My previous post on this subject outlined what I discovered when opening up the old gearbox. In short, the 1st gear bush was inserted the...
An inevitable whine!
The gearbox had a nasty whine (typical, I suppose, of old Series Landy's that have worked hard...) when driven before strip-down, which increased in tempo and pitch as you moved up the gears and increased speed. I thus thought it might have been a differential, transfer case, or gearbox output shaft bearing. So, when dismantling the box I was on the lookout for a nasty surprise, like a collapsed bearing or badly worn gear.
Following the workshop manual closely, I stripped the box down to its individual components, taking lots of photos and observing each bearing and component in detail hoping to find an obvious cause of the horrendous whine. To my disappointment (ironically), every bearing was a smooth as silk, and every gear was crisp and clean, as if brand new. The elusive cause of the whine was not making itself known, and I was becoming worried that I'd have to reassemble the box not knowing if I had found the cause or not (not ideal, as the gearbox is probably the hardest part to get to once the vehicle is assembled and complete).
Whilst pondering over the possible cause of the now infamous whine, I noticed that the 1st gear in the main gearbox had some heat marks on it. It was a black/blue colour, indicating it had reached fairly high temperatures at some stage. On trying to remove the 1st gear, I noticed it was stuck on its bearing, and had to be encouraged off using a press. Once off, it was immediately apparent what the issue was. The bearing had cracked through in several places (no doubt due to the heat) and was binding on the 1st gear. As the 1st gear spins on its bearing at all times other than when the vehicle is traveling in 1st, this would explain the observed effect.
The obvious question then was, what caused the bearing to get hot in the first place. On close inspection, it became apparent that the bronze bush had been inserted onto the main shaft backwards, and the oil feed holes in the 1st gear did not line up with the grooved oil passage in the bush. In the picture to the right, one can even see the black heat mark inside the gear where the (somewhat dry) oil passage on the bush ran, and it is offset from the oil feed hole (it is left of the holes). If oil could not feed the bush as designed, it must have overheated and failed.
When I disassembled the 'box, I laid all 492 parts out neatly and logically on a dedicated workbench, along with all the new bearings and seals I was able to order, figuring I'd thus remember how to put it all back together again..... Er, maybe my brain's not the youthful, effective, just plain sterling version it used to be, because it all looked pretty foreign when trying to figure out how to paste it all back together! Thankfully I had the workshop manual and parts catalogue, else I'd still be playing with the giant jigsaw puzzle to this day.
The main gearbox went together fairly successfully. Not having a lathe, I had to "lap" the bushes using water paper to get the right fit and end-float. Despite the old bearings feeling silky smooth, I did replace all bearings with new, as well as all seals (obviously). I tried replacing the notoriously bad selector shaft seals (square, plastic, archaic items) with o-rings, figuring they would provide a snugger fit, and thus keep the gear oil safely ensconced where it should be (which, on a Series Landy, is typically on your driveway or workshop floor!).
The transfer box posed a more complex and taxing exercise... Despite getting the perfect end-float on the high-speed gear, and the perfectly on-spec pre-load on the tapered roller bearings of the output shaft whilst on the bench, when the shaft was inserted into the box (via an extremely complex gymnastics routine, requiring Olympic-level contortion and flexibility, nerves of steel and the patience of Job!), everything went out the window! A total of five such Olympic routines was required before the shaft was perfect (in the end, it was merely a non-cooperative circlip that was the culprit).
To finish the job off, each and every nut, bolt, plate and clip was zinc plated before being returned to its rightful home. Even though the insides of the transmission brake (a uniquely Land Rover arrangement, whereby the handbrake locks the drive shaft and not the wheels) were destined to be covered in gear oil (from the uniquely Land Rover arrangement of insisting the rear output shaft MUST leak no matter what you do, and in this case, directly into the transmission brake housing...) and covered with a brake drum, I still wanted all the internal parts to be plated, and look like new. The end result was quite pleasing.
The final product looked really fine, and even better than a new one would, I imagine. Knowing the insides were all perfect and within spec was also reassuring. Not being able to wait for the engine to be ready before fitting to the vehicle, I went ahead and lowered the gearbox into her final resting place (hopefully that is not a metaphor!). Can't wait to try her out on the road!