Toyota V6 3rd's and 4cyl 3rd's

MIG'DHORSE · Oct 19, 2006

Toyota V6 3rd's vs. 4cyl 3rd's

is it possible to swap a v6 3rd member into an 85 front axle without trouble? And truly, what is the difference between the two? I know the 4cyl is weaker, but is it that big of a strength difference? I have 2 4 cyl 3rds and im wondering if the 5.29 and arb/ detroit i have planned to install in them will be worth installing in the 4cyl 3rds, or if i should just puke up some more cash and go for the 6 cyl or hi pinion. Thanks.

Tech Tim · Oct 19, 2006

MIG'DHORSE said:
is it possible to swap a v6 3rd member into an 85 front axle without trouble? And truly, what is the difference between the two? I know the 4cyl is weaker, but is it that big of a strength difference? I have 2 4 cyl 3rds and im wondering if the 5.29 and arb/ detroit i have planned to install in them will be worth installing in the 4cyl 3rds, or if i should just puke up some more cash and go for the 6 cyl or hi pinion. Thanks.

Yes, the 3rds will swap back and forth.

The big differences between the two:

6 cyl side bearing bore is 83mm ID
4 cyl side bearing bore is 80mm ID

6 cyl differential bearing journal is 50mm OD
4 cyl diff bearing journal is 45mm OD

With a 50mm brg journal OD the 6 cyl differential is stronger and will allow a larger dia. axle shaft to be installed. Can get custom cut side gears for a 6 cyl ARB, don't know if anyone is doing larger spline sides for other lockers.

You can put a 6 cyl differential in a 4 cyl case with a conversion bearing.

The larger 83mm bearing will give a better side load than the smaller 80mm bearing, however the 6cyl to 4cyl side bearing will have a better radial load, so it would be stronger for the loads we put on differentials. But the problem with that swap is:

The 6 cyl 3rd has a bit more webbing on the outside, this will help keep the pinion from flexing as much as it does in the 4 cyl 3rd.

MIG'DHORSE · Oct 19, 2006

...so if i want 30 spl longs, then does that mean i need a v6 3rd. because the 30 spl are a thicker axle? i'm just trying to get all of this straight before i start my buildup. thanks tim.

skrause · Oct 19, 2006

MIG'DHORSE said:
...so if i want 30 spl longs, then does that mean i need a v6 3rd. because the 30 spl are a thicker axle? i'm just trying to get all of this straight before i start my buildup. thanks tim.

No, they'll fit any Toy 8" diff.

Tech Tim · Oct 20, 2006

MIG'DHORSE said:
...so if i want 30 spl longs, then does that mean i need a v6 3rd. because the 30 spl are a thicker axle? i'm just trying to get all of this straight before i start my buildup. thanks tim.