Posted by Cees Willig from Holland on December 26, 1999 at 20:42:07:

In Reply to: whine from gearbox posted by Tony devon uk on December 22, 1999 at 08:17:09:

Hello,

If whine in 1, 2 & 3 but NOT in 4th, then gearbox itself is subject of investigation.
4th = prise directe, hence input ex clutch is direct connection to output to transfer case (no real heat development under (heavy) load, hence ideal for prolonged towing, gearbox virtually does not wear in this gear).
In 1, 2 & 3 the input is connected via the input shaft gears to layshaft to corresponding gear on output shaft.

If whine occurs in older gearboxes, then this is indication of (taper) bearing failure.
Of course in your situation at this stage it will be difficult to judge taper bearing preloading by rotating input shaft by hand and engaging various gears (requires experience), at new bearings this is relatively stiff going, requiring a mild break-in load & refresh gearbox oil after, say, 1000 miles. Mild break-in load (not too high revs etc., no real / heavy labour) allows notably preloaded taper bearings to settle without causing damage (new taper bearings are normally set slightly stiffer than already run in bearings (at e.g. re-using bearings which are in good shape)). Box is after oil refresh and 1000 to 2000 miles ready for the real loads, refresh oil again after 3000 to 4000 miles (gearbox wears mostly by metal (wear) parts floating around and getting in between, notably, bearings, creating local overloads on running surfaces and in due time scratches and worse such as pitting. Hence regular oil change greatly prolongs gearbox mission life. I use the amount of deposits on the magnetic plug as indication to decide next service interval, as soon as minimal wear is present, one can prolong the interval accordingly.

If gearbox is assembled by experienced mechanic, it will be very rare that bearings will fail prematurely. Faulty fitting procedures are most likely cause of bearing failure (notably uneven forces at pressing bearing running ring into seat/ misalignment by not secure enough fitting, putting force on wrong area. However, statistically about 20% of bearings fail before the indicated bearing life (data when I did vacation scholarship at SKF already some time ago).

By the way did you know that a taper bearing roll has a "circular" surface of (depending on bearing size) 1 to 3 micro meter (1/1000 mm to 3/1000 mm) above the ideal taper line? This is required to prevent a minimal misalignment wrecking the bearing (if absent then load is taken by either top or bottom of the taper roller) and under preload is sort of flattened by the load. Smoothness of the bearing surface is also very important for bearing life, don't save money overhere and apply the smoothest surface (class 1 or 2 at SKF if I am correct, class 3 has the standard surface spec. and class 1 and 2 receive substantial additional surface treatment). Having worked in a bearing manufacturing plant knowing the vital details on the micrometer scale, it is amazing how these parts are manufactured which such small tolerances and at impressing throughputs.

Note that LR gearboxes are rarely quiet, especially the older ones. Our 1983 LR 110 originally featured LT95 box which played a slightly different tune for each gear selected right from the start (and in 4 th one could estimate the transfer boxes' temperature by the loadness of the whine), synchromeshes were also exceptionally clear to hear functioning (an audable check on gearbox functioning). Sadly the LR factory did not support 200Tdi matched to LT95, hence 5 speed gearbox.

If possible get sound experience with another Series III and interview owner on sound development over the year.
From experience on Series I & II, IIa (I grew up in these, some years ago a refresh on/ off road in a IIa, a fantastic standard), I know that the gearbox does play its tunes, especially when the saddle/ seatbase is bare metal. Try some carpet, you would be amazed how much more civilised it becomes.

Of course make sure oil level is OK and proper oil spec is applied.
Have you already drained existing oil and inspected it? Should a taper/ ball bearing having failed, no doubt that metal chips can be found in the drained oil.

Success, Cees Willig