What did I break?

[vthokie]

Hey guys, well I was wheeling with some friends on Friday and as I was attempting to get over one of the obstacles, I heard a nice loud "pop" and lost power up front. My first assumption was I snapped a cv axle...but it appears that this might not be the case. I took out the axle, but the outer part(where the cage is with the bearings) is not broken at all. The inner part that snaps into the diff is still in the diff... We left it in to keep it sealed. We were afraid I may have sheared the shaft in the diff, but now we are not so sure.

If it was sheared in the diff, then the inner part that snaps in should be easy to remove right? If it sheared before the snap ring on the splined shaft then only part of this would come out. Well it wouldn't budge when we tried to pry it out, so it appears that the inner half of the cv may still be intact.

We looked at an exploded diagram of the differential, and it appears there are 2 shafts inside the differential that in turn spin the cv alxes. What are the chances that one of these are broken?

When i jack up the front driver side, and spin the front drive shaft, the front driver side should spin because this is an open differential. The easiest side will turn, correct? Well, when spinning the drive shaft, I am able to hold the inner part of the cv shaft, and prevent it from turning. So if the drive shaft is spinning, but the inner section of the cv shaft isn't, wouldn't that mean somewhere in between is broken?

We thought that I may have blown the front diff gears, but I drove home with 2 shafts in, so the wheels would turn the shafts, which would spin the gears in the differential. I thought if I messed up the gears some sort of grinding or noise would be heard, but it is not. You can sort of hear the gears meshing if you spin the shaft, which doesn't make much sense that they would be messed up.

At the moment we are thinking that one of these secondary shafts must be broken, but i have never heard of anyone having this issue. Most people just say the cv broke, and replace it...

I have some friends that will be helping me drop the diff this week to see what went wrong, but i was just curious to see what anyone else thought?

** I realize this may not make much sense, so if you are not understanding something let me know what, and I will try to explain it better. I will try to get pictures in a few days.

 

[t4r4life]

i fully understand what you are saying and my guess is the shaft inside because if you snap a tooth in the gears you would still have power, if the shaft is snapped then all power would be lost and you would only hear grinding noise coming from the broken shaft grinding each other when you turn the cvs, hope that makes sense

 

[Singtoe]

That was a lot of reading.


You can't turn the front drive shaft unless your in 2wd. It would be locked with the rear drive shaft if it is 4wd.

If the 4runner is in 2wd, the ADD will be disconnected and you still won't be able to spin front axles by turning the drive shaft.

If the CV jointys aren't busted, then the ADD coupler might have broke, a front spider gear broke, or your coupler in transfer case broke.


This was a rear spider/axle gear from the rear of a 4runner busted.

 

[vthokie]

Singtoe thanks for the pic. I understand what you mean about the front drive shaft not being able to spin if it is in 4wd because its locked. If I spin the cv's and i dont hear any grinding then wouldn't that mean that the gears are alright? Something is broken for sure.

The noise seemed to come from the very front, right where the front diff was, so that's what I am hoping for. I wouldn't want to drop the diff, then realize it might be in the transfercase. How likely is it that it would be in the transfercase?

This week I will be taking it apart... what are my options for replacement parts? Is my only realistic option the dealer?

 

[Singtoe]

To do a definitive test.

To test the Transfer case. Chalk the front tires, Stick it in 4wd, jack the rear end up, crawl under truck and turn the rear drive shaft. The front drive shaft should turn too. If it doesn't, then the transfer case is dead.

If the transfer case passes test, then the diff or the CV joints are the culpert. You said that the CV shafts are fine so it is either the Spider gear or the ADD coupler. You will never know until you break it down.


FWIW, I have a front diff assembly, and a transfer case in the advent you need one.

 

[vthokie]

To do a definitive test.

To test the Transfer case. Chalk the front tires, Stick it in 4wd, jack the rear end up, crawl under truck and turn the rear drive shaft. The front drive shaft should turn too. If it doesn't, then the transfer case is dead.

If the transfer case passes test, then the diff or the CV joints are the culpert. You said that the CV shafts are fine so it is either the Spider gear or the ADD coupler. You will never know until you break it down.


FWIW, I have a front diff assembly, and a transfer case in the advent you need one.

I'll give that a try, and it is good to know that you have both lol, I might be getting in touch with you depending on what ends up being broken.

 

[techno]

You might consider draining the front diff fluid and examining it closely for bits a metal. If something gave way in there (and I think it did from your trouble-shooting explanation) there is a chance that you now have floaties in the fluid. This can help confirm a diagnosis.

 

[sn0wrunner]

was it a stock OEM axle, or aftermarket? Just curious. The aftermarket ones are known for breaking off in the diff.

I'm interested to see what is broken.

 

[vthokie]

I believe they are toyota axles. I was supposed to be taking it apart tonight, but something came up so it is getting pushed back to maybe friday or early next week

 

[vthokie]

Well my friend is busy this week and I have exams all of next week, so this just keeps getting pushed back. I'm just eager to tear into this and see what happened. I was wondering if I could get some opinions of whether it is alright to drive or not. I did drive it probably 350 miles since this had happened. I drove home from school and back, and now it is sitting in the parking lot of my apartment complex... Originally just because of the pop we figured it was a shaft inside the differential, but other people say it was more likely the spider gears. What are the chances that these sheared and got eaten up? If that was the case wouldn't we have heard some noise driving back? After the 1 loud pop I never heard a grind or rattle at all, and I was definitely paying attention trying to hear something. My main concern is that if I continue to drive it, would I be more likely to do more damage, or is the damage done? I would prefer to tear into it sooner rather than later, but the timing is just bad. My friend has a shop hes going to let me use, so it shouldn't be too bad of a job.

 

[J-money$$$]

just a few points on your thoughts on how this front diff works that are not quite right.

The drivers side cv goes into the carrier itself. The passenger side goes in the add tube, and that connects to the add stub shaft which then goes into the carrier. Spinning the tires with them off the ground IE. on jackstands to test if something is busted doesnt do anything really unless you have it 4wd . The add needs to be engaged to connect the passenger side to the carrier.

ANd another big confusion i see by many is that most people think that the ring and pinion in the front diff spin while in 2wd. This is absolutely wrong. The stock carrier is an open diff so the only thing spinning is the spider gears in the carrier. So if you blew up the ring and pinion its possible to still drive home in 2wd without any issues as long as the two little spider gears and side gears were un-damaged.

I have heard of one of the intermediate shafts breaking. My buddy broke one wheeling his tacoma out at the hammers. But he is double locked and on 35's... I doubt you broke that, they are beefy.


The most likely culprit is the wimpy spider gears. They wear with every mile. They really are the weak link of the front diff. Drain the oil. Im sure there will be nice specks of metal. Maybe some chunks. I have seen these blow up and cause the exact proble you describe. Yeah dont drive it anymore either!!!!!!! thats bad if there is peices of metal floating around and wrecked spider gear bits. IT will screw up all of the bearings too. GET IT OUT ASAP

 

[techno]

I already told you to drain the oil, and now j-money has told you to drain the oil, so DRAIN THE OIL.
If little bits of metal come out, don't drive it. If the oil seems clean and ok, then you'll be ok to drive for a while. You don't need a buddy to do this. Simply drop the front skid plate and take the diff drain plug out. You don't even need to put it up on jack stands.

 

[vthokie]

I know I know, you guys are right. Originally it was supposed to be like 4 days before i cracked it open, but plans changed so I kind of forgot. I went and picked up some gear oil today, so the next dry day, I will be changing out the gear oil and taking a look at what comes out! J-money you are right I don't exactly understand everything about the front diff. I do have a question though. So lets say the passenger side cv is in, but the driver side cv shaft is gone. (part is holding the wheel bearing together, and part is still in the diff keeping it sealed. So essentially there is no shaft on the driver side... What is moving when I drive if that is how it is set up?

 

[vthokie]

Well I changed the front diff oil today and found some small bits of metal. There were some small shavings too but about 4 small chunks were on the drain plug magnet. What is my next step?