79 series diff in bj40???

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Joined
Jan 21, 2006
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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:
 
roverx said:
have a few qs:
1. is the 79 rear dif a center diff??

Offset diff just like a 40 or a 75.

roverx said:
2. how wider is the track compared to the bj40/ difference in axel lenght

I can't tell you for sure, but the published track widths are within 10mm from a 75 series. Of course those figures are affected by wheel offset and tire widths. What I see is 1410mm for a steel split rim and 1460mm for the RV package with alloy rims.

roverx said:
3. can the differential assembly from a 75 be used in the 79 housing?

No. Different axle shaft spline counts and different gear ratio.

roverx said:
4. would the mod be practical?

No, keep in mind the 79 diff has a 5 lug pattern. And the gear ratio issue above.

Unless you swap the entire 79 front diff (that is entire front axle to you North Americans :) ). Then the steering mechanism would be quite interesting, but probably can be done.

One thing about the genuine disc axle is that the parking brake is not as effective as the parking brake of the drum axle, unless now you have a transfer mounted parking brake. Of course the main disc braking system itself is better in the mud, needs less maintenance, etc. but what you gain in the rear doesn't contribute as much to overall braking performance as gains in the front. You'll gain much better braking by using HZJ75 front calipers on the BJ40.

Do you have access to a 93+ 75 series diff? Those are much easier to use as the wheel bolt pattern as well as the gear ratio are correct.

Dave
 
Thanks dave :)

I guess I'll have to go have a look at the diffs.
 
beanz2 said:
No. Different axle shaft spline counts and different gear ratio.

let me know .. the 75 have 4.11 gear set and the 79 .. ?

Both have ( I thought ) 30 splines 1.31" axle diam right . ?
 
beanz2 said:
4.30

32 splines and larger shaft (not sure of size)

Dave

4.30 .. very very interesting .. I ear that some 80 series come with 4.30 .. ? that's right . ? are those 4.30 interchangables with my 80 series diff right ...
 
Most of the 100 series got the 4.30, but AFAIK the 80 does not. No, the diff wouldn't fit your 80 either.

Dave
 
the auto diesel 100 series got 4.100 diff and the manual got 3.909 the UZJ100 got the 4.3

the auto 81 series got the 4.1 and the manual got 3.7
 
crushers said:
the auto diesel 100 series got 4.100 diff and the manual got 3.909 the UZJ100 got the 4.3

the auto 81 series got the 4.1 and the manual got 3.7

Here all 80 that I know and seen ( auto or manual ) have 4.11 gears.
 

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