioned to them.........

I do know the new TRD SE edition FJ does come with a factory A-TRAC + Locker functionality and it's been released that ALL future FJ's will have it.

First off, I doubt they'd ask specifically if the A-Trac has been hacked into, because this is not widely known. So I guess your gamesmanship isn't based on being open, but rather on a "don't ask, don't tell" scenario.

Not trying to dog on you, but unfortunately, being less than forthright by withholding relaevant information ultimately is likely to obscure the issue and perhaps prevent/delay identification of a defect.

I understand your unwillingness to possibly present evidence of your action that may put yourself at fault because it may cost you money, but I have always found honesty is the best policy.

As far as the hack mattering, I honestly don't know exactly what it accomplishes or how it affects the system.

I haven't dug into this very much, and perhaps maybe I'm just an idiot, but I *think* the A-trac "hack" leaves the rear "differential braking" operational. In the other FJC's, A-trac is completely disabled when the diff is locked.

What I mean by "differential braking" is the A-Trac's ability to apply braking force differentially, one wheel at a time.

I know the new TRD ones have A-trac capability + RR Diff Lock, but I don't know if they have disabled the rear "differential braking" or not.

I would have to imagine they did, because I just can't understand using "differential braking" on a locked axles.

 

[Jomentum]

rear diff

There is a 05 silver 4runner in my shop right now with the ring gear missing all the teeth and the trans whirrring. I was trying to warranty the diff but I'm
Stuck now with both problems and I know Toyota will kick back the warranty repairs if I do BOTH! I can USUALL slip one repair in...
It' an LSD rear

 

[99FlowedTaco]

There is a 05 silver 4runner in my shop right now with the ring gear missing all the teeth and the trans whirrring. I was trying to warranty the diff but I'm
Stuck now with both problems and I know Toyota will kick back the warranty repairs if I do BOTH! I can USUALL slip one repair in...
It' an LSD rear

if it was me fix tranny and i'd fix the rear 3rd myself.

 

[Valkyrie]

It' an LSD rear

Really??

That's odd- it's the large ring gear isn't it?

 

[Gnwhite]

Thats one issue that i am worried about and why i have not done the hack. I have heard that the rear diffs are a weak link but i dont know how bad they are. I am not having an issue at this time but I admit i dont get as much wheeling time as i really want at this point.

 

[Jomentum]

Really??

That's odd- it's the large ring gear isn't it?

No, its the 7, or i would take the lsd out and use it in my T-100

 

[fast frank]

First off, I doubt they'd ask specifically if the A-Trac has been hacked into, because this is not widely known. So I guess your gamesmanship isn't based on being open, but rather on a "don't ask, don't tell" scenario.

Not trying to dog on you, but unfortunately, being less than forthright by withholding relaevant information ultimately is likely to obscure the issue and perhaps prevent/delay identification of a defect.

I understand your unwillingness to possibly present evidence of your action that may put yourself at fault because it may cost you money, but I have always found honesty is the best policy.

As far as the hack mattering, I honestly don't know exactly what it accomplishes or how it affects the system.

I haven't dug into this very much, and perhaps maybe I'm just an idiot, but I *think* the A-trac "hack" leaves the rear "differential braking" operational. In the other FJC's, A-trac is completely disabled when the diff is locked.

What I mean by "differential braking" is the A-Trac's ability to apply braking force differentially, one wheel at a time.

I know the new TRD ones have A-trac capability + RR Diff Lock, but I don't know if they have disabled the rear "differential braking" or not.

I would have to imagine they did, because I just can't understand using "differential braking" on a locked axles.

Why would the computer decide to apply brakes to one side of the rear axle if both rear tires are turning at the same speed?

 

[Valkyrie]

It doesn't... or it shouldn't. That's why I would like to know what exactly is disabled in the hack, what kind of functionality remains and how the A-Trac / RR Diff interface works on the TRD...

 

[Hotrodguru]

Well...dealer called and surprised me. Said the FJ was ready to go so I went down and picked it up . Wanted to talk to the tech who serviced the truck but he left early.

They replaced the following: (not sure what all the parts are though)

410111 DIFFERENTIAL CARRIER ASSY R&R
97986 TRAN, MAU LIC#: 86802
41110-60A00 CARRIER ASSY, DIFFER
42181-60130 GASKET, DIFFERENTIAL
VV831 VAL HP GEAR OIL 80W90
00475-1BF03 BRAKE FLUID

It doesn't... or it shouldn't. That's why I would like to know what exactly is disabled in the hack, what kind of functionality remains and how the A-Trac / RR Diff interface works on the TRD...

I think they go into this in way more detail on the FJ Forums.

 

[grillmasterp]

Good news...BTW- What Dealership did you go to?