What did I break in my driveline, KZJ78

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Lomoski

Lomoski

Joined
Nov 24, 2017
Threads
38
Messages
280
Location
Canada
Hi friends,

Well, here's the story. I was out wheeling all day on Sunday. Lots of snow, dirt and wet roads. I drove home in 4x4 and then this morning I hopped in the truck and started to drive to work in 4x4 on dry roads. As I was backing out and turning there was a very loud bang from somewhere that i can only guess was front left. Now when i'm driving in 4x4 the rear end feels like it binds and hops a bit very intermittently. So. Where do I start. Is there a likely weak spot that I have damaged?

Any Help is appreciated.

1995 kzj78 with 3'' dobinsons lift 33x10.5x15
 
Lomoski said:
Hi friends,

Well, here's the story. I was out wheeling all day on Sunday. Lots of snow, dirt and wet roads. I drove home in 4x4 and then this morning I hopped in the truck and started to drive to work in 4x4 on dry roads. As I was backing out and turning there was a very loud bang from somewhere that i can only guess was front left. Now when i'm driving in 4x4 the rear end feels like it binds and hops a bit very intermittently. So. Where do I start. Is there a likely weak spot that I have damaged?

Any Help is appreciated.

1995 kzj78 with 3'' dobinsons lift 33x10.5x15
Click to expand...

I'm afraid you've probably damaged your rear diff in a bad way (maybe broke some teeth off the ring/pinion).

The cardinal rule to driving a 4x4 with no center diff, is to always take it out of 4x4 when on high traction surfaces. Also, our diffs are weakest in reverse. Turning sharp puts the most binding force on the drive train. So by reversing on high traction while turning sharp, you've done everything possible to bind up the drive train in the worst way.

Don't drive the truck anymore! Contact some of the JDM parts places and see if they have a rear third member for a KZJ78. Drain your rear diff an look for chunks of metal.

Edit: it's also possible you've damaged a front birfield.... You could jack up the front and put the axle housing on jack stands. With the t-case in 2wd, you can spin everything by hand and see how it feels. Do the same with the rear axle for that matter. Make sure you chock the wheels to keep it from rolling.
 
GTSSportCoupe said:
I'm afraid you've probably damaged your rear diff in a bad way (maybe broke some teeth off the ring/pinion).

The cardinal rule to driving a 4x4 with no center diff, is to always take it out of 4x4 when on high traction surfaces. Also, our diffs are weakest in reverse. Turning sharp puts the most binding force on the drive train. So by reversing on high traction while turning sharp, you've done everything possible to bind up the drive train in the worst way.

Don't drive the truck anymore! Contact some of the JDM parts places and see if they have a rear third member for a KZJ78. Drain your rear diff an look for chunks of metal.

Edit: it's also possible you've damaged a front birfield.... You could jack up the front and put the axle housing on jack stands. With the t-case in 2wd, you can spin everything by hand and see how it feels. Do the same with the rear axle for that matter. Make sure you chock the wheels to keep it from rolling.
Click to expand...


Yeah, I am definitely aware of the "cardinal rule"! I was decaffeinated and tired on a Monday morning heading to work and completely forgot I parked it in 4x4 last night! Definitely my own boneheadedness, I'm just glad it didn't happen when I was way out in the middle of the mountains yesterday with no cell service. So with the hopping it's likely the rear diff that would have bound up? I will check my birfs as well. I literally just rebuilt them a couple months ago so I'm really hoping that's not the case. I was hoping it wasn't a pinion but it seems likely since it's just one diff that "hops" when I'm driving. Can I replace the ring and pinion or do I need a whole new third member? Also if I'm getting a new third member can i find a elocker at the same time?


Thanks again. I was expecting the worst.
 
Lomoski said:
Yeah, I am definitely aware of the "cardinal rule"! I was decaffeinated and tired on a Monday morning heading to work and completely forgot I parked it in 4x4 last night! Definitely my own boneheadedness, I'm just glad it didn't happen when I was way out in the middle of the mountains yesterday with no cell service. So with the hopping it's likely the rear diff that would have bound up? I will check my birfs as well. I literally just rebuilt them a couple months ago so I'm really hoping that's not the case. I was hoping it wasn't a pinion but it seems likely since it's just one diff that "hops" when I'm driving. Can I replace the ring and pinion or do I need a whole new third member? Also if I'm getting a new third member can i find a elocker at the same time?


Thanks again. I was expecting the worst.
Click to expand...

Just blame it on the time change; LOL.

I haven't repaired a broken diff, so can't say for sure if you can just replace the gears only or not. It probably is situation specific. It's possible spider gears and bearings etc. could have sustained damage too. Don't really know until you take it apart.

Yes! Now is the perfect time to get a locking rear diff for sure! Think of it as an opportunity for upgrade rather than an inconvenient and expensive repair!
 
JimmyPrado said:
Does the back end do the same thing when it’s in 2 WD?
Click to expand...
I ha
GTSSportCoupe said:
Just blame it on the time change; LOL.

I haven't repaired a broken diff, so can't say for sure if you can just replace the gears only or not. It probably is situation specific. It's possible spider gears and bearings etc. could have sustained damage too. Don't really know until you take it apart.

Yes! Now is the perfect time to get a locking rear diff for sure! Think of it as an opportunity for upgrade rather than an inconvenient and expensive repair!
Click to expand...


Yeah, It was definitely the time change. What a stupid draconian thing to continue on with!

Well I was thinking about a locker anyways, so now's the opportunity I guess. I wonder if I can find a whole 3rd member with a locker that will fit our weird gear sizes. These things are old, they break. It's ironic it was in my parking lot though. So I can't get too upset.

I think I'll take this into my local Toyota offroad shop. We have had snow on the ground for the past 2 months already here.
 
Lomoski said:
I ha


Yeah, It was definitely the time change. What a stupid draconian thing to continue on with!

Well I was thinking about a locker anyways, so now's the opportunity I guess. I wonder if I can find a whole 3rd member with a locker that will fit our weird gear sizes. These things are old, they break. It's ironic it was in my parking lot though. So I can't get too upset.

I think I'll take this into my local Toyota offroad shop. We have had snow on the ground for the past 2 months already here.
Click to expand...

Try contacting the places that part these trucks like jdmparts.ca and rocky mountain imports to see if they have what you need. Definitely try to find the whole 3rd. I think you'll probably need one from a KZJ78 to fit right.... But you can spend time on ToyoDIY and Megazip to cross parts and see if 4Runner diffs etc. are compatible..... I think it was more the LJ78 4.88 gears that were really specific. I thought for some reason the KZJ78 4.3 is more general. But I'm just guessing here.
 
From Megazip:

41110Carrier Assy, Differential, Rear
[05.1993 - 04.1996] KZJ7# ＊ＦＧＲ＝４３：１０＝４．３００,ｱｸｽﾙｺ-ﾄﾞ=G284		41110-26161US $2,687.70
SHOW
replacement
Carrier Assy, Differential, Rear
[05.1993 - 04.1996] KZJ7# ＊ＦＧＲ＝４３：１０＝４．３００,ｱｸｽﾙｺ-ﾄﾞ=G284		41110-3D022from US $1,181.56
SHOW
41110Carrier Assy, Differential, Rear
[05.1993 - 11.1995] KZJ7# ＊ＦＧＲ＝４３：１０＝４．３００,*AXC=G285,ｱﾘ(LSD)		41110-35640US $3,873.45
SHOW
replacement
Carrier Assy, Differential, Rear
[05.1993 - 11.1995] KZJ7# ＊ＦＧＲ＝４３：１０＝４．３００,*AXC=G285,ｱﾘ(LSD)		41110-3D042US $2,656.08
SHOW
41110Carrier Assy, Differential, Rear
[05.1993 - 04.1996] KZJ7# ＊ＦＧＲ＝４３：１０＝４．３００,ｱﾘ(ﾃﾞﾌﾛﾂｸ) & ｱｸｽﾙｺ-ﾄﾞ=G284		41110-35650US $2,703.51
SHOW
41110Carrier Assy, Differential, Rear
[11.1995 - 04.1996] KZJ7# ＊ＦＧＲ＝４３：１０＝４．３００,*AXC=G285,ｱﾘ(LSD)		41110-3D040US $3,225.24
SHOW
replacement
Carrier Assy, Differential, Rear
[11.1995 - 04.1996] KZJ7# ＊ＦＧＲ＝４３：１０＝４．３００,*AXC=G285,ｱﾘ(LSD)		41110-3D042US $2,656.08
SHOW
 
Well, the first diff part number in that list does cross to 2nd gen 4runners with v6 and 5spd.....

I haven't checked the others yet.....
 
GTSSportCoupe said:
Well, the first diff part number in that list does cross to 2nd gen 4runners with v6 and 5spd.....

I haven't checked the others yet.....
Click to expand...
Well those aren't cheap! I think you're right about the 4.3 being more standardized. I think it's a high pinion too. I'll send a message to rocky mountain etc. Thanks!
 
Lomoski said:
Well those aren't cheap! I think you're right about the 4.3 being more standardized. I think it's a high pinion too. I'll send a message to rocky mountain etc. Thanks!
Click to expand...

No prob. If you do manage to find a factory e-locker diff, you will have to modify your axle housing a bit to make it fit.... I think @kbushnz knows quite a bit about this stuff. Hopefully he chimes in here...
 
GTSSportCoupe said:
No prob. If you do manage to find a factory e-locker diff, you will have to modify your axle housing a bit to make it fit.... I think @kbushnz knows quite a bit about this stuff. Hopefully he chimes in here...
Click to expand...
Yeah I think you need to cut a hole in your axle housing, but I believe it is in fact possible. Bad timing, there's too much snow on the ground for me to do the work on my driveway. Oh well, now I get lockers!
 
clintnz said:
I would jack it up & check through the driveline before pulling stuff apart, ordering parts or panicking too much. It could be something as simple as a fubared driveshaft UJ.

Cheers
Clint
Click to expand...

^^^ Super good advice! Not sure why I did not think about u-joints..... :bang:
 
I took a Harrop rear e-locker meant for my BJ74 to a diff and gearbox shop.
They swapped all that stuff out in about 2 hours including access hole for wires.
They had never done one of these lockers or a 70 series before but they had no troubles.
A specialty shop makes all the difference.

Definitely jack the truck up, remove wheels and turn things by hand to pinpoint problem areas.
 
Hello,
So I drained my front and rear diff. Fluid was still clear in the front, it was replaced maybe 10000 km ago. No metal flakes on the magnet. The rear was royal purple with maybe 50k km ago. There was some sludge on the magnet but no metal flakes and no sheen in the oil. So i'm assuming I didn't break anything in there. I jacked the front up and turned the wheels by hand while pointing straight forward and at full lock while the hubs were locked. No popping or grinding in the differential and no rubbing or popping from the birfs. So again i'm assuming that means everything is fine there. I guess next would be to drain the center diff and see if there is any shavings or metal in there. I also did a visual and "rattle" test of the u joints. No concerns there. Am I missing anything? If I haven't seen any obvious metal shavings or pieces should I be relatively confident I got away with one?

Thanks guys.
 
Does it steer okay?
When I destroyed a birfield steering would bind at the knuckle. Jack it up and turn steering fully both ways left right.
 
jblueridge said:
Does it steer okay?
When I destroyed a birfield steering would bind at the knuckle. Jack it up and turn steering fully both ways left right.
Click to expand...
Yeah I was able to steer it by hand (grabbing the wheel and steering it) in both directions to full lock while hubs engaged and able to rotate the tires full rotations in both directions while at both locks and while straight forward. When I am pressed up against something though like a rock or something it will bind. But that was happening before said bang.
 
Sounds to me like the front end is good then. My steering binds when the wheels are up against something too.

If I were you I'd probably jack up and check the rear end next, and t-case after that.

I was really hoping you'd find a messed up u-joint....
 
GTSSportCoupe said:
Sounds to me like the front end is good then. My steering binds when the wheels are up against something too.

If I were you I'd probably check the rear end next, and t-case after that.

I was really hoping you'd find a messed up u-joint....
Click to expand...
Yeah it seems to me that the front end is good. I drained the rear oil as well and other than some very fine black sludge on the magnet that seems reasonable for 50k km on the oil. I didn't get a chance to jack up the rear end and spin the wheels but I'm guessing that will check out fine. The t-case oil only has maybe 15k km on it so i'll drain that next and see what it looks like. If the t case checks out fine where do I go next? I should also say that my birfs were rebuilt maybe 15k km ago as well.

Thanks for all the help guys. Still looking into lockers!
 
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