bigmalcy Posted January 25, 2020 Report Share Posted January 25, 2020 (edited) EDIT... I originally thought it was a half shaft failure... turns out it is gearbox related. Grinding in 1st gear and reverse with very little drive. 2nd/ 3rd / 4th all ok with or without o/d. Looking for diagnosis while I start the process of removing the box and engine... at least this will give me a chance to fix that oil leak and a few other things. Original post: What a shame - just after thinking how well the car was driving and looking (and also consciously thinking how risky it was to be having such thoughts), a half shaft decided enough was enough... at least I hope it was the half shaft! I think I was partly to blame... or fully to blame... I forgot the handbrake was on and then when I took off from the lights, the car pulled away for a split second and then something went pop! I'm trying to re-assure myself that the half shaft should be able to take that sort of load, and so was probably going to break eventually anyway... not sure if that is true or not. Anyway - time to get hands dirty and confirm what's what. Two photos attached are the start of the day, full of promise, and the situation about 1hr later! Edited January 25, 2020 by bigmalcy Quote Link to post Share on other sites
John Morrison Posted January 25, 2020 Report Share Posted January 25, 2020 Ouch, but not the end of the world, you'll be mobile again in no time. John. Quote Link to post Share on other sites
bigmalcy Posted January 25, 2020 Author Report Share Posted January 25, 2020 Well it looks like I jumped the gun... Both half shafts are ok... With car jacked up at rear and engine running she crunches and grinds like the proverbial in 1st and also in reverse. 2nd/ 3rd / 4th with and without o/d all spin the rear wheels without any accompanying noise so I am hoping that that discounts any o/d issues. Engine and box definitely coming out... presume the fact that it's reverse and 1st only may be a clue as to the cause? What is the common link (I know next to nothing about these boxes). Quote Link to post Share on other sites
bigmalcy Posted January 26, 2020 Author Report Share Posted January 26, 2020 I should really do some reading before turning to you lot... Based on my trusty Moss catalogue, it looks like reverse gear may operate through the 1st gear cog on the output shaft...? So it looks like I'm probably up for a 1st gear countershaft + reverse gear + 1st gear. Is now the time to install a later box with 1st gear synchro rather than fix the old one...? Quote Link to post Share on other sites
BlueTR3A-5EKT Posted January 26, 2020 Report Share Posted January 26, 2020 Sounds like the golden trio to me too. Peter W Quote Link to post Share on other sites
bigmalcy Posted January 26, 2020 Author Report Share Posted January 26, 2020 So - now I'm researching options for fitting an all synchro box. I've found the following box on the bay, but keen to understand what I need to consider... e.g. can I easily fit my top cover with o/d switches and selectors etc to this box? Is swapping the o/d unit over from my box to a non-o/d box straightforward? What other Triumph boxes can I use... 2000, GT6, etc? Which boxes require an adaptor for the rear mounting? TIA for your advice! https://www.ebay.com/itm/Full-Synchromesh-Transmission-Gearbox-for-Triumph-TR3-TR4-TR4A-TR250-TR6-TVR2500/323993648335?hash=item4b6f86bccf:g:KgQAAOSwXSZd3dYW&autorefresh=true Quote Link to post Share on other sites
Chilliman Posted January 26, 2020 Report Share Posted January 26, 2020 I'm making a bit of an assumption that you have an original A type O/D on your current box? In answer to the first question, I can't see why it wouldn't be a straight swap for the top cover & if you did encounter any issues it's no great issue to drill & tap those raised plinths on the non O/D box to provide the correct locations for the overdrive inhibitor switches & a reverse light switch while you're about it. As for swapping them over - no, it's not straight forward as you have to strip both boxes & transfer the shorter output shaft from the O/D box to the new all synchro box...certainly do-able & I've done several but not for the feint hearted. As for other boxes - a lot can be adapted, the common ones being the stag, Triumph 2000 & 2500, I don't know anything about the GT6 box & suspect it's not compatible. Quote Link to post Share on other sites
Fireman049 Posted January 26, 2020 Report Share Posted January 26, 2020 (edited) . Edited April 15, 2020 by Fireman049 Quote Link to post Share on other sites
Graham Harris Posted January 26, 2020 Report Share Posted January 26, 2020 The top cover will fit but you may need to change the selector folks from the new one to the old and i'm not sure about the output shaft from the three synchro box it could be different but that box you are looking at looks to be in great shape. Graham Quote Link to post Share on other sites
Fireman049 Posted January 26, 2020 Report Share Posted January 26, 2020 (edited) . Edited April 15, 2020 by Fireman049 Quote Link to post Share on other sites
Lebro Posted January 26, 2020 Report Share Posted January 26, 2020 Does that answer your question Tom ? Bob Quote Link to post Share on other sites
Fireman049 Posted January 26, 2020 Report Share Posted January 26, 2020 (edited) . Edited April 15, 2020 by Fireman049 Quote Link to post Share on other sites
bigmalcy Posted January 27, 2020 Author Report Share Posted January 27, 2020 (edited) Hi guys Thanks for all the responses... I think I've found a suitable 4-synchro box here in Aus with J type o/d. Based on prices of spares I reckon that's the path I will go down. Can anyone confirm that the gear ratios in the later boxes are the same as the original box with A type overdrive? Thanks again for your inputs! Edited January 27, 2020 by bigmalcy Quote Link to post Share on other sites
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