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TR3 / 3A overdrive


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As part of my TR3A project I retrofitted overdrive because I figured it would be the same miserable experience as the TR6 without overdrive. At highway speeds the engine is revving its nuts off with the associated wearing noise. The TR3 may be different since it is more open, perhaps we dont go as fast but I doubt it.

 

Stan

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Steve,

 

The answer is that o/d is even more important on a TR3, as

1) the TR6 axle ratio is 3.45, allowing lower revs in 4th, and

2) the TR3 is noisier so the drop in revs is a greater benefit.

 

AlanR

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My car was originally built without OD and it retook the road a few years ago that way. We installed an OD (a gift from a friend) last summer, so I now have before/after impressions on the same car.

 

It's nice to have, but frankly not need to have. It would depend mainly on how much open road / motorway driving one does. Above 70 mph it indeed makes a difference to lower the engine revs. Around town and on winding country roads it can be fun to use the overdrive switch rather than the gearshift at times, but to be honest I was fine without it.

 

My car was originally supplied with a 4-synchromesh gearbox. A "rationalised gearbox" they called it in the build records, since I guess the 3-synchro was gone as the TR4 came into production. I would MUCH rather have 4 speed synchro than overdrive.

Edited by Don H.
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I have a 3a and I've just bought a reconditioned overdrive box to replace the standard one. The standard box revs quite high over 60mph and the overdrive is a welcome relief from the noise

I have to admit, I'm not bothered about the 3 vs 4 synchro box. Just make sure you've come to a full stop before changing into first gear.

 

The other issue I found was that when I thought about selling just after Christmas, not having an o/d box seemed to be a big issue to most people, perhaps because there are so many cars with it fitted. A bit like some people expect Sat Nav in a a modern car and avoid one that doesn't have it fitted (as indeed I did this weekend on a poorly specced Z4 - why buy one without sat nav etc when one that has it fitted is pretty much the same price second hand).

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Agree with Bob and disagree with Don, OD a distinct advantage especially on a longish run and makes motorway driving when necessary much more relaxed it also gives you intermediate gears which can be quite useful.

 

The 3 synchro box is fine, you can always DDC if you are not stationary, for me OD much preferred to 4 synchro box.

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A few years ago I had an o/d fitted to my 3A as the car had when I got it a TR2 box. now a TR4 box with a 22% o/d, what was standard as o/d on TRs, I think.

If you do a lot of miles and no racing or traffic light competition you might go for a higher rate like 25 or 29%

It does not only bring noise down, but also fuel consumption.. :)

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Hah! You guys must not live in a city whose abundant four-way stop signs have led to a definition in urban slang. Look up "St Louis stop" sometime -- this city is nuts for its stop signs. That full-stop-into-first-gear business is a major PITA here!

 

+1 with Bob -- both full synchro and OD are nice.

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In the early 1960s, my first TR2 didn't have overdrive and it had the normal drum brakes. Having scared myself many times with lack of brakes when decelerating from high speeds (one could legally travel at well over 70 mph then) and being concerned at running the engine at very high speed, I determined that my next TR MUST have disc front brakes and overdrive.

I was lucky to find a TR2 which had overdrive and had been converted to discs - bliss! Being a TR2, economy was very good, too. I just wish that I had known that a Girling axle would fit a TR2, as I was for ever having oil seals replaced at the rear.

 

For travelling longer distances, I think that a 3.7 axle with overdrive means that one can happily keep up with modern traffic and although the brakes may not have all the clever modern anti-lock add-ons, they are still very good indeed (and a servo is quite unnecessary).

 

Ian Cornish

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"Look up "St Louis stop" sometime -- this city is nuts for its stop signs. That full-stop-into-first-gear business is a major PITA here!"

 

Don - I have the original 3-speed synchro box with O/D that came with the TR3A in 1958. I love it.

 

I often move away from a stop sign in 2nd gear and it pulls away slowly, but smoothly and I avoid 1st gear quite often.

 

Don Elliott

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Don - I have the original 3-speed synchro box with O/D that came with the TR3A in 1958. I love it.I often move away from a stop sign in 2nd gear and it pulls away slowly, but smoothly and I avoid 1st gear quite often.Don Elliott

Glad you're happy with what ya got, Don. Have you ever driven a full-synchro sidescreen car, BTW? I love old tech, but full sychro is the way to go, IMO.

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Thinking that overdrive is mostly a 'Fifth' gear for cruising, is missing most of the advatages of having it,

 

Third - overdrive third - top - overdrive top, is, on the right roads marvelous gearing.

 

John.

Edited by john
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What the heck is the problem with a non-synchro first gear ? So you have to double declutch, is that such a big deal ? It's only a matter of operating hands and feet in unison.

 

And if the appendages are working well, skip the clutch pedal anyway . . . . . it's a luxury, not a necessity once you're on the move.

 

As for moving off slowly in second to avoid first . . . . . holy mackerel, strewth, give me strength. Buy a modern with a slush pump box ?

 

Cheers

 

Alec

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"Look up "St Louis stop" sometime -- this city is nuts for its stop signs. That full-stop-into-first-gear business is a major PITA here!"

 

Don - I have the original 3-speed synchro box with O/D that came with the TR3A in 1958. I love it.

 

I often move away from a stop sign in 2nd gear and it pulls away slowly, but smoothly and I avoid 1st gear quite often.

 

Don Elliott

Like the added O/D just for the fuel economy and less wear and tear aspects.

 

The four STOP sign intersections don't work here. The only one I know of down the coast, changed one direction to GIVE WAY signs, I guess after a few prangs.

US friends briefed me on the FIFO routine observed there. here it would work on who has the quickest reflexes and biggest ego.

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What the heck is the problem with a non-synchro first gear ? So you have to double declutch, is that such a big deal ? It's only a matter of operating hands and feet in unison.

 

And if the appendages are working well, skip the clutch pedal anyway . . . . . it's a luxury, not a necessity once you're on the move.

 

As for moving off slowly in second to avoid first . . . . . holy mackerel, strewth, give me strength. Buy a modern with a slush pump box ?

 

Cheers

 

Alec

After you've knocked a tooth off your cluster gear you'll be sorry you didnt come to a complete stop. The three gear box is definately the weakest link in a really robust car.

Edited by bnw
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Like the added O/D just for the fuel economy and less wear and tear aspects.

 

The four STOP sign intersections don't work here. The only one I know of down the coast, changed one direction to GIVE WAY signs, I guess after a few prangs.

US friends briefed me on the FIFO routine observed there. here it would work on who has the quickest reflexes and biggest ego.

What you need are mini roundabouts - lots of em in a big circle

You can go both ways round the big circle.

Here are some views of the one in Swindon

 

image the magic roundabout swindon

 

Cheers

Peter W

PS It is a lot easier than 'Spaghetti Junction', where if you get on the wrong route your stuffed.

 

PPS I had a TR2 with o/d on top only - my long run to work was miserably noisy with the top up when the o/d stopped working (as it did frequently). The best solution was fit a second silencer then repair the overdrive

Edited by BlueTR3A-5EKT
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I've been able to choose between an all synchro non overdrive TR3B and a 3 synchro TR3A with overdrive. Both had 3.7:1 diffs.

 

Which went on highway runs - always the overdrive car for the more relaxed engine revs. Fuel saving was 4-5 mpg (offset by the cost of an eventual overdrive rebuild). It's also about flicking the O/D toggle switch up and down through the mountains. I've tried other cars with a column lever and a gearstick slider switch, but neither had quite the same charm.

 

Viv

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" After you've knocked a tooth off your cluster gear you'll be sorry you didnt come to a complete stop. The three gear box is definately the weakest link in a really robust car. "

 

If I ever succeed in knocking a tooth off any gear, I'll let you know . . . . . first time for everything . . . . . :rolleyes:;)

 

I learned to drive switching between 3 and 4 speed crash boxes, 3-synchro and crash first, and Wilson preselector . . . . . none of which presented a problem, even if it was necessary sometimes to remind oneself which was the pedal order. Switching pedals to the more modern layout solved that one ! Practice makes if not perfect, at least a reliable routine.

 

Cheers

 

Alec

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I think I need a double declutching lesson.. I understand the principle, use the clutch and put gearbox into neutral, synchronize engine and input shaft rotational speed using the accelerator, use the clutch again to go into the next gear.

 

For example, I'm approaching a stop sign in the TR3 and I'm in second gear. I shift into neutral with the intention of going into my non synchro first gear as I approach the stop sign. What am I supposed to be doing with the accelerator at this time to make that transition seamless ?. How will I know it is ok to pop it into first gear as I approach the stop sign, still moving forward ?

 

Stan

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It's about road speeds, gear ratios, and engine revs, Stan. The idea is to blip the throttle to get the gears spinning at the right speed to slot into engagement at the speed they'll be when fully engaged.

 

One can practice by shifting smoothly between gears at speed without the clutch, especially raising the revs during downshifts.

 

It comes with practice. I've done it plenty, although I'm apparently in the minority in not considering double-clutching one of the charms of TR driving. (smile). Maybe it's having big feet in a little car. Or too many full stops in my area.

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I lost that cluster gear tooth on my first TR3 back in 1966. I attempted to fix it myself with disasterous results, the worst being that I tried to bolt the gearbox back in without having used a pilot shaft first (new clutch) and broke the bellhousing into two pieces. I was 17 years old. 49 years and several TR3s later, I still, to this day always stop, drop back to second to stop any input shaft movement and then go into 1st. I love to drive domestic (American) standard transmission cars without using the clutch both on upshifts and downshifts just to test my skills, but I would never do that with a British gearbox. Too much respect for the British car I think.

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