[Fot] Big TR OD and Gearbox rebuilding - reversing

Fri Mar 14 13:23:02 MDT 2014

Wishbone Classics makes a nice upgrade to the A-type overdrive planet gear
and carrier assembly where they machine out a deeper pocket in the case for
the bronze thrust washer (Moss part number 866-560) and install one of
double thickness and stronger material.  This is a difficult DIY procedure
because you have to remove the three gears in the carrier which are not
designed/intended for removal.  I found pieces of what was left of the
original washer in my filter screen. The rest was ground into gold dust.

On Fri, Mar 14, 2014 at 10:46 AM, Larry Young <cartravel at pobox.com> wrote:

> 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>
> > >>
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> > >>
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