Now I know why v8's are full time 4wd!
- Thread starter duffdog
- Start date
BlackWorksInc
New member
Yeah, since up-sizing to the 35's I've been more conscious of not letting the wheels spin up and stop as much as I used to in the 33's (i.e. try and power up an obstacle by speed and letting them spin up faster in the air because they aren't grabbing anything before slamming onto the ground). Granted with the 35's I've also noticed they grip better than my old 33's did aired down, so it's not as bad to crawl over stuff.
Additionally, [MENTION=122163]duffdog[/MENTION] it could have just been driver error. I know it's not what you want to hear, but this past winter we saw about a half dozen Tundras and Tacomas that blew their front or rear diffs because they spun their tires in the snow/ice and when it hit pavement, the sudden grip snapped the diffs. We had one that literally shattered the ring in a good 5 inch long section and jammed it so hard through the rear axle housing it started to poke through the metal. It's about excessive shock load on the assembly, you can easily generate far more impact force (i.e. the force imparted on the ring & pinion when say the tires are spun up 40mph and then suddenly hit pavement and stop momentarily) than what the vehicle was ever designed for in certain situations.
Regearing will help, also adjusting your driving to match the fact your running a lot more unsprung weight than factory or even 33's. I've been playing with my 35's for a bit now and have been pretty hard on the 4th gen with them. Most of the time I'm in 4Hi and using lower transmission gear and throttle management to off-road over obstacles all on stock gears (I do need to regear at some point though).
Post Note-
BLAIR! What's up!
You ever coming to Bend? We have good beer!
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chompster4runner
New member
Yeah, since up-sizing to the 35's I've been more conscious of not letting the wheels spin up and stop as much as I used to in the 33's (i.e. try and power up an obstacle by speed and letting them spin up faster in the air because they aren't grabbing anything before slamming onto the ground). Granted with the 35's I've also noticed they grip better than my old 33's did aired down, so it's not as bad to crawl over stuff.
Additionally, [MENTION=122163]duffdog[/MENTION] it could have just been driver error. I know it's not what you want to hear, but this past winter we saw about a half dozen Tundras and Tacomas that blew their front or rear diffs because they spun their tires in the snow/ice and when it hit pavement, the sudden grip snapped the diffs. We had one that literally shattered the ring in a good 5 inch long section and jammed it so hard through the rear axle housing it started to poke through the metal. It's about excessive shock load on the assembly, you can easily generate far more impact force (i.e. the force imparted on the ring & pinion when say the tires are spun up 40mph and then suddenly hit pavement and stop momentarily) than what the vehicle was ever designed for in certain situations.
Regearing will help, also adjusting your driving to match the fact your running a lot more unsprung weight than factory or even 33's. I've been playing with my 35's for a bit now and have been pretty hard on the 4th gen with them. Most of the time I'm in 4Hi and using lower transmission gear and throttle management to off-road over obstacles all on stock gears (I do need to regear at some point though).
Post Note-
BLAIR! What's up!
Bend does have some good beers...
Yeah, since up-sizing to the 35's I've been more conscious of not letting the wheels spin up and stop as much as I used to in the 33's (i.e. try and power up an obstacle by speed and letting them spin up faster in the air because they aren't grabbing anything before slamming onto the ground). Granted with the 35's I've also noticed they grip better than my old 33's did aired down, so it's not as bad to crawl over stuff.
Additionally, [MENTION=122163]duffdog[/MENTION] it could have just been driver error. I know it's not what you want to hear, but this past winter we saw about a half dozen Tundras and Tacomas that blew their front or rear diffs because they spun their tires in the snow/ice and when it hit pavement, the sudden grip snapped the diffs. We had one that literally shattered the ring in a good 5 inch long section and jammed it so hard through the rear axle housing it started to poke through the metal. It's about excessive shock load on the assembly, you can easily generate far more impact force (i.e. the force imparted on the ring & pinion when say the tires are spun up 40mph and then suddenly hit pavement and stop momentarily) than what the vehicle was ever designed for in certain situations.
Regearing will help, also adjusting your driving to match the fact your running a lot more unsprung weight than factory or even 33's. I've been playing with my 35's for a bit now and have been pretty hard on the 4th gen with them. Most of the time I'm in 4Hi and using lower transmission gear and throttle management to off-road over obstacles all on stock gears (I do need to regear at some point though).
Post Note-
BLAIR! What's up!
I know its easy to say "You were flooring it!" or "the wheels were spinning like crazy and dropped on a rock" or something like that, but none of it was the case. I was already up a small obstacle with all the tires touching the ground and had the throttle at 50% or less. If "driver error" means using the vehicle for any purpose other than parking it then there is a seriously bad design flaw here. I have broken a ring and pinion on an 87 4 cylinder 4runner with all stock equipment trying to pull out a fullsize stuck chevy before. Now, multiply the torque from a 22re times 3 and you have the power from the 2uz. I think that using the same ring gear on both vehicles is a bad idea. Now, just for fun, I picked up a tundra rear end which is complete with the 3rd member and will be looking into getting that modified to work with the 4runner. Its my opinion that things which can break were poorly designed. As an engineer I am not allowed to design anything like that. I can't simply say: well, this component is too expensive to make work correctly, so I will just use a cheaper one and derate the entire product.
But here is a question: does anyone know if the tundra 9.5" rear end will accept a land cruiser 80 series rear elocker??? That would be one awesome axle in my opinion.
If the broken 3rd member has not been already torn down, it would be interesting to measure the ring-pinion backlash on an undamaged section of the gears, and also do a paint pattern on that good section. There is lot of difference between blaming a failure on an inadequate design vs. it being caused by a worn or improper gear setup. As I mentioned before, if backlash is excessive, or pinion depth is inadequate, it's a failure waiting to happen under high torque loads.
Inv4drZm
Senior Member
The tundra axle is a 10.5" IIRC. The 80 series is a 9.5" so I doubt the elocker will bolt up based on the numbers alone, but I'm just speculating. I am planning on getting a diamond rear axle with a 9.5" LC diff. Complete swap over, no fabrication necessary. Correct width, shock mounts, same brakes, more GC than the 8" housing, easy peasy.
Inv4drZm
Senior Member
If you wheel it hard its only a matter of time IMO. Add larger tires like 33-35s and a locker and you're really asking for it.
toyo
Member
That's very true my friend. I have several guys in our group that literally beat the crap out of them and then they wonder why shit breaks.
Asking for it or not, sh!t happens! One time in Moab we arrived late so decided an easy trail was in order. Hit the first obstacle and blew a CV. Another time snow wheeling I was going through a small drift, turned my wheels halfway though and bang. Another CV gone. Another time the guy behind me needed a tug so I put it in reverse to help him and just got a bunch of noise. Yep, another CV gone. Like I said, sh!t happens!
You want to play, you gotta pay!
BlackWorksInc
New member
[MENTION=122163]duffdog[/MENTION]
But you're trying to say your singular experience is definitive, while many of use who either are regularly running 35's or have seen failures are saying it's less likely due to design and more due to variables the user introduced or did not address (wear & tear for example). They were never designed for 35's, the drivetrain was never really meant to handle the kind of unsprung weight we throw on our rigs with heavier wheels and tires. There have been issues with the pinion spacer collapsing on some people because the engineers I guess did not decide to use a solid spacer, if that occurs your pinion to ring gear spacing is wrong and that could cause issues as was mentioned earlier. Also as I mentioned give enough shock load that could be another issue, shock load can be introduced in many ways not just wheels spinning in the air.
Additionally you were driving the vehicle in a modified 2WD set-up (modified because it's not a true 2WD setup) which means you're using momentum more to travel over obstacles than grip in most cases, another factor and variable. The point we're all making is that while our diffs aren't exactly invulnerable, the tendency for them to grenade is not as common (just look at how often we get "blown rear end" threads on this forum, not very often and usually it's easily traced back to it not being a stock vehicle). So you coming in and off the bat with little to no real hard data besides anecdotal evidence, stating that the design is flawed and inherently weak, is coming off more as being angry and spiteful than factual. Considering these drivetrains have been out on the road for over a decade with minimal issues under towing off-roading, daily driving, recovery, ect. Most of the failures can often be attributed to modifications, operator error, and/or wear & tear.
We're trying to suss out details, data, and variables to get a better idea why your unit failed because it's less likely it's because "it's a bad design" and more because of variables introduced by the situation and/or user.
But you're trying to say your singular experience is definitive, while many of use who either are regularly running 35's or have seen failures are saying it's less likely due to design and more due to variables the user introduced or did not address (wear & tear for example). They were never designed for 35's, the drivetrain was never really meant to handle the kind of unsprung weight we throw on our rigs with heavier wheels and tires. There have been issues with the pinion spacer collapsing on some people because the engineers I guess did not decide to use a solid spacer, if that occurs your pinion to ring gear spacing is wrong and that could cause issues as was mentioned earlier. Also as I mentioned give enough shock load that could be another issue, shock load can be introduced in many ways not just wheels spinning in the air.
Additionally you were driving the vehicle in a modified 2WD set-up (modified because it's not a true 2WD setup) which means you're using momentum more to travel over obstacles than grip in most cases, another factor and variable. The point we're all making is that while our diffs aren't exactly invulnerable, the tendency for them to grenade is not as common (just look at how often we get "blown rear end" threads on this forum, not very often and usually it's easily traced back to it not being a stock vehicle). So you coming in and off the bat with little to no real hard data besides anecdotal evidence, stating that the design is flawed and inherently weak, is coming off more as being angry and spiteful than factual. Considering these drivetrains have been out on the road for over a decade with minimal issues under towing off-roading, daily driving, recovery, ect. Most of the failures can often be attributed to modifications, operator error, and/or wear & tear.
We're trying to suss out details, data, and variables to get a better idea why your unit failed because it's less likely it's because "it's a bad design" and more because of variables introduced by the situation and/or user.
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There are 2 different Tundra rear ends. One is a 10.5 and the other is a 9.5. I have the 9.5.
In regards to the LC rear axle. Why not just use the existing LC rear axle as is and remove a few mounts and reweld them where needed? That has to be about $3000 cheaper than a diamond axle with the same ring gear strength.
fact: a 95hp truck has an 8" ring gear
fact: a 270hp truck has the same ring gear as a 95hp truck
conclusion: design is poor. End of story. Since we are on the subject, please explain why Toyota felt it necessary to include a 9.5" ring gear on the 100 series LC with the same engine and 4wd system as the 4th gen 4runner if there is truly no engineering purpose for it? I find it hard to believe that it was completely accidental. I mean, sometimes I just cut and paste designs as well, but in this case there would be a cost difference and possibly- gasp! - a performance difference.
Inv4drZm
Senior Member
Ah, the second gen Tundras with the 4.7l came with the 9.5" diff.
The diamond axle gives you more ground clearance, bolts on using all stock brakes, etc, allowing you to keep atrac and whatever else you need your original wheel speed sensors for. I don't have to spend time hacking off stuff and fabricating shock mounts and spring perches, and of course it's made of beefier metal than the stock LC diff.
The primary driver for the design of the diff and axles is the weight (which determines max traction) of the truck, not the torque of the engine. Any 4wd vehicle with adequate lo-range gearing for off-road use is capable of snapping an axle or otherwise wrecking the drive train in a locked wheel situation. This is true even for the lowly 4cylinder 22re. It's just a consequence of the large gear ratios involved. Here are some numbers for a 2nd gen 22re with a manual tranny:
Total gear ratio ~= 42:1 in lo range 1st.
22re max torque = 150 ft-lbs.
Max torque at axle > 6000 ft.lbs.
Front CV's break at about 2500-3000 ft lbs, based on diameter. Rear axles are probably good for around 4000 ft.lbs. See a problem here?
What normally saves the hardware is loss of traction. That, plus open diffs cut the max torque to each axle by a factor of 2. Add lockers and larger tires and you can easily be 2.5x past Toyota's design criteria. (Larger tires increase the torque on the drive train for the same tractive effort.)
Stock 4runners aren't significantly heavier now than they were in 1990, so stock traction is about the same. Thus a similar drive train. The LC is considerably heavier, so needs a beefier drive train. [MENTION=122163]duffdog[/MENTION], your vehicle is probably also a good 1000 lbs heavier than stock given the equipment you've got on it. All of that changes the equations.
Toyota could design a drivetrain that would be unbreakable by any engine they sell. However, it would be considerably heavier and more expensive, and would offer no value to 99.5% of their customers, including the offroad ones. I can guarantee you that the Toyota engineers understood exactly what they were doing in this area. It's not "poor" or "careless" design; it's design that meets reasonable parameters but avoids over design. Finding that balance is a requirement for staying in business.
Excellent post and very note worthy. If we don't operate the machines within the design spec, then it's on us to increase the strength/durability. Blaming the manufacture for something that we operate outside of their design criteria and then whining about the failures is childish.
hwell:
BlackWorksInc
New member
[MENTION=134884]RonJR[/MENTION]
Made a great explanation, so there's no reason to trample over it. But I will point out your first mistake is starting your assumption with HP numbers and not Torque at the rear wheels, horse power will have minimal value vs. torque in these applications. Additionally you need to factor in final drive ratios and vehicle weight as well as unsprung weight (again a very critical component here being overlooked). The rear ends are very similar but constructions and materials are improved in the newer 4th gen units compared to their 70's & 80's brethren, a 1980's mini-truck rear end will not bolt up without issue on a 4th gen and vice versa. Improvements and design changes have been made over the years, so while there is some parts commonality and interchangebility, there is almost 30 years of design and engineering improvements along the way.
The Land Cruisers have always been over built, no question about that; but again they are a heavier vehicle as was pointed out earlier, they're also typically 50% more expensive than a 4Runner. You're singular failure and your emotional investment in that failure does not eliminate or eradicate many 4th gen V8's doing perfectly fine towing, off-roading, and handling 35's. That's a strong data set that shows the drivetrain to be fairly well designed in the long run. If these rear ends were that poorly designed, I'd expect to see "another blown rear-end" thread on the first page of the forum every month. As an engineer I would imagine you look at all data available before making snap judgement and assements of designs and failures.
I don't blame Toyota for my 4th gen's Spindle bending like a strip of taffy when I smacked a log at 30mph, shot the 4Runner up in the air and then forced it back down on 35's. Hitting the log aside, just the additional weight of the 35's, armour, and so on was enough to eventually bend/bow the spindles at some point if I was going to keep slamming/jumping her around. The vehicle is operating beyond it's original specifications and as such I have to adjust my driving habits (i.e. avoid directly hitting logs head on, jumping the vehicle, slamming the vehicle around) or I have to reinforce the weaker sections (i.e. gusset the spindles).
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What you typed right there probably looks good on paper but is totally wrong. I happen to have a 22re 4runner with 33's and 5.29's on it. I is not possible to break the rear diff with that engine (if you know how to set up gears). What happens when you put it in 4lo and in 1st gear and then floor it (or dump the clutch at 5000 rpm) when the truck is tied to a tree with a chain is...nothing at all. The truck simply stalls out and doesn't move. I have experimented with this at length by repeating the "revving the engine and dumping the clutch" when trying to get out a stuck chevy fullsize truck for 30 minutes and still could not break the ring gear. Granted, I do gears myself and had a v6 diff installed in the rear, but the ring gear is the same diameter as the 4 cylinder. What does happen after 40 repeated tries at dumping the clutch while the truck is tied to an unmovable object is that the case hardening on the pinion gear actually gives out and the steel folds on itself and lifts away from the base material, and still does not break the teeth on the ring gear! I may still have that pinion gear somewhere.
To your point of not being significantly heavier...I don't think that 1000lbs is insignificant, but that is just my opinion. And you are not correct about the ring gear being sized for weight, they are sized to match the projected tow rating. 6100lb Maybach cars have 8.2" ring gears...a vehicle both heavier and more powerful than a 4runner, according to your logic, it should have a 10" ring gear, which it does not.
If I learned anything by actually being an engineer who engineers things that actually work, I can tell you that you definitely cannot "guarantee" anything at any time. It could have literally been a management decision to just use the cheapest possible gear that they could find laying around from the previous production run of forklifts. There is no way you know anything more than me about the design of the 4th generation 4runner rear differential unless are the person who stamped the engineering document and released it to production. I guess you might be the person who designed the rear differential and sat in meetings while bean counters grilled you in Japanese on how to make it cheaper while avoiding lawsuits, but I find that possibility remote.
There is a lot of cheerleading about Toyota, which I wish would go away. Toyota is the best because they make things that are literally 10 years ahead of everyone else. But they do make mistakes. This rear end design was a mistake and it is my opinion that it was "corrected" by lowering the torque output of the subsequent 4runner model.
BlackWorksInc
New member
Actually if anything Toyota is behind 5~10yrs in most aspects compared to everyone else. They were and are late to the game with GDI, turbo-charging (well sorta late there), they are late to the game with Stop/Start (god, WHY the **** did they decide to go with Start/Stop BS!?), they are typically behind on the more fanciful creature comforts compared to other brands.
What they do is take what technology they have and typically design it and build it to a quality that stands up. The A750E & A750F transmissions have held up pretty damn well for almost 20 some years? The 2UZ-FE is an ancient design, but holds up well and doesn't let down for the most part.
Even these rear ends you claim to be poorly designed and talk about as if they're made of glass have done remarkably well for over a decade in the Tacoma, FJ, 4Runner, T100, ect. all while being beat to hell by owners on a daily basis from a stock and modified standpoint. Toyota's innovation is not as cutting edge as people might think; much of their reliability and their success has been from incrementally improving existing designs for decades and making sure they stand up. Look at the 1GR-FE, the A750, the 2UZ-FE, the Tundra, ect. these platforms are decades old in over-all design, engineering, and construction; but there's hundreds of minute changes throughout the years to improve the same tired design.
The "problem" was not "corrected by reducing torque output", in fact torque output bumped up slightly with the Dual VVTi 1GR-FE. They did go to a slightly larger rear axle, probably to improve towing & strength; that's a strong possibility (but hard to say as none of us were there when that decision to update the axle was made). But again, you're putting your blinders on to ignore decades of reliability from these rear-ends because yours blew up when you pushed it beyond it's designed limits. We've all been trying to be fairly polite and point out that your case is not the norm, but the exception, particularly due to mitigating circumstances of your vehicle being modified well beyond factory specs. You continue to make baseless accusations, have no supporting evidence besides one questionably controlled empirical test with a 1980's vehicle (not stock mind you, with an updated ring and pinion as you admit). You have consistently ignored when others point these failings out and have consistently tried to present your feelings as fact in the face of common sense data.
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