79 series diff in bj40? (1 Viewer)

Joined
Jan 21, 2006
Messages
15
hi guys!

planning on modifying my bj40 into disks all round. do you guys think that a diff swap with a 79 series diff would be practical (a set is available cheap!), of course would have to weld in new spring anchors.

have a few qs:
1. is the 79 rear dif a center diff??
2. how wider is the track compared to the bj40/ difference in axel lenght
3. can the differential assembly from a 75 be used in the 79 housing?
4. would the mod be practical?

really need some help here guys :confused:
 

Josie'sLandCruiser

Stop calling it a "FJ."
Joined
Feb 4, 2005
Messages
5,261
Location
Seattle, USA
Hi All:

It sounds like you are speaking of swapping-in the whole 79 Series axle housing, not just the third member.

The 79 Series axle assembly is a bit wider than the 40 Series axle assembly. It would require custom spring perches, as you mention. The rear 79 Series third member *might* bolt-up to the 40 Series axle housing (??)

So, your BJ40 has adrum brake front axle assembly? If so the disc brake parts from the 4wd Toyota Hi Lux pick-up can be swapped onto the drum brake axle housing.

Does your BJ40 have a full-floating rear axle assembly? If so front disc brake parts can be fitted to the rear full-floater axle to obtain rear disc brakes.

Regards,

Alan
Seattle
 
Joined
Oct 22, 2011
Messages
92
Hi,

Has anyone any update on this? Has anyone successfully placed 70 series axels beneath a 40 series?

I'd love to see some photos as I'm contemplating this on my 40 series build....

Please pm if you can
 

Tapage

Club 4X4 Panamá
Joined
Apr 4, 2003
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keep in mind 79 series are new .. means 5 wheel studs and front 8" HP .. so if you gonna swap both complete can be done.

Actually with time and $$$ everything can be done .. :D

Another point to see it's for us 79 series came with 4.30 ( HZJ79 ) assuming your 40 axles are 4.10 or 3.70
 
Joined
May 3, 2004
Messages
2,312
Location
Utardia
The simple answer is, no, a 79 series rear end won't work easily.

I looked at a 79 series full floater a few months back. It had the 3" drums rather than the 2", was already set up for a Spring over.

But.

I already had spend the money on 4.88's for my stock Cruiser diff and had a lock rite.
The housing will accept the earlier 'Cruiser diff housing, but the axle shafts won't work as they are 33 spline rather than 30 spline. So you'd need to get some custom full floater shafts made -they are different than the stock cruiser full floaters.

To use the Diff that came with the axle housing, I would have had to obtain a new locker and gearset and go through the setup. The only locker currently available for that diff (other than OEM, which the housing I was looking at didn't have) is the ARB Air locker. While not a bad choice in locker, they aren't exactly inexpensive.

Last, the rims are different as they are 5 on 200mm. So I would have had to obtain 3 rims (2 for each side, 1 for a spare) and would have had to carry 2 spares. In the end, I decided that making that diff work wouldn't have been worth while in terms of time, money and effort.

If you're looking for rear disc brakes and have a semi floater, just do MonteCarlo RDB's, Simple, easy, and cheap.
 
Joined
Jun 25, 2007
Messages
345
Location
Far North Queensland
i am running HZJ75 diffs in my 40,disc all round,not too hard,best mod i have done,it drives unreal now,no diving around on bad roads,stops like a demon also,like someone said anything can be done with time and effort
 
Joined
May 3, 2004
Messages
2,312
Location
Utardia
i am running HZJ75 diffs in my 40,disc all round,not too hard,best mod i have done,it drives unreal now,no diving around on bad roads,stops like a demon also,like someone said anything can be done with time and effort

75 series stuff is pretty much bolt in and go.
Had the FF I was looking at been a 75 series axle, it would be under my 40 as we speak.

the 79 series stuff is completely new and is slightly different enough that using it in a 40 without doing BOTH axles is a PITA.

And Expensive.
 

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