AnswerID: 29782 Submitted: Monday, Sep 01, 2003 at 15:15
Member - DOZER
replied:
Most mechanics will tell you to stay out of overdrive altogether. Some on this list use it when towing, but treat it with cotton wool, and change down at the slightest hill or head wind. There gearboxes are hanging together so far.
The problem is that earlier boxes were a 4 speed with a 5th tacked on the back and they failed prematurely. Todays boxes are designed better with 5th in the middle of the layshaft.
From a purely theoretical point of view, 4th gear is straight through the gearbox and minimal wear will occur, but 5th is using the layshaft and all the bearings on the mainshaft, layshaft and input shaft have maximum torque applied to them (@ approx 2000 rpm) so things start to heat up and if anything is going to kill the box it will be this type of condition.
Same goes for autos in o/d as the ratio is higher than a manuals.
Remember, to get x amount of torque to the rear wheels in 5th gear, 1.3 times x amount must be put in at the motor end of the box.
Andrewwheredayathinkwer mike?
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