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Original Telaio Rosso
A More Technical Look at the TR Gearbox


   On the left is a copy of an official Moto Guzzi parts list for the Telaio Rosso gearbox. The caption for the page translates as....Specially Fitted on 1st Series (First 150 Machines "Telaio Rosso") It is one of two different gear sets that I have seen quoted as used in the TR bikes, but the only one that I've seen as part of an official factory publication. The other source that I have seen is Guzziology, but I'm not sure what their source for the tooth counts and ratios was. One of the three Telaio Rosso owners near me quoted me the same ratios and I believe his source was the Italian motorcycle magazine Motociclismo. He also quoted rear drive ratios of 8:35 and 9:37. An 8:35 ratio rear drive makes sense to me and is what I believe the TRs have on them. The 9:37 alternative ratio is, I believe, an error. Even current Moto Guzzi models are over geared with an 8:33 rear drive which is a tick lower than a 9:37.


     The following chart shows the tooth counts and ratios from Guzziology and are referred to as Early V7 Sport.

Gear Tooth Count Ratio Overall
Primary     16/22  1.375
   1st     15/27  1.800  10.828
   2nd     19/24  1.263    7.597
   3rd     22/21    .954    5.739
   4th     24/19    .791    4.758
   5th     25/17*    .680    4.090
  Final       8/35

 * Guzziology showed a tooth count of 25/24 for fifth gear, but I believe that was a typo.




      On the right is an enlarged view of the part numbers and descriptions from the official Moto Guzzi Telaio parts list. If you look up the parts numbers given for the gears in this list, a direct substitution is given for standard five speed gears complete with standard tooth counts given. It would seem that the gears in this reference are the same as those used in all standard street helical gearboxes. Either way, when you look at the overall gear ratios for a standard five speed below they are so close to the ratios quoted by Guzziology for the Telaio Rosso, you would be hard pressed to feel the difference on the street.

Gear Tooth Count Ratio Overall
Primary      17/21   1.235  
    1st      14/28  2.000  10.808
    2nd      18/25  1.338    7.506
    3rd      21/22  1.047    5.661
    4th      23/20    .869    4.699
    5th      24/18    .750    4.053
  Final       8/35   4.375  


     The specific ratios for the gears are quite different in the two references, but when combined with the different primary ratios used, the overall ratios are very close to each other.

      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.