Anyone found the limits of F series axle (now with twisted axles photos)

[1JZ-Rolla]

I had a pair of my F series axles twist about half as much as that, but in the reverse direction, cause it happened when the tailshaft snapped at speed, sheared the pinion at the flange, then bound the ring & pinion gears locking the rear wheels I guess you could say that was not really normal operating conditions though.......

It appears that you have less than original contact between the splines of the axle and the "spider" gears in the diff centre. Mine is the same since switching from an MA61 LSD centre to the Toyota Tru-trac, the MA61 covered an extra 5mm or so of the axle. Would this affect anything with how much force it takes to twist, or would it only change the point where it eventually breaks?

Cheers
Phil

[TheStitt]

i'm not sure,

[oldcorollas]

given that the spline area is weaker, if you have enough force to twist it, it will twist regardless of spline engagement.. that just changes the area of non-twisted spline...

ie... the same torque has to be transferred to the axle. you coudl effectively consider the point just outside the engaged spline to have that full axle torque, regardless of the engagement length....(to a point..)

reducing spline engagement may increase the size of the elastic twist of the open splined area... and having no exposed spline is probably best, but realistically, there is always some spline exposed, and that will always have potential crack starters, or, area for twist.

can the engagement be increased by altering the end of the housing?

[LeeRoy]

What about using longer axles or having some longer axles shortened to suit?

[The Real Roadrunner]

cant get longer F series axles than what is already in there unless you go billets.

if you reduce the non engaged spline i believe that it will 1 take more force to twist it but the downside is that you are reducing the amount that it can twist b4 it shears completely)

that spline engagement length is definately 5mm shorter than it should be though and is certainly something i would look into fixing.

cheers
linden

[1JZ-Rolla]

that spline engagement length is definately 5mm shorter than it should be though and is certainly something i would look into fixing.

cheers
linden

I think its an inherent problem when fitting an IRS centre to a live F-series housing, so anyone that has fitted true-trac or IS200 torsens to corona/crown diffs will have the same issue, just most get away with it in lighter cars/less power/no traction situations perhaps. Stitty's car with 7 people on board and hektic clutch dumps probably doesn't fit this category

I noticed the problem with mine on first assembly after swapping out the MA61 centre, but as you mentioned Linden, longer billet axles or a shorter diff housing are the only methods to fix it. I expected mine to have twisted with the harsh shifting of the auto, but on inspection recently they are surviving........... wait till we get to WSID with sticky rubber though

[gianttomato]

Put it in on the other side and see if you can untwist it.

As for further engagement, I can't remember what limits things here. Can you mill a bit off the mounting face of the diff? Or do the bearings limit how far the axle goes in? Can the axle be machined a little so the bearing sits further in? I'd imagine this will depend on whether the diff is an MS112 style or MX13/23 one.....

[The Real Roadrunner]

Put it in on the other side and see if you can untwist it.

As for further engagement, I can't remember what limits things here. Can you mill a bit off the mounting face of the diff? Or do the bearings limit how far the axle goes in? Can the axle be machined a little so the bearing sits further in? I'd imagine this will depend on whether the diff is an MS112 style or MX13/23 one.....

even tough i think GT was just taking the piss, please put them back together the same way they came out. metal doesn't seem to take too well to being worked back and forth as it will "work harden" and shear very easily.

the only way to get them to sit in further is to shorten the housing by taking the carriers off then removing metal from the tubes and welding the carriers back on, if you just move the bearing on the axle it will change the offset of the mounting flange and cause issues with brakes not lining up as they should.

cheers
linden

[gianttomato]

even tough i think GT was just taking the piss...

Completely taking the piss!

Completely overlooked the brakes not lining up.