Designedr use of a Fairey OD - start in OD or engage in fourth gear?

[WilsBoar]

What is the designed use for the Fairey? In regards to using it for an increased highway speed (increased and speed used as relevant terms!), is it designed not to be engaged until you get to higher RPMs in fourth gear and then you engage the OD at that point? Or is is better to keep it engaged through all four gears from the start if you know you would like to take advantage of the high speed capability?

I have not tried to engage the OD running in fourth gear yet as I just installed the SIII tranny and OD. I would rather not have it all sound like a blender full of bolts if it is not designed to be shifted into OD while underway.

Thanks!

Derek

[TedW]

IIRC the instruction book tells you to engage it when you are wound up in fourth gear - which is what I usually do. It will put the least strain on your mechanicals. However, I admit that I am also prone to leaving it engaged and starting out in first from a full stop with it engaged: I then can wind up in first and shift straight into third.

This is easier to accomplish if you have a strong engine and 15" tires (I have 235/85/16's - no problem). And I tend not to do it if I'm going uphill from a full stop.

Just my $0.02. I suspect that your query will bring forth lots of different opinions.

[Linus Tremaine]

Overdrives are not the strongest things in the world. They have their own synchros and can be shifted while you are driving. However, it is a better idea to not use it in lower gears. I use mine only as a functional fifth gear and to split 3rd and 4th on hills. Using it in first gear or in low range puts more stress on it than I am comfortable with. Sometimes I leave it in by accident and take off in first, but I prefer not to do that.

[I Leak Oil]

A properly working fairey can be switched in or out at any speed\gear. Whether or not it's good to use it in 1st or not is debatable but I've never had the need for it other than in 4th and on a rare occasion, 3rd.

[scatterling]

I agree. Mostly used in 4th and sometimes in 3rd to split gears going up a hill. Just depress the clutch and shift it like the other gears.

[mearstrae]

My overdrive is the 70's version used on V-8's with LT95 trans [Defenders and Range Rovers], it is bigger than other Fairey overdrive units. And it is still recommended for use only in 3rd and 4th, high range.

'95 R.R. Classic LWB
'76 Series III Hybrid 109
'70 Rover 3500S

[kels]

Please don't engage your fairey overdrive in first or second - it will blow up very quickly. It's designed as a 5th gear and will take occasional use as a 3rd-4th splitter, but that's all.

Cheers,

Adam

[stomper]

As others have said, just depress the clutch, and engage the overdrive. I use it like a 5th gear, but if I am cruising at 45mph in 4th gear, I will often engage it to lower the RPMs. I can slow down to around 30mph, and still accelerate on a flat road (slowly) without needing to disengage/downshift. It is designed to assist in fuel economy by lowering the RPMs of the engine, not really designed as a whole set of additional gears.

[knac1234]

FWIW,

I tend to use the split 3rd gear often. And, of course, I use it to lower the revs in 4th gear at "speed!" That said, other than by accident, I haven't used it in 1st or 2nd. Guess I'm just used to that as my MGB has an inhibitor switch on its OD, allowing it to function only in 3rd and 4th. I know it's a totally different beast, but tis what I'm used to!

Julian

[73series88]

same
3d splitter and 5th
aaron

[antichrist]

My Fairey manual makes not mention of only using it in 4th, or 3rd and fourth. In the "Operation" section all is says it that the overdrive should be treated as a separate gearbox. My Toro manual (which is the same basic design as the Fariey) says pretty much the same.

FWIW I had a friend in the '70's who had one in his 88 which he used to tow his Airstream trailer and he used it as a secondary gearbox, using it in all gears.
His typical shift pattern was:
1st -> 1st + OD -> 2nd -> 2nd + OD -> 3rd -> 3rd + OD -> 4th -> 4th + OD ->

[WilsBoar]

Thanks everyone. I appreciate all the comments and advice.

Derek