I thought the axle shaft diameters were the same on the 30 spline axles? How are the lockers interchangeable if they are not. I also remember the Australians saying once that the semifloating axles were actually stronger than the fullfloaters as they were a bit larger. Not in bearing load carrying capacity, but in actual axle strength. It could have all been hogwash. I'm not an engineer. Birf stength the 80s are like 30% larger.
As far as Shaft diameter is concerned, the area wher the shaft seals ride is larger in diameter on an 80. EG the part number for the tube seal on a 40,55,60 is 90311-33085, indicating a shaft diameter of 33 mm and the 80 series part number is 90310-35010, indicating a shaft diameter of 35 mm.
tube seal and shaft size are irrelevant.....on a FJ40, the shaft "enlarges" at that point to provide the seal surface. I'm gonna go on a limb and state the 80 enlarges more...lol
The side gears of a 40 and 80 series are both 30 spline, front and rear. Since spline "sizes" are all relatively identical, this is your weakest point. In order for any size diameter shaft to fit into that side gear, it must neck down to that 30-spline diameter. Additionally, on birfields, the FJ40/55/60/62 is 27 spline where it inserts into the birf, and that's why 90+% of all front end breaks occur at this neck down point (assuming upgraded birfs which in stock form is weaker) (even shafts designs which eliminate the retaining clip groove are weakest at this point)
Break a rear FJ40 shaft (I have) and it breaks in the spline area, just where it begins to neck larger for the balance of the shaft size.
Additionally, a thicker shaft allows less opportunity for equal twisting distribution down the entirety of the shaft. PIG from PolyPerformance is promoing 300M minitruck shafts right now, he's kept the diameter SMALL and greatly strengthened the material...this will allow the shaft to deflect more under shock load, but still be stronger. (see the Vendor forum at pirate4x4.com/forum)
Birfields, the 80 wins hands down. But front inners and rears, because of the spline counts, are effectively similar.
Given identical materials and design, spline counts = strength. 27 vs 30 vs 31 vs 35 vs 40....since each spline is the same size, the only way to add more splines is to increase diameter.
(BTW, am I allowed to argue with cdan, or will he vaporize me?!?) hehehe
>> (BTW, am I allowed to argue with cdan, or will he vaporize me?!?) <<
Even though C-Dan was "Queen for a day", I doubt anyone got screen shots of his lofty status. The smartest thing you have done this year is remove his "Forum God" standing and return him back to Hall Monitor. You should have no fear of vaporization by C-Dan.... However, I *do* have screenshots of my ability to do "Global Destruction" on this forum. Unfortunately this takes all of us out at the same time.
Now for more discussion, full float versus semi-float. A fullfloat rear axle shaft is sized identically down it's entire length, in order to maintain it's removeability status without dropping spindles and such. However, semi float shaft is LARGER throughout the entire length, excepting the spline area. STRENGTH-wise, the semi is stronger, however greater vehicle load capacity is maintained with a fullfloat since the weight is on the tapered bearings and not on the shaft itself.