GCC Spec 80s with H4 Button…what does it do?

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I’m shopping around for an 80 while I’m stationed in Bahrain. Every one I’ve looked at so far (2x automatic, 1x manual) has an H4 button in where the CDL switch is normally located. I’ve asked for help in the Importing forum, but no help there. Hoping some of you GCC residents here can help me out.
What does that H4 button do? Are the GCC 80s not full-time 4WD, like the 60s? All three trucks I’ve seen, the H4 button doesn’t indicate anything at all on the instrument cluster, and I haven’t crawled under in the dirty street/sand parking lots during rainy season to grab the front driveshaft.
GCC residents, is there anything I need to keep an eye out for while I’m on the hunt?
 

WarDamnEagle

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I figured with 8 different engine combos in 80-series around the world with a lot of models, some may have come with it. As you are well aware the vacuum actuated tcase was used on 70-series all through the 1990’s. That is also why I said looking at the tcase solves the mystery. Perhaps someone swapped in a 70-series powertrain? Or FJ62. 🤷🏼‍♂️

Cheers
Doubtful any swaps like that in Bahrain.
 
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Ok, so here's the deal. Those rigs have a HF1A part-time transfer case. Most of those are manual lever shift, but apparently there's an option for a "motor shift type" which uses the H4 switch and a motor actuator, as opposed to the "direct shift type" which uses the lever. This is described in RM184E, looking at page TF-49. What does the transfer shift knob look like on these rigs?
I didn’t take a photo of the actual transfer knob, but the options are:
H
N
L4
DCEA76DF-01E8-43B7-9193-6CEE64EB7B6B.jpeg
 
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It makes sense to me that they have a part time transfer case. I just don’t get why there’s no indication at all whether the truck is in 2 or 4.
 
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I didn’t take a photo of the actual transfer knob, but the options are:
H
N
L4
View attachment 2882455
Figured as much. So the way these transfers work, it looks like you can only switch into H4 using the electronic switch to drive the actuator. You still have manual lever shift to get into L4 though, which will manually enable the front prop shaft along the way. Either way, the "4WD" light on the cluster will light up based on the switch on the transfer case which indicates whether the front prop shaft is engaged.

I honestly don't know why anyone would want this kind of config, but there you go.
 
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And just to be perfectly clear, this is different from "CDL" because there's still no centre differential to lock. All this H4 button does is drive a motor actuator to enable the front prop shaft. So instead of the traditional "H2, H4, N, L4" shift pattern on the lever, you end up with "H, N, L4". So the switch between H2/H4 is electronically controlled.
 
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Figured as much. So the way these transfers work, it looks like you can only switch into H4 using the electronic switch to drive the actuator. You still have manual lever shift to get into L4 though, which will manually enable the front prop shaft along the way. Either way, the "4WD" light on the cluster will light up based on the switch on the transfer case which indicates whether the front prop shaft is engaged.

I honestly don't know why anyone would want this kind of config, but there you go.
So either the light is bad or the motor actuator is bad. Easy way to tell would be to put it in H4 and grab the front shaft. I guess the next one I look at, I’ll need to be ready to crawl under the truck. Thanks for your help.
 

TomH

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I never knew the Land Cruiser had this option but 1st gen Tacoma's / 3rd gen 4Runner's have a push button 4-high system, only the button says 4WD and is mounted on the shift lever. Been using a button for 4-high on my Tacoma for 25 years now. It allows shifting into 4-high at speeds up to 60 mph.
 
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I never knew the Land Cruiser had this option but 1st gen Tacoma's / 3rd gen 4Runner's have a push button 4-high system, only the button says 4WD and is mounted on the shift lever. Been using a button for 4-high on my Tacoma for 25 years now. It allows shifting into 4-high at speeds up to 60 mph.
The same is actually true of the lever shift type. You can swap between H2/H4 when on the move, no need to stop. I think the owner's manual mentions something to this effect too, but I'd have to check.
 
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Not in USA market 80's.
There's synchro rings on HI gear in Aussie H2FA tcase, not USA version.
I'm talking about on the HF1A between H2/H4. That shift is safe at any speed, no need to slow down or press the clutch. Since I had it open already:
1641184767957.png


I slow the vehicle down before switching to/from L4 because of the extreme speed differences, but if you're going slow enough and use the clutch, you don't have to stop for that either.
 

mudgudgeon

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I'm talking about on the HF1A between H2/H4. That shift is safe at any speed, no need to slow down or press the clutch. Since I had it open already:
View attachment 2882475

I slow the vehicle down before switching to/from L4 because of the extreme speed differences, but if you're going slow enough and use the clutch, you don't have to stop for that either.

Yeah, I realised that about 3 seconds after I posted
 

80t0ylc

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Not in USA market 80's.
There's synchro rings on HI gear in Aussie H2FA tcase, not USA version.
The US spec 80's all seem to have the center diff or tcase offset so both drive shafts and axle diffs are also offset (or not centered on the axle left to right). My question is: Is the H2FA tcase rear drive shaft in line so rear diff is centered on the axle? The reason I ask is that I've always thought that for a part time sytem, that configuration is most efficient. Straight through in 2WD to the rear would spin fewer gears in tcase and be less drag on drive train. As opposed to the OEM 80 series setup where both drive shafts are offset. Another reason why I believe that part time conversion of the OEM tcases with free wheeling hubs, still doesn't give you much better mpg. I kinda like the H4 part time setup. Seems like it would be more fuel efficient.

@TXinVA if the H2FA tcase is confirmed straight through design, you might want to re-check one of those 80's you looked at or any others you look at with the H4 button just to see drive train configuration. I know I'd want to confirm that if better mpg was a priority.
 
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So either the light is bad or the motor actuator is bad. Easy way to tell would be to put it in H4 and grab the front shaft. I guess the next one I look at, I’ll need to be ready to crawl under the truck. Thanks for your help.
Thought I'd reply to this because I realised the quickest way to figure out why it's not lighting up on the dash is just to pop it into L4. If the "4WD" light doesn't illuminate on the cluster, it's the bulb, wiring, or position switch on the TC that's to blame. You will be in L4 if you put it there using the shifter, regardless of whether the H4 switch is pressed or not.

If you don't get the 4WD light when you press H4, but you do in L4, it's the motor actuator, wiring, or H4 switch that's faulty.

Also note, you might have to move the vehicle a few inches for H4 to engage. There are some internal positions where the HF1A doesn't let you lever shift into H4 from H2, or doesn't light up on the dash when you do. Moving slightly makes it easier to pop in, and the movement shifts whatever needs to move inside to press on the position switch. I suspect the motor actuator will be similar, in which case it's probably easier to get H4 to engage when rolling slightly.
 

mudgudgeon

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The US spec 80's all seem to have the center diff or tcase offset so both drive shafts and axle diffs are also offset (or not centered on the axle left to right). My question is: Is the H2FA tcase rear drive shaft in line so rear diff is centered on the axle? The reason I ask is that I've always thought that for a part time sytem, that configuration is most efficient. Straight through in 2WD to the rear would spin fewer gears in tcase and be less drag on drive train. As opposed to the OEM 80 series setup where both drive shafts are offset. Another reason why I believe that part time conversion of the OEM tcases with free wheeling hubs, still doesn't give you much better mpg. I kinda like the H4 part time setup. Seems like it would be more fuel efficient.

@TXinVA if the H2FA tcase is confirmed straight through design, you might want to re-check one of those 80's you looked at or any others you look at with the H4 button just to see drive train configuration. I know I'd want to confirm that if better mpg was a priority.

All 80 series have the same family of tcase.
Output shaft configuration is the same on all.
The main difference are
1HFA - part time
2HFA - full time
2HFAV - full time with viscous coupling.

There's minor differences in different markets such as synchro rings on high gear in Australian models with 2HFA* but not USA models,
PTO cover plates in some markets not others.

Going by the functionality nemesis posted, the H4 button has got to be controlling an actuator to engage the front drive shaft, and possibly locking hubs.

It would be interesting to have a VIN and built plate for a vehicle with the H4 button to see what the differences are
 
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As for a VIN, actually mine comes up with the H4 system being a valid option. The H4 switch is listed as valid for my vehicle. At the other end, there are four possible part numbers listed for my transfer assy based on the VIN:
36130-60031 - "Standard" HF1A transfer, which is what my vehicle was actually fitted with.
36130-60071 - HF1A transfer with PTO (Power Take Off)
36130-60041 - HF1A transfer with ELC (Electric Control Transfer - the H4 switch)
36130-60081 - HF1A transfer with ELC and PTO

EDIT: And here's the actuator plus gear (36410-60050) which is still available new from the looks of it:
1641213962364.png
 

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