BustedRear_994runner

Hey, have a 99 4runner SR5. Broke two axles in three months under normal driving conditions. Kind of a long story, any thoughts or theories are much appreciated:

A few years back, I had a bad left rear inner axle seal (who hasn't). Replaced the seal, but at the sametime decided to replace the bearing (I forget why) and must have slightly muffed the spacing on the axle, so the axle continued to leak over the next year or so.

Then a couple months ago, at a light, touched the gas, heard a loud 'cLunk', lost rear wheel drive... the axle spline was sheared on the last 1/2 or so of the axle.

I picked up a salvaged axle (the whole setup), swapped it in, inspected the diff first, there was no damage... just had to replace the brake shoes, beautiful. Drove on it for over a month, no issues. (Changed the gear oil a few times over that period, just to make sure there were no left over metal shavings in the diff.)

Then a few days ago I had it inspected. It passed, but the dude said my rear brakes were set too loose, so he took it upon himself to tighten 'em up. He set them way too tight though. It was like driving with the e-brake half on or better. I had planned on loosening them back up this weekend, but yesterday my girlfriend took the truck out and, at a light, touched the gas, heard a loud 'cLunk', lost rear wheel drive... AGAIN.

She brought it back using 4-wheel drive. I'm going to pull it apart tonight, so not 100% sure yet if its that left rear axle again, but that's what I'm expecting to see.

Assuming that's what I find (sheared left rear axle spline)... My question will be, should the axle have been able to handle the force of the tight rear brakes? Or did the tight rear brakes merely add to some other issue, given that this is the second axle in 3 months? Could it be something with the diff (even though it looked totally clean before...)?

sorry for the long post
Thanks again.

Dirt Master80

The axel should easily beable to hold the brakes. I think they may have just added to another problem. maybe the bearing you replaced isnt in straight, so its loading pressure on the axle. Could also be a bend housing, or you had the bad luck of getting a juck axel. hopefully its the axel and the problems fixed with a new one.

4Runner202020

you could give these axles a shot if you wanna dish the money...

http://polyperformance.com/shop/1995...fts-p-778.html

85excab

is it the 3.4 supercharged?
ive abused the hell out of my rear axle with a lincoln locker on 37's and never broke one.
might be the other side, did the previous owner abuse the hell out of it?

crolison

was it the same axle side that you replaced before? If you replaced the whole set up (like i would) you would have different bearings. Sounds like your housing might be bent

BustedRear_994runner

4Runner202020, thanks for the link. The thought of chromolly's crossed my mind, but seems hard to justify given the cirmcumstances (wasn't beating the stocker's or anything).

85excab, 3.4 but not supercharged. It is possible that it's the axle on other side, I'll know for sure after I pull them tonight. I'll let you guys know what I find.

crolison, yep, I replaced the whole left rear setup from salvage. Ran great for a little over a month, until the inspection mechanic tightened my brakes (too tight in my opinion), then I broke down a couple days later.

Can't imagine that I have a bent housing. Bought the truck back in '03 and it was pretty clean at the time. The whole thing pretty much started with the bad left axle seal a couple years ago.

Hopefully it is just bad luck on my part. I'll let you all know what I find tonight.
Thanks for all the feedback!

Maj

Are you saying the axle sheared in the middle of where the splines are? If thats the case, you did muff the bearing install and the splines weren't full engaged. I recall another post recently about a guy breaking axles and I think it was because the axle was too short or bearing improperly positioned.

BustedRear_994runner

Hey Maj - yes, the spacing was definately off on the first axle that broke, but the axle I replaced it with was already completely setup with correct spacing, and the same thing happened again about a month later (yesterday morning).

I just got the axle out tonight (had to pry like hell to get it out) and confirmed what I suspected, it's the left rear axle again. Looks exactly like the last one that broke a few months ago.

I took a couple pictures... You can see what appears to be light/normal wear on the last 1.5" of spline, but the last .25" of spline is sheared clear off. I'm starting to think there might be something out of whack with the differential itself...





Something I haven't quite figured out about the 4runner differential... the left side of the diff seems to have two independent spider gears that ride side by side, whereas the right side only has one solid gear, haven't seen anything like that before on a domestic diff. It's like the left inner gear is only grabbing the last .25" of spline for some reason.

Is something busted in the diff? Think I should pull the diff and take it to someone who knows what they're looking at for a possible rebuild?? I'm hesitant to just throw another axle in there and hope for the best... Not sure what my best option is at this point.

Thanks again guys for any advice...

SoCalPaul

I think something's wrong in the diff & the axle splines are not fully engaged.

Maj

[QUOTE=It's like the left inner gear is only grabbing the last .25" of spline for some reason.

Is something busted in the diff? Think I should pull the diff and take it to someone who knows what they're looking at for a possible rebuild?? I'm hesitant to just throw another axle in there and hope for the best... Not sure what my best option is at this point.

Thanks again guys for any advice...[/QUOTE]

Yup, the splines in the diff got buggered up from the first axle failure. The third member is relatively easy to remove. You can then take the assembly to someone for an estimate to repair. Compare that with quotes from junkyards for a used third member and make a decision.

BustedRear_994runner

**UPDATE**

I took out the rear diff this morning... the left side spider gear is cracked in half!? Only the last 1/4 or 1/2 is still intact. So, that's why the axle runs for a while, but eventually gives up and shears the little bit of spline that's making contact with the remaining gear.

I have no idea how the hell that could've happen, seems like a very unusual place for a rear to fail.

Anyone know where I can find a decent salvaged 3rd member??

Dirt Master80

Glad you found the problem. I has a couple of good third members with stock 4.10 gears. No noises or issues I just swaped them out for complete new ones from Randy's with 5.29's and detroits

BustedRear_994runner

Hey DirtMaster,
Are they from a 3rd generation (96-02) w/ 4x4, ABS and no locker by any chance? Not sure to what extent all that matters, but don't want to risk screwing up the transfer case with an imperfect match.

Let me know, Thanks!

crolison

Don't matter, its an 8" housing it will fit in yours with no problem, just gotta make sure your front is 4.10's.

Dirt Master80

There out of my 80 completley stock, no locker and 4.10 gears . Maybe some of the other guys can help but im pretty sure all 8" thirds are interchangeable. Im not sure of your location but the shiping could be expinsive, I Think they way 50pd