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Discussion Starter #1
went Upstate NY a few weeks ago w two buddys from my dealership, both tundra owners

Me : 05 DCAB w 5100's on 33's
Joe: 05 DCAB w 5100's on 33's
Stefano: 03 ACAB w 5100's on 31's
(all among other mods)

Joe and I BOTH blew our front Diff's in reverse in 4LO, I was backing up to get out of a stream/obstacle, rocked it a few times, BANG! crunch crunch crunch, and my tundra is reduced to an oversized mustang... thats friggen CRAPPY,

Joe lines up in his to pull me out... gets into 4LO, takes the slack outta my Snatch strap, gives it a liittle gas, BANG! crunch crunch crunch... He rolled down his window, and said "...Really?... thats it??" (not to mention this is his 2nd front diff)

Needless to say, we got our diff's covered. But holy ****, i can't trust 4LO in my truck anymore. TWO Diff's w/ little stress on them broken in 15 minutes of wheelin' (in 4LO in reverse)

Think its cuz of the A-TRAC, holding one wheel then unleashing all the torque to the front drive when the other one gets traction??
cant be cuz they were cold, it was a 2 hour drive upstate, NY.

an '07 or up wouldnt be any different cuz the ring and pinions are the same damn size
This truck has me seriously considering a Ford

we swapped our diffs about 3 weeks ago, and 4wd is workin' like new, buut
HOW GOOD IS NEW???
can i ever Wheel this truck again (most specifically in 4LO in reverse)???
 

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Your solution lies in a solid axle or less skinney pedal reverse is when your front gearset is going to be at it's weakest as you are driving on the coast side of the gears so try to avoid that. If you could figure out how to shoehorn in a 07+ tundra diff they are much larger, hell even the 05+ tacoma and FJ diff is significantly larger.
 

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Tranny's and diff's are weak in reverse. Almost all the design criteria is based on forces caused by forward motion.

For this reason, never down shift an auto trans hard at high rpm and never pull anything in reverse.

All that said, Toyota R&D IS NOT what it used to be.
 

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Discussion Starter #4
the internals to the front diff to the new 2nd gen tundra are all the same though, no?


and i agree, the new stuff is NOT what it used to be my '05 tundra just ISN'T built to the quality my '94 truck was, granted the tundra has infinitely more balls


siiigh
 

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Tranny's and diff's are weak in reverse. Almost all the design criteria is based on forces caused by forward motion.

For this reason, never down shift an auto trans hard at high rpm and never pull anything in reverse.

All that said, Toyota R&D IS NOT what it used to be.
How is a diff weaker in reverse:confused:
 

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How is a diff weaker in reverse:confused:
have u ever looked at the angle that gears are cut. significantly weaker in reverse, thats why u never want to snatch someone out in reverse.
 

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have u ever looked at the angle that gears are cut. significantly weaker in reverse, thats why u never want to snatch someone out in reverse.
Whether you shear off a tooth against the front or back of the helix, you are still shearing the same tooth. The gears aren't designed with a helix to strengthen the driving face. They are designed that way to keep them from howling.

The Tundra's front diff may in fact be weak, but I have wheeled lots of vehicles with supposedly weak front diffs and never broken one. Most notably a '69 Bronco with a 302 V8 and a dana 30 front end. Everybody told me it would never survive. I wheeled that rig for a decade and sold it with the original front end still going fine. The reason is that I'm damn careful to keep from applying shock loads to it. What this driver's buddy did was not a snatch. It was a static pull.

I've snatched enormous things out of my way, including a huge douglas fir in reverse, but I never let the force get transfered to my drivetrain. I accelerate back taking up the slack and just as it gets taken up I push in the clutch. My frame takes the full load. I never do hard static pulls to get others out either. If it calls for a hard static pull it gets the winch, or they get left. The reason is simple: you break shit. A stuck vehicle can require many times it's weight to extract it. Breaking a diff the way these broke, doesn't prove to me that they are weak.

Reversing out of a stuck is a similar deal. First off you are trying to get out using a gear that is typically higher than the one that got you stuck in the first place. That means you are probably leaning on it more. The Tundra produces a ton of torque, and if you couple that with bigger tires, something has to give. I'll also add that front diffs are almost always weaker by design. They don't do heavy towing or high mileage. It's also a blessing because a broken front still leaves the truck driveable.

I'm just saying, you can break any tool if you don't know how to use it. If you made an unbreakable truck it would be too heavy to wheel at all. I'm not trying to piss anybody off. I'm just trying to help maybe save another expensive mishap. I wasn't there, but from the description given my guess is that both breakages were the result of driver error.

Teryx
 

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Discussion Starter #8
I wasn't there, but from the description given my guess is that both breakages were the result of driver error.

Teryx


I can definitely accept that, man. I'll never be offended by constructive criticism

also point taken that Joe should have pulled me out facing away from me, rather than backing up.

for myself, trying to get "unstuck" what should i have done differently? (joe wouldnt have needed to pull me if my diff didn't go)
 

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Discussion Starter #10
While I don't own a Tundra, I've also broken gears in reverse. I will never again do hard pulls in reverse. Best to pull from the rear going forward, otherwise use a winch.
so i shouldn't have even tried "unstucking" (haha) myself in 4LO?

what do i do differently next time?
 

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so i shouldn't have even tried "unstucking" (haha) myself in 4LO?

what do i do differently next time?
for starters, take a different line of travel.

and if/when its a bad stuck dont try so hard to get ''unstuck'' thats why i never try anything too 'difficult' if im alone in the woods. i always have a friend to pull me out if i decide to do something that i might get stuck...

with that being said, ill remember to not get pulled or pull some one out going in reverse! thanks for that tip!
 

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Differentials do have more strength in one direction over the other. This has to do with whether the pinion is above differential center-line (high pinion) or below (low pinion). And yes, it is due to the way gears are cut.

Low Pinion in rear = High strength pulling forward, less pulling in reverse

High Pinion in rear = opposite


Low pinion in front = High strength pulling in reverse, less pulling forward

High pinion in front = High strength pulling forward, less in reverse.


I'd guess that the front diff's (IFS/Solid axle doesn't matter here) are high pinion. When you were stuck down hill trying to back up, more weight/traction was on the front differential, in it's weakest mode.

A vehicle equipped Low rear, high front is VERY strong pulling forward significantly weaker pulling in reverse.
 

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I can definitely accept that, man. I'll never be offended by constructive criticism

also point taken that Joe should have pulled me out facing away from me, rather than backing up.

for myself, trying to get "unstuck" what should i have done differently? (joe wouldnt have needed to pull me if my diff didn't go)
Since whichever end you pull from gets the highest percentage of the load in many cases, it IS best to pull from the back. It has nothing to do with the gears being weaker in reverse. You just want the heavy load on the strongest axle. If you feel the suspension compressing when you start to pull, STOP, and turn the truck aound so the back takes the load. Disengaging the drivetrain just before the snatch eliminates every chance of drivetrain damage to the pulling vehicle, but a true snatch is not always the best course or even possible. The snatching truck needs room to run. Trucks that are stuck in goo are good candidates for a snatch if the snatching truck can reach hard ground. I'm assuming you were stuck in rocks right? You've got to be careful there because a hard snatch could really tweak something. Without a winch, I would have got wet with a jack and put something under the wheel to get it out of the bind, then a gentle reverse with a gentle assist from your buddy would have probably gotten you out. You know I've been doing this shit for 39 years and no two deals are ever exactly the same. That's why I walk gently with the armchair quarterbacking. I had a similar situation years ago in a fairly deep water crossing (alone). Most of my trips are alone. I had to get out and it was a real mess. I had water almost to my knees INSIDE a 3/4 ton truck. I had to work in the water by feel, because I couldn't see a damn thing, but..I got out of the situation with no damage except a soaked interior. These days I avoid shit like that because I've been wet too many times :). Trying to cross deep water without really knowing what was down there was just plain stupid, but I was younger you know? If I come to deep water now I park and have a picnic.

These are just ideas you know. The more fuck-ups you have, the better you get at figuring out what to do, and I've had a LOT of fuck-ups:D

I admire your willingness to listen and hear me out!

Teryx
 

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While I don't own a Tundra, I've also broken gears in reverse. I will never again do hard pulls in reverse. Best to pull from the rear going forward, otherwise use a winch.
x2.


It isn't unsafe to try and extract your self in reverse, just don't put a lot of throttle or spinning tires into the effort--your truck weighs so much and has a certain amount of traction, it takes that amount of effort to either move the truck or spin the tires. If the tires spin before the truck tries to move, you're gonna have to do something different like use a locker or strap or dig the tires out. I try and drive out of any 'stuck' I am in--If my tires spin and the truck doesn't even move, I'm done with that scenario; experience has taught me that I'm only going to make that situation worse.
 

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Differentials do have more strength in one direction over the other. This has to do with whether the pinion is above differential center-line (high pinion) or below (low pinion). And yes, it is due to the way gears are cut.

Low Pinion in rear = High strength pulling forward, less pulling in reverse

High Pinion in rear = opposite


Low pinion in front = High strength pulling in reverse, less pulling forward

High pinion in front = High strength pulling forward, less in reverse.


I'd guess that the front diff's (IFS/Solid axle doesn't matter here) are high pinion. When you were stuck down hill trying to back up, more weight/traction was on the front differential, in it's weakest mode.

A vehicle equipped Low rear, high front is VERY strong pulling forward significantly weaker pulling in reverse.
Do you have a reference for that? If so I stand corrected.
Teryx
 

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Do you have a reference for that? If so I stand corrected.
Teryx
Lot's of research when 'designing' for my truck. Learned a lot about factory designs -Ford trucks in the 70's had the hi-front lo-rear; which is one of the reasons Ford axles are sought after for axle swaps. There's a lot of technical about the shape of the gear teeth being stronger on the front than from the rear-has to do with the fact that the pinion will try and push the ring gear away from it in it's 'reverse' direction and then when the ring gear has deflected so much, there's no longer the full surface area of the gear tooth supporting the load and it breaks. Learned a lot on Pirate.

I ended up with a low-pinion front, and am o.k. with it because if I end up nose-down and am backing up (a common stuck in the rocks :D ), I have full gear strength.
 

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Lot's of research when 'designing' for my truck. Learned a lot about factory designs -Ford trucks in the 70's had the hi-front lo-rear; which is one of the reasons Ford axles are sought after for axle swaps. There's a lot of technical about the shape of the gear teeth being stronger on the front than from the rear-has to do with the fact that the pinion will try and push the ring gear away from it in it's 'reverse' direction and then when the ring gear has deflected so much, there's no longer the full surface area of the gear tooth supporting the load and it breaks. Learned a lot on Pirate.

I ended up with a low-pinion front, and am o.k. with it because if I end up nose-down and am backing up (a common stuck in the rocks :D ), I have full gear strength.
That's news to me. I can see where wear would be accelerated in reverse, but not ultimate strength. Alot of stuff gets said on forums that is just misinformation passed down and down. I'll admit I could be wrong but I'd like to see a technical memo from a gear manufacturer, or some similar document. If you have a link, help me out :)
Teryx
 

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the internals to the front diff to the new 2nd gen tundra are all the same though, no?


and i agree, the new stuff is NOT what it used to be my '05 tundra just ISN'T built to the quality my '94 truck was, granted the tundra has infinitely more balls


siiigh
'05-06
8" ring gear, 53mm bearing, 33mm/1.31" 30sp shafts

'07-present
8" ring gear, 58mm bearing, 35mm/1.37" 34spl shafts

time for an upgrade? :p
 

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Discussion Starter #19
'05-06
8" ring gear, 53mm bearing, 33mm/1.31" 30sp shafts

'07-present
8" ring gear, 58mm bearing, 35mm/1.37" 34spl shafts

time for an upgrade? :p

haha yeaaaa

honestly man, that would be siick, i just don't need it BAD enough, ya know? now i know what not to do with my truck, a swap would be BAD ASS, just unnecessary at this point lol
 

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Going John Galt
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haha yeaaaa

honestly man, that would be siick, i just don't need it BAD enough, ya know? now i know what not to do with my truck, a swap would be BAD ASS, just unnecessary at this point lol
now the question is...would the new Tundra diff/axles fit the new Tacoma? ;)
 
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