[Fot] Big TR OD and Gearbox rebuilding - reversing

davehogye dlhogye at comcast.net
Fri Mar 14 09:24:53 MDT 2014 

I agree completely with Jason. This is great information and the kind that should be published for future reference. 
Thanks for sharing Larry and Jack. 


Dave H. 

----- Original Message -----
From: jason at multivintage.com 
To: "Larry Young" <cartravel at pobox.com>, fot-bounces at autox.team.net, "Jack Wheeler" <jwheeler1947 at yahoo.com> 
Cc: FOT at autox.team.net 
Sent: Friday, March 14, 2014 7:54:28 AM 
Subject: Re: [Fot] Big TR OD and Gearbox rebuilding - reversing 

Wow. What a great info post for the books. 
I love this group! 
Jason Ostrowski 
Friendly Ghost Racing 
Sent via BlackBerry by AT&T 

-----Original Message----- 
From: Larry Young <cartravel at pobox.com> 
Sender: fot-bounces at autox.team.netDate: Fri, 14 Mar 2014 09:46:15 
To: Jack Wheeler<jwheeler1947 at yahoo.com> 
Cc: FOT at autox.team.net<FOT at autox.team.net> 
Subject: Re: [Fot] Big TR OD and Gearbox rebuilding - reversing 

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. 
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