Stag type Thrust Bearings.
It is well known in Triumph circles that the Stag gearbox is generally much stronger than the TR and saloon gearbox for two reasons.
1.The bearings on the mainshaft are steel and therefore not prone to breakage.
2.The laygear which was weak throughout the TR and saloon car range was uprated. This uprate had two distinct parts, an extra bearing in the loaded end of the laygear (making 3 in total) and roller thrusts.
It would be great if you just put a Stag gearbox straight into a TR but you can t, so, modifications are required to fit a Stag gearbox to a TR, which is possible, but you can also with much less grief, change a TR gearbox to Stag specification as per the modifications listed above.
The mainshaft modifications are easy to incorporate and are therefore done as a matter of course in our gearbox rebuilds. The extra bearing in the laygear is also easy to incorporate and is therefore included in our first level of gearbox uprate. We sell the gears on an exchange basis too.
The final part, the inclusion of roller thrust washers is far from easy and not for the faint hearted. It is important to understand that it is necessary for the gearbox casing to be machined to accommodate the roller thrusts as Stag gearbox casings differ in this area from all the other gearbox casings (which are otherwise similar) in this respect. The roller thrust kit consists of a cage of rollers and a thrust washer either side fitted at both ends of the lay gear assembly. This combination of thrust washers and roller thrust bearing is rather thicker than the standard TR solid thrust bearing therefore the gearbox casing needs to be machined out to accommodate the extra length.
Three kits are available
RTR1266K. This simple kit consists of a pack of thrust bearings and special washers that allow the stag concept to be incorporated into a TR gearbox using a standard TR layshaft (very slightly smaller than a Stag part). This kit will improve the reliability of all gearboxes in all cases unless exceptionally high loads are encountered.
RTR1266-1K. This kit consists of a pack of thrust bearings and washers modified in design concept such that when fitted to a TR gearbox it will more reliably transmit the highest TR power and torque, still using a standard TR layshaft (smaller than a stag part). This design uses a top hat thrust washer at the front and the rear of the laygear for the bearings sit on. This kit would only be needed (and the significant extra cost warranted) in exceptional circumstances.
RTR1266-2K. This kit consists of a pack of thrust bearings and washers to the standard Stag specification requiring a Stag layshaft (slightly larger than the TR part) to be used. When fitted to a TR gearbox this kit requires the added work of boring the gearbox casing to take the larger Stag layshaft thus making it a poor choice in the light of the two kits above. It is most likely to be useful where a gearbox rebuild reveals that the casing is in fact a Stag part.
Machining
The gearbox casing has to be machined out to accept the deeper thrust bearing packs and then fine-tuned to give the correct end float. Alternatively the end thrust washers, which are deliberately left thick, can be machined to the exact thickness required to give .004 to .006"overall end float. Machining the gearbox isn t an exact science for this reason.
Sometimes gearboxes have had the inner thrust faces damaged by exploding rear (and sometimes front) layshaft bearings, so machining the faces is "as necessary". Sounds amateur but it both makes sense and works in real life. Fitting instructions are included with the kits that explain this procedure fully.
For TR applications making the rear washer to Stag specification doesn t make sense as it would be necessary to bore out the layshaft holes in the gearbox casing, purchase a Stag shaft and find a Stag laygear. Our front and rear spacers have an accurate internal diameter to fit a TR layshaft, and this means either a 16 or 17tooth laygear can be used, according to TR model. Stags only use 17tooth gears.