Jonathan Smith Posted November 30, 2019 Report Share Posted November 30, 2019 I’m looking for an A type overdrive TR4 or 4A gearbox and would appreciate if any one could help with how I can check the gearbox to ensure it’s a TR gearbox - gearbox and overdrive serial numbers or any other visible notification marks or things to look out for Jonathan Quote Link to post Share on other sites
Bob Smith Posted December 1, 2019 Report Share Posted December 1, 2019 Jonathan, Genuine original TR4 & 4A gearboxes have a number stamped on the LHS of the gearbox casting where the clutch release cross shaft is located. TR4 gearboxes are stamped CTxxxxx & 4A gearboxes are stamped CT5xxxx and upwards. I have a spare TR4 overdrive gearbox & "A" series overdrive that is no longer needed as my TR4 has now been sold. Quote Link to post Share on other sites
Jonathan Smith Posted December 1, 2019 Author Report Share Posted December 1, 2019 10 hours ago, Bob Smith said: Jonathan, Genuine original TR4 & 4A gearboxes have a number stamped on the LHS of the gearbox casting where the clutch release cross shaft is located. TR4 gearboxes are stamped CTxxxxx & 4A gearboxes are stamped CT5xxxx and upwards. I have a spare TR4 overdrive gearbox & "A" series overdrive that is no longer needed as my TR4 has now been sold. Thanks Bob. PM sent re gearbox Quote Link to post Share on other sites
rcreweread Posted December 1, 2019 Report Share Posted December 1, 2019 12 hours ago, Bob Smith said: Jonathan, Genuine original TR4 & 4A gearboxes have a number stamped on the LHS of the gearbox casting where the clutch release cross shaft is located. TR4 gearboxes are stamped CTxxxxx & 4A gearboxes are stamped CT5xxxx and upwards. Jonathan/Bob I have no wish to disagree with Bob ( and I'm not sure I am but it depends on how you read Bobs response) but my info on gearbox numbering shows that TR4 gearboxes were stamped CT up to somewhere in the late 50000s and 4A units CT from there onwards. For example the following may help: TR4 - CT 7040 TR4 - CT 13037 TR4 - CT 56830 TR4 - CT 57298 TR4A - CT 63616 TR4A - CT 69471 I don't know what the exact changeover point was but I'm sure someone with more knowledge than me will be along shortly to confirm. As for TR4/4A A type overdrives, the info I have states that early TR4 ODs were serial numbered 22/61374, later TR4 and live axle TR4A ones were 22/61712, and all IRS 4A, 5 & 6 were 22/61753 or sometimes 22/61985. Do bear in mind that most original A type ODs are likely to have been rebuilt at least once and many non TR A types have been converted to full TR spec such that the only differentiating aspect is the serial number on the casing, Some rebuiders remove these original plates and replace with their own, numbered to equate to the particular application they are being sold for and their own sequencing - nothing wrong with this at all, in my view, but nobody can know where that OD actually originated so if you you are adamant you want a genuine, original A type, the above info will hopefully help Hope this helps but if you want any further info, then please get in touch Cheers Rich Quote Link to post Share on other sites
Footstuck Posted March 2, 2023 Report Share Posted March 2, 2023 Hi to all I don't know if this is the latest thread on Gearbox numbers but . . . The picture is from my box, and I first bought the car in or around 1981, its an E Reg car. Does this number look good as an original Gearbox? It haas an A Type overdrive? It looks to have a date stamp 11/1/66 although look for yourselves and see what you think. I have never swapped the box so if the numbers do not tally It must have been changed prior to my first period of ownership, as my friend owned it for 17 of those years. If i get a Birth certificate, will it give me any Info on G/box numbers? if so where would i get one? Thanks for any help . Regards Nick Quote Link to post Share on other sites
John Morrison Posted March 2, 2023 Report Share Posted March 2, 2023 Yes nick, slots in perfectly with the above John. Quote Link to post Share on other sites
Ralph Whitaker Posted March 3, 2023 Report Share Posted March 3, 2023 Hi Nick. You can get a "Birth certificate" as you describe it from BMIHT at Gaydon, cost around £40 I think, but the gearbox and axle numbers are not shown, at least not on my Heritage certificate, and gearbox and axle numbers did not correspond to engine numbers, and engine numbers did not always (if ever) match chassis (commission) number. Ralph Quote Link to post Share on other sites
Footstuck Posted March 6, 2023 Report Share Posted March 6, 2023 Thanks for the help. The gearbox stamping is approximately 200 or so digits away from the chassis number, so I guess that’s close enough as you can hope for? Thanks again regards from Nick Quote Link to post Share on other sites
stuart Posted March 6, 2023 Report Share Posted March 6, 2023 6 hours ago, Footstuck said: Thanks for the help. The gearbox stamping is approximately 200 or so digits away from the chassis number, so I guess that’s close enough as you can hope for? Thanks again regards from Nick Theyre never exactly the same due to applications elsewhere. Stuart. Quote Link to post Share on other sites
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