R151F/HZJ78: More Overdrive? (1 Viewer)

[SimonInAustralia]

R151F/HZJ78: More/Higher-Ratio Overdrive?

I need more overdrive, as in a higher ratio, in 5th gear/high range, from my R151F gearbox and transfer case in my HZJ78.

Reason is to have lower revs at highway cruising speed, 110kp/h for example.

(diff ratio and tyre size changes are not an option in this situation)


One option is Marks 4WD Adapters Gearmaster rock crawling transfer case gears, which would change the 1:1 high range transfer gear to 0.92:1 (lowering engine revs at 100kp/h), as well as changing the low range transfer gear from 2.295:1 to 2.82:1 (which is also useful).

Problem with that is the $1825AU cost.


Any other options for a higher ratio high range overdrive, such as alternative replacement transfer gears, replacement 5th and possibly other transmission gears, etc.?


(diff ratio and tyre size changes are not an option in this situation)


Thanks.

 

[Clint79]

i could do with droping my 5th gear revs for 110kmph they sit just under 3g with my h150, the rest of the gear ratios are awsum

 

[andrewm42]

I am currently having a 1HD-T/ H151F/ HF2A transplanted into my 2001 model HZJ 78. - Due to the HZJ having diffs with a ratio of 4.3:1 as compared to the HDJ-80s 3.72:1 I too need to lengthen all my gears. My HZJ currently runs 285/75R16s.

I am looking at Mark's transfer gear as a cheaper option than replacing the diffs.

In 4 weeks time I will be able to tell you about the changes.

Regards

Andrew

 

[Clint79]

Can you change your diff centers to 80 series ones? there is plenty of them around
All my ratios are nice and flowing bar the 5 speed that revs out its not to bad but could be a bit better.
i thought Aus 80 series ratios were 4.01 and cruisers with the h55f like the 75 series had 4.11 ratio maybe the turbo D 80's have the different ratio
where abouts are the 3.72 ratios from in the world
sounds like a cool conversion you will have to post up some pics and info

 

[andrewm42]

The reason I am replacing the motor/etc rather than buying a HDJ78 is that in Germany - there are no HDJ 78s.

A donor HDJ-80 is providing the internals for this conversion - I have 2 left hands, so I am letting my trusty workshop do the work for me - so I don't know how many photos I will be able to provide. IIRC, the manual HDJ 80s have a ratio of 3.72, or 3.5. The automatics have approx. 4.1...

The HDJ78 in Australia has a the H150F + 4.1 diff....

I thought I read somewhere here that the internals of the 80 series rear diff won't fit into the HZJ diff housing...

Cheers

Andrew

 

[psweber]

I need more overdrive, as in a higher ratio, in 5th gear/high range, from my R151F gearbox and transfer case in my HZJ78.
....
Any other options for a higher ratio high range overdrive, such as alternative replacement transfer gears, replacement 5th and possibly other transmission gears, etc.?

Thanks.

Here is my post to another thread you might be interested in if you have not already found a solution.


Greetings fellow mudders. I have been in contact with Safari systems about their 5th gear set that they "no longer carry" Here is the official scoop. Seems they only made an initial run of 50 sets and installed them all, and yet they kept them on their web site.
Maybe to tempt guys like me. I really wanted a set and tried several avenues to procure one set or even a set of drawings so I could have them reproduced. Even big $ would not get the Mfg to produce me a 1-off set. However.....
Here is the big news... they will do another run of 50 if I can get people to commit. This may be hard but even though I am a newbie here and I am still building my trust level with you guys, I am willing to give it a shot. I am willing to run the finances but they want 50% up front before starting production. Once they receive the deposit it will be approximately 8wks ex. works Melbourne. The MSRP is $1595 AUD. Of course I will not be paying the full retail so I am willing to give my fellow mudders a 20% discount that would be $1275 AUD each plus shipping to your location. I will try and negotiate to have Safari ship them direct to each person but these are still details down the road to work out. First I need to determine the level of interest before going ahead with this endeavour. One final note from Safari "...Toyota made a change to the R151F transmission at some stage in 2011 on the Wide-Nose HZJ70 Landcruisers, which was incompatible with our 5th gear set. We could not pinpoint which countries/regions this effected, or exactly when the change came into effect." You can check out ToyoDIY for compatibility.
So here is the deal:
1 set R151F - 5th gear set SGHZJ70C for $1275+shipping, import taxes etc.
Who is interested? Let me know
http://www.safarisnorkel.com/turbo/1hz_76/gears1.jpg

 

[crushers]

factory R151 OD ratio is: 0.838 which is 16% ratio
this one is offering 20% ratio, increase of only 4% IF i am reading this right
Marks is offering a 8% t.case reduction (0.670) which is a 33% reduction over 4th gear 1/1.

care to enlighten me on the real benefit of this gear set?

 

[psweber]

Mark's gears vs Safari 5th gear ratio.

factory R151 OD ratio is: 0.838 which is 16% ratio
this one is offering 20% ratio, increase of only 4% IF i am reading this right
Marks is offering a 8% t.case reduction (0.670) which is a 33% reduction over 4th gear 1/1.

care to enlighten me on the real benefit of this gear set?

Enlightenment This is a 20% increase over stock therefore .664
With the stock 5th of .838 RPMs at 120kph are 2870 but with this set those are reduced to 2300RPM. Where as in my case I tend to drive about 100kph (when I find a good patch of road) my RPMs would be reduced to ~1900RPM which is very comfortable/economical for my 1HZ. The other benefit is that it only affects the 5th gear and not the whole range whereas Mark's gears are on the output and thus affect all gears forward and reverse.
Further in relation to $ achieve a similar increase with Mark's gears I would also have to change my front and rear diff gears which would more than double the cost this would of course still affect the ratios of 1st-4th gears.
I wrote Mark's about the possibility of custom making a 5th gear set for me but they were not interested though I may go for their 44% reduction in the future. It is a sweet mod
Hope that answers your questions. It is a replacement 5th gear set only for us who drive on-road sometimes.

 

[crushers]

enlightened i am
20% over stock is substantial.
i drive, on average, 85-95 k/h around here. too bad there isn't a gear set for the R141, i love the gearing of the R141 but sadly it is just a 4 speed. OD of this gearing would be perfect behind a PZ or HZ.

congrats on doing the work on this, sadly i have little need of the gear set.

best of luck in the group buy.

 

[Gilly]

i'd be interested in that. Let me know how you get on with numbers.

 

[psweber]

I'll add you to the list, though we are getting off to a slow start.

 

[Sowikal]

I'll add you to the list, though we are getting off to a slow start.

Any luck with this buy? I may be interested in getting added to the list.

 

[psweber]

So very sorry to those who are interested. There do not seem to be enough R151F transmissions in NA or in the hands of enthusiasts to generate enough demand. Not likely for another 5+ yes buy my estimate. At that point I may give it another go but for now I am dropping the idea.

 

[crushers]

now that the USA can get the LJ71/78, KZJ71/78, PZJ70, you will see more of a possibility

 

[psweber]

Thanks for that input. Maybe in a year or so if enthusiasts get ahold of them I will take another stab at it.

 

[Sowikal]

Thanks for that input. Maybe in a year or so if enthusiasts get ahold of them I will take another stab at it.

No worries. I suppose that most trucks with the r151 are not being driven on roads where 100+kh is a possibility, at least, from what I remember, not in Africa.