15/02/2022
On the bench. Mk8 rebuild day 4
After shrinking the pinion shaft and layshaft rear bearings in, top gear end float is set to 0.010” to match the new bearing installation. Shims are required if clearance is too great, or else the first reverse hub must be precision ground to length.
In this box the hub had to be shortened to accept the new style HB pinion bearing, and the reverse slider was similarly relieved. We use a precision tool room surface grinder in house to ensure the end face is accurately ground to length and square to the spline bore. We then shim the stack on the fork setting jig to accurately match the in case clearance.
Next step is to install the selector rod detents and and lockout plungers, ensuring adequate rod retention in gear and neutral and an even shift pressure.
As the selector forks have been disassembled (and we’re replaced in this rebuild) the fork position must be adjusted to ensure full dog engagement without over engaging the clutch ring. Over engagement causes increased wear, difficult shifting and costs horsepower. Under engagement can cause increased wear on the corners of dogs on both gears and clutch rings as well as jumping out of gear.
Forward gear forks must be adjusted in the jig to enable measurement of the 0.005” clearance on the dog teeth.
To check for correct adjustment of the reverse slider we always scope the box for visual confirmation that everything is meshing properly and not binding.
The complete gear set is now ready to install with the layshaft stack. Careful insertion is required to ensure the input shaft spline and sleeve doesn’t become displaced, because it isn’t supported when the box is out of the car.
Torque the pinion and layshaft nuts, fit the selector finger (hockey stick) and end cover. A quick run through the gears, and it’s ready to go back in the car.
We can perform service, repair and fork adjustment in house without having the main case as long as top gear end float has be verified prior to the gear set and bearing carrier being sent in.
Now if only I can keep this box in site at PI…
