DJB350Z Posted October 9, 2022 Report Share Posted October 9, 2022 Hi, I have a complete GT6 overdrive gearbox. From what I research these are D type units from the factory. In the box of spares I got with my project I have one of these J type adapters: https://rimmerbros.com/Item--i-312305 Any clues what PO was trying to do here? J type better than D? I guess the adapter by itself is useless and you need other bits as well for a conversion? Link to comment Share on other sites More sharing options...
Josef Posted October 9, 2022 Report Share Posted October 9, 2022 Now the part you’ve linked Rimmers is showing as being for the TR6, 2000 and Stag. I’m fairly sure that the small chassis cars had one type of overdrive adaptor for the single rail and one for the three rail boxes, and that these would take both D and J type overdrives. The J type is a stronger unit nominally. But I don’t think it’s worth searching out one to change out for the D type you have. The adaptor is not much use by itself you’re right, but it does have value! 1 Link to comment Share on other sites More sharing options...
johny Posted October 9, 2022 Report Share Posted October 9, 2022 well yes the J type is supposed to be an improvement on the D and is recommended if increasing the engine power output - fitting a 2.5 litre for example. However to keep the gearbox the same length (the standard OD gearbox is already a tight fit) the adaptor needed to fit the J type is part number 313085 not the one you have. Note: a new mainshaft is also needed as the drive to D and J types is different.... 1 Link to comment Share on other sites More sharing options...
Wagger Posted October 9, 2022 Report Share Posted October 9, 2022 2 hours ago, Josef said: Now the part you’ve linked Rimmers is showing as being for the TR6, 2000 and Stag. I’m fairly sure that the small chassis cars had one type of overdrive adaptor for the single rail and one for the three rail boxes, and that these would take both D and J type overdrives. The J type is a stronger unit nominally. But I don’t think it’s worth searching out one to change out for the D type you have. The adaptor is not much use by itself you’re right, but it does have value! I have a J type with no adaptor plate. How much do you want for it? Then I can look for the mainshaft and propshaft. PO's removed the overdrive but not the badge. Link to comment Share on other sites More sharing options...
Clive Posted October 9, 2022 Report Share Posted October 9, 2022 2 minutes ago, Wagger said: I have a J type with no adaptor plate. How much do you want for it? Then I can look for the mainshaft and propshaft. PO's removed the overdrive but not the badge. Be aware that adapter plate is for a big saloon/stag/TR/sprint box. I have doubts it will fit a small chassis gearbox. You need the thinner adapter used on early dolly 1850s and countless conversions to fit a J type to your gearbox (I need one too, I have a spitfire 3 rail j type gearbox here, apparently reconditioned, but no OD/adapter/remote etc Link to comment Share on other sites More sharing options...
Wagger Posted October 9, 2022 Report Share Posted October 9, 2022 3 minutes ago, clive said: Be aware that adapter plate is for a big saloon/stag/TR/sprint box. I have doubts it will fit a small chassis gearbox. You need the thinner adapter used on early dolly 1850s and countless conversions to fit a J type to your gearbox (I need one too, I have a spitfire 3 rail j type gearbox here, apparently reconditioned, but no OD/adapter/remote etc OK so are any of you looking for a J type overdrive. I have also been considering fitting a Mazda 5 speed conversion as it is lighter. Just rather too expensive. Link to comment Share on other sites More sharing options...
Wagger Posted October 9, 2022 Report Share Posted October 9, 2022 I have the 3 rail gearbox fitted on GT6 and some Dolly's. Which plate do I need? Link to comment Share on other sites More sharing options...
Clive Posted October 9, 2022 Report Share Posted October 9, 2022 24 minutes ago, Wagger said: I have the 3 rail gearbox fitted on GT6 and some Dolly's. Which plate do I need? https://www.canleyclassics.com/?product=overdrive-adapter-plate But by the time you have found all te other bits and bobs, the MX5 conversion looks good value especially as it is VERY strong and all new. Downside it doesn't fit the vitesse/GT6, down to tunnel size and gearstick position. Have a look at Nicks DIY conversion on the sideways forum. Link to comment Share on other sites More sharing options...
Wagger Posted October 9, 2022 Report Share Posted October 9, 2022 11 minutes ago, clive said: https://www.canleyclassics.com/?product=overdrive-adapter-plate But by the time you have found all te other bits and bobs, the MX5 conversion looks good value especially as it is VERY strong and all new. Downside it doesn't fit the vitesse/GT6, down to tunnel size and gearstick position. Have a look at Nicks DIY conversion on the sideways forum. Thanks Clive. Plenty to think about. It is the do-ing that is the problem. Link to comment Share on other sites More sharing options...
johny Posted October 9, 2022 Report Share Posted October 9, 2022 Thats interesting then, so if you have a 3 rail box with D type OD a Jtype should bolt straight on IF you change the mainshaft of course.... Link to comment Share on other sites More sharing options...
Wagger Posted October 9, 2022 Report Share Posted October 9, 2022 9 minutes ago, johny said: Thats interesting then, so if you have a 3 rail box with D type OD a Jtype should bolt straight on IF you change the mainshaft of course.... Problem is that PO's removed the original engine, gearbox and o/d and fitted a non overdrive 3 rail box on a 2500TC engine. It has a 3.63:1 diff and speedo is accurate. Not too bothered really, but would like to return the car to an 'As supplied' state, or find the bits so that sons can do it when they inherit it. Link to comment Share on other sites More sharing options...
johny Posted October 9, 2022 Report Share Posted October 9, 2022 That might have been done because the 3 rail box seems to be stronger in non OD form. In fact if youre like me, not a great OD fan, a 3.27 diff would probably be a viable alternative solution although this would require a speedo change/recalibration... Link to comment Share on other sites More sharing options...
Wagger Posted October 9, 2022 Report Share Posted October 9, 2022 13 minutes ago, johny said: That might have been done because the 3 rail box seems to be stronger in non OD form. In fact if youre like me, not a great OD fan, a 3.27 diff would probably be a viable alternative solution although this would require a speedo change/recalibration... The 3.63:1 diff is tougher than the standard 3.27:1. (according to most on the forum). As it is, I can take off in 1st or 2nd, and go straight into 4th. I do not get to dual carriageways in it, so it is adequate for current use. Link to comment Share on other sites More sharing options...
johny Posted October 9, 2022 Report Share Posted October 9, 2022 So why do you want OD then? I suppose the need to have the strongest possible diff depends on how youre going to drive it.... Link to comment Share on other sites More sharing options...
Clive Posted October 9, 2022 Report Share Posted October 9, 2022 2 hours ago, johny said: Thats interesting then, so if you have a 3 rail box with D type OD a Jtype should bolt straight on IF you change the mainshaft of course.... Possibly. There may be some other things to change? but as mentioned elsewhere, it would be a good idea to get the first motion shaft machined out and use a big tipped mainshaft. The canley adapter plate may be machined to be dual purpose? Link to comment Share on other sites More sharing options...
johny Posted October 9, 2022 Report Share Posted October 9, 2022 Ive always wondered about the big tip mod as although its relatively easy to machine out the input shaft what about then hardening the surface the bearing runs on? Link to comment Share on other sites More sharing options...
Wagger Posted October 9, 2022 Report Share Posted October 9, 2022 1 hour ago, johny said: So why do you want OD then? I suppose the need to have the strongest possible diff depends on how youre going to drive it.... Only because the badge says it has one. I was carrying it in the boot just for authenticity. I am repeating myself here, but I did add an overdrive to a 1600/6 in 1974. Messed the sychro up due to a 'Helper'. It saved revs, but no fuel and made it easier on the ear. I tend to agree. No much going for o/d unless it works on 2nd, 3rd and 4th like the TR's. You really only get one more gear. Liked it on my 1850 Dolly though as it did 38mpg. Link to comment Share on other sites More sharing options...
Nick Jones Posted October 9, 2022 Report Share Posted October 9, 2022 4 hours ago, Wagger said: I have also been considering fitting a Mazda 5 speed conversion as it is lighter. You have a source for an MX-5 gearbox conversion for a GT6? I know Vitesse Transmissions was working on one, but were struggling a bit. Maybe they’ve cracked it now but will be £3k+ As far as I know I have the only GT6 with MX5 gearbox attached to a Triumph 6 in existence. Getting it in there was a bit of a mission. Nick Link to comment Share on other sites More sharing options...
Wagger Posted October 9, 2022 Report Share Posted October 9, 2022 3 minutes ago, Nick Jones said: You have a source for an MX-5 gearbox conversion for a GT6? I know Vitesse Transmissions was working on one, but were struggling a bit. Maybe they’ve cracked it now but will be £3k+ As far as I know I have the only GT6 with MX5 gearbox attached to a Triumph 6 in existence. Getting it in there was a bit of a mission. Nick It's the name 'Vitesse Transmissions' that confused me. Coincidence, like there is a Rover Vitesse. Would love to see pictures of yours. Should be possible in a 2L Vitesse if it works in a GT6. Link to comment Share on other sites More sharing options...
Nick Jones Posted October 9, 2022 Report Share Posted October 9, 2022 Longish story. Previously posted I think. https://sideways-technologies.co.uk/forums/index.php?/topic/8925-mazda-gearboxes-some-bstard-told-me-it-was-impossible-so-i-had-to-do-it/#comments Link to comment Share on other sites More sharing options...
Wagger Posted October 9, 2022 Report Share Posted October 9, 2022 21 minutes ago, Nick Jones said: Longish story. Previously posted I think. https://sideways-technologies.co.uk/forums/index.php?/topic/8925-mazda-gearboxes-some-bstard-told-me-it-was-impossible-so-i-had-to-do-it/#comments Thanks for that Nick. Shows great determination. I'm past 75 now and have issues. Will collect all of the missing parts and pass it back to my eldest son who found the car for me. Grandson likes cars too and yearns for an MX5. It could last late into this century. Link to comment Share on other sites More sharing options...
Clive Posted October 10, 2022 Report Share Posted October 10, 2022 torrington bearing has a thin outer shell. Care needed so that oil can still get in. ie bearing shallow enough that the existing drilling works, or drill a new feed. Link to comment Share on other sites More sharing options...
johny Posted October 10, 2022 Report Share Posted October 10, 2022 Right yes must be the only way to do it but unfortunately the best cup needle roller bearing I can find is 18 x 24mm which is good for the mainshaft tip but rather wide so needs 5mm taking out of the input shaft bore diameter and then might risk oil starvation🙁 Link to comment Share on other sites More sharing options...
Recommended Posts
Create an account or sign in to comment
You need to be a member in order to leave a comment
Create an account
Sign up for a new account in our community. It's easy!
Register a new accountSign in
Already have an account? Sign in here.
Sign In Now