When considering acquiring a vehicle for restoration, the chances are that the gearbox will be a manual. Most UK and European cars produced in the Fifties and Sixties were fitted with manual gearboxes, with automatic transmissions much less prevalent than they are today.
If the car under consideration is a runner and can be test driven, the picture will be a lot less clouded with most of the problems afflict gearboxes coming into the light during even the shortest drives.
This could be a result of transmission fluid levels that have fallen below the red line.
If smoke and a burning smell begin to emit from the gearbox housing during a short run, this could mean that either the transmission fluid is burning or the transmission system is overheating.
Another almost sure sign that is all not well with the gearbox is when the gears start to slip or make grinding noises when changing gear or even both!
These problems indicate that the gearbox, while still functioning, has become worn and will need a major overhaul in the near future.
If the engine does not turn over, the situation regarding the gearbox and its state of health will be a lot less clear, although it does not always signify that because the engine does not run, the gearbox is not in good condition.
What challenges lie within the gearbox will remain a mystery until it has been disassembled and is up on the bench.
Before taking this step, the restorer must ensure that all fluids have been drained out of the engine and gearbox.
The next stage can be more of a challenge.
Separating the gearbox from the engine could mean freeing many rusted bolts – a time-consuming process made easier by having a powerful pneumatic impact drill and lots of lubricants.
As in any disassembly, digital photographs should be taken along the way and any parts removed clearly labelled.
Consisting of a series of toothed gear wheels fixed on shafts, gearbox assemblies are located within a closed casing filled with transmission fluid.
The fluid is there to clean the moving parts as well as to keep them lubricated under the constant friction caused when the metal parts engage.
Despite the levels of fluid in the gearbox, its parts are being continuously worn down. The wearing down problem will be exacerbated if the previous owners allowed the transmission fluid levels to fall below the red line, causing intense heat within the gearbox, dramatically increasing wear and tear.
Overhauling a manual transmission should not be outwith the capabilities of a capable mechanic, provided they have access to the specialist tools necessary.
There are no shortcuts to restoring a manual gearbox, with the complete dismantling of the gearbox being a must. Once every part has been stripped down and cleaned, a thorough inspection should be made with each component gone over carefully.
Signs to look for are if any of the gears pitted or grooved or have teeth missing.
Other faults can include damage to the ends of the teeth, meaning that they will need to be replaced.
Gears that have suffered only a few minor dents or scrapes can sometimes be cleaned up with a stone or fine file. If the problems are more serious, the services of a machine shop will be required, or replacement parts can be bought in.
Reconstructing the gearbox is the reverse of dismantling, with the restorer following the steps laid out in the owner’s manual, treading warily all the way.
There are several alternatives available for those who find the thought of handling their gearbox restoration a prospect too much to deal with.
First of all, there are many reputable companies around that will make a professional job of restoring or repairing a gearbox employing well-trained personnel with access to the proper equipment.
This option comes at a price- but may often be the best solution.
Reconditioned gearboxes, if purchased from a respectable company, should come with some guarantee not only that it is in working order but will continue to operate for the next year at least.
Once the gearbox is back in place, any oil seals should be replaced with new and more modern oil seals.
If the restoration vehicle has an automatic transmission and turns out to be problematic, repairing and rebuilding it is an entirely different prospect, usually requiring specialist equipment to do the job correctly.
The best option is to find a professional company and trust the job to them.