TReslaV8 Posted July 10, 2019 Share Posted July 10, 2019 Idle curiosity, but having just completed a 450 mile trip, I was wondering whether anyone knows if there is a suitable 6 speed box for a TR7 V8 (SD1 engine) ? The LT77 in my car seems to be awfully low geared in fifth for comfortable 70-80mph cruising. David Quote Link to comment Share on other sites More sharing options...
Clive Posted July 10, 2019 Share Posted July 10, 2019 I think the usual solution is to swap diffs? I am not certain the 6 speed boxes have a significantly longer top gear than most 5 speed boxes, just closer ratios ( or the rx8 which has a crawler first gear, making it in reality a close ratio 5 speed box) Quote Link to comment Share on other sites More sharing options...
glang Posted July 10, 2019 Share Posted July 10, 2019 As Clive says a different ratio, assuming there is one, would do the job but youd have to judge whether 1st gear could handle it as the last thing you want is to have to slip the clutch in slow moving traffic etc Quote Link to comment Share on other sites More sharing options...
Clive Posted July 10, 2019 Share Posted July 10, 2019 Just looked in my old "Triumphtune" catalogue. 27 years old... Anyway, in the tr7v8 conversion section, it gives the following info on diffs: 3.90 std tr7, unsuitable in a V8 20.7mph/1000rpm 3.45 for fast acceleration, but low cruising speed. 23.4mph/1000rpm 3.08 etc tr8 and Rover sdi, good all-rounder. 26.3 mph/1000rpm 2.84 high speed cruising 28.5mph/1000rpm Above speed/revs based on 185/70 13 tyres Small changes are available using bigger tyres, but no idea big you can go. Quote Link to comment Share on other sites More sharing options...
TReslaV8 Posted July 10, 2019 Author Share Posted July 10, 2019 That sounds interesting, now where to find a 3.08 or 2.84!? Thanks again. David Quote Link to comment Share on other sites More sharing options...
Clive Posted July 11, 2019 Share Posted July 11, 2019 Afraid I can't help with that, but tr7 specialists may be able to help? Quote Link to comment Share on other sites More sharing options...
glang Posted July 11, 2019 Share Posted July 11, 2019 Rimmers say they are expecting CWP with those ratios in August and of course you might as well put in a LSD at the same time Quote Link to comment Share on other sites More sharing options...
TReslaV8 Posted July 11, 2019 Author Share Posted July 11, 2019 Brilliant, thanks one and all, much appreciated. David Quote Link to comment Share on other sites More sharing options...
Steve AKA vitessesteve Posted July 12, 2019 Share Posted July 12, 2019 I would try try talking to Robsport or S & S Preparations. Quote Link to comment Share on other sites More sharing options...
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