Transfer case options (1 Viewer)

[fireball]

Greetings all,

My BJ74 build has stalled a bit, but a recent trip has afforded a bit of clarity and a mission statement of what I want to be able to do with the truck: "Confidently wheel and keep up with a built 80 on 35s".

I think a major piece of that puzzle will be either a transfer case regearing, or perhaps a Blackbox. I have been reading up on the Blackbox and searching and can't find any info for anyone who has actually installed one. There are a few different options for keeping the stock t-case and adding gears, namely 3.3:1 or 4:1 and then keeping hi range as-is or going 10% under or 10% over.

Would love to have some input and hear some thoughts from folks on the right move. Specs on my truck are as follows: 13bt with h55 5spd, 4.11 stock gears and currently running 33" MTs. Considering swithcing to 35x11x5x17s to help accomplish goal above.

Thanks in advance for any insight!

 

[MyCruiserisaHogBeast]

Greetings all,

My BJ74 build has stalled a bit, but a recent trip has afforded a bit of clarity and a mission statement of what I want to be able to do with the truck: "Confidently wheel and keep up with a built 80 on 35s".

View attachment 2084947

I think a major piece of that puzzle will be either a transfer case regearing, or perhaps a Blackbox. I have been reading up on the Blackbox and searching and can't find any info for anyone who has actually installed one. There are a few different options for keeping the stock t-case and adding gears, namely 3.3:1 or 4:1 and then keeping hi range as-is or going 10% under or 10% over.

Would love to have some input and hear some thoughts from folks on the right move. Specs on my truck are as follows: 13bt with h55 5spd, 4.11 stock gears and currently running 33" MTs. Considering swithcing to 35x11x5x17s to help accomplish goal above.

Thanks in advance for any insight!

I have the same basic truck as you with the same plans yaaaay!!!!! I’m currently sitting on 33s as well. Runs great on the street!

I recently sold my Cummins powered FJ62 running an H55F/Marlin Toybox/split case. The gearing. Was. Awesome. I mean straight up hold-my-beer climb anything, put a s*** eating grin on your face as you crawl over boulders bigger than what you should be climbing over amazingness... but custom is a pain in the ass sometimes, and all of this gearing came with a lot of complications. Back when I ran a shop I’d tell customers that. I didn’t follow my own advice on the last one and learned a lot of hard lessons with that truck.

I’ve heard great things about the Blackboxes, but I’m going back to simplicity. I’m going to run 4:1 gears, which should put the gearing in the sweet spot for 35s with the 10% underdrive, and it’ll be enough gearing on the trails to get me in and out of everything I’ll want to get in to. I’ll be doing some axle shaft upgrades and try to keep the weight down as much as a I can to make sure everything holds together and that’ll about do it.

Looking forward to seeing what you decide on!

 

[bj70_guy]

My BJ74 build has stalled a bit, but a recent trip has afforded a bit of clarity and a mission statement of what I want to be able to do with the truck: "Confidently wheel and keep up with a built 80 on 35s".

So you're converting to coils then?

I don't know anyone around here with a blackbox, and they're made pretty close by. Looks cool though.

FWIW my truck has 315/75R16s, 4.11s, and Marks T case gears with 3.05:1 low and 1.08:1 high range. The low range is great. If I were doing it again I would just get standard 1:1 high range. The 13B-T/H55F/4.11 combo will turn the 35s just fine. On highway hauls I end up turning higher RPMs than necessary to run 75 mph.

One of our pals has been running the 4:1 set in a BJ42 on 37s for a few years and so far so good. 4 speed tranny though so higher 1st gear.
They weren't available when I did mine or I would have been tempted.

 

[fireball]

The tcase gears are obviously the easier option. I’m surprised no one is running the black box and that it’s not more popular. Seems like a fantastic option but I’m not interested in being a gineua pig.

What would the drawback of the 4:1 be? Top speed in 4lo down to sub 20mph and the need to shift between hi and low more often when on the trail?

With 33s, I can run 75mph in the Highway quite comfortable so would want to keep hi range gearing the same. Not sure that is possible with the combos I see offered? :

 

[MyCruiserisaHogBeast]

The tcase gears are obviously the easier option. I’m surprised no one is running the black box and that it’s not more popular. Seems like a fantastic option but I’m not interested in being a gineua pig.

What would the drawback of the 4:1 be? Top speed in 4lo down to sub 20mph and the need to shift between hi and low more often when on the trail?

With 33s, I can run 75mph in the Highway quite comfortable so would want to keep hi range gearing the same. Not sure that is possible with the combos I see offered? :

View attachment 2085240

You wouldn't be a guinea pig per se, I know of a couple of guys running it with an H55F and they're really happy. It all depends on what your priorities are.

One thing I discovered on my last rig with an H55F was that it's not really an optimal gear spread for a highway machine, I don't think Toyota was overly concerned about cruising speed when they put these things together, from they factory they had like a 30" tires with 4.11 gears. Like yours, mine cruises great with the 33s! I can do 75mph all day long (although I find it's just happier at 70). You can do the math and get a good idea where it'll land with the 10% reduction with an online calculator. Right now 2469 RPM (rounding) gets us 70mph with 33s, with 10% reduction and 35s you land at 2604 RPM, which isn't that big of a difference. With factory size tires you're around 2800 RPM at 70 so you're still cruising "under geared" compared to factory. It's basically like putting 4.56 gears in there with 35s.

Top speed in 4 low is obviously a thing, but as long as you're not trying to run around in 5th (weak) you should be able to cruise around most stuff at idle. The nice thing is shifting between high and low on these trucks is pretty easy. The one drawback though is sand. 1st is pretty low and should get you through most of it, but the nice thing about having a gear reduction box is the ability to use the factory 2:1 reduction, which is great in the sand ( 1st to dig yourself out, 2nd gear to rip around soft stuff).

The last thing that I've learned over the years with this thing is that unless you're building a rig that is meant to be trailered, you spend 99% of your time on the street, even if you're only driving it to the trailhead on the weekends. I built my last rig to do both, and it drove awesome... but it liked to cannibalize driveline parts and spent half the time I owned it broken, which defeated the purpose of having it. For me with this new one I'm going for a compromise, focusing on reliability keeping it as close to factory as I can, overbuilding what needs to be overbuilt and going for simplicity.

 

[FJBen]

Were you not able to keep up with a built 80?
What kind of wheeling are you wanting to do?

Flexxy coil spring, 35's, auto, 10" of wheel base make it a different beast. I've had built 80's from stock to super flexxy and they are one of the best easiest point and shoot wheelers around.

Gearing would be a good start and personally I would do the 4:1.
Tweaking the suspension/shocks/leaf may help to try and get all of the flex out of it you can with leaf springs. Other wise 3/4 link/coil swap setup. You could go SOA and have great flex with flat springs, but your height would be up there.
And since the HZJ74 (and some other models 98 and up especially in South America) ran basically the 80 series coil front ends, parts can be found/made from a 80 series...again may be cheaper to fab up.

You are already locked, so your wheelbase will be better in some spots, worse than others. Much better in rear departure angle.

Were you dragging or hitting on anything? As you know, all 33s/35s are not equal with some 33's being just as tall as some claimed 35's. What do your current 33's measure out at?

I find technical wheeling SO much easier with an auto, but I enjoy driving the H55f much more.

As for RPM's, I"m not sure what people like to push the 13BT to. I don't think Toyota had 75+ in mind with the BJ74s but I could be wrong. I'm basically the same as you. My actuall 33" tires are 32.75 so fairly close and I'm 2350~2400RPMs at 65. Feels pretty good at that. At 75 I'm 2750RPMs, and I never drive it at that, just seems not as happy, but hey Toyota may think it has zero issue and can run all day at that.

 

[MyCruiserisaHogBeast]

Were you not able to keep up with a built 80?
What kind of wheeling are you wanting to do?

Flexxy coil spring, 35's, auto, 10" of wheel base make it a different beast. I've had built 80's from stock to super flexxy and they are one of the best easiest point and shoot wheelers around.

Gearing would be a good start and personally I would do the 4:1.
Tweaking the suspension/shocks/leaf may help to try and get all of the flex out of it you can with leaf springs. Other wise 3/4 link/coil swap setup. You could go SOA and have great flex with flat springs, but your height would be up there.
And since the HZJ74 (and some other models 98 and up especially in South America) ran basically the 80 series coil front ends, parts can be found/made from a 80 series...again may be cheaper to fab up.

You are already locked, so your wheelbase will be better in some spots, worse than others. Much better in rear departure angle.

Were you dragging or hitting on anything? As you know, all 33s/35s are not equal with some 33's being just as tall as some claimed 35's. What do your current 33's measure out at?

I find technical wheeling SO much easier with an auto, but I enjoy driving the H55f much more.

As for RPM's, I"m not sure what people like to push the 13BT to. I don't think Toyota had 75+ in mind with the BJ74s but I could be wrong. I'm basically the same as you. My actuall 33" tires are 32.75 so fairly close and I'm 2350~2400RPMs at 65. Feels pretty good at that. At 75 I'm 2750RPMs, and I never drive it at that, just seems not as happy, but hey Toyota may think it has zero issue and can run all day at that.

You don’t need coils to party there’s nothing wrong with leaf springs

 

[FJBen]

You don’t need coils to party there’s nothing wrong with leaf springs

I agree.
Then I'd go 35's, 4:1 and call it a day.

 

[fireball]

Great points guys, I appreciate all the feedback thus far!

To clarify the mission statement, I want to be able to comfortably do Hole in the Rock trail. I want to be able to drive 6hrs of pavement up to Vermont and wheel up there with my friends (similar mix to HiTR, some higher speed gravel and dirt, some tight technical rocky and muddy sections, a good overall mix). I am not as concerned with pure rock crawling.

I did HiTR and two years of the Vermont Overland Trophy with my built 100 and it did well. It wasn't as fun as the BJ74 would have been, and sustained decent body damage up in VT due to tight trails. With the 74 and it's 5spd and stock t-case gearing, i would not have been as comfortable as with the 100. The t-case gears sound like the easier / straightforward option. However the blackbox sounds like the most elegant solution to retain both highway drivability and ultra low gearing.

The drawback of the 4:1s is increased shifting b/w low and high, and increase rpm on the highway. And from research sounds like a decent bit of gear whine.

The drawback with the blackbox is that I would need to farm it out and with a limited amount of info and technical knowledge, not sure who would be best fit for that...

 

[hoser]

I have the Blackbox in my BJ74 but I have not been driving it too much due to fear of cooling issues with the blackbox. NWF is working on a redesign but I don't know the status of that. I might add an oil pump, cooler and reservoir. I'm just not thrilled about adding the complexity. I'm kicking myself for not getting a Toybox when I had the chance. You can read about the cooling issues in the 2nd half of this thread.

As for gearing. I run the H55, 4.1 and 35's powered by a 12HT. Cruising at 70-75 is perfect. Double low yields a crawl ratio around 105:1. The BB shifter is cable and so it doesn't have that positive engagement like the stock T-case.

I had considered the option of going with the 4:1 t-case but it seemed kinda slow for anything but technical terrain. 4:1 in 4th gear low range is almost the same as 1st gear in 4Hi. How fast can you go in 1st gear 4HI in a diesel? Not very fast... and so yes, I would imagine I would have to shift between LO and HI range fairly often.

 

[clintnz]

I have the Mark's Adapters 3.05 / 1.08 set in my cruiser, on 34-36" tyres 4.1 diffs. The ratios work great, although we don't do much super slow rock-crawl type stuff - going to 4:1 or lowering the diff ratios also could make sense for lots of rocks. I would definitely aim to drop the Hi range ratio a touch with a 13BT on 35's.

Big drawback with the Mark's gears is that they are quite noisy on the highway, even with a layer of Dynamat in the floor. We only do long trips occasionally so no big deal, but for punching out 6hrs on a regular basis they'd be pretty annoying.

Cheers
Clint

 

[MyCruiserisaHogBeast]

I have the Blackbox in my BJ74 but I have not been driving it too much due to fear of cooling issues with the blackbox. NWF is working on a redesign but I don't know the status of that. I might add an oil pump, cooler and reservoir. I'm just not thrilled about adding the complexity. I'm kicking myself for not getting a Toybox when I had the chance. You can read about the cooling issues in the 2nd half of this thread.

As for gearing. I run the H55, 4.1 and 35's powered by a 12HT. Cruising at 70-75 is perfect. Double low yields a crawl ratio around 105:1. The BB shifter is cable and so it doesn't have that positive engagement like the stock T-case.

I had considered the option of going with the 4:1 t-case but it seemed kinda slow for anything but technical terrain. 4:1 in 4th gear low range is almost the same as 1st gear in 4Hi. How fast can you go in 1st gear 4HI in a diesel? Not very fast... and so yes, I would imagine I would have to shift between LO and HI range fairly often.

I had the Toybox, and even Marlin himself couldn’t get the thing to hold together

Great points guys, I appreciate all the feedback thus far!

To clarify the mission statement, I want to be able to comfortably do Hole in the Rock trail. I want to be able to drive 6hrs of pavement up to Vermont and wheel up there with my friends (similar mix to HiTR, some higher speed gravel and dirt, some tight technical rocky and muddy sections, a good overall mix). I am not as concerned with pure rock crawling.

I did HiTR and two years of the Vermont Overland Trophy with my built 100 and it did well. It wasn't as fun as the BJ74 would have been, and sustained decent body damage up in VT due to tight trails. With the 74 and it's 5spd and stock t-case gearing, i would not have been as comfortable as with the 100. The t-case gears sound like the easier / straightforward option. However the blackbox sounds like the most elegant solution to retain both highway drivability and ultra low gearing.

The drawback of the 4:1s is increased shifting b/w low and high, and increase rpm on the highway. And from research sounds like a decent bit of gear whine.

The drawback with the blackbox is that I would need to farm it out and with a limited amount of info and technical knowledge, not sure who would be best fit for that...

I’d forgo a little inconvenience for a rock solid drivetrain, especially after my last fiasco.

My advice is this, speaking from experience: of you can’t do it yourself (even if you plan on having a shop do it) then you probably can’t fix it, and making a complex system that requires a lot work get the kinks out that you can’t fix is probably not the best idea IMO.

In my last truck I knew how to fix it, but I needed my own machine shop to do so, something I just didn’t have, and after three attempts to keep it together, two transmission rebuilds and a failure during every major outing I attempted to make I was out. Don’t be me!

 

[fireball]

So what is your final vote?

35s and the 3.3 low / 10% underdrive high tcase gears?

 

[bj70_guy]

Before you decide, throw somebody's 35s on your 74 and try driving it before settling on an under drive high range and see what you think. Do you still have a stock exhaust and how much boost are you running?

You'll want to move your front axle forward 1" when it's time to mount some for real.

 

[MyCruiserisaHogBeast]

So what is your final vote?

35s and the 3.3 low / 10% underdrive high tcase gears?

If it were me I’d say 4:1 having wheeled some crazy s***. For me the more gearing the better.

 

[MyCruiserisaHogBeast]

Before you decide, throw somebody's 35s on your 74 and try driving it before settling on an under drive high range and see what you think. Do you still have a stock exhaust and how much boost are you running?

You'll want to move your front axle forward 1" when it's time to mount some for real.

Sound advice!

 

[roscoFJ73]

from they factory they had like a 30" tires with 4.11 gears.

What model was that? All my 7* series had 16 in rims with tyres that were close to 32, I forget the metric equivalent. Some of the MWB had 15 inch rims but the tyre still brought them close the 32" height

 

[fireball]

Before you decide, throw somebody's 35s on your 74 and try driving it before settling on an under drive high range and see what you think. Do you still have a stock exhaust and how much boost are you running?

You'll want to move your front axle forward 1" when it's time to mount some for real.

I have already moved the axle forward. Got a 3” exhaust once I got the truck home, and running 12-14# boost.

I don’t want the underdrive (as I mentioned above I am very happy with current highway performance) but it looks like the 3.3 or 4.1 low range gears ONLY come with the 10% under drive. Am I confused?

 

[bj70_guy]

I have already moved the axle forward. Got a 3” exhaust once I got the truck home, and running 12-14# boost.

I don’t want the underdrive (as I mentioned above I am very happy with current highway performance) but it looks like the 3.3 or 4.1 low range gears ONLY come with the 10% under drive. Am I confused?

Cool, you're ready to go then.
Marks makes a 3.08:1 set with 1:1 high range

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Marks 4WD are Australia's leaders in the research, development and manufacturing of 4WD engine conversion, transmission conversion, low range gears, rock crawling gears and portal axles to suit Nissan Patrol & Toyota LandCruiser 4WD's

www.marks4wd.com

 

[hoser]

So what is your final vote?.... I don’t want the underdrive (as I mentioned above I am very happy with current highway performance) but it looks like the 3.3 or 4.1 low range gears ONLY come with the 10% under drive. Am I confused?

If you are happy with your highway gearing with 33's, then the 10% overdrive will be fine.... as long as you go 36" tires!
36/33=1.09%

I vote 4:1 with 10% under drive and 36" tires.

I think all the current t-case regear options have some amount of gear whine. If that bothers you, then you have no choice but to go with a doubler of some sort ($$$).