H55F Taller 5th gear

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Turbonazi77

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I am in the middle of rebuilding my H55F out of my HJ60. Currently it has a Fairey overdrive fitted inside the transfer case which after a tear down is showing signs of wear.

As much as I love the Fairey I am thinking of ditching it and getting a custom taller 5th gear set made. After close inspection today it is looking relatively straight forward.

I am thinking of a new ratio of approx .74 v's the original ratio of .85
This would give a 13% reduction in rpm. In my case with 33's and standard diff ratio I would be looking at 2000rpm@100kph and 2200 at just over 110kph.

Would many be interested in this gear set as I will probably have to get a few sets made to make the cost viable. What do people think?
 
I'm sure there would be people interested, however have you gone to a design company to get an estimate for this to be done?

Having custom gears made costs tons of money if you want it done correctly.
Just because a machine shop tells you they can make one doesn't mean you want to run it in your truck.
The amount of different forces and loading placed on gears is pretty substantial. I personally wouldn't run an aftermarket gear unless I knew it underwent a bunch of engineering analysis for stress and loading.

Just my two cents though.
 
Those are pretty much exactly the rpms I get with my HJ60 and auto, which has 0.717 overdrive,
and 31" tyres.
 
I'd love a deeper 5th in my h55, but I can't say it's a huge priority. I just run my 2fe (rebuilt, balanced bottom end) at 2900-3100 all day long at 70-75mph (31.5" tires and 4.56 diffs). Not exactly ideal, but so far it's working out just fine in practice... It'd be a lot easier to regear the diffs, but depending on the price I might be interested.
 
The issues are

Who is manufacturing the gears?
Is it engineered or reliable?
Of course, the cost of the gears?

Safari has the 5th taller gear. However, is not meant for H55F, is for R151.
If Safari is responsible in manufacturing side, peace of mind then.:grinpimp:
 
Would make to big a step between 4th and 5th gear, you would be constantly up and down gears. running 4.11 diff gears would give the rev range you want in 5th with better spacing for the other gears and you could use genuine toyota easily obtained parts.
just my 2c worth.
 
I'd also love a deeper 5th gear in my H55. While you're at it, think you could come up with a lower first gear?
 
I was planning on getting a reputable gearbox manufacturer to have a close look at it for me.
My work place often gets custom gears made for race cars, haven't seen any reliability issues with them. If it looks too expensive I will be fixing up the old fairey overdrive. Even driving in 4th plus overdrive is a lot more pleasant than original 5th! The old diesels don't sound comfortable anywhere near 3000rpm!
.
 
RAMZ said:
why not get a ranger torque splitter underdrive. :hhmm:
Click to expand...
This, only buy in the overdrive version. That would allow splitting gears too. With the H55 it would give a total of 20 forward gears and 4 reverses.
 
Any feasable way to attach a Gearvendors overdrive unit?
 
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