Martin Murray Posted February 21, 2023 Report Share Posted February 21, 2023 I'm puzzled by the rear overdrive casing on my Type A unit as the mounting has a vertical flange and not the normal flat horizontal one I see in all photos and parts listings ? Photos attached... Any ideas ?? Quote Link to post Share on other sites
Ralph Whitaker Posted February 22, 2023 Report Share Posted February 22, 2023 That is a saloon type overdrive. I have the same on my car with an adapter to fit the standard TR mounting rubber. Someone has made up a mounting for yours. I had to use an angle drive for the speedo cable as it comes out more horizontal, the TR item points downwards. Do you also have a saloon box with synchro on first gear? and how many interlink switches are there on the gearchange remote? does the o/d work on second gear as well as 3rd & 4th. Ralph Quote Link to post Share on other sites
Lebro Posted February 22, 2023 Report Share Posted February 22, 2023 +1 Bob Quote Link to post Share on other sites
rcreweread Posted February 22, 2023 Report Share Posted February 22, 2023 There should be an ID plate rivetted to the main body ( the round bit) - it's often on the top underneath the gear selector extension so difficult to read but I can't see any evidence of there being one there - this would allow us to fully ID the OD and it's ratio as I'm not sure it is a saloon one - I'm pretty sure most saloon and stag ones I've seen have the solenoid mounting on the side in a horizontal plane whereas the photos show it in a vertical plane. TR ones are also in a vertical plane but in quite a different arrangement. There is a mounting bracket which converts one of these to be used on a TR gearbox crossmember mounting but I don't think they are available anymore - I do have one spare if anyone is interested. Here is a photo which is very poor but gives a general idea of the bracket arrangement - I will try and find some better ones if anyone is interested Cheers Rich Quote Link to post Share on other sites
Charlie D Posted February 22, 2023 Report Share Posted February 22, 2023 I may be wrong but you may well find that the ratio of the speedo output turns to the propshaft turns is different to that of a TR overdrive/gearbox, in which case your speedo could be seriously out, unless it has been recalibrated. Charlie Quote Link to post Share on other sites
Lebro Posted February 22, 2023 Report Share Posted February 22, 2023 TR speedo dive is 2.5:1 reduction, saloon is 3.5:1 Bob Quote Link to post Share on other sites
Martin Murray Posted February 22, 2023 Author Report Share Posted February 22, 2023 Thanks for the replies so far ! The car was built in South Africa and this might explain the odd tail cover arrangement and I don't know what gears get overdrive yet as it wasn't working when I test drove it ? I'm getting the box and overdrive overhauled and might ask to have a normal tail cover fitted ? Quote Link to post Share on other sites
Lebro Posted February 22, 2023 Report Share Posted February 22, 2023 Its the same as fitted to Austin Healey's. Quote Link to post Share on other sites
rcreweread Posted February 22, 2023 Report Share Posted February 22, 2023 3 hours ago, rcreweread said: There should be an ID plate rivetted to the main body ( the round bit) - it's often on the top underneath the gear selector extension so difficult to read but I can't see any evidence of there being one there - this would allow us to fully ID the OD and it's ratio as I'm not sure it is a saloon one - I'm pretty sure most saloon and stag ones I've seen have the solenoid mounting on the side in a horizontal plane whereas the photos show it in a vertical plane. TR ones are also in a vertical plane but in quite a different arrangement. There is a mounting bracket which converts one of these to be used on a TR gearbox crossmember mounting but I don't think they are available anymore - I do have one spare if anyone is interested. Here is a photo which is very poor but gives a general idea of the bracket arrangement - I will try and find some better ones if anyone is interested Cheers Rich I've found the original bracket which I had cleaned up and also a saloon A type OD rear housing to show how I think it is supposed to fit together - it appears you have to remove the two studs and replace them with longer bolts ( I'm pretty sure they need to be UNC threads) and then fits nuts on their end to clamp it all together - hopefully the photos will illustrate this. You mentioned getting a correct rear housing and these are available new from the usual sources - I seem to recall they are around the £150 mark - if you are going this far, then I would suggest you check to see if the TR vertical solenoid mounting will fit your gearbox and if it does, get this as well - they should be available from the same sources. Cheers Rich Quote Link to post Share on other sites
Martin Murray Posted February 22, 2023 Author Report Share Posted February 22, 2023 Thanks very much everyone ! My transmission repairer has also confirmed that I have a saloon version and that they can return my unit to the correct TR3 spec when they reservice it. I've ordered the standard spec mounting block and the original chassis bracket is still with me, so I should be back to normal in a few weeks ? Regards Martin. Quote Link to post Share on other sites
Ralph Whitaker Posted February 23, 2023 Report Share Posted February 23, 2023 18 hours ago, Martin Murray said: Thanks for the replies so far ! The car was built in South Africa and this might explain the odd tail cover arrangement and I don't know what gears get overdrive yet as it wasn't working when I test drove it ? I'm getting the box and overdrive overhauled and might ask to have a normal tail cover fitted ? Check the speedo drive ratio and the no of turns of your speedo (marked on the speedo face). If the car has had a saloon gearbox and overdrive fitted at some point in it`s history your speedo could be reading 30% low. The speedo drive gear is machined on to the rear shaft of the o/d so cannot be easily changed, but the correct rear bell is available and the time to swap is while the o/d is in bits. The standard speedo has 1145 turns per mile ( I think I am right) which is correct for a speedo drive with 2.5 to 1 ratio and 3.7 to 1 diff ratio. Of course your speedo may have been re calibrated already, but only way you could tell would be to put a screwdriver or something in where the cable fits and turn it 1145 times and see if it clocks up 1 mile. But to my way of thinking if you are going to the trouble of having the o/d built with a TR rear case you may as well have the correct TR drive ratio and worry about the speedo later. Ralph Quote Link to post Share on other sites
Lebro Posted February 23, 2023 Report Share Posted February 23, 2023 You need approx 850 TPM for the saloon version. Bob Quote Link to post Share on other sites
Ralph Whitaker Posted February 24, 2023 Report Share Posted February 24, 2023 23 hours ago, Lebro said: You need approx 850 TPM for the saloon version. Bob That`s with a 3.7 rear axle ratio. I have a 4.1 axle so calculated mine to be 914 TPM. My speedo is converted now thanks to your input ages ago Bob, but not as straightforward as using a 2.5PI innards. I had to drill the casing to take the trip winder which came out the back of the Rootes Arrow series speedo and have a cable made with the clip on end fitting, but all worth it. A mile is a mile now, not 7/10s as it was before and speedo is correct over the entire range. Ralph Quote Link to post Share on other sites
Lebro Posted February 24, 2023 Report Share Posted February 24, 2023 Great stuff ! The 2.5PI speedo had the same trip reset out of the back as you describe. Bob Quote Link to post Share on other sites
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