There was a right royal row with TL DEAN at that time, because he was flogging people retipped mainshafts as "uprated" ones, and I considered this totally dishonest.įor nearly a decade we recycled out all the old D type overdrives from Vitesse and GT6, fitting J type in them and flogging off all the D type ones for old Spitfires, because the D type has a design fault in the oil system, making it jump out on RH corners.Ī lot of it was done at Kipping's in Coventry and we all made a jolly good living out of it. I was the first person to introduce the J type overdrive on the GT6, - strengthen the mainshaft and fit the later gears, back in 1983. That was the GT6 "B" box which used the same gear cut as the Mk2 but with larger syncro cones. They used exactly the same gear train as the Dolomite 1850, with the same weak 2nd gear thrusts & mainshaft spigot they used up until 1976. There is absolutely no truth in the rumour the gears were stronger. The GT6 was knocked on the head in 1973 (M reg), but a few remained in dealerships unsold and made it onto a N (74) plate, probably cos it was considered too thirsty with a 6 cylinder and wait for it.TWIN CARBURETTORS! It was due to fit the early dolomite 3 rail box as a retro fit but never made it, as you can imagine the anarchy with the 3 day week/oil crisis and Heath's government in 1973 I have this on good authority from the blokes at laycock.ġ18850 (spitfire was 40, sprint was 42, dolomite was 47.so you can see it was planned for AFTER the sprint and last Spitfire Mk4.due for 74-75). Sorry to disappoint you, but not a single GT6 left the factory with J type overdrive. I recall that Ford also had overdrives in the late '50s, but I don't know if Borg Warner made them for Ford.Only the very last GT6s had a J type overdrive and were, I believe, also fitted with the stronger Dolomite type gears with the closer GT6 ratios. Obviously, this was easier than adapting to a Cadillac 3-speed. Years ago, I watched a video on the Internet of a fellow who adapted a Borg Warner unit to a Muncie 4-speed.
LAYCOCK OVERDRIVE SERVICE IN THE U.K. MANUAL
The manual will probably not have dimensional specs for the parts. Less difficult is acquiring a late '50s Chevrolet shop manual which will have the description of how the overdrive operates, is controlled, and rebuilt. The difficulty is acquiring one of the Borg Warner units. If you love working with metal and cars, this is a worthy project. This plate would also have to be machined to accommodate some of the overdrive components like the solenoid. The big challenges in adapting a unit to a Cadillac manual transmission would be altering the output shaft and splines of the Cadillac transmission to fit the splines of the overdrive planet carrier, and machining a plate to adapt the overdrive to the rear of the Cadillac transmission case. The controls included a manual cable, a solenoid, a governor, and a wiring harness that included connections at the carburetor and ignition coil. The overdrive was a planetary gear unit with a one-way roller clutch. The unit was usually mated to a Saginaw 3-speed manual transmission. If I recall correctly, Borg Warner made about 2 million overdrives for GM between WWII (possibly before) through about 1970 - the later years mostly for trucks.
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