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<div> <font size="3">That is true for cars that remain equipped as delivered. However, many or most TR's were delivered without overdrive and many of us have since fitted overdrive transmission to our cars whilst keeping the stock (non-OD) differential. <br>
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<div><font size="3">I guess the short answer is: your mileage may vary.</font></div>
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<div><font size="3">Cheers</font><br>
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<div style="clear:both"><font size="4">Dave </font><br>
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<div style="font-family:arial,helvetica;font-size:10pt;color:black">-----Original Message-----<br>
From: John Macartney <John.Macartney@Ukpips.org.uk><br>
To: Dave MacKay <dave@mdmackay.ca><br>
Cc: Triumphs@autox.team.net<br>
Sent: Mon, Jun 1, 2020 2:24 pm<br>
Subject: Re: [TR] RPM speed calc<br>
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<div>It’s important to remember that cars without overdrive had a higher axle ratio than those with it. As an example, the GT6+ had a 3.27 final drive for non overdrive and 3.89 for overdrive. Just to complicate things, it was entirely possible to order a 3.27 diff with overdrive on top! The factory never promoted this facility for fairly obvious reasons. My own GT6 mk 2 was supplied like that becxause I knew my way around the factory build books. Iit made an excellent cruiser with good fuel consumption but could not pull more than 4000 rpm, even downhill on a motorway. That said, refuelling was a little less frequent.
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<div>Jonmac<br clear="none"><br clear="none">
<div dir="ltr" id="yiv9085228339AppleMailSignature">At the Battle of Waterloo, 1815:
<div>Lord Uxbridge: “By God, Sir - I’ve lost my leg”</div>
<div>Duke of Wellington: “By God, Sir - so you have!”</div>
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<div class="yiv9085228339yqt6140383728" id="yiv9085228339yqt63103">
<div dir="ltr"><br clear="none">On 1 Jun 2020, at 19:41, Dave MacKay <<a rel="nofollow" shape="rect" ymailto="mailto:dave@mdmackay.ca" target="_blank" href="mailto:dave@mdmackay.ca">dave@mdmackay.ca</a>> wrote:<br clear="none"><br clear="none"></div>
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<div class="yiv9085228339MsoPlainText">>Date: Sun, 31 May 2020 16:52:23 -0500</div>
<div class="yiv9085228339MsoPlainText">>From: bill beecher <<a rel="nofollow" shape="rect" ymailto="mailto:notakitcar@yahoo.com" target="_blank" href="mailto:notakitcar@yahoo.com">notakitcar@yahoo.com</a>></div>
<div class="yiv9085228339MsoPlainText">>Subject: [TR] RPM speed calc</div>
<div class="yiv9085228339MsoPlainText">> </div>
<div class="yiv9085228339MsoPlainText">>Came across this calculator with all the right input fields. But, I wonder how accurate it really is given the following input. </div>
<div class="yiv9085228339MsoPlainText">>TR3 with a 3.7 rear, OD at redline of 5,000rpm. Vredestein 165R/15 tires, 25.4? diameter. Should be moving along at 124mph!</div>
<div class="yiv9085228339MsoPlainText">> </div>
<div class="yiv9085228339MsoPlainText">><a rel="nofollow" shape="rect" target="_blank" href="https://wahiduddin.net/calc/calc_speed_rpm.htm">https://wahiduddin.net/calc/calc_speed_rpm.htm</a></div>
<div class="yiv9085228339MsoPlainText">> </div>
<div class="yiv9085228339MsoPlainText">>Anyone get a different answer? </div>
<div class="yiv9085228339MsoPlainText">>Bill</div>
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<div class="yiv9085228339MsoNormal">Here (attached) is a spreadsheet that I wrote to calculate speed versus rpm given different parameters. I wrote it to check my speedo after I installed an HVDA transmission. If the spreadsheet doesn’t make it through the list as an attachment, just e-mail me directly and I’ll send it to you.</div>
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<div class="yiv9085228339MsoNormal">With a standard Triumph gearbox + overdrive, and the parameters you gave, I calculate speed at 5000 rpm in top gear (with overdrive) as being 124.5 mph. Note that, I think that the tire diameter is 25.25”, slightly less than you indicated.</div>
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<div class="yiv9085228339MsoNormal">I hasten to add that calculating a speed and believing it’s achievable are two different things!</div>
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<div class="yiv9085228339MsoNormal">Regards,</div>
<div class="yiv9085228339MsoNormal"> </div>
<div class="yiv9085228339MsoNormal">Dave MacKay</div>
<div class="yiv9085228339MsoNormal">1960 TR3A s/n 68639L</div>
<div class="yiv9085228339MsoNormal">near Toronto, Canada</div>
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<div dir="ltr"><Triumph rpm to mph.xls></div>
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