[Fot] Big TR OD and Gearbox rebuilding - reversing

Larry Young cartravel at pobox.com
Fri Mar 14 08:46:15 MDT 2014 

I think Jack may have intended for this to go to the group.  During our 
6 years of racing, we had one mechanical problem with our A type overdrive.

On 3/12/2014 11:27 AM, Jack Wheeler wrote:
> For what it's worth, I ran with an A-Type overdrive in my TR-4 for 24 
> years, including the 1990 Runoffs which I won at Road Atlanta.  I 
> never had an overdrive failure and, as you suggested, I shimmed the 
> main spring, so that I was generating 550 - 600 lbs of pressure.  The 
> only maintenance I did was an annual oil change (Valvoline 50 Wt) and 
> cleaning of the filter.  The A-Type overdrive is bullet proof.  When I 
> got a used one, I would go through it completely and change any parts 
> that were worn or broken (bearings, shims and other moving parts), and 
> I was good to go for years.  Most of the overdrive failures I have 
> seen in street cars have been electrical - outside the overdrive unit 
> itself.
>
> I didn't use the overdrive at all tracks.  At short, tight tracks, 
> like Hallett, OK, or Blackhawk farms, I was as quick with the straight 
> close ratio 4-Speed without overdrive. However, at long tracks, like 
> Road Atlanta and Road America, I was a second or more quicker with a 
> 4.3 rear end and the overdrive.  The main benefit for me, was that it 
> gave me a better second gear, for tight turns coming onto long 
> straightaways (like turn 7 at Atlanta).  Without the overdrive, I 
> would have to use a 3.7 rear end for the long straight, which made my 
> second gear too high and my first gear too low for the tight turns.  
> With the 4.3 rear end, my second gear was perfect for the tight turns, 
> then the overdrive was there for the end of the long straights.
>
> I had all 6 gear ratios that were available, set up in housings, for 
> quick change (mine was an IRS car).  Between the 6 ratios and a close 
> ratio gearbox both with or without overdrive, I could set up the car 
> for optimum gearing at each track.  I used a 7,000 red line.  I hope 
> some of you can benefit from my experience.  Good luck.
>
> Jack
>
>
>
> On Wednesday, March 12, 2014 11:59 AM, Larry Young 
> <cartravel at pobox.com> wrote:
> If you look through the archives, you will find several times we've
> debated the J-type vs A-type overdrive for road racing. If you use it
> only on long straights, it really doesn't make much difference. There
> are other times when an overdrive is just more convenient and quicker
> than shifting the transmission.  In those cases I believe an A type
> overdrive is preferred.  An early one with the large accumulator which
> is shimmed for extra pressure will make the shifts virtually
> instantaneous.  You might also want to consider changing your rear axle
> to something like a 4.55 which will give 3.73 in 4th overdrive.
>
> Whenever I hear the comments about how overdrives easily fail, I mention
> that mine saved me once.  When a bad throw out bearing made the
> transmission impossible to shift, I put in 3rd and ran a couple of races
> using just 3rd and 3rd overdrive.  I think my lap times only dropped
> about one second.
>
> On 3/10/2014 6:47 PM, Marcel Van Mulders wrote:
> >  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 <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 <mailto: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 
> <mailto: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 
> <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.
> >> _______________________________________________
> >> fot at autox.team.net <mailto:fot at autox.team.net>
> >>
> >> http://www.fot-racing.com <http://www.fot-racing.com/>
> >>
> >> Donate: http://www.team.net/donate.html
> >> Archive: http://www.team.net/archive
> >> Forums: http://www.team.net/forums
> >> Unsubscribe/Manage:
> > http://autox.team.net/mailman/options/fot/tr4.tony@virgin.net
> > _______________________________________________
> > fot at autox.team.net <mailto:fot at autox.team.net>
> >
> > http://www.fot-racing.com <http://www.fot-racing.com/>
> >
> > Donate: http://www.team.net/donate.html
> > Archive: http://www.team.net/archive
> > Forums: http://www.team.net/forums
> > Unsubscribe/Manage: 
> http://autox.team.net/mailman/options/fot/cartravel@pobox.com
>
> _______________________________________________
> fot at autox.team.net <mailto:fot at autox.team.net>
>
> http://www.fot-racing.com <http://www.fot-racing.com/>
>
> Donate: http://www.team.net/donate.html
> Archive: http://www.team.net/archive
> Forums: http://www.team.net/forums
> Unsubscribe/Manage: 
> http://autox.team.net/mailman/options/fot/jwheeler1947@yahoo.com

More information about the Fot mailing list