Limits of strength on doubled transfer case

[IowaOffRoad]

I've searched the forum and haven't found a definitive answer to this question. I'm sure there is info on [404notfound] and other places, but I thought it would be beneficial to solicit the opinions and experience of the good people of IRATE.

Have wheeled a Toyota for years but haven't run a doubled T-case yet. Wanting to do it, but I've been reading other posts referring to cases breaking. How common is this? Are there more issues with this setup than that? I do understand that what engine you are running, what axles, what tires, what you are wheeling on (rocks, dirt, mud, combo), driving style (do you idle everywhere or are you usually airborne? (insert 'slow Toyota joke here)). I was hoping everyone who's running one could chime in with the details of your rig and your experiences.

My reason for doing so is I wheel hard with my current setup which is a light rig with 35's and mostly stock R motor, locked front/spool rear. I'm thinking of doubling a new rig I'm building for a family wheeler (93 4Runner that I'm wanting to swap in a small diesel, Toyota axles, Toyota 5 speed, 35-37 max tire, and a doubler. Thinking of leaving it IFS and doing a lift + Sawzall to clear 35's until I do a SAS. I rarely ever break anything even driving aggressively with my current rig and want the new rig to be tough enough to survive a long weekend of rocks/dirt with minimal breakage. I think with my roughly 100hp engine and relatively small tire I should be fine, but I want to be sure.

So, what are your experiences, what you'd do different, how you built a similar rig, how you've pushed the limits of the t-cases and how well they've survived. Basically, how big, how much power, how much tire can this withstand without fail?

 

[Clb]

8 trips thru the rubicon on 31" 4 :10 stock axles in the 83....
The doubler has not caused an issue
(I drive like you) it will challenge your eng. and trans\t case mounts tho!

Now the big tire taco with 37" tires at 225:1 loved to break shit but it was hackbuilt...

 

[IowaOffRoad]

8 trips thru the rubicon on 31" 4 :10 stock axles in the 83....
The doubler has not caused an issue
(I drive like you) it will challenge your eng. and trans\t case mounts tho!

Damn, thanks for reminding me, I need to replace ALL my mounts before we go to KROCKS next month. My shifter's are moving around quite a bit under load, and I heard the air cleaner hit the hood a couple times the last trip! Pretty sure 2 of 3 are broke... That's without a doubler. Got any upgrade mount rec's while you're here?

 

[Aisin]

4xinnovations mounts. The Trail Gear ones are garbage.

 

[Clb]

Bolt thru the eng mounts trick/limit straps on eng.
Fresh factory gearcase mounts (tight and clean) or some of the aftermarket eurothane (sp) mounts loud as fukk tho.

edit
The taco had all failgear ridgid mounts and it was afukkingnoying as hell after a 3 hr hwy. Haul home.
See that with a doubler you use ALL available mounting options.

 

[Briansc33]

See that with a doubler you use ALL available mounting options.

This. Chian the motor mounts, make sure every possible contact/mount is used effectively... On the other hand you need a bit of movement. 4xInnovavations mounts seems have solved most of my prior issues.

I've spent two Marlin cases in a Taco 3RZ, 37's, fully built Diamond 8" axles, full retard, loved the skinny pedal.

One case race/comp. '85 hopped up 22R, essentially same axles, full mounts throughout and chains. Took a bad hop on a climb. And pop.

Take it easy with bigger tires and good parts they'll hold, full retard? Go a different direction.

 

[YotaAtieToo]

I've wheeled toyota cases pretty hard for the most part of 14 years, as well as wheeled with a lot of guys who have broke them. They have their limits, but are very strong in the right application in my opinion.

I've broke 2 rear outputs, 1 case housing and twisted a front output well beyond what I would think was possible without snapping. All were with 37-39" sticky tires and 4.10s. All were doing something dumb. I also got a ton of use out of them without failure. Almost every failure I can think of was guys running big tires with 4.10s

Use the right gears for the tire size you are running. 5.29s for 35-37s and ~6.17 for 38-40" 7.17+ for 41"+

The other factor is the engine that's in front of it, they work great with 4cyl type power.

The other thing that is really hard on them is running low low, 1st gear and a bunch of rpms. Even with a little 4cyl, you're putting down a shit ton of tq with 2xx:1. If you are in low low 1st gear, be very easy with the throttle. If you need more speed, shift up.

 

[Aisin]

My last truck had your typical 2.28/4.7 combo. Both inputs were 23 spline and the output was an OG Longfield. I beat the fuck out of that truck. It was on 36 inch Iroks. Hawaii wheeling was dry dirt or snotty red clay mud so no traction basically.

 

[Slander]

I have had duals in my 3.4 1st gen tacoma since 2008. Wheeled a season with 4.7s in front of the stock tacoma chain case, stripped out the input, rebuilt it, then in 2010 built a lefty. Since then I have had duals with stock 2.28 infront of a lefty with my og marlin 4.7 gears in the lefty case and it's been fine, I also have marlin 30spline chromo outputs. Trucks now SAS on 37s, 5.29 diff gears, most of the time I crawl but I will rhomp on it as needed being in the SE. The only other drivetrain parts I have broken are the caps on a Toyota ujoint(my fault) and sheared the cross off an O'Riley's ujoint that replaced it. I used to have the 4xinnovations trans/tcase mount, but have since gone back to stock rubber and like it better, next time my steering box is out, the MM is getting chained. I will replace all this with a 4spd atlas when,or if, the Toyota stuff blows up.

 

[rattlewagon]

38s locked f/r. 2.28/4.7 23 spline. Have bent a front output and broken a set of TG 4.7 gears in the past 5 years of wheeling the setup. Output bearings get a little loose with square shafts, I just replace with other used bearings from parts cases. Engine mounts are through bolted and 2 tg bomb proof mounts under the casesheld up by a budbuilt and I still get a ton of movement. The rubber in the TG mounts are shot and cant be replaced. I welded them to the budbuilt because the little screws that hold it kept coming loose. Seems to be pretty reliable besides that.

We just did a fror style cross member and 4xi motor mounts in a friends runner and it seems wicked solid. That one is just stock clocked duals, all 21 spline, on 36s. it should hold up just fine. For a while the truck was stock ifs on 35s with a doubler. Floppy stock mounts, and only a single mount under the t case but held up great on open/open 35s and was a blast to drive like that.

 

[YotaAtieToo]

Be careful with the mounts that only grab the rear of the case, that's what cause my housing to break. You need the one that grabs the stock mounts as well.

 

[Alex123456]

I ran 21 spline duals with 5.29's and 39" Iroks for years with no issues at all. Low power, light truck, conservative driving for the most part.

Any I've seen break were 4.10's and heavy trucks.

Engine/trans/t-case mounts I've always hard mounted. 4xinnovations or Trail gear.

 

[Brecklin]

My old rig was an 87 pickup on Yota axles welded front and rear (with 4.10 gears), junkyard 22R engines (blew up quite a few), W56/stock duals and 38.5x16 wide Boggers.

Through the 4 years I ran the dual cases, I broke one stock input. I pounded the ever living hell out of the truck. Wannabe rock bouncing stuff, too many rev limiter clutch dumps to count, trying to yank out every single stuck vehicle I came across, etc.

I think you'll break your IFS before breaking the transfer cases.

 

[Arickvan]

This. Chian the motor mounts, make sure every possible contact/mount is used effectively... On the other hand you need a bit of movement. 4xInnovavations mounts seems have solved most of my prior issues.

I've spent two Marlin cases in a Taco 3RZ, 37's, fully built Diamond 8" axles, full retard, loved the skinny pedal.

One case race/comp. '85 hopped up 22R, essentially same axles, full mounts throughout and chains. Took a bad hop on a climb. And pop.

Take it easy with bigger tires and good parts they'll hold, full retard? Go a different direction.

follow up questions for this, auto or manual trans? and taco chain transfercase or gear driven?

my buddy has a 4 door taco on tons and 40s, auto with 2.28 gear doubler to stock taco chain case and hes eyeballing an atlas

 

[mobil1syn]

it is simple, dont drive like an idiot.

i prefer two 2.28 cases and dont think 4.7 in a rear case are useful.

 

[Slander]

follow up questions for this, auto or manual trans? and taco chain transfercase or gear driven?

my buddy has a 4 door taco on tons and 40s, auto with 2.28 gear doubler to stock taco chain case and hes eyeballing an atlas

I'm eyeing an atlas when my shit breaks because Toyota parts vendors suck worse and worse evrey year. I don't need to be sidelined for 8+months while marlin fishes their shipping container of japanese parts off the floor of the Pacific ocean, or whatever other excuse they come up with that month.

 

[Stingray]

I've got 2 rigs, 85- 22RE, manual, duals, 2.28/ 4.7, aftermarket mounts everywhere, both cases and motor mounts.
The vibration is like its solid mounted to the truck. (It's a bitch)but 5 years and nothing has moved or broke, I'm a Pussy with the throttle though. Wheeled JV and most of the Parker AZ area in that rig. mostly full body 4runner, on 35's detroits both ends.

second rig (Pictured)

97 3.4/auto dual gear driven cases.2.28/4.7 ( With the auto I probably could have just done the 4.7 case)
aftermarket mounts on both cases, new stock motor mounts, way less vibration, ( I daily this truck) with the dual cases you get some backlash with the auto, That truck is on 37's Detroit rear Elocker front. and has seen Big bear, Some of parker, and a been to JV. and driven to all of those places.
the 85 would be a nightmare. mechanically it would do it. my sanity (And hearing) would be gone.


not sure if any of this really answers the question


also strength wise I've had no reservations that the duals are as sturdy as a single case. properly mounted. ( Again.... I'm a pussy on the throttle)

 

[Clb]

it is simple, dont drive like an idiot.

i prefer two 2.28 cases and dont think 4.7 in a rear case are useful.

Ok desert racer jump in avatar
The extra gearing offered by the 4.7 depends on trail specific needs...

I'm eyeing an atlas when my shit breaks because Toyota parts vendors suck worse and worse evrey year. I don't need to be sidelined for 8+months while marlin fishes their shipping container of japanese parts off the floor of the Pacific ocean, or whatever other excuse they come up with that month.

My brother fromma nother muther!

 

[mobil1syn]

Ok desert racer jump in avatar
The extra gearing offered by the 4.7 depends on trail specific needs...

i had a single 4.7 case in my first truck and it was cool, but was lacking. mainly for the snow or where wheel speed was needed.

did stock case duals on my next truck and it was the right move.

 

[IowaOffRoad]

it is simple, dont drive like an idiot.

i prefer two 2.28 cases and dont think 4.7 in a rear case are useful.

I cannot guarantee non-idiot driving

My plan was doubled, stock geared cases, with the possibility of 4.7 in the rear later. I planned to keep the 4.10 factory gears until I did a SAS. Thought it would be cheaper than regearing 2 axles when the plan is to throw the front one away eventually.

follow up questions for this, auto or manual trans? and taco chain transfercase or gear driven?

my buddy has a 4 door taco on tons and 40s, auto with 2.28 gear doubler to stock taco chain case and hes eyeballing an atlas

Were you asking me? Planning on a 5 speed. I am actually jealous of an automatic, but am disinclined on basic principles to run one.
Yes, the Aisin auto is practically bulletproof, but the 5 speed is actually bulletproof, at least when upside down and on fire...

 

[Arickvan]

I cannot guarantee non-idiot driving

My plan was doubled, stock geared cases, with the possibility of 4.7 in the rear later. I planned to keep the 4.10 factory gears until I did a SAS. Thought it would be cheaper than regearing 2 axles when the plan is to throw the front one away eventually.

Were you asking me? Planning on a 5 speed. I am actually jealous of an automatic, but am disinclined on basic principles to run one.
Yes, the Aisin auto is practically bulletproof, but the 5 speed is actually bulletproof, at least when upside down and on fire...

no I asking Brian since he's wrecked a couple parts

The autos help avoid some of the shock load that the drivetrain gets

Supposedly no 3.4 autos with a taco box(gear doubler-chain transfer case) have had failures yet

 

[Briansc33]

follow up questions for this, auto or manual trans? and taco chain transfercase or gear driven?

my buddy has a 4 door taco on tons and 40s, auto with 2.28 gear doubler to stock taco chain case and hes eyeballing an atlas

Manual on the Taco, chain driven. 2:28 main, 4:7 reduction box. 8.4", 4:56 rear. 8" 4:56 front.

Manual with the comp truck, gear driven. 2:28 main, 4:7 reduction box. 8", 4:88 rear 8", 4:88 front.

If I had to do it again from scratch (of which I wont) 2:28/2:28 gear driven..

AW4 and Atlas 2 are in my future, as I now have a stroked motor with MS2 ignition and enough power to support an auto.

Although Mobile1 is correct I tend to go a bit retarded. Once I blow this setup, with the exception of the new motor, I'm done with Toyota drivetrains... Save the axles...I only run 37" stickies.

 

[YotaAtieToo]

it is simple, dont drive like an idiot.

i prefer two 2.28 cases and dont think 4.7 in a rear case are useful.

It's not quite enough for technical rock crawling. Duals with 4.7 and proper axle gears is extra damn low, but 2nd gear works great for all but super technical stuff and the options are nice. Single 4.7 is nice for a lot of in between stuff, and 2.28 is super useful as well.

 

[Slander]

It's not quite enough for technical rock crawling. Duals with 4.7 and proper axle gears is extra damn low, but 2nd gear works great for all but super technical stuff and the options are nice. Single 4.7 is nice for a lot of in between stuff, and 2.28 is super useful as well.

This. I love all the options having 2.28 and 4.7 gives you with the 5spd. Most of the time I'm cruising around in 2nd-4th in 4.7 on the trail and use the 2.28 in the technical stuff. Generally I'm bumping stuff in 4.7 and some gear if I need wheel speed. I would not be happy with two 2.28 cases even with 5.29s and the 3.4.

 

[Briansc33]

It's not quite enough for technical rock crawling. Duals with 4.7 and proper axle gears is extra damn low, but 2nd gear works great for all but super technical stuff and the options are nice. Single 4.7 is nice for a lot of in between stuff, and 2.28 is super useful as well.

When you're just bouncing through shit, carrying momentum with the occasional clutch dump, 2:28 in itself works just fine.
Recently I have not found a use for something as low as as two 4:7 cases.

Edit: A 4:7 case at all.

 

[Clb]

Sounds like a desert denizen to me....
gears (low) rock.
wheel speed is not hard to make.d
I R into technical rock

remember op asked about strength...

 

[IowaOffRoad]

Here’s my reasoning, tell me how stupid I am

Current rig, which I’m mostly happy with:

5.29s, g56, stick gear drive, crawl ratio 47.28

2 stock lows = 5.19

First version build plan for ‘runner:
Stock 4.10s (it may have 4.56s, and I have a parts 91 auto that has 31s that may have 4.88), doubled stock gear drives, G series 5 speed. Worst case (4.10) crawl ratio: 83.5. As I’m cheap it seems like the budget option. Probably next going to SAS with 4.88/5.29 , then a 4.7 in one case if I’m still not happy. Seems to be the best bang for the buck compared to 4.7s or axle gears first.
If I do end up with 1 case with 4.7s, should I do the main case or reduction box? Seems the main case would be the strongest, especially if I go to a 23 spline.

 

[YotaAtieToo]

When you're just bouncing through shit, carrying momentum with the occasional clutch dump, 2:28 in itself works just fine.
Recently I have not found a use for something as low as as two 4:7 cases.

Edit: A 4:7 case at all.

Go try and run a long trail like Fordyce or any of the decent hammer trails. Your clutch and/or back will be smoked 1/3-1/2 way though.

Dual stocks is manageable.

 

[Briansc33]

Go try and run a long trail like Fordyce or any of the decent hammer trails. Your clutch and/or back will be smoked 1/3-1/2 way though.

Dual stocks is manageable.

Yes, I have, many in one day. And no, they weren't.

 

[Squamch]

Trailmart motor mounts, FROR style tcase crossmember. 94 xtra cab, locked f/r, strong 22re, w56, 36" TSLs. I tend to poke, poke, poke, then try third gear double low on the Rev limiter.
Only thing I broke was a rear output.
Before and since then, I've had a few single case trucks, on 31-36" tire. Never broke a case. 95% of the cases I've seen broken were 37"+ tires, and/or tons.