Triumph TR3B (TCF) TR4-4A-5-250 Constant Pinion & Mainshafts - 4 Synchro
4 synchro gearboxes original to the cars supported by this catalogue have gearbox numbers prefixed by CT (TR4, TR4A) or CD (TR5, TR250).
This section and the previous one dealing with external gearbox contain information relevant to original fitment gearboxes. If your gearbox has a number subsequent to CD20281, or a prefix of CC or CF, then you are in possession of a later TR6 unit which differs in important details and is not covered here. We would suggest in this instance that you should acquire our TR6 parts catalogue.
Having said that, there is a chart at the end of this section which groups the major TR6 gearbox changes together, thus making the substitution of groups of later components into an earlier gearbox an easier task to understand (for example, if you wish to fit the post-73 taller first gear and laygear, nos 152803 and UKC662 respectively).
If your gearbox number has any other prefix, it is likely to have been donated to the TR cause by a Triumph saloon at some point in its history, and while it will be similar in most respects there will be detail differences you will need to be aware of before embarking on a rebuild. Please contact us for further information if this should be the case.
Lastly, if you have an overdrive gearbox, it should be coupled to an A type overdrive to be original. Later TR6s and saloons used a J type unit (adaptor brackets are available to fit the J type into earlier TR chassis). The manufacturer’s plate on the overdrive body will tell you if yours is an A or J type. If the plate is missing or illegible, look at the underside of the overdrive - the A type has a large screw cap, whereas the J type has a cast ribbed rectangular cover plate. The recommendation if you find the latter is the same as before - locate and note down the prefix and gearbox number, then contact us for further information.