Royzeboyze Posted March 25, 2009 Report Share Posted March 25, 2009 Overdrive fitting to TR3A Can anyone recommend a firm to fit an overdrive unit to a TR3A. I have purchased a J type gearbox/overdrive unit that fits a 2500/S. I have read about all the changes that need to be made including flywheel, rear engine mounting, flange etc., also overdrive springs, thrust race, cross shaft, clutch etc. I want a price comparison, I have been quoted about £1000 by a well known specialist in Suffolk. I wonder if any members have any experience in having a unit fitted and the cost? Quote Link to post Share on other sites
david ferry Posted March 25, 2009 Report Share Posted March 25, 2009 First of all, welcome to the TR Register Forum. I don't know how much you have paid for the J type saloon overdrive gearbox. However, I would sell it on and source an A type TR overdrive box and fit that as it will go straight in, be correct and possibly end up cheaper. Using the gearbox you currently have will clearly involve a lot of messing around, wich costs money, and it will never be correct for your car. Good luck. Regards. David Quote Link to post Share on other sites
marko Posted March 26, 2009 Report Share Posted March 26, 2009 The J Type box is a more robust gearbox and can be fitted without any major issues. You can also modify it to engage overdrive in 2nd gear as well if required (like an A Type box). We have a gearbox specialist "in house" at Classic Marques and he can do this conversion for you at a very competitive rate, he has more than 30 years experience and he also does diff and engine rebuilds (fast road or standard, amongst lots of other things) Regards Mark www.classic-marques.co.uk Quote Link to post Share on other sites
Tr4Tony Posted March 26, 2009 Report Share Posted March 26, 2009 Also try Overdrive Repair Services in Sheffield ..... they will advise you on the issues with fitting a J type saloon box to a TR as well. There are quit a few, but if you put the time in to replace or to manufacture the right parts properly you can make it fit and operate satisfactorily. £1000 sounds like proper money for a proper job, make sure you get what you pay for. As David says, J types were fitted onto to the late TR6. Regards Tony Quote Link to post Share on other sites
ianc Posted March 26, 2009 Report Share Posted March 26, 2009 I have heard that the overdrive fitted to Triumph saloons may not provide the same ratio change as the A or J type overdrive fitted to TRs. The overdrive fitted to TRs has an engaged ratio of 0.82, which reduces engine speed to 82% (e.g. 5000 rpm in top reduces to 4100 rpm in overdrive top). Laycock made overdrives with all sorts of ratios - somewhere here I have the Laycock manuals from the mid-1960s, and they cover a variety of cars from Humbers to TRs. I believe that some saloons have engaged ratios as low as 0.7, which would mean that 5000 rpm would drop to 3500 rpm when overdrive is engaged. One might consider this an advantage, but it is an advantage ONLY if the engine is capable of shifting the car with such high gearing! The 0.82 ratio was very well-chosen by Triumph - it enabled the TR2 to achieve the same maximum speed in direct top and in overdrive top. Cars were sold - I seem to recollect that the Spitfire was an example - where the maximum in overdrive top was lower than in direct top, which is pretty useless in my book! I would check the ratio in this J-type overdrive before going further - if it has a ratio below 0.82, I think you could be very disappointed were you to spend £1000 and then find that the car doesn't perform well. Ian Cornish Quote Link to post Share on other sites
arthur r Posted April 2, 2009 Report Share Posted April 2, 2009 Overdrive fitting to TR3A Can anyone recommend a firm to fit an overdrive unit to a TR3A. I have purchased a J type gearbox/overdrive unit that fits a 2500/S. I have read about all the changes that need to be made including flywheel, rear engine mounting, flange etc., also overdrive springs, thrust race, cross shaft, clutch etc. I want a price comparison, I have been quoted about £1000 by a well known specialist in Suffolk. I wonder if any members have any experience in having a unit fitted and the cost? I used Kingston Sportcars Tony Linsey Dean Good quality and service Quote Link to post Share on other sites
pfenlon Posted April 2, 2009 Report Share Posted April 2, 2009 The J Type box is a more robust gearbox and can be fitted without any major issues. You can also modify it to engage overdrive in 2nd gear as well if required (like an A Type box). We have a gearbox specialist "in house" at Classic Marques and he can do this conversion for you at a very competitive rate, he has more than 30 years experience and he also does diff and engine rebuilds (fast road or standard, amongst lots of other things) Regards Mark www.classic-marques.co.uk A good few years ago I fitted a J type O/D to my TR4. I used a bracket supplied eventually by Moss for the back of the gearbox. It was a lashup job and certainly not robust in any way shape or form, in fact it was very poor. Has a new improved bracket now appeared Mark or do you make your own? Quote Link to post Share on other sites
david ferry Posted April 2, 2009 Report Share Posted April 2, 2009 Peter, The first version of the Moss conversion bracketry was poor and Moss have made changes to it in their second version which is what has been sold for a couple of years or so. One big problem with the first version was that the input shaft and the crank were not quite in the same plane. This will cause problems indestruction of the gearbox over a period of time. Now that Pete Cox is posting on the forum, he may comment although he may wish to remain silent as any comments may have to be made in his capacity at Moss which some on the forum seem to have a problem with. I don't! The second version is much better but I still think that the fitment of the correct type of gearbox is always a far better solution rather than trying to fit a J type gearbox into an A type chassis. Clearly others don't agree and perhaps this may be down to the fact that TR J type gearboxes are in greater supply and are much easier to find than TR A type overdrive gearboxes. I think the laws of supply and demand drive the prices of TR A type overdrive gearboxes higher than the cost of TR J type overdrive gearboxes. David Quote Link to post Share on other sites
pfenlon Posted April 2, 2009 Report Share Posted April 2, 2009 (edited) David I couldnt agree more, I fitted an A type O/D box to my TR3A and it was so easy to fit, as designed, a good job which you just knew would stand the test of time. If you are watching and reading Pete Cox, we would value your comments you know. Edited April 2, 2009 by pfenlon Quote Link to post Share on other sites
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