Now I know why v8's are full time 4wd!

[duffdog]

So, out wheeling yesterday I discovered why the v8 is full time 4wd. when trying to get up a hill, I busted a front CV. No biggie, just tie the cv stub to the lower a-arm and keep driving in 2wd.

Wrong. I tried to get up a mild hill with some slippery rocks and blew the rear diff...I was shocked that such a small amount of power could blow the ring and pinion in 2wd after I had been romping on the truck in 4wd all day. It seems that the rear end is simply not capable of handling all the torque from the v8 by itself. The truck needs the additional traction from the front wheels to help distribute the torque. That is disappointing to say the least, but Ill always remember to have an extra front CV axle in the truck when I go wheeling. Its really easy to pop one in and avoid having to worry about blowing the ring and pinion again.

Just fair warning.

And BTW -- anybody have a factory 3.73 ring and pinion? because I need one fast!

 

[T4R2014]

Which explains why Tundras have a part-time transfer case with 2WD. You were being abusive my friend. I'm not even trying to be a d!ck, because I blew up a diff with a smaller engine.

Oh, and I'm guessing you were in 4HI? Even more stress.

 

[techoguy]

That's a bad trail day! how did you drive in 2wd? Disconnect the front drive shaft?

How many miles do you have on the rig? I'm curious if it was already starting to fail. I can't image the rear end would be any tifferent than the 2wd v6 and the torque isn't that much different. Of course I could be wrong.



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[J-Roc]

That's a bad trail day! how did you drive in 2wd? Disconnect the front drive shaft?

How many miles do you have on the rig? I'm curious if it was already starting to fail. I can't image the rear end would be any tifferent than the 2wd v6 and the torque isn't that much different. Of course I could be wrong.



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Also would like to know the process of getting it into 2WD

 

[techoguy]

wait, i just noticed your signature says you have elockers in the rear. Were those engaged too?

 

[m85476585]

They sold 2WD V8s (just not multi-mode), so the rear can certainly handle it, unless those have different gearing or something.

 

[CXS]

Also would like to know the process of getting it into 2WD

If you blow a CV just lock the center diff and you can drive it home. Of course you have of remove the CV or strap what remains out of the way since it'll still be spinning.

 

[CXS]

You were being abusive my friend.

Very curious about the details, how much of an obstacle? How heavy on the throttle? Original CV's or aftermarket? Other conditions?

I've blown 3 CV's myself but none until passing 175k and know the Toyota CV's are much better than aftermarket junk being sold. Please decribe just what "romping" you were doing, wondering it you're a "just hammer it" guy or not.

 

[MACT4R]

They sold 2WD V8s (just not multi-mode), so the rear can certainly handle it, unless those have different gearing or something.

Yep, they sold 2wd v8's and I have one with spartan locker that I offroad. I've gone many places and well more than capable most trails. Gear is still 3.73. I use my 3rd gen if I'm going black diamond or mod rock crawling.

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[Sporin]

That's a curious amount of breakage, we need more details.

 

[duffdog]

Which explains why Tundras have a part-time transfer case with 2WD. You were being abusive my friend. I'm not even trying to be a d!ck, because I blew up a diff with a smaller engine.

Oh, and I'm guessing you were in 4HI? Even more stress.

I don't think I was being abusive...that much. I was in 4lo with the rear elocker engaged and the stub shaft broken off from the front diff. I guess technically the truck was in 4wd, but with nothing on one side of an open diff there really is no drive on the front 2 wheels.

I was going up a ~30 degree incline with loose rocks and I did not even make it to the incline, there was a short 4 foot lip that I had to get a 10mph running start to get up, and from there a right turn. As soon as I made the right turn the diff popped and I could hear the grinding. I was about 1/2 throttle at that point.

 

[T4R2014]

I don't think I was being abusive...that much. I was in 4lo with the rear elocker engaged and the stub shaft broken off from the front diff. I guess technically the truck was in 4wd, but with nothing on one side of an open diff there really is no drive on the front 2 wheels.

I was going up a ~30 degree incline with loose rocks and I did not even make it to the incline, there was a short 4 foot lip that I had to get a 10mph running start to get up, and from there a right turn. As soon as I made the right turn the diff popped and I could hear the grinding. I was about 1/2 throttle at that point.

Meant to say 4LO*

I'd just chalk it up a a lesson learned. Wheeling is fun but you've gotta pay to play sometimes.

 

[BlackWorksInc]

I've done some shit to the 4Runner that I was genuinely worried I'd snap and axle or blow a diff... held up good so far.

Hell I even got attacked by a log on the trail!

 

[dkyleb]

This is like the 5th or 6th 4th gen I've heard of grenading a ring and pinion with the rear diff locked. I think I'll be sticking with ATRAC and a winch...

 

[CruzadoBlanco]

Blowing a CV axle would require you to lock the center diff to even move. When I blew my first CV I got on the road and unlocked the Tcase to discover the truck would send most of the power to the front. Had to lock the center up to even get it to move down the road.

Personally it sounds like your were just flooring it up the obstacle. Or did you get the elocker from an early FJ cruiser including the R&P? Those did suffer from a bad run of R&Ps. Ive personally never had an issue with my diffs and ive pushed mine hard. My locker is however from a 3rd gen runner with my OEM R&P.

 

[oldmansimek]

Your rear end definitely blew because of the massive power difference that your V8 has compared to the V6 :rofl:

 

[duffdog]

Blowing a CV axle would require you to lock the center diff to even move. When I blew my first CV I got on the road and unlocked the Tcase to discover the truck would send most of the power to the front. Had to lock the center up to even get it to move down the road.

Personally it sounds like your were just flooring it up the obstacle. Or did you get the elocker from an early FJ cruiser including the R&P? Those did suffer from a bad run of R&Ps. Ive personally never had an issue with my diffs and ive pushed mine hard. My locker is however from a 3rd gen runner with my OEM R&P.

The ring and pinion were the factory ring and pinion from my truck, I just had it put on an elocker 3rd from a Tacoma. After I get the truck back, I think I am going to chill on the hard wheeling with the 4th gen and stick to using my exo'd 89 SAS 4runner for all my wheeling.

 

[CruzadoBlanco]

The ring and pinion were the factory ring and pinion from my truck, I just had it put on an elocker 3rd from a Tacoma. After I get the truck back, I think I am going to chill on the hard wheeling with the 4th gen and stick to using my exo'd 89 SAS 4runner for all my wheeling.

im building my first gen so i can stop slamming my 4th gens body into rocks and trees, the body damage is real.

 

[RonJR]

Fulltime 4wd or not, Toyota expects you to be in 4wd when in low range. The stock transfer cases won't allow 2wd operation in low range. You essentially worked around that by removing the front CV. You also added to the stress on the R&P by making a turn with the diff locked.

That being said, I wouldn't have expected the rear diff to blow, but it should be noted that there is very little difference between the rear diff in the 4th gen behind the 4.7L V8, and the diff designed for the 3.0L V6 in the 2nd gens. About 2x difference in engine torque, however. I think Toyota might have gotten a little complacent about the toughness and reliability of their 8-inch 4-pinion diff and pushed it a little hard in the V8 application. They probably also (rightly) assumed that fewer and fewer people would be seriously offroading the newer generation 4runners, so maybe decided to take a chance.

The most likely root cause was either shock loads, excessive backlash between ring and pinion, or a worn or improperly set pinion bearing. Either of the latter two will allow the pinion to engage the ring gear at a too shallow a depth, inviting the teeth to slip past each other. Once that happens it's pretty much all over.

 

[CXS]

I think I am going to chill on the hard wheeling with the 4th gen and stick to using my exo'd 89 SAS 4runner for all my wheeling.

Aha! I think I get it now. layball: