Differences between 94 1HZ & 91 HDT running gear

[stinger]

I have recently sourced myself a 1991 HDT GXL 80 Series Cruiser. I also have a 1994 HZJ 80 series (which has been rolled).

I am looking at moving a lot of my running gear from my HZJ to the HDT and am trying to work out any differences between the two. Main issues are:
1. Diff ratios - are they the same (my 1HZ enitre axle assemblies have been rebuilt so in great condition). I know the 94 also had upgrade brakes.
2. Transfer Cases - HZJ is part time, HDT full time, would rather run part time case due to Long Field axles and 5 inch lift, but is there any variation in the internal ratios.
3. Gear Box - any difference in ratios?, just wondering...
4. Clutch - again my rebuilt in the 1HZ, but I think the HDT had a different clutch

I have tried to search these out but no luck.
Thanks

[80's_delirious]

I have recently sourced myself a 1991 HDT GXL 80 Series Cruiser. I also have a 1994 HZJ 80 series (which has been rolled).

I am looking at moving a lot of my running gear from my HZJ to the HDT and am trying to work out any differences between the two. Main issues are:
1. Diff ratios - are they the same (my 1HZ enitre axle assemblies have been rebuilt so in great condition). I know the 94 also had upgrade brakes. ratios are all the same, brake upgrade happened in 92
2. Transfer Cases - HZJ is part time, HDT full time, would rather run part time case due to Long Field axles and 5 inch lift, but is there any variation in the internal ratios. ratios are the same, but the rear driveshaft are different lengths
3. Gear Box - any difference in ratios?, just wondering...1HD-T had higher 1st and 2nd gear ratio, all the others are the same, the boxes are essentially the same
4. Clutch - again my rebuilt in the 1HZ, but I think the HDT had a different clutch the 1HZ had 275mm clutch and 21spline input shaft for the gearbox, 1HD-T had 300mm clutch and 14spline input shaft on the gearbox.

I have tried to search these out but no luck.

Thanks

[stinger]

Wow, that was quick and very detailed, exactly what I was after. Thanks

I like the idea of lower 1st and 2nd gears, but would like to keep the clutch out of the HDT.

Can you swap the input shafts between boxes so I keep the low gearing and the bigger clutch? Or would recomend just getting lower gears for the transfer case?

[80's_delirious]

To swap the input shaft, you have to dis-assemble the whole box, not a good prospect unless you intend to do a rebuild.
You can use the 1HD-T pressure plate and buy an Isuzu NPR truck friction plate to get the 300mm clutch.
The 1HD-T handle the higher gearing pretty well unless you are in steep rocky stuff.

Transfer gears would be good if you do a lot of steep offroad work

[stinger]

I like to use the car for slow technical stuff so the lower gearing sounds good to me.

Checked out marks and lower gears for transfer case $1300 for a set of gears.

The Isuzu truck frictionplate sounds like the easy way out but I want to keep both vehicles running, so might just swap the transfer cases and look at gearing options latter if I am not happy.

[stinger]

Just an update incase anyone else was looking at the same thing...

I just dropped into Direct Clutch Services in Brisbane (Albion) to get a new clutch, friction plate and bearings just to replace the standard items in the 1HDT motor and gear box.

While there I posed the question to them about mating up the 1HZ gear box to the 1HDT using the larger clutch... Guess what, no problems, had the parts sitting on the shelf. So I got the larger pressure plate & clutch with the right internal spline to take the standard 1HZ gear box output shaft... The part numbers on the reciept were "DCS HDJ75 Clutch Kit 119U + 225"

[TheBigBoy]

DCS is awsome. I sat down with them and got a clutch I couldnt be happier with. Higher spec than a tuff clutch, Isuzu torque cover, super high pressure plate, organic material so soft on the foot. Really know their stuff and would highly recommend them.