h151 vs h152

[SteelHunterFJ80]

I have been going back an forth on upgrading to a H152 tranny instead of my keeping H151. When I go on longer trips, there is a fair amount of highway and in my truck with the 1HDFT motor I'm about 2800 rpm at 70 mph with true 35 inch tires. I could go with a TCase overdrive gear change which would knock down the RPMs by about 280 which, eventually, I will probably do but the 5th gear in the H152 knocks off 20% of the RPM. And the H152 supposedly has a higher 2nd gear which would be nice but not absolutely necessary given I am looking at better RPMs/load/engine noise on the highway.

Now here is where the plot thickens. While doing research on the differences I came across this Facebook thread that stated the H151 is much stronger and last longer between services than the H151. As you can see below, there is a reasoned argument for this and I wanted to get the forums thought on this.


H151 vs H152 which is better?

IS THE H152 BETTER THAN THE H151
My answer is no
The only good thing about the H152 was the higher 5th gear ratio and yes it's definitely a good thing but that's all.
There is now the same higher 5th gear ratio kit available to convert your H151 which makes the H152 box a backwards step.
The H151 with the 5th gear upgrade becomes a better cheaper and stronger option than the H152 and here is why.
I do not recommend the H152 in it's standard format to any high horsepower customers as it is a cheaper inferior copy of the H151 and is built to a price not a standard with the quality of most parts reduced
For example
- 1st gear kog is now a single piece cast gear with a single one pice synchro the H151 1st gear kog is forged steel and machined- it's also made from two separate parts to form the gear
- on the H152 Toyota decided to save costs by removing the two thrust washers on the maine shaft and allow the gear to rub directly with the bearing.
- Toyota saved costs and machining on the synchro's as they are now Teflon coated (bonded) instead of full brass - if the wrong oil is used or servicing isn't maintained correctly the bonded material can deteriorate/dissolve.
- even the quality of the machining on the coffin

teeth of the gears has been reduced to save the $$$
- and not to mention again the weaker 5th gear hub (on a previous post) which is designed to fail if loaded. - the H151 had the full spline hub
- even the selector folks have changed to a cheaper material and casting and are more prone to wearing out
- on the H151 The maine shifter rod was supported by a caged ball bearing to make it last forever. The H152 shifter rod runs directly in the housing (wearing the housing)
My point here is to inform people about what they are buying and what they currently have.
The H151 was designed to last 30years and then be overhauled to go another 30years.
The H152 was designed to fail if loaded beyond Toyota's new torque loading or wear out in 10-15years and throw it away.
Some workshops will sell you a H152 and say it's a better, stronger option- it's just not true
It used to be the only option for the higher 5th gear but now there is "SIX"

 

[ikarus]

To make it more difficult, did you see the same guy announced the H153?

But I'm not sure what to make of his H152 vs H151 argument because I would assume if he's anti H152, he would be anti H153 right? But he seems excited about it.

 

[SteelHunterFJ80]

See I wasn't too sure what to make of his 151 vs 152 argument either. I just don't know transmission mechanics well enough... but I sure would be interested in hearing from those knowledgeable in this area.

I'm not particularly interested in the h153. From what I've read, the lower gears are even shorter which didn't help my application at all.

Here us what I found online:

The bespoke H153 series five-speed manual gearbox that will be offered in the LandCruiser 70 Series from October has unique gear ratios and additional components Toyota says suit its high torque and tough customer usage.

It has been calibrated with shorter first-, second- and third gear ratios to aid off-the-line performance, while a triple synchronisation mechanism has been added to the first gear to promote smoother changes.

A longer fifth gear helps improve fuel economy as well as reducing engine noise at highway speeds.

A flywheel compatible with a 12-inch clutch has been newly adopted, ensuring excellent engagement and maximum delivery of power to the road.

 

[AussieHJCruza]

They must need shorter lower gears because the 1GD is lacking in displacement

 

[Mag71k5]

There is now the same higher 5th gear ratio kit available to convert your H151 which makes the H152 box a backwards step.

Ive seen a few H151's floating around on fb marketplace or landcruiser pages, they probably need rebuilds, but if you wanted that taller 5th youd have to pull it apart anyway. Maybe this is something to look into?

 

[SteelHunterFJ80]

Ive seen a few H151's floating around on fb marketplace or landcruiser pages, they probably need rebuilds, but if you wanted that taller 5th youd have to pull it apart anyway. Maybe this is something to look into?

Yeah for sure, I saw a few too but they seem to have all been sold. Mine is in tip top shape having recently been rebuilt. But something to consider.

I am still wondering what all the more knowledgeable members think of the original opinion of GXL....is the H151 in fact a stronger, longer lasting transmission? @OGBeno @SNLC @orangefj45 @cruiseroutfit @Kernal @cruiserdan

 

[mudgudgeon]

To make it more difficult, did you see the same guy announced the H153?

View attachment 4094157

But I'm not sure what to make of his H152 vs H151 argument because I would assume if he's anti H152, he would be anti H153 right? But he seems excited about it.

Sounds like someone has a vested interest in selling conversion kits for the H151.

@SteelHunterFJ80 i think the H151 1st gear ratio is too high for offroad work, especially on 35s.
I found at times, towing about 1tonne (1000kg) 1st gear was too high for a start on a hill. I would use 1st, Low Range-> 2nd LO -> 2nd HI too get moving. Aussie spec and JDM transfer cases let you shift from LO to HI while rolling.

H153 has the lowest 1st & 2nd ratios of all the H15# series boxes. If you were buying new, I think this would be the ultimate combination.
I don't see much disadvantage in a lower 1st. If it's lower than you need on road, take off in 2nd.

I found 35's with standard gearing made 5th in the H151 a little too tall sometimes too. I found I definitely had to downshift a lot earlier than when on 33s. 33s are about a 5% increase in final drive ratios, 35s a little less than 10% aka 10% less torque at the tyres.

I think a H153 with 20% over drive 5th and 35s would benefit from/need t-case regearing, or diff regearing.

IMO 27-2800RPM is right in the sweet spot for these engines. They'll happily run at that RPM day in, day out.

27-2800RPM leaves a reserve of lower rpm torque to push up a hill, ave a reserve of high rpm horsepower to accelerate to pass that truck before that lane merges.
Drop cruising rpm much below that, and you need to downshift far more often to crest that hill.

In reference to strength, i don't see there being any significant difference from 151 - 152
R151 gearboxes suffered a lot if failures in aussie hzj105 diesel cruisers. R151 Ilis a significantly lighter duty gear box using much narrower gears and smaller shafts.
From what I've looked at H152 and h152 are using essentially the same parts, just different toof count on gears

 

[orangefj45]

Obviously there’s a lot of info floating around.
There are a few things to keep in mind:

The taller 5th gear set will not work on all H151F transmissions.

Yes, the H152F is not quite a strong but realistically, that only applies to vehicles that make a lot more powered than in a stock application.

Georg @ Valley Hybrids

 

[Lead Head]

I know nothing about the H151 or 152 specifically, but I will chime in as someone with some experience in manufacturing and mechanical systems:

1) That "cast" first gear on the H152 has the exact same texture and surface quality as the "forged" H151 gear. I am really curious as to how he ascertained that the H152 first gear is cast? I would be shocked if any transmission, anywhere, had cast gears inside them. Automotive transmissions have very high shock-loads, which just are not appropriate for cast iron. Additionally it is very difficult to get cast iron to the necessary hardness that a transmission gear tooth requires. That gear just looks like a very nice high quality forging to me. Couple of other things to note:

• The synchronizer cone appears much larger on the H152 gear, which should allow for quicker synchronization and easier shifts into 1st while rolling.
• The engagement dogs being part of the gear does unfortunately mean the gear is junk if you managed to grind or strip the dogs off, but notice the dogs are longer, meaning hopefully they'll be less prone to grinding and pop-outs.

So with all that being said, I ask, is it a problem? Are we seeing H152s blow up 1st gears or strip out the dog teeth anymore than a H151 did?

2) I don't see the issue with having the gears rub directly on the inner bearing races. The thrust washers were the same diameter of the inner race, and ball bearing inner races are ultra-hard and ground perfectly flat. The thrust washers were likely just completely unnecessary.

...and I iterate, is it a problem? Are we seeing high levels of wear on those inner bearing races or the mating gear faces enough that it's causing huge issues?

3) The switching of the shift rail from roller balls to riding directly in the case is definitely a "cheapening", but I also believe the linear ball bearing was an extreme extravagance to begin with. Millions upon millions of aluminum-case manual transmissions run their shift rails directly in bores in the case. It's in a closed area, constantly bathed in oil, with no contaminants.

so once again, is it a problem? Are we seeing these shift rail bores so worn out that it's causing an issue?

4) Look at those synchros. There's just as much brass on either one. The difference is the H152s are a composite part with a friction-enhancing material bonded to the exterior of the brass. Does he really think a process require multiple operations (casting, machining, cleaning, bonding) a synchronizer ring is somehow cheaper than just a single machined synchro? The bonded friction material increases the synchro's effectiveness, making the transmission shift quicker and more smoothly. The trade off being that once/if the friction material wears away, the synchro will lose effectiveness. It's a trade off.

It's entirely possible all of these things ARE problems, and the H152 is a toilet compared to the H151. But you can't just look at something and say "oh that's worse" without really understanding any of the underlying engineering. I'd like to see evidence of extreme case wear from the shifter, gear faces being worn from riding on the bearing race, wasted 1st gears, etc...

 

[fjbj40]

After driving a VDJ79 Ute, with a h152, in Australia 2 years ago I can say it’s not a super smooth shifting transmission.

I’m hoping the h151 I have is smoother.

 

[mudgudgeon]

After driving a VDJ79 Ute, with a h152, in Australia 2 years ago I can say it’s not a super smooth shifting transmission.

I’m hoping the h151 I have is smoother.

All the h15# transmissions are not 'super smooth shifting'. Particularly if you expect it to shift like a Miata.
The gears are big and heavy, the synchronisers have always been barely up to the task.
They will shift smoother if you match engine RPM to the gear you are selecting
They are very sensitive to what oil is used in them.

 

[fjbj40]

All the h15# transmissions are not 'super smooth shifting'. Particularly if you expect it to shift like a Miata.
The gears are big and heavy, the synchronisers have always been barely up to the task.
They will shift smoother if you match engine RPM to the gear you are selecting
They are very sensitive to what oil is used in them.

From research it seems Redline MT is good?

All I know is looking forward to getting rid of the auto!

 

[mudgudgeon]

From research it seems Redline MT is good?

All I know is looking forward to getting rid of the auto!

Yes,

and yes.

 

[SNLC]

FYI, the H152 was designed for and came behind the 1VD v8 turbo diesel. Released in 2016. This after Toyota ran the H151 behind the v8 TD from 2008-2016. The H151 came behind the turbo diesel inline sixes before the 1VD was released.

Cheers

 

[alia176]

I did the ratio calcs and the H153f seems like a good contender for my particular vehicle. The H152f would also do well for my needs. At my elevation, with the turbo and 35s, the A343f is doing a bangup job of keeping it in OD bulk of the time. Basically, this transmission doesn't piss me off anymore which makes me think I'm after the same performance using a 5sp manual. Crawl ratio is irrelevant to me as all the manuals have silly 1st gear. Admittedly, I find myself setting the cruise at 80 mph due to the trannny staying in OD as I go over smaller hills.

If my numbers are inaccurate, please lmk.

 

[orangefj45]

I know nothing about the H151 or 152 specifically, but I will chime in as someone with some experience in manufacturing and mechanical systems:

1) That "cast" first gear on the H152 has the exact same texture and surface quality as the "forged" H151 gear. I am really curious as to how he ascertained that the H152 first gear is cast? I would be shocked if any transmission, anywhere, had cast gears inside them. Automotive transmissions have very high shock-loads, which just are not appropriate for cast iron. Additionally it is very difficult to get cast iron to the necessary hardness that a transmission gear tooth requires. That gear just looks like a very nice high quality forging to me. Couple of other things to note:

• The synchronizer cone appears much larger on the H152 gear, which should allow for quicker synchronization and easier shifts into 1st while rolling.
• The engagement dogs being part of the gear does unfortunately mean the gear is junk if you managed to grind or strip the dogs off, but notice the dogs are longer, meaning hopefully they'll be less prone to grinding and pop-outs.

So with all that being said, I ask, is it a problem? Are we seeing H152s blow up 1st gears or strip out the dog teeth anymore than a H151 did?

2) I don't see the issue with having the gears rub directly on the inner bearing races. The thrust washers were the same diameter of the inner race, and ball bearing inner races are ultra-hard and ground perfectly flat. The thrust washers were likely just completely unnecessary.

...and I iterate, is it a problem? Are we seeing high levels of wear on those inner bearing races or the mating gear faces enough that it's causing huge issues?

3) The switching of the shift rail from roller balls to riding directly in the case is definitely a "cheapening", but I also believe the linear ball bearing was an extreme extravagance to begin with. Millions upon millions of aluminum-case manual transmissions run their shift rails directly in bores in the case. It's in a closed area, constantly bathed in oil, with no contaminants.

so once again, is it a problem? Are we seeing these shift rail bores so worn out that it's causing an issue?

4) Look at those synchros. There's just as much brass on either one. The difference is the H152s are a composite part with a friction-enhancing material bonded to the exterior of the brass. Does he really think a process require multiple operations (casting, machining, cleaning, bonding) a synchronizer ring is somehow cheaper than just a single machined synchro? The bonded friction material increases the synchro's effectiveness, making the transmission shift quicker and more smoothly. The trade off being that once/if the friction material wears away, the synchro will lose effectiveness. It's a trade off.

It's entirely possible all of these things ARE problems, and the H152 is a toilet compared to the H151. But you can't just look at something and say "oh that's worse" without really understanding any of the underlying engineering. I'd like to see evidence of extreme case wear from the shifter, gear faces being worn from riding on the bearing race, wasted 1st gears, etc...

Great post. Thanks for taking the time to write and post this info!!!!!

Georg @ Valley Hybrids & Terrain Tamer

 

[SteelHunterFJ80]

Sounds like someone has a vested interest in selling conversion kits for the H151.

@SteelHunterFJ80 i think the H151 1st gear ratio is too high for offroad work, especially on 35s.
I found at times, towing about 1tonne (1000kg) 1st gear was too high for a start on a hill. I would use 1st, Low Range-> 2nd LO -> 2nd HI too get moving. Aussie spec and JDM transfer cases let you shift from LO to HI while rolling.

H153 has the lowest 1st & 2nd ratios of all the H15# series boxes. If you were buying new, I think this would be the ultimate combination.
I don't see much disadvantage in a lower 1st. If it's lower than you need on road, take off in 2nd.

I found 35's with standard gearing made 5th in the H151 a little too tall sometimes too. I found I definitely had to downshift a lot earlier than when on 33s. 33s are about a 5% increase in final drive ratios, 35s a little less than 10% aka 10% less torque at the tyres.

I think a H153 with 20% over drive 5th and 35s would benefit from/need t-case regearing, or diff regearing.

IMO 27-2800RPM is right in the sweet spot for these engines. They'll happily run at that RPM day in, day out.

27-2800RPM leaves a reserve of lower rpm torque to push up a hill, ave a reserve of high rpm horsepower to accelerate to pass that truck before that lane merges.
Drop cruising rpm much below that, and you need to downshift far more often to crest that hill.

In reference to strength, i don't see there being any significant difference from 151 - 152
R151 gearboxes suffered a lot if failures in aussie hzj105 diesel cruisers. R151 Ilis a significantly lighter duty gear box using much narrower gears and smaller shafts.
From what I've looked at H152 and h152 are using essentially the same parts, just different toof count on gears

Yes, I thought of the vested interest as well. But some of his arguments sounded valid to a newbie like me. I thought I would tap into the collective knowledge here as I don't have that great of a working knowledge of transmissions and only a basic understanding of gearing.

For my set up, 1st gear is perfect for most of my offroad applications. I don't wheel my rig very hard, sometimes the occasional offroad park but I do a lot of over landing type trips. There are a few fishing places that I go to that have really steep grades on the way down and keeping it in first gear has made it a piece of cake. Didn't even have to touch the brakes or need to put it in low. I've only had to put my TC in low twice in the snow and it did great. And about 12 times a year I tow over a thousand pounds.

That being said, about half the time I start off in 2nd gear anyway. But when towing I can see how it might be different. Can you tell me which Aussie spec or JDM transfer case allows you to shift from low to high? Is that the same as the 7 pin mod on a HF2A?

And I agree that the engine can run quite well at 2700 rpms, but for my motor I might need lower gearing. I have a red wheel GTurbo, +30 injectors, 15 mm injection pump, inter-cooler and 4 inch snorkel along with PDI box. I can get full boost at 2200 rpm in 5th on the highway if I hammer it. I have played around with different speeds and differnet gears and for cruising along the highway, the truck is really pleasant and quite a bit quieter around 2100 rpm. In current trim with the H151 and true 35s I am at about 2700.

So before doing the 5th gear upgrade on my current transmission or doing over and under drive gears in the transfer case I thought perhaps the H152 would better suit my needs. And after hearing more feedback from the forum and crunching some numbers it doesn't seem to make sense.

 

[SteelHunterFJ80]

From research it seems Redline MT is good?

All I know is looking forward to getting rid of the auto!

I've been using Redline and its great. @Rock40 recommended it to me

 

[SteelHunterFJ80]

Obviously there’s a lot of info floating around.
There are a few things to keep in mind:

The taller 5th gear set will not work on all H151F transmissions.

Yes, the H152F is not quite a strong but realistically, that only applies to vehicles that make a lot more powered than in a stock application.

Georg @ Valley Hybrids

Priceless information here for me.....Since I am running a lot more power than a stock application I would like to keep the H151. How can I find out if my transmission isn't one of the ones that a taller 5th gear will work on and do you sell that part?

This is the one I was looking at from Terrain Tamer:

 

[mudgudgeon]

Can you tell me which Aussie spec or JDM transfer case allows you to shift from low to high? Is that the same as the 7 pin mod on a HF2A?

I believe all the Aussie and JDM t cases have synchros on the HI range gear, but not on LO. This means you can change to HI while driving, but need to come to a stop to change to LO.
The way i do it, get up to speed in LO, shift up to 2nd or 3rd, once the revs are up, and you're sonewhere you can coast a bit and ready to shift to HI, slip the gearbox into neutral, shift the Tcase to neutral, pause briefly, then shift into Hi, select a gear, clutch out, drive away.

LO 2nd --> HI 2nd works well, but you can drive it to LO 3rd --> Hi 2nd, or LO 4th --> Hi 3rd.
For an auto transmission, shift to neutral to unload the drivetrain

I have played around with different speeds and differnet gears and for cruising along the highway, the truck is really pleasant and quite a bit quieter around 2100 rpm.

Your Gturbo set up is gonna have way more power than a stock engine, so maybe 2100rpm at crusting speeds will work.

My thoughts are 2100rpm doesn't put you much above peak torque. If you come to a hill that causes RPM to drop, you don't have much room before youre down shifting.
Diesels are slow revving compared to a gas engine, but they are happy to rev, just noisy.

I think you want to keep engine speed in the middle of the power curve, some where between peak torque and peak horsepower.
Peak torque is approx 1800rpm, peak power 3800rpm. Your engine is happiest around the middle of that 2000rpm spread.

Good defensive driving habit is keep 10-20% of that usable rev range in reseve. At the low end, 1800rpm + 15% of your useable rev range puts you right at 2100rpm. This gives you room to back off to avoid traffic shenanigans but power in reserve to get back on the gas to avoid traffic, or on the high end, stay 10-20% under peak power so you have some power in reserve to be able to get on the gas and get clear of muppetry


All my cruisers have been similarly geared. With my current fzj80, if I down shift as revs drop to 2000rpm, a down shift puts it at about 2250rpm to maintain or increase speed. This keeps the engine a big further into the power band without labouring the engine to maintain speed