When originally assembled, Aristides; the nut is torqued in increments.measuring the preload each time. As nut torque is increased, the spacer starts to collapse - which influences bearing play. There is no specific torque on the nut - it is tightened until the spacer is compressed enough to give the correct preload, indicating correct bearing play.
So the initial nut torque may be anywhere, nominally up to some 130 lbsft. It is immaterial to refitting after a seal change - the nut is torqued to the mark made before it was unscrewed. In this position; the original bearing play is retained by the thickness of the collapsed spacer.
(In theory; if bearings are worn; further, very slight, nut tightening may be done to correct bearing play - but in practice; worn bearings should be replaced…)
The lash on the pinion shaft is the play between pinion and crown wheel. The shaft is moving freely, except for the friction between the shaft and in the bearings - and this is measured by the preload torque on the axle. The preload does not refer to the load/torque on the nut - but the force required to start the axle moving. It’s important that the axle is fully backed, taking up the lash, before the preload torques is measured…
The specs given for preload torque with old bearings is 20 - 25 lbs/in and with new bearings; 30 - 40 lbs/in.
Your ‘8’ and ‘11’ lbs/in is somewhat odd - and does indeed imply that the collapsible was not crushed enough initially to give the proper bearing play. That the preload torque increased with 80 lbs/ft nut torque does imply further crushing.
If your readings are correct; in theory; you should then further increase the nut torque until you reach a preload reading within the specs given. I would dearly like to know what the readings, including releasing torque on the nut before unbolting! But I see no other reason for the low reading - unless something is seriously amiss with the pinion shaft bearings. Or your measuring procedure/tools are plain wrong…
And if the preload torque exceeds 45 lbs/in; the bearing play is too tight - and the collapsible spacer must be replaced - going through the initial preload set-up. Which would be ‘inconvenient’…
The whole point of these operations is to get the bearing play correct - as measured by preload torque…
xj6 85 Sov Europe (UK/NZ)