Thread: SERIES overdrive with auto box?

depends on which overdrive, generally Ive found double clutching helps them no end when it comes to shifting so assuming that your transmission doesnt do neutral real well then yes you would have to stop to shift.

and no, providing you arent to hard on the right boot when you take off taking off in either ratio wont hurt the overdrive

The Fairey overdrive has got synchromesh, and at least on the one I have, it works very well. If your synchromesh is working it would handle changing with the transmission in neutral without any problems, and probably even in gear provided it is not driving or overrun. If the overdrive is under load when you try to change, it will be almost impossible to move the lever without forcing it, and from neutral to in gear will simply not go in if there is too much speed difference, so there is little chance of doing anything other than a bit of wear on the synchromesh trying it.

The Fairey overdrive is rather fragile, and has a small oil reservoir, so I would be rather cautious about using it from a standstill, particularly with the larger engine, even with an auto - the lack of shock loading will probably stop you from breaking anything, but if, for example, starting off up a steep hill or heavily loaded, or accelerating rapidly to high speed, is likely to give relatively rapid wear and is likely to overheat the overdrive.

John

With a little practice you should be able to engage it by matching the engine speed to your road speed in top gear, and it will just slide in.

Fraser

If you have a 4.1L engine and an auto, I would fit 4.11 diffs instead of an overdrive.

Originally Posted by isuzurover

If you have a 4.1L engine and an auto, I would fit 4.11 diffs instead of an overdrive.

My choice too.It would be a hell of a lot quieter to boot. Pat

Originally Posted by isuzurover

If you have a 4.1L engine and an auto, I would fit 4.11 diffs instead of an overdrive.

Or even better, IMHO, a set of high-speed transfer case gears. 28% taller high range gearing but standard low range gearing is retained. Going to 4.11 from 4.7 diff ratios is only a 14% taller ratio and applies to low range as well. If buying it all new, I'd think the HS transfer gears would be a lot cheaper than two 4.11 CW&P sets?

Made my SIII/GMH 202 much nicer to drive on the highway - about 1000 less rpm @100km/h.
Ian

Originally Posted by Leo109

but standard low range gearing is retained.

All true, except for this bit.

Low range is increased slightly with the HRTC. This also precludes you from fitting the 2.89:1 low range gears from a suffix B SIIA. Which would more than compensate for 4.11s.

Also, depending on the mods which have been done to the t-case to fit the auto, custom work may need to be done which would increase the costs. The HRTC conversion requires the intermediate shaft hole in the t-case housing to be welded up and a new hole machined. If the t-case or the input gear are custom (due to the C4 conversion), then you will need to ship them off to whoever still does this conversion (ashcroft???) and get them modified.

I don't know about yours, but my auto conversion comes out through the rear of the transfer case in the position of the PTO/overdrive position, so I can't fit anything to the rear of the transfer case.