DB2 to DB MkIII Gearboxes, including overdrive gearboxes, reliable & almost leakless gearboxes.
Rebuilding a DB2 to MkIII gearbox looks easy at 1st but the more you fully study them the more complex (or poorly designed !!) they become & certainly aren't easy to rebuild properly, reliably & leakless.
If you look at the Aston Martin DB2 to DB MkIII Workshop manual under rebuilds for gearboxes there aren't any tolerances or measurements, especially how to make the synchro bronze cones work & get the gear pairs aligned, indeed the last paragraph in the WS Manual states 'each gearbox is reassembled in the reverse order of the operations enumerated' without any measuring of tolerances & settings !. A disaster waiting to happen.
For a long time Four Ashes rebuilt gearboxes with assembly 'as the workshop manual', then with the power of the engine being upped all the time & no development of the gearbox & after several breakages, most often of 3rd gears, Chris started to think that the tolerances as we found them whilst stripping & assembling were wrong, so using his knowledge of Manta A series, Classic Mini, MGB & some Ford gearboxes + a great many Workshop manuals & what Jack had taught him, he started to back calculate every gearbox tolerance.
With finding some very interesting documents about DB2 gearboxes, he found that he was exactly right so the 1st 10 or so gearboxes built under Chris's settings were more or less right, so now we know the correct laygear endfloat & gear endfloat (on mainshaft) & distances between gear synchro rings.
Since then Chris has gone further & obtained David Brown drawings, now the gearboxes need to be able to withstand 250 + hp, 230+ lbs ft of torque, more than twice the DB2 outputs - all gearboxes are built with a dedicated build procedure & some redesigned parts that are made to stop the gearboxes leaking oil, be more reliable & generally nicer to use.
Chris worked out in 2007 how to make the overdrive gearbox reliable for racing, rallying or just having fun on the road, this mod is incorporated into every overdrive gearbox rebuild, it's not used by other companies unless they have stripped one of our gearboxes !
The Parts we have made & are in stock include:
New STD 3rd gear pairs,
New mainshafts - just the overdrive in STD copper plated & Close Ratio Needle roller types, we have plenty of used STD mainshafts.
STD 4 speed (non overdrive) with copper plated or Close Ratio roller type mainshafts will be made once we have run out of stock.
2nd gears will be made shortly.
Laygears (Countershaft) are about to be made & good ones are being rebuilt with a welded on 1st gear,
high strength bronze thrust washers are made now to stop excess wear on the layshaft
A laygear thrust washer to needle roller bearing conversion is about to be made, this reduces friction & heat, lessens the HP loss through the transmission.
we have just made the selector fork rings 55948 (operating rings), typical AM, there is more than one size.
We now have DB MkIII 'as original' overdrive gearbox kits ready for sale & DB2 - DB2/4 overdrive gearbox conversions will shortly ready for sale (expected sometime in 2020), all with Four Ashes legendary attention to detail.
Since then we have found our own colleagues & friends who can rebuild DB4 David Brown, DB5/6/S6 & V8 ZF gearboxes, DB5/ 6 & S6 BW Auto gearboxes and DB7 i6 Auto & Manual gearboxes.
see Engine Rebuilds
Please note that we are Independent Aston Martin Specialists & have no connection with Aston Martin themselves other than selling their parts.