H152 Fitment on 80-Series/Best Gearing Options

[CaptBeardilocks]

I've started down this rabbit-hole and was looking for some advice.

I have an 80-series fitted with a 1HDT/H151/HF2AV and stock US market diff gearing. Engine is running GTurbo/Intercooler/3" exhaust/etc and makes decent power. Currently on 33" tires. I live in my rig full time so it's quite heavy. I spend most of time running fire roads and average rough dirt, but I do wheel it harder on occasion to get where I need to be (I'm not out looking for difficult obstacles in any way) and only run highway when I have to, but then it's usually a full coast to coast run.

My two-fold (or multi-fold) problem is/are:
-5th gear in the H151 is not nearly high enough for modern highway speeds at reasonable RPMs. 35s would help ever so slightly with this, but likely not enough.
-1st gear also seems a bit low and I sometimes struggle not to lug it if the truck is pointed uphill at all. Obviously 35s will make this worse.
-In Low I could also use a lower 1st for crawling.
-It is a very early H151 (1990) and the parts are NLA to rebuild it so eventually it will have to be replaced (currently it's functioning fine however).
-I am considering jumping up to 35" tires which of course has me looking at re-gearing, currently looking at the transfer case as opposed to diffs if I swap to the H152.

Any input/thoughts/advice on what set-up might be the best for me moving forward? I've read that with decent power (like my set-up) 35s and an H152 are a pretty good pair with H152's lower first and higher overdrive. Can anyone confirm?

I'm also open to re-gearing the transfer case with 10% under Low and ... I'm not sure where I would need to be for High with 35s on my truck. Over and Under gearing is available. Kurt has a few nice charts on tire-size and gearing options but they're all for the US Market gas/auto set-ups.

 

[cruiseroutfit]

Following up on your PM/Email here so perhaps others can follow along and share their thoughts too.

Fwiw, the gear charts I've prepared really are not diesel, gas, auto or manual trans specific, in fact they make no difference what is in front of the t-case as the reduction or overdrive is the same net effect, higher or lower RPM's in high and/or low range.

10% overdrive gears in the T-case (TCG9007ODHR) will lower your RPM's in all high and low range gears by 10% (actual 9.12%) at the same before/after speed.

You mentioned: "1st gear also seems a bit low and I sometimes struggle not to lug it if the truck is pointed uphill at all. Obviously 35s will make this worse."

Do you in fact mean 1st gear is a bit high i.e. not enough power and you want a lower 1st gear? Unfortunately the high range overdrive t-case gears will only make that 10% worse. Your only fix there is a different transmission with a lower first gear and ideally a much higher overdrive too, solving your power in 1st and your RPM's in 5th. That's a tough ask. There are higher OD 5th gear options available for the H15x variants.

IF you can get by with the 1st gear you have, the solution imo would be high range overdrive (10% lower RPM's) combined with 3.1:1 low range gears. This would give you a net 0.912:1 in high range and 3.024:1 in low range.

The 20% lower net gearing in low range will really help with the "In Low I could also use a lower 1st for crawling" you're hoping for.

Long answer made short. There isn't axle and or t-case gears that can solve your want/need for a lower 1st gear and a higher 5th gear simultaneously.

 

[CaptBeardilocks]

Hey Kurt,

Thanks for the detailed reply!

Yes, I did misspeak on 1st gear. The gearing is too high. I talked myself in circles. Lol. I actually think I can solve the first gear issue in part with a bit of tuning to get a bit more power.

After some more research, the H152 has about a 11% lower first gear (if my math is correct, it might not be... 4.081 vs 4.529) and an overdrive gearing of around 17% higher (again...math... .881 vs .750). So that box alone would go a long way to get the ratios more modern. And probably not too much more expensive than rebuilding a H151 with fresh syncros/bearings and a higher overdrive gear, since oddly the H152 is available from US dealers. I wonder what US market truck that comes in?

That combined with the 10% Over High and 20% Under Low sets combined with 35s would make a pretty ideal final drive ratio for my set up.

Thanks! Now I just need to win the lotto.

EDIT: Need to get the calculator back out after the coffee kicks in & I'm fully conscious and sort out final drive ratios. I think an H152 with my current 33s would be just about the best compromise, transfer case left stock. However going up to 35s I might actually want to go 10% Under High Range in the T-case, equivalent to going to 4.56 in the diffs. Which seems to be the consensus for 35s with the 1HDT.

 

[HDJ79R]

.............. My two-fold (or multi-fold) problem is/are:
-5th gear in the H151 is not nearly high enough for modern highway speeds at reasonable RPMs. 35s would help ever so slightly with this, but likely not enough.
-1st gear also seems a bit low and I sometimes struggle not to lug it if the truck is pointed uphill at all. Obviously 35s will make this worse.
-In Low I could also use a lower 1st for crawling.
-It is a very early H151 (1990) and the parts are NLA to rebuild it so eventually it will have to be replaced (currently it's functioning fine however).
-I am considering jumping up to 35" tires which of course has me looking at re-gearing, currently looking at the transfer case as opposed to diffs if I swap to the H152.

Any input/thoughts/advice on what set-up might be the best for me moving forward? I've read that with decent power (like my set-up) 35s and an H152 are a pretty good pair with H152's lower first and higher overdrive. Can anyone confirm? ..................

I'm currently builing a H152 starting from a H151 that came out of a VDJ V8, that cost me $200... (although my HDJ79 already has a H151).

H152 gear ratios are:
1st - 4.529:1 - same as H150 from HZJ8x - 1HZ non-turbo, NOT the H151 from HDJ8x / 1HDT or later 151's which had 4.08:1 1st gear,
2nd - 2.465:1 - new ratio not used before in H150 / H151,
3rd - 1.490:1 - same as H150 / H151,
4th- 1.000:1 - ditto above / unchanged,
5th - 0.751:1 - new ratio not used before.

There are also ratio converson kits available here in Australia for H151's :
1) - a 5th gear only kit with a 0.736 5th gear,
2) - a different kit that has a 2.465:1 2nd gear, and a 0.736 5th gear.

The reason i'm building one up primarily is because, 1- it's a lower cost than a new 152, and 2- because i can.

 

[CaptBeardilocks]

Very cool that you're building your own. I would consider the same, but my very early H151 has no parts available for rebuild (synchros etc).

I had read that 2nd was the same ratio in in the 151 & 152. Maybe they made an early & later 152?

 

[HDJ79R]

Very cool that you're building your own. I would consider the same, but my very early H151 has no parts available for rebuild (synchros etc).

I had read that 2nd was the same ratio in in the 151 & 152. Maybe they made an early & later 152?

As far as i'm aware there is only one version of H152, which was a re-design for VDJ7* series V8, available from approx 2018...

They change 2nd as well to give a better spread, and i'm looking forward to that.

I'm not sure if other versions are available in the US, but i very much doubt it...

JUst take notice that, the shifter mounting location on H151 between 70 series and 100 series is different. A 7x series box has the shifter into the top of the main case, the 100 series into the rear case, so you need to research that for your 80 where it fits, else you could get stuck with a gearbox designed for a 7x series that may have the wrong shifter location.

There seems to be a lot of incorrect information about ratios, and getting even new kit ratio information from suppliers is like extracting teeth. It amazes me that people will buy these kits without even knowing the correct info, but apparently they do.

ONE OTHER THING : a H152 will have the wrong input shaft for the 6 cylinder. Because the V8 box has a longer input shaft and a different spline count, so you'd need to change that on a new H152 as well, and requires the swapping in of a 6 cylinder H151 input shaft.

 

[rick_d]

In a few hours I have a 370 mile drive ahead of me. In the 79, I have 32.5" tires, 3.90:1 diffs, and the H152 behind a HDT. I can run 83 mph at 2,500 RPM most of the way there. For my truck (highway with destination modest 4wd) the system works. Matt, consider that. The first gear maxes at 16 mph or something low so not great for commuter stuff.

152 first gears same. 0.75:1 fifth versus the 0.88 standard for 150/151

 

[CaptBeardilocks]

Man, you’re right on confusing info on gearing. I’ve definitely read that the 152 first gear is higher than 151. And that it’s the same. Lol.

@HDJ79R My 151 is in an 80 series. Any idea which box fits (70 or 100) has the same shift location as the 80? AFAIK there’s only one box available in the US market and it wouldn’t be for the 70 or the 100. Tundra maybe? I have no idea.

Part number available in the US is 33030-60C51. Pretty sure I got that from an 80 series build on this site….

 

[rick_d]

All h15x are same except separated SEAT 100 series where the shifter is moved behind the steel intermediate plate.

 

[CaptBeardilocks]

Got it. Thanks Rick!

 

[mudgudgeon]

actually think I can solve the first gear issue in part with a bit of tuning to get a bit more power.

The problem with 1st gear is lack of torque before the engine makes power.

I had hdj81, H151, 4.1 diff gears and 33s or 35s offroad.
1st gear was always too high in steep or rocky terrain.
The 1HDT lacks torque until it's on boost above 1300-1500rpm ish.

With H152, larger tyres, and 33s, I would lean towards 4.56 diff gears, and low range gear reduction.

With 4.1 diff gears, you may not get a lot of use from the taller H152 5th gear. I found running 33" tyres and 4.1 diff gears with an R151 (diffeent 5th gear ratio) 5th gear fell in a rev range that wasn't useful. More than a slight hill, I was dropping back to 4th far more frequently. As a result, there's no fuel economy gain

 

[mudgudgeon]

After reading Rick's post, if he is correct in saying H152 has 4.529 1st gear ratio, that would make it far more appealing. I was of the belief h152 shared gear ratios with h151

H150 in HZJ80 series made a big difference offroad with the lower 1st & 2nd gear, and higher compression/ higher torque 1hz for crawling.

For a heavy rig, I'd still seriously consider transfer case gearing

 

[HDJ79R]

After reading Rick's post, if he is correct in saying H152 has 4.529 1st gear ratio, that would make it far more appealing. I was of the belief h152 shared gear ratios with h151

I've driven a late model V8 diesel, they are a shorter 1st.

Here's one of many places you will find the H152 1st gear ratio quoted half way doen the page, and whilst this not an "offical" article, it is correct :

Toyota Land Cruiser LC79 2020 review: single cab, cab chassis GVM test

Toyota's 70 Series Land Cruiser is unique in the Australian 4x4 market. With Mercedes-Benz's decision to cease local sales of its $120K G-Professional in 2019, the LC79 is now the only single-cab cab-chassis off-roader available with the unmatched strength, durability and off-road performance of...

www.carsguide.com.au

 

[SNLC]

This Cruiser has 4.11 diff gears, 255 tires, H152 and an FTE.




Cheers

 

[SNLC]

Highways acceleration.



Highway cruising.




Cheers

 

[AussieHJCruza]

H152 has 4.529 1st (same as H150) 2.294 2nd (same as H151; H150 has 2.462 ratio)
3rd is the same 1.490, 4th is obviously 1:1 and 5th is .750 in the H152 vs .881 for 150/151.

4.11 and 35s with the 4.529 first gear is IMHO perfect, but if you're going to hop the engine up, be mindful that with a decent size turbo for power, if you run through the hills often you'll be back in 4th if you make peak torque much over 2k rpm in my experience.

EDIT: Had 2nd gear around the wrong way.

 

[frankenyota]

I have a H151 from an early FZJ80 series that l want to put behind a 15BF. Would like to have the lower 5th gear ratio to drop revs at 100-100km/h. The 15BF has a lot of low down torque and doesn’t rev very high compared to the 1FZ and 1HD# engines.
@HDJ79R who makes the kits to convert the 5th gear ratios in Australia?
I think l should be ok with the rest of the gearing running 4.11 diffs and the 15B will be turboed.
This is the ratios from the OEM manual for the H150/H151

 

[AussieHJCruza]

Terrain Tamer does a kit

 

[frankenyota]

Thanks @AussieHJCruza, I’ll check it out.
Weighing up rebuilding a H151 or buying a new H152

 

[AussieHJCruza]

Thanks @AussieHJCruza, I’ll check it out.
Weighing up rebuilding a H151 or buying a new H152

If you're paying labour, H152 is pretty similar money.