BJ73/74 owners with 35's and T case gears- looking for opinions on gearing

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May 22, 2014
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Hey all,

I'm only really looking for people with personal experience with 34/35/36 inch tires who have opted to do low range T case gearing. I'm looking for some "buttometer" type anecdotes.

I'm setting up my H55F/cable locked BJ74 as an all around daily drivable adventure rig that needs to be a competent highway machine. I'm building it to be as moderate and bulletproof as possible with some smart drivetrain mods, as much armor as needed, and the right sized tires that'll get me where I need to go in style and class. The end goal is 35" tires, low t case gears, bumpers/sliders/ with a roof rack and RTT. It'll mostly be used for family friendly adventures, but a couple of times a year I want to be able to tackle some Rubicons, Moabs, etc without worrying about blowing things up. I like low gearing and I like rigs that idle up things.

I have Nitro Chromoly axle shafts and was planning on running the factory gears, relying on T case gears. After talking to Kurt from Cruiser Outfitters, he said I should at least consider 3.3:1 gears with factory high range. My plan has been 4:1 gears with a 10% under drive.

So here's the question: anyone done the 3.3:1 gears with 35" tires and a 13BT? I know people have 4:1 gears with under drive, but looking for your opinions too. I am not planning on juicing my 13BT beyond possibly adding a small intercooler and shimming the waste gate for a couple of extra pounds of boosty deliciousness. As it is it's on 33s and it does everything I ask and gets 20-22 mpg which is where I want to be. It's slow without being too slow, which is fine with me. The 13BT is fine power wise, but does not have the freight train-like terrain consuming lumpiness of the 4BT powered cruiser or the miraculously stable low RPM performance of 1HZ powered Cruisers I have owned, which is why I lean toward 4:1 low range gears. Thoughts?
 
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My 3.05 low range & 35/36's works well but my 1UZ is a torquier motor than the 13BT of course. (edit: 4.1 diffs in mine) Plus we don't do much rock crawling- I think with a smaller motor & more rocks on the menu the 4.1 would make good sense.

Cheers
Clint
 
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Oct 8, 2003
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Other than the RTT, my 74 is set up pretty close to your plan - 35s, bumpers, sliders, skid plates etc. I have a 2.5" exhaust with a free flowing Aeroturbine muffler and the boost set around 13.5 lbs.

My truck has stock 4.11s and the Marks 3.05:1 low/1.08:1 high range gears. If I were doing it again I would opt for the stock high range ratio. It would put the highway rims in a much nicer spot, and the 13B-T/H55F will power it nicely.

I'm happy with the 3.05s, though I'd be happy to have a little lower low range gearing in the T case. I don't know just how much case material needs to be hogged out to fit the 4:1 set. It was pretty minimal with the 3.05s.

Short version: I'd say Kurt is right on point 👍
 
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Other than the RTT, my 74 is set up pretty close to your plan - 35s, bumpers, sliders, skid plates etc. I have a 2.5" exhaust with a free flowing Aeroturbine muffler and the boost set around 13.5 lbs.

My truck has stock 4.11s and the Marks 3.05:1 low/1.08:1 high range gears. If I were doing it again I would opt for the stock high range ratio. It would put the highway rims in a much nicer spot, and the 13B-T/H55F will power it nicely.

I'm happy with the 3.05s, though I'd be happy to have a little lower low range gearing in the T case. I don't know just how much case material needs to be hogged out to fit the 4:1 set. It was pretty minimal with the 3.05s.

Short version: I'd say Kurt is right on point 👍
What are you looking at for highway RPMs? How about fuel economy? Other than highway cruising does the gearing feel right?

Cruiser Outfitters is going to set up the case for me, all I have to do is bolt it in. I can only do this once I would hate to wish I had done something else. I know that one way or another the deeper low range will get me to where I need to go, but I am a huge fan of gearing. But, offroad is like, less than 1% of what I'll be using this for. I'm actually more concerned about road manners. I can't stand an under geared truck, and right now it's adequate, even slightly peppy off the line.

I am afraid with the RTT (which is removable and won't be up there all the time), 35s and a little added weight, it'll lose its mojo. Unfortunately the H55F is a little short on the overdrive. I guess I'd rather have a truck that feels good and has to cruise at 65 instead of 70. I live in LA anyway, 70 mph is a fantasy, but if that 10% means that I lose 2mpg on the highway it is meaningful enough for me to put some thought into it. If this was a 1HZ I wouldn't worry too much but the 13BT has only enough legs on it to make the truck practical, if I loose too much it'll kinda suck.
 
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Oct 8, 2003
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What are you looking at for highway RPMs? How about fuel economy? Other than highway cruising does the gearing feel right?

Cruiser Outfitters is going to set up the case for me, all I have to do is bolt it in. I can only do this once I would hate to wish I had done something else. I know that one way or another the deeper low range will get me to where I need to go, but I am a huge fan of gearing. But, offroad is like, less than 1% of what I'll be using this for. I'm actually more concerned about road manners. I can't stand an under geared truck, and right now it's adequate, even slightly peppy off the line.

I am afraid with the RTT (which is removable and won't be up there all the time), 35s and a little added weight, it'll lose its mojo. Unfortunately the H55F is a little short on the overdrive. I guess I'd rather have a truck that feels good and has to cruise at 65 instead of 70. I live in LA anyway, 70 mph is a fantasy, but if that 10% means that I lose 2mpg on the highway it is meaningful enough for me to put some thought into it. If this was a 1HZ I wouldn't worry too much but the 13BT has only enough legs on it to make the truck practical, if I loose too much it'll kinda suck.
2400 rpm at 100 km/h (60 mph).
It will cruise at 75 mph but IIRC its up around 2800 rpm... which I have still done for long periods at a time. That's from (a dim) memory so I'd have to take it out and confirm.

I don't track my mileage regularly, and until recently the truck has been off the road for the last year and a half so again a dim memory, but I think I average 22-23 mp imperial g, combined city and highway. That'd be 19 mp US g give or take. My best ever tank was 29 mpImpG (24 mpUSg) with the low gears and a set of worn 255/85R16s, going a mind numbing 55 mph following a trailer-towing FJ Cruiser home from Moab :lol:

I think its geared a little low everywhere. Having recently driven another BJ74 set up the same as mine but with a stock T case I like it much better. YMMV.

@Greg_B could probably give you a mileage estimate of a heavy-ish 74 with stock high range. And a direct comparison of a stock high range vs 1.08:1

You'll need to move the front axle forward 3/4"-1" forward to fit 35s - I'd suggest you do that, then borrow a buddy's 35s for a high range test run before you commit to your T case gearing of choice. Depending on what rims you're going to run you may need spacers as well to get the correct backspacing.
 

NM Frontier

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I'll be watching this, I have an auto trans so not quite the same but I have similar questions of if t case gears are the way to go. And what ratio in low range and/or overdrive reduction.
 
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2400 rpm at 100 km/h (60 mph).
It will cruise at 75 mph but IIRC its up around 2800 rpm... which I have still done for long periods at a time. That's from (a dim) memory so I'd have to take it out and confirm.

I don't track my mileage regularly, and until recently the truck has been off the road for the last year and a half so again a dim memory, but I think I average 22-23 mp imperial g, combined city and highway. That'd be 19 mp US g give or take. My best ever tank was 29 mpImpG (24 mpUSg) with the low gears and a set of worn 255/85R16s, going a mind numbing 55 mph following a trailer-towing FJ Cruiser home from Moab :lol:

I think its geared a little low everywhere. Having recently driven another BJ74 set up the same as mine but with a stock T case I like it much better. YMMV.

@Greg_B could probably give you a mileage estimate of a heavy-ish 74 with stock high range. And a direct comparison of a stock high range vs 1.08:1

You'll need to move the front axle forward 3/4"-1" forward to fit 35s - I'd suggest you do that, then borrow a buddy's 35s for a high range test run before you commit to your T case gearing of choice. Depending on what rims you're going to run you may need spacers as well to get the correct backspacing.
Good info! My calculations put me at 2550 RPM at about 70 with the 10% reduction and 35s, still below factory with factory tires. I've built a lot of vehicles, I have a feeling that with factory high range gearing it'll be just a little slow. Leaning towards 4:1 gears. I am trying to sell my 37s so I can get into a set of 35s I found. If it works out I can test them side by side before my case is here. I'm planning on drilling the spring pads out to move the axle forward. Trying to figure out how far forward I can go before I reach steering bind. I'm in California and we're on lockdown right now so I don't have access to the shop to test things out, trying to come up with projects I can do from home.
 
Joined
May 22, 2014
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I'll be watching this, I have an auto trans so not quite the same but I have similar questions of if t case gears are the way to go. And what ratio in low range and/or overdrive reduction.
Having build a lot of trucks and working in motorsports for a long time, I can tell you T case gears are never a bad thing. You have a taller cruising gear so you have a little more wiggle room as far as cruising RPMs go, and the that auto is a slug so I'd probably just go for the 10% reduction right out of the gate. My $.02
 

ForealBoreal

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Apr 18, 2009
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I forget the difference between highway revs between the auto and the h55f.
My H55f HZJ77 with 255s @ 100km/hr was 2250rpm.

My advice to you because you want to road trip the thing is put the set off gears that don’t affect your high range. You’ll enjoy the rpm drop for interstate/highway use for what it is.

I’m curious how my 79 does with the 4.3 diff gears vs the 4.11 and a set of 255s. Not like it really matters anyway. A set of t case gears might be slick in that rig
 
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Mar 28, 2002
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I ran the same setup as @bj70_guy for 14 years and approx 143,000kms: BJ74 with Marks 1:08/3:05 stock turbo set to 13-14psi and 2.5" exhaust with aeroturbine 2525 muffler, storage box loaded up all the time in the back, protection bars all around and it's been on 315's for a number of years. In January of this year the H55F needed work so it was swapped out with a working H55F with stock t-case (daily drive just now so wanted it up and running right away). This has given a great immediate comparison. Immediate difference was relief of the gear whine gone! It will be interesting to pull the t-case apart and inspect as it has the tapered roller bearings for the idler as opposed to the stock needle bearings. When(if) the t-case gets back into the BJ74 I'll run dino gear oil in the t-case with Molyslip gear additive (had been running straight MT90 in conjunction with the H55F) to see if that makes a difference.

None of that is directly answering your question so lets get to it...

I've only had it onto the backroads and trails twice since the swap and know I will miss the gear reduction in low when needing to go slow so my only comment for low range would be: I believe it was before the Marks gears I knocked the engine into reverse rotation at least once (maybe twice if memory serves) on a small rock crawl called Can Opener when idling through a rock garden. 3:1 is nice and if doing rocks 4:1 would be nicer. With the comment that if you're with a group and going between obstacles on the flat you will be constantly switching between low and high range to keep up. I had to do this on ACT 2006 on multiple days between numerous river crossings as 5th gear low range was to slow to keep up.

With the stock t-case on the highway (Canadian speeds of 100kph and 110kph typically) the rpm just a needle width above 2400 RPM at 110 kph (68.4mph)-(GPS verified). Around town I've had to relearn to drive it and found myself for the 1st few days dropping from 4th into 3rd a lot as I relearned the shift points. The spread between 3rd and 4th is wide and I would have been lugging it if I continued driving as I had for years.

So I am of two minds. If you are going to be doing a lot of highway driving stock high range is great to maintain 1:1.

In town and with the 1:08 reduction in high range I did not notice the spread between 3rd and 4th as much (or was simply oblivious to it as I had gotten used to driving it that one way for years) . I am constantly reminded of it now. But the change is fresh still.

If I was to go with new t-case gears and maintain my current setup I "think" I would be inclined to go with 1:1 high range, having the reduction in low range only. The 13BT has enough to move the rig around fast enough for me with stock fueling, while maintaining fuel economy, once you up to boost a little and put a larger free flowing exhaust in place. But I am still relearning it.

I have been tracking my fuel consumption on Fuelly.

hth's
gb
 
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Aug 21, 2006
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My truck is setup differently so I might not have relevant experience to add.

'86 BJ70 / 3B with AXT turbo added / H55 / transfer case re-geared by Georg @ Valley (6% overdrive in 2wd) / 3:73 R&P / 33x10.5 tires

As a result, the truck will cruise at ~70mph in the range of 2300 rpm and 1100 deg F at turbine inlet. At this speed/rpm, I got slightly better than 20 mpg. FYI, I did limp home from an event a few years ago where I held my speed to ~55 mph @ ~ 1900 rpm. When I checked my mpg's after that trip, I was astonished that they were 27.5 (I wish I had the time and the self control to let the 3B cruise like this).

The step between 33 inch tires and 35 would probably be a huge step for this truck, so my setup and experiences might be close enough to your plan to be of serious interest.

Good luck with your BJ74 and looking forward to reading your experiences.
 
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Mar 11, 2007
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Mine is H55F, 35's, 4.1:1 diffs and 2.3:1 low range, brings is back to stock ratio, is good for most stuff and light rock crawling type stuff. Anything serious needs to be lower. Most of my driving is high country stuff and hard technical tracks and I find the ratios good, tops out about 60 kmh in 5th low range. Fuel economy is not rpm dependant like you would think, I ran for a few hours towing 1600-1800kg at 2800 rpm wih 31's and got the best economy I have had in years. FYI I run 25psi boost/ WTA and 3'' exhaust.
 

FJBen

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Mine is H55F, 35's, 4.1:1 diffs and 2.3:1 low range, brings is back to stock ratio, is good for most stuff and light rock crawling type stuff. Anything serious needs to be lower. Most of my driving is high country stuff and hard technical tracks and I find the ratios good, tops out about 60 kmh in 5th low range. Fuel economy is not rpm dependant like you would think, I ran for a few hours towing 1600-1800kg at 2800 rpm wih 31's and got the best economy I have had in years. FYI I run 25psi boost/ WTA and 3'' exhaust.

When you or others are saying 3" exhaust, are you building a new elbow off the turbo for 3" or just running 3" pipe from the factory down elbow on the turbo?

I find my EGT and MPG FAR more depedant on headwinds (which I fight a lot). 60ish 2200 rpms seems like a really happy spot for it, 65 is fine, I just find my mpg goes down if I'm on 65.. EGT's go from 650s to 800's, 4 ~8psi at 60mph. A big headwind and 65mph had me at 10psi, 1000~1100 the other day.
 
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I ran the same setup as @bj70_guy for 14 years and approx 143,000kms: BJ74 with Marks 1:08/3:05 stock turbo set to 13-14psi and 2.5" exhaust with aeroturbine 2525 muffler, storage box loaded up all the time in the back, protection bars all around and it's been on 315's for a number of years. In January of this year the H55F needed work so it was swapped out with a working H55F with stock t-case (daily drive just now so wanted it up and running right away). This has given a great immediate comparison. Immediate difference was relief of the gear whine gone! It will be interesting to pull the t-case apart and inspect as it has the tapered roller bearings for the idler as opposed to the stock needle bearings. When(if) the t-case gets back into the BJ74 I'll run dino gear oil in the t-case with Molyslip gear additive (had been running straight MT90 in conjunction with the H55F) to see if that makes a difference.

None of that is directly answering your question so lets get to it...

I've only had it onto the backroads and trails twice since the swap and know I will miss the gear reduction in low when needing to go slow so my only comment for low range would be: I believe it was before the Marks gears I knocked the engine into reverse rotation at least once (maybe twice if memory serves) on a small rock crawl called Can Opener when idling through a rock garden. 3:1 is nice and if doing rocks 4:1 would be nicer. With the comment that if you're with a group and going between obstacles on the flat you will be constantly switching between low and high range to keep up. I had to do this on ACT 2006 on multiple days between numerous river crossings as 5th gear low range was to slow to keep up.

With the stock t-case on the highway (Canadian speeds of 100kph and 110kph typically) the rpm just a needle width above 2400 RPM at 110 kph (68.4mph)-(GPS verified). Around town I've had to relearn to drive it and found myself for the 1st few days dropping from 4th into 3rd a lot as I relearned the shift points. The spread between 3rd and 4th is wide and I would have been lugging it if I continued driving as I had for years.

So I am of two minds. If you are going to be doing a lot of highway driving stock high range is great to maintain 1:1.

In town and with the 1:08 reduction in high range I did not notice the spread between 3rd and 4th as much (or was simply oblivious to it as I had gotten used to driving it that one way for years) . I am constantly reminded of it now. But the change is fresh still.

If I was to go with new t-case gears and maintain my current setup I "think" I would be inclined to go with 1:1 high range, having the reduction in low range only. The 13BT has enough to move the rig around fast enough for me with stock fueling, while maintaining fuel economy, once you up to boost a little and put a larger free flowing exhaust in place. But I am still relearning it.

I have been tracking my fuel consumption on Fuelly.

hth's
gb

Great comparison, that's what I was hoping to find. What size tire are you running?
 
Joined
Apr 11, 2010
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156
 
 
On my BJ74 I've got a 3 inch exhaust, mamba TD05H-16G, 3 inch exhaust and dump pipe, more boost and some more fuel. Gearbox is a h55F with the marks 3.05 low range/ standard 1:1 high range. I've got 4.11 diff gears and 255/85R16s. My usage is a mix of longer distance touring then playing on harder tracks once there.

Offroad it is great, yeah tracks with 3km of fast running, 150m of technical stuff and then 3km of fast running over and over again will see you going between low and high range, but it's very rare. I worried about it a lot more before I got the gears than was actually reflected in reality after I had them.

On highway it is pretty good, at 110km/h I do find myself occasionally looking for 6th, but definitely not enough to see me jump to 3.7:1 diff gears.

I think I'd be marginal on a 35s, but I'm about to do some work chasing a bit more power and I'm optimistic that afterwards, it would all work fine on 35s or even 36s.
 
Joined
Mar 28, 2002
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Great comparison, that's what I was hoping to find. What size tire are you running?
315/75R16. I have run this setup with 35x10.5R16 SSR's, 255/85R16 and for the a good number of years now 315/75R16. As mentioned above you have to move the front axle forward a bit and even then I could not fit new MTR/K's as they are one of the larger 315's.

hth's
gb
 
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315/75R16. I have run this setup with 35x10.5R16 SSR's, 255/85R16 and for the a good number of years now 315/75R16. As mentioned above you have to move the front axle forward a bit and even then I could not fit new MTR/K's as they are one of the larger 315's.

hth's
gb
How did you like the 35x10.50s?
 
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