The illustration to the left shows highlighted parts and numbers for the pieces that were unique to the Telaio Rosso as related to standard five speed parts. In some cases, I believe, the only difference is an updated part number. One part which is not shown as unique to the TRs is the shift fork shaft. The TR shaft is a modified five speed shaft, so should be included. These internals are much more closely related to five speed internals than four speed. The gears run on needle roller bearings instead of bronze bushings like in the four speeds. The engagement collar (sleeve, sliding muff) for third and forth gear, slides directly on the lay shaft in a TR box. Standard five speed gearboxes use a separtate splined sleeve that is fitted to the lay shaft between third and forth gear. It locates the gears, locks the inner bearing races in place so that they do not rotate, sets the distance between 3rd and 4th and is a replaceable part between the two gears that typically see the most shifts. The TR gearbox holds third gear in place with a snap ring. Forth gear and the lay shaft housing bearing are also held in place by a snap ring. This is a weakness in the TR gearboxes that allows the inner steel race to spin on the lay shaft which leads to both radial and axial wear to the races, as well as wear to the lay shaft. If a nut was fitted to the housing end of the lay shaft as in the standard five speed, it would clamp all of the inner races so that they wouldn't spin on the lay shaft. Only the gears and the roller bearings would rotate as intended by design. If the wear becomes extreme, the gears can be both overengaged and underengaged by the sliding muffs which leads to rounded engagement dogs, jumping out of gear, shift fork wear and eventually the snap rings become displaced. Then all hell breaks loose.
Five speed internals do not fit these special modified sand cast four speed housings, neither do standard five speed gearbox covers. I mentioned earlier in my TR pages that I will be building a few of these Telaio Rosso gearboxes. It is these very problems that I was just pointing out that I am going to resolve beforehand so that they will be as reliable as a standard five speed.
Click Here to see pictures of an indexed Telaio Rosso gearset.