Offroad drivetrain durability as tire size increases

[bigdaddy2021]

What’s your experience been, with mild, moderate, and extreme trails as far as drivetrain durability as tire size has increased ?
(Moab trails, Rubicon/Dusy, deep water/hill climbs in the ozarks, etc)

If you’ve had a failure, can you describe? A failure would be something like a front CV axle, driveshaft, rear axle shaft, steering linkage, ring/pinion gear issue, rear locker breakage, etc. Not really focused on increased service intervals for CV boots, bearings, ujoints, fluid, etc., unless they were key to the mechanical failure in question. Mostly looking to gather some objective info for myself and other folks looking to do some trail riding.

(sorry for the repost - had to edit the poll. Also realised all poll options should mention offroad use. Thanks!)

 

[repo]

What’s your experience been, with mild, moderate, and extreme trails as far as drivetrain durability as tire size has increased ?
(Moab trails, Rubicon/Dusy, deep water/hill climbs in the ozarks, etc)

If you’ve had a failure, can you describe? A failure would be something like a front CV axle, driveshaft, rear axle shaft, steering linkage, ring/pinion gear issue, rear locker breakage, etc.

Not really focused on increased service intervals for CV boots, bearings, ujoints, fluid, etc., unless they were key to the mechanical failure in question

Looking to gather some objective info for folks looking to do some trail riding.

There is the theory that you want to break CVs before anything else because they are so easy to fix and carry spares. You can use the same argument about avoiding diff drops. You could go pretty deep in to fortifying the driveline but the sacrificial CV axle thing makes sense to me.

 

[bigdaddy2021]

There is the theory that you want to break CVs before anything else because they are so easy to fix and carry spares. You can use the same argument about avoiding diff drops. You could go pretty deep in to fortifying the driveline but the sacrificial CV axle thing makes sense to me.

Agreed. Shock loads on the drivetrain are bad, in general, but if you had to choose a fuse, that's a good choice, IMO.

What I love, too, as confirmed by a few folks, is that CV's are the same on driver/passenger sides, so 1 spare will cover both.

 

[Jetboy]

Supposedly current Toyota design is to make sure the U joints are the weakest link. But I'd guess it's actually CV first, then front diff, then rear diff, then ??? CVs are pretty cheap and easy to swap as compared to almost anything else you could break.

There used to be a commercial product that as basically special drive flanges for the drive shafts with bolts designed to sheer at a specific torque. So you would have a designed driveline fuse and it would only require replacing the bolts and you'd keep a few spare sets. Not sure if it's still around.

I don't know what it takes to break a driveline part on a 5th gen, but they're pretty damn strong and the engine isn't exactly a monster. Mine has been incredibly durable. I have no hesitation about 34" tires in any offroad condition. The front CVs are much stronger than I ever thought they would be. I have two spare CV axles and I assumed when I started wheeling it I'd be replacing them periodically. I still have both of them wrapped in the shipping packaging... lol.

 

[bigdaddy2021]

Interesting numbers so far. About what i’ve come to expect based on trends i see online.

 

[bigdaddy2021]

Supposedly current Toyota design is to make sure the U joints are the weakest link. But I'd guess it's actually CV first, then front diff, then rear diff, then ??? CVs are pretty cheap and easy to swap as compared to almost anything else you could break.

There used to be a commercial product that as basically special drive flanges for the drive shafts with bolts designed to sheer at a specific torque. So you would have a designed driveline fuse and it would only require replacing the bolts and you'd keep a few spare sets. Not sure if it's still around.

I don't know what it takes to break a driveline part on a 5th gen, but they're pretty damn strong and the engine isn't exactly a monster. Mine has been incredibly durable. I have no hesitation about 34" tires in any offroad condition. The front CVs are much stronger than I ever thought they would be. I have two spare CV axles and I assumed when I started wheeling it I'd be replacing them periodically. I still have both of them wrapped in the shipping packaging... lol.

That’s awesome, thx for posting up your experiences.

I see some rigs with 4.10’s and 4.56’s. Wonder if the thinner ring gear teeth hold up as well.

 

[Toyotatrade]

Cheap 33s (32.8) mud terrains. best tires I've ever owned

I bought some of the cheapest mud terrains I could find that had good reviews. Turns out these are the best tires I've ever owned. They are Patagonia's mud terrain and have a super aggressive pattern. I've had BFG AT or MT's on every truck I have had except my 2002 Limited. I have had the Micky Thompson MTs and Yoko MTs and these cheap Patagonia MTs are better in every aspect. They are the lowest noise mudders you will ever hear on and off road. They have over 10k miles and have tons of tread left, they handle great on and off road but they are unreal in the mud, sand and dirt. I go places in 2wd I could never go with any other tire as I have proved to many a friend. They are a bit lacking in the rain and have\will never go on snow (Born and raised in California and terrified of the snow}.

I rebuilt my front end and installed all new rear bushings before these tires ever hit the road so that may play a roll in the greatness of them but I have had zero problems with my drive-train that are related to these tires.

 

[TRD PANTHER]

Supposedly current Toyota design is to make sure the U joints are the weakest link. But I'd guess it's actually CV first, then front diff, then rear diff, then ??? CVs are pretty cheap and easy to swap as compared to almost anything else you could break.

There used to be a commercial product that as basically special drive flanges for the drive shafts with bolts designed to sheer at a specific torque. So you would have a designed driveline fuse and it would only require replacing the bolts and you'd keep a few spare sets. Not sure if it's still around.

I don't know what it takes to break a driveline part on a 5th gen, but they're pretty damn strong and the engine isn't exactly a monster. Mine has been incredibly durable. I have no hesitation about 34" tires in any offroad condition. The front CVs are much stronger than I ever thought they would be. I have two spare CV axles and I assumed when I started wheeling it I'd be replacing them periodically. I still have both of them wrapped in the shipping packaging... lol.

As I recall, awhile back you did the Rubicon with your 4Runner and damaged the front skid plate, but otherwise had no other major issues.

 

[Jetboy]

As I recall, awhile back you did the Rubicon with your 4Runner and damaged the front skid plate, but otherwise had no other major issues.

Yep. I've done that twice and had no mechanical problems. Drivetrain is really strong. Just skid plates that were pretty well trashed. To be fair - the skid plates actually did their job. They protected everything above them. They just looked pretty bad by the end. But the drivetrain had no issues. I have 34" (285/75/17) tires. Keep in mind that on those same trips there were multiple axle failures in our group include an 80 series land cruiser broke axle shaft and an FJ60 that broke both front birfields.

I did add an aux trans oil cooler. Otherwise it's totally stock drivetrain.

The only issues I've had over 7 years is the needle bearing front diff (warranty fix), some rusted/stripped skid plate bolts that needed to be re-threaded or replaced, and the lower control arm cam hardware seized, but only the front adjusters on both sides. It's pretty bulletproof so far for me. Having owned older IFS Toyotas - I'm thoroughly impressed by how much stronger the current setup is than the older stuff. It's night and day.

 

[Jetboy]

That’s awesome, thx for posting up your experiences.

I see some rigs with 4.10’s and 4.56’s. Wonder if the thinner ring gear teeth hold up as well.

There's no 4.10 gears made for the 5th gen. I have a set of 4.56 diffs that I put in and then took back out. For daily driver use the 3.73 is better IMO. I think 4.10 would be ideal. I did talk to circle K about making 4.10 gears and they can, but I didn't pursue due to a big minimum order quantity.

I don't think the difference in tooth mesh is significant. My guess is that they would be just as strong or close if the gears are setup properly. Setting up gears is not easy and I think a lot of aftermarket gear failures are due to poor setups. I wouldn't be concerned about the strength of the teeth with 4.56 or 4.10. The biggest issue with tooth failure is pinion deflection. The 8.2 diff made the pinion massively stronger than the old 8inch diff. The pinion shaft size where the main pinion bearing sits is now bigger than a normal Dana 60. So there should be very little deflection under load. I wouldn't be concerned about diff gear strength. Not in the rear anyway. Front - maybe. In reverse, nose down, with a lot of load I could see it being an issue because of the high pinion clamshell design (it's weak in reverse). But I've yet to have any actual issues with it so far.

Just for a little comparison perspective - sorry about the orientation - the top pinion is a 4.56 pinion for the 8.2 rear diff. The bottom is a 4.10 pinion from an 8" axle. The 8.2 really is a major improvement despite nominally only being slightly larger.

This is a front 8" clamshell right and old 8" solid axle carrier left. What you'll notice is that the newer carrier has significantly larger bearings and those also are necessary to resist deflection under load. The differential gear its self is pretty comparable in size. Front pinion is also very robust.

Edit: one more pic example - 5th gen CV vs minitruck birfield size:

 

[bigdaddy2021]

Correct, sorry! meant 4.56's and 4.88's - was just shopping Nitro gear install kits. '10-Current Toyota 4Runner Front and Rear Gear Package Kit

Thank you for the comparison pics. Very good illustration for a visual person like me.

There's no 4.10 gears made for the 5th gen. I have a set of 4.56 diffs that I put in and then took back out. For daily driver use the 3.73 is better IMO. I think 4.10 would be ideal. I did talk to circle K about making 4.10 gears and they can, but I didn't pursue due to a big minimum order quantity.

I don't think the difference in tooth mesh is significant. My guess is that they would be just as strong or close if the gears are setup properly. Setting up gears is not easy and I think a lot of aftermarket gear failures are due to poor setups. I wouldn't be concerned about the strength of the teeth with 4.56 or 4.10. The biggest issue with tooth failure is pinion deflection. The 8.2 diff made the pinion massively stronger than the old 8inch diff. The pinion shaft size where the main pinion bearing sits is now bigger than a normal Dana 60. So there should be very little deflection under load. I wouldn't be concerned about diff gear strength. Not in the rear anyway. Front - maybe. In reverse, nose down, with a lot of load I could see it being an issue because of the high pinion clamshell design (it's weak in reverse). But I've yet to have any actual issues with it so far.

Just for a little comparison perspective - sorry about the orientation - the top pinion is a 4.56 pinion for the 8.2 rear diff. The bottom is a 4.10 pinion from an 8" axle. The 8.2 really is a major improvement despite nominally only being slightly larger.

This is a front 8" clamshell right and old 8" solid axle carrier left. What you'll notice is that the newer carrier has significantly larger bearings and those also are necessary to resist deflection under load. The differential gear its self is pretty comparable in size. Front pinion is also very robust.

Edit: one more pic example - 5th gen CV vs minitruck birfield size:

 

[bigdaddy2021]

Found a few examples of 4runners on 37's where the install seems correctly done, and the driver seems "spirited" but not abusive:

<iframe width="560" height="315" src="https://www.youtube.com/embed/KzkC_0ke7O0" title="YouTube video player" frameborder="0" allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture" allowfullscreen></iframe>


and then this is the common result that I'm seeing:

Stock CV's get blasted,
They replace them a few times,
Then they spend booku bucks for RCV's, thereby moving the "Fuse" to a yet to be determined component. So it would seem that 34's/35's might be the upper limit for trouble-free operation of the stock drivetrain with moderate/conservative driving:

 

[honda250xtitan]

e rated 33's, minimal lift (2-2.5" front) zero issues. its been airborne a few times. absolutely thrashed in baja, get back on road, drives like you never did anything crazy. proper shock damping is important people.

i feel like abusing it how we do isnt as hard on components as the guys doing slower stuff in rock gardens and what not. i'm never at full lock full articulation. (prolly the best way to bend a tie rod and blow out a cv)

 

[bigdaddy2021]

e rated 33's, minimal lift (2-2.5" front) zero issues. its been airborne a few times. absolutely thrashed in baja, get back on road, drives like you never did anything crazy. proper shock damping is important people.

i feel like abusing it how we do isnt as hard on components as the guys doing slower stuff in rock gardens and what not. i'm never at full lock full articulation. (prolly the best way to bend a tie rod and blow out a cv)

Thanks for your perspective. I agree, full lock, full articulation is probably the bane of both U-jointed solid axle rigs and IFS CV-type axle shafts.

I feel like we put our 32's, 3"/2.5" lift, ATRAC/Locker/MTS through it's paces in Moab on mild/moderate trails. 4runner never even broke a sweat and with only 8k miles on the clock and a new suspension system, it was more of a break-in than anything. We're going to be hitting some more moderate stuff in about 2 weeks.

<iframe width="560" height="315" src="https://www.youtube.com/embed/WinL2W8oQqY" title="YouTube video player" frameborder="0" allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture" allowfullscreen></iframe>

 

[mrblah]

With 33's: Worn out steering rack, destroyed alignment cam tabs, worn out suspension bushings, and blown shocks. Also hotter transmission temps.

With 35's: destroy CV's and tie rods fairly easily, destroyed steering racks and bent spindles in addition to the above.

Ended up with 34's because i didn't want to deal with blown CV's and tie rods. However, there is not alot of data points on 34's so i'm not sure where they stand in terms of reliability and drivetrain compromise. To mitigate risk, I went with a lighter 34's Mt to give me peace of mind.

I wouldn't say all of the damage of the above is attributed to larger tires, it could be what we were also doing at the time. Some damage more likely to happen desert running vs rock crawling and vise versa. Other damage is bound to happen if u go offroading versus flexing at the parking lot of REI.

In my mind, CV and tie rods are the weak links going above 33, because the rest i mentioned can be upgraded or prevented.

 

[bigdaddy2021]

With 33's: Worn out steering rack, destroyed alignment cam tabs, worn out suspension bushings, and blown shocks. Also hotter transmission temps.

With 35's: destroy CV's and tie rods fairly easily, destroyed steering racks in addition to the above.

Ended up with 34's because i didn't want to deal with blown CV's and tie rods. However, there is not alot of data points on 34's so i'm not sure where they stand in terms of reliability and drivetrain compromise. To mitigate risk, I went with a lighter 34's Mt to give me peace of mind.

Great info to have, thanks for sharing this.

Questions:
Can you share your 34" tire info/specs?
Also, can you share trail ratings and conditions you were on before the mech. failures? Rocks, mud, sand, 5+ rated trail, etc.

 

[Jetboy]

I think it's very hard to get a really good answer of where the limits are because of so many variables.

It varies so much by how the driver uses the vehicle. For example when you start to bounce on a rock ledge, do you back off or pedal down? How many bounces do you let it go before easing off. Does the driver try to force the tires to turn when bound up or back off when they feel the steering rack max out? that probably makes the difference between blown rack or not in a lot of cases.

Experienced drivers tend to make vehicles last a lot longer. I've broken multiple steering arms and boxes in my trail rigs. It's just something you learn from breaking things how far you can go.

The weight is a huge factor that varies a lot. I see so many 4Runners loaded with weight and are at a lot more risk than a stock weight vehicle. Weight kills performance and parts.

Tires matter a lot too. Sticky tires at low pressure have a lot more traction than hard rubber tires at street pressure.

And terrain is also a big factor. Shock loads tend to be the worst for drive train parts. So spinning in mud for example is a really good way to blow up a diff or axle. I rarely see broken junk in Moab on slickrock outside of bouncing causing shock loads. Traction is really high, but rarely is there a spinning tires and then instant traction. And using momentum on slickrock is almost never the right choice. But on a big muddy rocky hill in the east - you might need to use momentum and spinning tires to get up that risks more shock loads.

Anyway, just sort of a comment that there's probably not a one-size-fits-all solution. It seems like 33-35" tires are pretty functional. 37's are maybe too much for the front end. Rear axles seem to be able to handle almost any tire size you can fit, which honestly is remarkable given the weight of the 4R and size of the axle. Going beyond 35s - I'd be swapping vehicles for a Land Cruiser. When you run through the list of upgrades needed for durability, it's cheaper to just swap for a land cruiser.

 

[Jakeepoo3]

Is this poll based on stock gear ratios?? Running 33's, I want bigger but regearing looks $$$$$. No problems on 33's with diff drop. Anyone jack there stock drivetrain up on bigger than 33's??

 

[mrblah]

Great info to have, thanks for sharing this.

Questions:
Can you share your 34" tire info/specs?
Also, can you share trail ratings and conditions you were on before the mech. failures? Rocks, mud, sand, 5+ rated trail, etc.

Vehicle: heavily armored, regeared, twin locked, and completely gusset/armored mid travel setup.

Yokohama geolander 285/75/17, measures 34.1, 63lbs. I think these and km3's are your lightest 34 MT's. I went with the Yoko's over KM3 because i wanted a true 34..

Desert Mobbing (anzo/mohave road): blown king shock, wore out suspension bushing, starting to bend alignment tabs, wore out steering rack, bent spindle on 33.s

rock obstacle (valley of moon): blown tie rod/CV on 35's.

Hill climb/ mixed atv/cow trail (bodie hills/mammoth, ca): blown shock on a rock, bent rear lower link, high trans temp, destroyed alignment tabs, and Destroyed lower A arm bushings on 33's.

Sand/dune (boxcar canyon, NV): no damage on 33.

Mud (private property): no damage.

Moab, Utah (fins and things): no damage on 33

Canyonlands, Utah: mix trails: no damage on 33

Victoria Mtn, NM: No damage, mix trails on 33's..

Easy way of thinking: While, i broke and bent alot of things on 33's, I didn't have to carry spares to make it home.

 

[borfoo3]

Compared to my 200 LC, the 4Runner has an inherent drivetrain safety feature called: 'lack of power'

I found that front CV's in high power / snappy torque vehicles with upsized tires seem to be less forgiving with too much skinny pedal.