QuestionOk, I'm about to get my 1st Spit, a 73, 1500. The tranny is a straight 4 no OD. I plan on doing a complete restoration and upgrades to the engine. ie: twin SU's. cam, exhaust.... I want to drive the car to work when I'm finished. Roughly 40 miles all highway. Should I seriously consider a tranny upgrade or will I do just fine with getting the engine to breath better :). Remember I'm new
thanks,
Chris
AnswerChris,
The eternal question. To overdrive or not?
Pros: Better gas mileage. Less stress on the engine. Less stress on the driver (less engine noise while driving). Potentially better cruising speed.
Cons: Cost. Additional point of failure.
Well, if the highway commute is "at speed" and not "at crawl" as most highway trips can be these days (I used to be in the Washington DC area ;) then there will be benefits to having the o/d. Or even just making long distance trips in the car.
If money is no object then you'll find it an enjoyable addition to the car. I won't quote prices (all the major suppliers are happy to do that ;) but don't forget that you'll also need a different driveshaft, gear shift lever and trans mounting plate on the frame.
If you find a D-type overdrive you can use the later Spitfire non-o/d driveshaft. That way you'll even be correct for your year Spitfire. Otherwise you'll wind up going with a J-type from a later Spitfire.
If you go with a used transmission you'd be well served to find one that can be "demonstrated" before you buy it. Some of the suppliers/rebuilders will only sell overdrive units on an exchange basis so you might need to have a rebuildable core to start with.
Another option if you want to "keep it Triumph" is to fit an optional Spitfire 3.63 ratio differential (instead of the stock 3.89) or the GT6 3.27. That will kill some of the off the line performance, but if you're going to play some other games like the twin SUs and bumped compression it might not be too bad a compromise.
Cheers,
Jim
