Pete GT6 Posted August 20, 2017 Report Share Posted August 20, 2017 Hi guys, Trying to find out if the gearbox number for my car is correct and if it is/was an overdrive unit. (There is no over drive on there now.) Number on the casing is 15c3 8 Thanks Pete Link to comment Share on other sites More sharing options...
Clive Posted August 21, 2017 Report Share Posted August 21, 2017 You need to get the actual stamped number. It is on the flat machined horizontal face, at the front corner next to where the drivers knee would be. On a GT6 it would be KC or KE prefix dependig or marque. If your car originally had overdrive, it would have O (as opposed to 0, zero) as a suffix on the commission number. And the diff ratio would be 3.89 (KD prefix) Non od cars had 3.27 diff prefix KC. Stamped on the underside of the diff. Link to comment Share on other sites More sharing options...
Pete GT6 Posted August 21, 2017 Author Report Share Posted August 21, 2017 Thanks Clive, I will have a look for the stamped number on the gearbox. I didnt realise there was one. Also my commission number doesn't have any O or o's in the number prefix or not. So this answers the question. Thanks for your help. Link to comment Share on other sites More sharing options...
dougbgt6 Posted August 21, 2017 Report Share Posted August 21, 2017 Other way around I think Clive Haynes confirms GT6 without OD 3.89 GT6 with OD 3.27 Link to comment Share on other sites More sharing options...
68vitesse Posted August 21, 2017 Report Share Posted August 21, 2017 My book lists GT6 123 - OD 3.89 GT6 123 Std. 3.27 I can not imagine why you would fit overdrive to a car and then give it a diff. which would give even lower rpm. Regards Paul Link to comment Share on other sites More sharing options...
Pete Lewis Posted August 21, 2017 Report Share Posted August 21, 2017 its all down to things like gradability, and torque if you over gear it wont pull, cant hill start and increase clutch slip times to get started . a 3.27 + OD gives a silly ratio , might suit the torque of a 2500 ,....just Link to comment Share on other sites More sharing options...
dougbgt6 Posted August 21, 2017 Report Share Posted August 21, 2017 I have my Haynes open at page 132 and it definitely says: Vitesse 2-litre and GT6 3.89 : 1 GT6 with overdrive 3.27 : 1 Is the bible mistaken!!! I bought it in 1982, I wonder if I can get my money back? Link to comment Share on other sites More sharing options...
68vitesse Posted August 21, 2017 Report Share Posted August 21, 2017 Just looked in my Haynes manual, date in front cover 1973 price £2.50, page 116. Perhaps we should start a class action to get our money back. Regards Paul Link to comment Share on other sites More sharing options...
Pete Lewis Posted August 21, 2017 Report Share Posted August 21, 2017 the triumph wsm is as above , sorry Doug ,, its refund time or get a proper book !!! Ha Dtype is + 20% or x 0.8 a 3.89:1 +od is 21.8 miles per 1000 a 3.27:1 + od is 25.9 per 1000 Pete Link to comment Share on other sites More sharing options...
dougbgt6 Posted August 21, 2017 Report Share Posted August 21, 2017 My Haynes is newer than Pauls, so how come mines wrong? Link to comment Share on other sites More sharing options...
Clive Posted August 21, 2017 Report Share Posted August 21, 2017 Haynes probably did a typo when copying the wsm. 3.89+od gives the same revs as 3.27 (no od) My vitesse ran 3.27 plus of until I broke the 3rd diff. Swapped to 3.63 and job done. That diff then did a few years in my zetec spit prior to the move to a Scooby diff... Sorry for thread drift. Link to comment Share on other sites More sharing options...
Clive Posted August 21, 2017 Report Share Posted August 21, 2017 Haynes probably did a typo when copying the wsm. 3.89+od gives the same revs as 3.27 (no od) My vitesse ran 3.27 plus of until I broke the 3rd diff. Swapped to 3.63 and job done. That diff then did a few years in my zetec spit prior to the move to a Scooby diff... Sorry for thread drift. Link to comment Share on other sites More sharing options...
Colin Lindsay Posted August 21, 2017 Report Share Posted August 21, 2017 I had a 3.63:1 Spitfire diff in my GT6 with overdrive, I removed it after a very short while and went back to the original non-overdrive version which gives a nice relaxed drive at speed but average acceleration. I'm not a boy racer so getting away from the traffic lights doesn't worry me in the slightest. Link to comment Share on other sites More sharing options...
dougbgt6 Posted August 21, 2017 Report Share Posted August 21, 2017 No, stop it! My head hurts. I'm going to lie down. Link to comment Share on other sites More sharing options...
Pete Lewis Posted August 21, 2017 Report Share Posted August 21, 2017 Aha dark room and green tea is calling. yuk pete Link to comment Share on other sites More sharing options...
dougbgt6 Posted August 21, 2017 Report Share Posted August 21, 2017 I was thinking more the golden throat nargler of the grouse like nature. Link to comment Share on other sites More sharing options...
Gully Posted August 21, 2017 Report Share Posted August 21, 2017 My 1974 Haynes is correct... More confusion... Gully Link to comment Share on other sites More sharing options...
68vitesse Posted August 22, 2017 Report Share Posted August 22, 2017 Found another Haynes manual, date on front page 1987 page 132 . Vitesse 2L and GT6 with overdrive 3.89 GT6 3.27 So corrected at some point. Just been looking in a Haynes manual for Dolomite 1500 for information on J type overdrive. Lists one rear axle ratio as 3.89 but Early 3 rail gearbox 4th 1:1 overall ratio 3.89:1 Later single rail box 4th 1:1 overall ratio 3.90:1 ??????????????????????????? Regards Paul Link to comment Share on other sites More sharing options...
Clive Posted August 23, 2017 Report Share Posted August 23, 2017 Late 1500 dolly's had 3.63! A manual where you have to hope the info you need is correct is worrying! Link to comment Share on other sites More sharing options...
Pete Lewis Posted August 23, 2017 Report Share Posted August 23, 2017 Even the genuine Triumph wsm have a few odd misprints if you got the orig dawings/blueprints there will be odd parts that never got corrected On Trucks we had a TSA temporary substitution authority tied in to the engineering design signed off by all parties to allow deviations without altering the base drawings or design if needs must . used to correct simple errors or supply problems , keeping the lines running and solving quality problems all logged and recorded but often did not change the base engineering drawings or data which would need a part number suffix adding. Link to comment Share on other sites More sharing options...
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