5 speed Transmission and 4WD switch Questions 1995 80 series 1HDT (1 Viewer)

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I have exactly the same set up as you. There is a green 4X light on the dash when the button is pushed. your bulb may just be burned out
Same trans too. I have no problem down shifting from second to first and just use the 90 wt they sell at the bomba in Cobano (bulk) I do see the odd 151 for sale on Market place.
 
You'll find to down shift from second to first with the H151 behind a 1HD-T, you almost need to be at a slow walking speed.
Double declutching can help, and stab the throttle to bring the engine speed up 500rpm as you shift down into 1st

The H150, H151 gearboxes are known to have issues with synchro rings particularly in the early years

I highly recommend changing the gear oil to redline as mentioned earlier, or I like to use Castrol VMX-M (the last 'M' is important). It's the same grade as what Toyota specify, but a slightly lighter oil, and has anti friction additives in it. It's a cheap and simple exercise to change the oil, and it can make a huge difference. I find it takes a few 1000 miles for it to really take effect, and changing it again after 10-15k miles helps more.

So, interestingly enough, what I have found is double clutching it and giving it a shot of fuel to bring the RPMs up makes it more easy to shift into first gear at higher speeds. I guess that just lends credence to the "2nd to 1st gear synchros are shot" theory?
 
So, interestingly enough, what I have found is double clutching it and giving it a shot of fuel to bring the RPMs up makes it more easy to shift into first gear at higher speeds. I guess that just lends credence to the "2nd to 1st gear synchros are shot" theory?

Yes probably
It's still very worthwhile changing the oil. Cheap, and easy experiment.
My HDJ81 was a bear to downshift. I was all set to have the H151 rebuilt, then read about the different oils. Changing the oil made it perfectly manageable. Still notchy in some instances when cold, but I never did a rebuild
 
It's also worth checking your clutch is 100% disengaging, otherwise the synchros are trying to deal with the inertia of the engine too and not just bringing the gear to the correct speed.


It's worth remembering the H15# boxes are a big, heavy transmission.
The gears are large and heavy. Much heavier than a typical car transmission, and heavier than other cruiser gearboxes.
It's more truck gearbox than sports car.

The synchros have a lot of work to do.
I taught my son to drive in my FZJ80/H151 recently. It's synchros are a little lazy, and he was clashing gears.
I told him he needed to make a deliberate pause as the shifter passed through neutral, then a slow-ish but definite shift into gear.
 
I am actually driving a manual diesel 200 series here in Dubai which has the H150F box in it. I can't stand the 5th gear and am getting the H152F gearbox in from Australia. Manual LC200 diesels have been de-tuned to 430nm from the factory which (down from 650nm in the automatics). I think the biggest limiting factor is the clutch. I'm finding that it slips a little and shudders in 2nd gear at low RPMs.

After a fair amount of research, the plan is actually to put in a 1300nm billet flywheel/clutch combo from NPC (also in Australia) and a piggyback ECO to bring that torque number up a bit (I'm hoping for around 800nm)

Also to note - the H152 is a direct replacement for the H150 but not for the H151 as I believe they have different input shaft lengths.
 
posted it twice for some reason. Sorry
 

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