[Fot] Big TR OD and Gearbox rebuilding - reversing

[Marcel Van Mulders]

 You must be Tony Sheach from the article in Kas Kastner's book "Triumphs,
race cars, street cars and special cars". Flat out rallying is something to
have respect for!
In 1997 I bought a rough TR3 and restored it as a road car, with a Triumph
Saloon J-type O/D and fitted the logic device of Revington. Indeed it worked
great, doing exactly what you expect in every situation with just one push
switch to command. In fact the small box is still in my car, but when I
started road racing the TR3, the O/D was removed because I saw much failures
and at that time I was not convinced it would make the car faster and top
speed in 4th gear with a 3.9:1 rear axle was 120mph.It also makes the car
10kgs heavier. Contrary to the USA (and UK?), the use of an O/D in road
racing TR's is rare in Europe.
But I've changed my mind (thanks to Chris Marx!) and will fit a J-type O/D
together with a higher rear axle ratio. The logic switch box of Revington is
unused since 10 years and it has 6 pins/wires, so I don't thrust it enough.
A hold relais and push switch will do, because I will only use the o/d on
4th gear. The overdrive is sapping some power and I would only engage it on
long straights. 
Marcel, Belgium.

-----Oorspronkelijk bericht-----
Van: TR4 Tony [mailto:tr4.tony at virgin.net] 
Verzonden: maandag 10 maart 2014 8:36
Aan: Marcel Van Mulders
CC: Larry Young; fot at autox.team.net
Onderwerp: Re: [Fot] Big TR OD and Gearbox rebuilding - reversing

Marcel

Revington TR and TR Enterprises in the UK supply such a part already, both
slightly different but very effective - I use the Revington one and have
done so for 10 years as they were the original maker. Both are equally good.

It works very well on my TR4 with an A type overdrive, very reliable and
because I use a 4.875 cw&p plus a 28% overdrive I get a direct switch up and
down a full gear due to the gear / rear end and overdriven ratios - for
example I don't have to shift across the gate from 2nd to 3rd as overdrive
2nd = direct 3rd.

similarly I can drop from OD top straight to 2nd by heel and towing across
the gearbox and shifting out of overdrive automatically without activating
the switch ie hands on wheel and lever. This makes my entry to low speed
corners when trail braking very quick, and handbrake turns very tight (I've
got to be quick between the gear lever and handle!) as I don't reach for 1st
to come out of a tight one for the two or three seconds that I need to pull
the car round 180 degrees. 

I know you guys don't do handbrake turns, but they save you from big
accidents more often than I like to admit ... 

Regards

Tony 



Sent from my iPhone

> On 9 Mar 2014, at 19:34, "Marcel Van Mulders"
<van.mulders.marcel at telenet.be> wrote:
> 
> Thanks. I'm thinking of using a J-type with a push switch actuating a hold
> relais, and keeping the gearbox case switch. Changing gear will
> automatically disengage the overdrive. I would also mount an override
switch
> directly between battery12V+ and the solenoid, just in case the push
switch
> would be dead. But my engine is still on a dyno, 5 weeks before the 1st
2014
> saison race...
> Marcel, Belgium
> -----Oorspronkelijk bericht-----
> Van: Larry Young [mailto:cartravel at pobox.com] 
> Verzonden: zondag 9 maart 2014 19:54
> Aan: Marcel Van Mulders
> Onderwerp: Re: [Fot] Big TR OD and Gearbox rebuilding - reversing
> 
> The J type has the same unidirectional clutch, so it has the same problem
as
> the A type.  However, all of these units leak down after a while when the
> pump stops.  The A type leaks down more slowly because of all the fluid
> stored in the accumulator.  The J type without an accumulator, will leak
> down much more quickly (maybe 10 seconds vs. at least several several
> minutes).  For example, if you stop, shift to reverse and start backing
up,
> it will likely be disengaged.  The leak down rate also depends on the
> condition of all the various seals within the overdrive. One A type that I
> rebuilt would hold pressure for several days, but that was exceptional.
> Larry
> 
>> On 3/9/2014 10:14 AM, Marcel Van Mulders wrote:
>> Not quite the same subject : it's very unhealthy to an A-type to 
>> reverse the car with the overdrive engaged for some unorthodox reason. 
>> Can you wreck a J-type overdrive in the same circumstances?
>> Marcel, Belgium.
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