80 series differential on a 40 series?

[rideglobally]

Diamond Axel is building my rear axel housing. instead of taking the differential on my 40 series i am thinking of changing my differentials front and rear to an 80 series. my rear differential came with a locker from Australia and i am thinking i should not take that apart, someone else can use it.

what is the difference between an 80 series differential and a 40 series, which one is better. if both are the same the easier route for me is to get another 40 series differential and just change out the rear. what do you all think?

i have a 12ht engine with a 5 speed transmission...... thanks

 

[amaurer]

Diamond Axel is building my rear axel housing. instead of taking the differential on my 40 series i am thinking of changing my differentials front and rear to an 80 series. my rear differential came with a locker from Australia and i am thinking i should not take that apart, someone else can use it.

what is the difference between an 80 series differential and a 40 series, which one is better. if both are the same the easier route for me is to get another 40 series differential and just change out the rear. what do you all think?

i have a 12ht engine with a 5 speed transmission...... thanks

You can use an 80-series rear third in the front OR rear of your 40.

But you can't use an 80-series front at all - its a high pinion design.

80-series rears also came in an electric locking flavor, which you can use in a 40-series IF a) you have a full floating rear axle, and b) you buy a special axle shaft. As lockers go, it has a weakness in that, if it breaks an axle shaft, removal can be very very complicated (like, cut-the-axle-housing-apart complicated). However, as for strength of the differential carrier itself, the locking type from an 80 is definitely meatier than a 40 carrier (dunno how the non-locking 80-series type compares). Still, you're going to break a lot of other stuff before the carrier pops, IMO.

80-series rear locking diffs take some fiddling to install. Here is my thread on it: https://forum.ih8mud.com/40-55-seri...tall-40-series-ff-rear.html?highlight=elocker

80-series rear standard diffs should be a drop-in, though I suspect there are no advantages.

 

[rusty_tlc]

The 80 R&P work great in a 40 differential. stock ratio is 4.10 compared to the 40 stock ratio of 4.11 but it doesn't cause any problems if you mix them on the F&R.

I'm sure someone will correct me if I'm wrong but I believe the 80 has a fine spline pinion shaft that is supposed to be more robust than the 40 pinion gear splines.

 

[rideglobally]

You can use an 80-series rear third in the front OR rear of your 40.

But you can't use an 80-series front at all - its a high pinion design.

80-series rear locking diffs take some fiddling to install. Here is my thread on it: https://forum.ih8mud.com/40-55-seri...tall-40-series-ff-rear.html?highlight=elocker

80-series rear standard diffs should be a drop-in, though I suspect there are no advantages.

am i reading this correctly, i can use a 80 series rear on the front? i am thinking of using the aussie lockers (auto locking) on this set up. what do you think of that. if there is no advantage to installing an 80 series differential on my 40, it is more simple for me to just install a 40 in the rear, that way i do not have to replace the front differential.

The 80 R&P work great in a 40 differential. stock ratio is 4.10 compared to the 40 stock ratio of 4.11 but it doesn't cause any problems if you mix them on the F&R.

is this correct you can mix it??

thank for all the info.

 

[rideglobally]

what is gear ratio of my front differential?

i have search and i could not find it. i know there is a trick where you mark your drive shaft and tire then rotate the drive shaft to figure out the gear ratio. how does it work? how do you determine ratio by the number of rotation?

my cruiser is a 1982 hj 47 from Australia. what is the gear ratio?

i am thinking of putting a 1996 80 series on my rear, the differential is from the US, i am told it is 4:11. if my front differential is 4:11 it will save me a lot of money..... thanks

 

[Chamba]

Unless it has been changed, your 82 HJ47 from Australia has 4:11 gears in the diff. The 3:73 from 79-83 in the FJ40 (and all the US Spec FJ60s) was a US Spec item, and as far as I know, never came down here.

I brought a set back with me when I was home a few months ago to put in my FJ40 LX, as I could not find them here. They were an option here in the HJ61 with the 12HT, but they are a bit hard to come by in the wreckers.

Cheers,

Josh

 

[rideglobally]

i am certain that they have not been changed.... thanks

Unless it has been changed, your 82 HJ47 from Australia has 4:11 gears in the diff. The 3:73 from 79-83 in the FJ40 (and all the US Spec FJ60s) was a US Spec item, and as far as I know, never came down here.

I brought a set back with me when I was home a few months ago to put in my FJ40 LX, as I could not find them here. They were an option here in the HJ61 with the 12HT, but they are a bit hard to come by in the wreckers.

Cheers,

Josh