MissSpentYouth Posted June 22, 2011 Report Share Posted June 22, 2011 Hi, Given the rarity and hence cost of an overdrive box for a TR6 has any one ever had a go at trying to fit a J type OD to the rear of their non OD box, one from another Triumph ? Other Triumphs with J type OD that come up regularly on eBay include Spitfire, GT6, Dolomite & Sprint and Stag. You would need to source a longer mainshaft but I am guessing they are easily available at not too much cost, I think they might be interchagable with the Sprint for CR cars. The output flange shouldn't pose to many problems at worse a modified UJ on the end of the prop. What concerns me is the adaptor plate that mounts the OD to the rear of the box ? Maybe could make one up by cutting the redundant flange off the old gearbox tail (the bit that the OD replaces) similary cutting the adaptor plate that mates the OD to the unwanted gearbox i.e. sprint and welding the two bits together ? Are all input drive shafts to J type OD's the same or are there loads of different shaft diameters and spline counts ? bet its the latter :-( If you could crack this one then I think you would have a ready market especially if you could use the LH OD from rubber bumper MGB's as these are really common. cheers Ben. Quote Link to post Share on other sites
WWT338J Posted June 23, 2011 Report Share Posted June 23, 2011 Ben A number of years ago Overdrive Repair Services added an A-type overdrive to my gearbox (which they reconditioned). I sourced an A-type OD from a Triumph saloon. The rear mounting is different (at a strange angle) but this was removed and welded back on at the correct angle. The potential advantage of the A-type over the J-type is OD on second gear. David Quote Link to post Share on other sites
Alec Pringle Posted June 23, 2011 Report Share Posted June 23, 2011 Hi Ben, overdrive units, and components, are not that rare, expensive or difficult to find . . . . patience is a virtue here ! The relevant alternative gearbox and/or overdrive donors for TR6 are the 2000/2500 saloon range, Dolomite Sprint, and Stag - for all practical purposes, that is. None are exactly a straight swap however, and will require the services of a TR transmission specialist and a not insubstantial bag of shekels. It is possible to adapt other overdrive fitments for TR6 application, but it is not straightforward - and requires wholesale replacement of internal components. Which is another way of saying not cost-effective, not by a long chalk. Cheers, Alec Quote Link to post Share on other sites
RonA Posted June 23, 2011 Report Share Posted June 23, 2011 Hi Ben If you have a late TR6 non OD gearbox and you can rebuild gearboxes it is a relatively easy and cheap job to fit a Dolly Sprint overdrive, the Sprint OD is the only Triumph one that has the same working pressure as the TR6, although the Stag and Saloon ODs will work OK. I did this conversion a number of years ago, basically you need the longer mainshaft, a Sprint OD and adapter and you need to either buy a TR6 output flange to fit the propshaft or modify the Sprint one, but this requires a lathe. Obviously you need switches and electrics. If you can get a Sprint gearbox and OD unit this will supply the parts you need, ie the longer mainshaft from the Sprint box is used in the TR6. If you have a later 'J Type chassis all you need are the relevant mountings, it gets a lot more complicated if you have an earlier gearbox and chassis. The only thing that gave me problems was getting the speedo to read correctly, I've learned to live with it but sometime I must get round to removing it and sending it to be re-calibrated. As I said it's a good number of years since I did this job so I've probably forgotten a lot of details, if you decide to go ahead pm me and I'll look up the details of what was done at the time. RonA Quote Link to post Share on other sites
rpurchon Posted June 23, 2011 Report Share Posted June 23, 2011 (edited) Hi, Given the rarity and hence cost of an overdrive box for a TR6 has any one ever had a go at trying to fit a J type OD to the rear of their non OD box, one from another Triumph ? Other Triumphs with J type OD that come up regularly on eBay include Spitfire, GT6, Dolomite & Sprint and Stag. You would need to source a longer mainshaft but I am guessing they are easily available at not too much cost, I think they might be interchagable with the Sprint for CR cars. The output flange shouldn't pose to many problems at worse a modified UJ on the end of the prop. What concerns me is the adaptor plate that mounts the OD to the rear of the box ? Maybe could make one up by cutting the redundant flange off the old gearbox tail (the bit that the OD replaces) similary cutting the adaptor plate that mates the OD to the unwanted gearbox i.e. sprint and welding the two bits together ? Are all input drive shafts to J type OD's the same or are there loads of different shaft diameters and spline counts ? bet its the latter :-( If you could crack this one then I think you would have a ready market especially if you could use the LH OD from rubber bumper MGB's as these are really common. cheers Ben. find your self a gearbox/overdrive from a saloon. 2.0 2.5 have 25% od. 2.5pi 28% od. use saloon clutch plate,change speedo drive gears [easy], correct rear drive flange and thats its. richard Edited June 23, 2011 by rpurchon Quote Link to post Share on other sites
Alec Pringle Posted June 23, 2011 Report Share Posted June 23, 2011 Until, that is, the saloon overdrive lets go under the unaccustomed strain . . . . not being internally identical to a TR6 unit. Cheers, Alec Quote Link to post Share on other sites
Ian Vincent Posted June 23, 2011 Report Share Posted June 23, 2011 Until, that is, the saloon overdrive lets go under the unaccustomed strain . . . . not being internally identical to a TR6 unit. Cheers, Alec Send the saloon overdrive to ORS (Overdrive Repair Services) in Sheffield and for about £500 (it may have gone up now, that was the price a couple of years ago) they will convert it to a TR unit with the correct number of springs and stronger pressure relief valve spring, change the saloon rear casing for a TR casing and generally check it over. Rgds Ian Quote Link to post Share on other sites
fblue73 Posted June 23, 2011 Report Share Posted June 23, 2011 Over here in the US, a good substitute is a j-type from a 76-86 Volvo 200 series; there were a ton of them built and most are worthless now. Not sure how many were sold in the UK. The bugaboo is finding an adaptor housing. The shorter mainshaft if available new form several sources [moss, VB, quantum mechanics as is the correct speedometer gears to convert to TR6]. Count on some expense when overhauling the gearbox "whilest in there" and then acquire new electric harness and switch. The overdrive unit is probably the least costly of the whole conversion. Quote Link to post Share on other sites
rpurchon Posted June 23, 2011 Report Share Posted June 23, 2011 Until, that is, the saloon overdrive lets go under the unaccustomed strain . . . . not being internally identical to a TR6 unit. Cheers, Alec this bloke wants a od for his car, and so do lots of other people judging by the number of posts that come up time after time. this is the simplest and cheapest way to get a overdrive if you diy.and i presume we are talking about diy. but every one chips in with negative comments like,not enough springs in it[A types].it wont have the correct 1/4" bigger input shaft[saloons] the working pressure wont be enough.and so on. and lots of people will understandably think its just too complicated,i live with the car the way it is. 2.0 saloon might be a bit down on power but not a lot.a 2.5saloon similar power a 2.5 pi the same power as a tr but dont forget these are heavier cars than a tr. i have never heard they suffered from slipping overdrives. All J type units are all exactly the same inside.barring a small difference in working pressure. but this is controled by dash pot/relief valve which is easy to get at through bottom cover on th OD. easy to get from under the car,and no need to remove from car. whenever i have picked up a gbox/od on ebay, the sellers always say i scrapped the car due to rust but the gbox was really good.so good i saved it? find a saloon gbox a cheap solution you wont regret. richard Quote Link to post Share on other sites
Austin Branson Posted June 23, 2011 Report Share Posted June 23, 2011 Ben A number of years ago Overdrive Repair Services added an A-type overdrive to my gearbox (which they reconditioned). I sourced an A-type OD from a Triumph saloon. The rear mounting is different (at a strange angle) but this was removed and welded back on at the correct angle. The potential advantage of the A-type over the J-type is OD on second gear. David David, I have a 74 CF with J type overdrive, I got another micro-switch from TR Enterprises, and now have O/D on 2nd - was it a bad idea? It seems to work OK, but a bit tardy dropping in (in 2nd gear). Austin Quote Link to post Share on other sites
currylager Posted June 24, 2011 Report Share Posted June 24, 2011 So am I right in thinking I could also use a stag box too? I have the non od on my 250 and need longer legs without a mortgage!!!! Quote Link to post Share on other sites
rpurchon Posted June 24, 2011 Report Share Posted June 24, 2011 So am I right in thinking I could also use a stag box too? I have the non od on my 250 and need longer legs without a mortgage!!!! yes and no ? the stag box input shaft is too long. you would have to swap the input shaft and counter shaft gear from your 250.remove od and pull gbox in bits. you could also hit a snag with the spigot bearing size. presuming its a j type stag box. again its much simpler with a saloon box. but the stag is best gbox with better laygear bearings. richard Quote Link to post Share on other sites
MissSpentYouth Posted June 24, 2011 Author Report Share Posted June 24, 2011 Hi All, Great thanks for all your posts. So in summary if it is a later CR car then a Sprint box and OD looks like a good solution swap out the mainshaft and machine the output flange, followed by a Stag OD and new mainshaft, not to mention a 2000/2500 saloon possibly using the clutch plate from the saloon as the input shaft is smaller. What about earlier CP cars as A type OD's seem pretty rare (expensive) I am guessing fitting a J type OD to an earlier box is a no no does the saloon car swap still work ? do earlier saloons also have the earlier boxes with A type OD's ? Is it possible to fit a later saloon gearbox and J type OD with the clutch plate to an earlier CP TR6 ? Does the bell housing still mate up OK, Spigot bush size the same ? Can you make up your own rear gearbox mount to overcome the chassis difference or would you need to chop a bit out and in effect convert to CR spec chassis ? In answer to questions above, yes I am mechanically literate and happy to rebuild the gearbox swap mainshafts and speedo drive gears over. I doubt the saloon car OD would prove weaker as it is engine torque and vehical weight which kills transmissions not power I suspect the torque from a 2.5 PI is not so disimilar to a TR6 and a TR6 must be a shed load lighter. Quote Link to post Share on other sites
Mike Collins Posted June 25, 2011 Report Share Posted June 25, 2011 "Is it possible to fit a later saloon gearbox and J type OD with the clutch plate to an earlier CP TR6 ? Does the bell housing still mate up OK, Spigot bush size the same ? Can you make up your own rear gearbox mount to overcome the chassis difference or would you need to chop a bit out and in effect convert to CR spec chassis ?" That's what I did two years ago. Bell housing fits, I did not change the spigot bush but I had to swap the nose piece. Making the rear mount was a bit of a pain, some info from ths US showed a mount cantilevered back from the original chassis pads. That looked to me to introduce too much twisting in the pads and I was not prepared to weld the chassis. I compromised with a rear crosspiece clamped to the chassis to reduce the lever arm. I used a pair of vertical cotton reel type shock mounts, if I have to remove the gearbox again I will arrange them to give more sideways location, there is a faint shuddering in the drive line at medium speed under power. Adding the interlock switch for second gear makes for much easier town driving, 28% reduction, in and out of overdrive saves a lot of gear changing. If used at low power settings I can't see it hurting the J. The oil pump is driven in proportion to road speed so engagement will not be instant but it works down to 20mph or so. In fact if your lazy like me and normally drive an automatic, leaving the OD switch on and changing from first to second the delay in engagement is about right. The output flange and speedo gear I bought at Malvern two years ago, ORS I think, speed readings are within 2-3 mph over most of the range. This 'box has been in for two years and probably 12,000 miles or more. Yes it is possible. I can probably dig out some photographs if you're interested. Mike. Quote Link to post Share on other sites
MissSpentYouth Posted June 25, 2011 Author Report Share Posted June 25, 2011 Hi Mike, Thats really interesting so the later gearbox and OD is in effect shorter than the earlier one so no problems with interference only that the rear gearbox mount is in effect suspended in mid air between the chassis rails so a little bit of fabrication can produce a cross piece that can be bolted between the chassis rails and likely could be made to take the standard rear rubber mount. Yes I suspect those cotton real mounts are a little wobbly they are more aimed at hanging exhausts though I seem remember using them myself to put a 1500 Dolly OD box in a Spitfire about 20 years ago (blimey that makes me feel old). Assume the gear lever still comes up in the same place cant see why Triumph would have moved it. Great stuff lots of options then thanks for all your help. Quote Link to post Share on other sites
rpurchon Posted June 25, 2011 Report Share Posted June 25, 2011 Hi Mike, Thats really interesting so the later gearbox and OD is in effect shorter than the earlier one so no problems with interference only that the rear gearbox mount is in effect suspended in mid air between the chassis rails so a little bit of fabrication can produce a cross piece that can be bolted between the chassis rails and likely could be made to take the standard rear rubber mount. Yes I suspect those cotton real mounts are a little wobbly they are more aimed at hanging exhausts though I seem remember using them myself to put a 1500 Dolly OD box in a Spitfire about 20 years ago (blimey that makes me feel old). Assume the gear lever still comes up in the same place cant see why Triumph would have moved it. Great stuff lots of options then thanks for all your help. heres what i have found messing with gboxs.tr stag sprint saloons, the gear casings are all the same and all have the same bolt patterns to back plate on engine. inside the gearbox they are all the same.[so long as you swap all the gears on the mainshaft from 1 box to another and dont mix them] you can put all the bits from a Atype mainshaft onto a jtype mainshaft and vice versa. stag and sprint have longer input shaft.stag have different laygear bearings.[you would have to use stag laygear in a stag casing] all the gearboxs are the same lenght overdrive or non overdrive. gearstick always same position. the overdrive fits onto the back of the gear casing using a adapter plate.Atype adapter or Jtype adapter, both will fit any gear case any Atype overdrive will fit onto a Atype back plate ie from a jag a rover healey or even a ferrari. same with j types except ford transit. richard Quote Link to post Share on other sites
MissSpentYouth Posted June 28, 2011 Author Report Share Posted June 28, 2011 Hi Richard thanks for the information. So for an early TR6 I could buy an overdrive gearbox with an A type OD from a Volvo Amazon buy a longer main shaft from Rimmers for £168 ouch plus a new adaptor plate from Rimmers £78 plus a bunch of gaskets ... and I would be there ? You mentioned all gearbox's and OD gearbox's are all the same lenght, why was the chassis changed between CP and CR cars then ? cheers Ben Quote Link to post Share on other sites
Mike Collins Posted June 28, 2011 Report Share Posted June 28, 2011 The position and type of the rear mount changes between A and J. The latter has it's chassis mounts a few inches aft and slightly lower than the A. I don't think it affects the position of the output flange and therefore the propshaft length significantly. Mike. Quote Link to post Share on other sites
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.