Can anyone point me in the right direction for a web site that explains how an overdrive unit works with the transfer case. I am having trouble understanding how switching one extra gear in or out of the transfer box (say an LT230) alters the ratios.
Thanks Smokeyone
Try
The overdrive unit does not consist of one gear - it is a two speed (direct and step-up) gearbox that mounts on the PTO location of the transfer box and replaces the gear on the back of the gearbox main shaft. It has concentric input and output shafts, and in direct they are locked together so that it just behaves as if the original gear were there. In overdrive the gearbox main shaft drives a step up gear set - actually four gears, one on the input shaft, two on a layshaft, and one on the concentric output shaft, so that the first gear in the transfer case is now going faster than the gearbox main shaft. Hope this helps - the description is actually for a Series Landrover overdrive, but the RR/90/110 works exactly the same way. JD
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