This is why you fit a 5 speed box.

abowie · Post by **abowie** » Sun Dec 13, 2015 7:18 am

2000 rpm at 100 kph.

Post by **Heuer** » Sun Dec 13, 2015 10:44 am

Doesn't it also depend on the diff ratio?

Post by **mgcjag** » Sun Dec 13, 2015 11:12 am

Hi Andrew.....great time to post this.....Aussie,s first off the mark doing there bit after the Paris climate agreement..

Nickleback · Post by **Nickleback** » Sun Dec 13, 2015 11:29 am

Which diff / ratio with which gearbox ?
I'd be very interested to know more, if the gearbox did not actually involve modifying the tunnel / bodywork ?

malcolm · Post by **malcolm** » Sun Dec 13, 2015 11:43 am

Has your car really only done 28,000 miles? Great find if so.

norman m. macleod · Post by **norman m. macleod** » Sun Dec 13, 2015 12:03 pm

Hi Andrew,
I suspect that you may have smaller kilometres in South Australia than we do in Western Australia, your speedometer is showing 70 mph, which is 112.65 km/hr., not 100 km/hr. as per your post........?
I too have a 5-speed, but on a 3.31 diff., would be interesting to compare notes ( I have a heavily modified Xj6 Series lll up front......)
Mmmmm............
Regards,
Norman.

abowie · Post by **abowie** » Sun Dec 13, 2015 8:27 pm

3.54 diff.

JT5 box from Medtronics; no modifications at all to fit. See http://www.projectetype.com/index.php/t ... t5-in.html

I reckon it's really 128,000. It was being driven in 2009 when it was purchased and had plus 20 pistons and a good amount of engine wear.

Speedo is totally inaccurate. The white dots are 60, 100 and 110 kph by my GPS.

Nickleback · Post by **Nickleback** » Sun Dec 13, 2015 9:26 pm

Thanks Andrew,
Good write up on the link although it looks very tight :o
So this is the kit:
http://www.5speeds.com/6cylkit.html
With a std 3.54 diff which has to be installed with the IRS out ?

PeterCrespin · Post by **PeterCrespin** » Mon Dec 14, 2015 2:41 am

abowie wrote:Speedo is totally inaccurate. The white dots are 60, 100 and 110 kph by my GPS.

Can't see the serial number on the speedo. Is it the original diff? Which top gear overdrive ratio did you choose?

alfred · Post by **alfred** » Mon Dec 14, 2015 3:53 am

nice to see someone else using the kiss principle to correct their spedo. Mine has a yellow dot for 100 km and a red one for 120.

Alfred

abowie · Post by **abowie** » Mon Dec 14, 2015 4:57 am

PeterCrespin wrote:
abowie wrote:Speedo is totally inaccurate. The white dots are 60, 100 and 110 kph by my GPS.
Can't see the serial number on the speedo. Is it the original diff? Which top gear overdrive ratio did you choose?

It's the speedo that came with the car but it doesn't actually go back to zero when the car is stationary. You get about 10mph just for sitting in the seat....

Diff is the original 3.54 and the OD is O.73.

abowie · Post by **abowie** » Mon Dec 14, 2015 6:07 am

Nickleback wrote:Thanks Andrew,
Good write up on the link although it looks very tight :o
So this is the kit:
http://www.5speeds.com/6cylkit.html
With a std 3.54 diff which has to be installed with the IRS out ?

3 of us couldn't work out how to get it in. Paul C says that you don't need to drop the IRS but there was no way it was going in. Paul also says not to install the box with the sliding yoke in the gearbox as this can damage the seal.

Dropping the IRS really wasn't an issue on my car as it had just been fully rebuilt anyway. It really does only take perhaps 10 mins to get it out when everything is clean and new and you and your helpers know how to do it.

christopher storey · Post by **christopher storey** » Mon Dec 14, 2015 8:27 am

I hate to tell you this, Andrew, but your numbers don't stack up. 0.73 fifth with a 3.54 final drive produces an overall fifth gear of 2.5842 . With a 3.07 final drive, the mph/1000 is approximately ( it slightly depends on tyres ) 24.8 mph . 3.07 divided by 2.5842 = 29.46

So at 2000 rpm your true speed is 59 mph .

abowie · Post by **abowie** » Mon Dec 14, 2015 8:29 am

christopher storey wrote:I hate to tell you this, Andrew, but your numbers don't stack up. 0.73 fifth with a 3.54 final drive produces an overall fifth gear of 2.5842 . With a 3.07 final drive, the mph/1000 is approximately ( it slightly depends on tyres ) 24.8 mph . 3.07 divided by 2.5842 = 29.46

So at 2000 rpm your true speed is 59 mph .

Nerd!!

Post by **mgcjag** » Mon Dec 14, 2015 9:23 am

Just to try to get this a bit clearer the photo shows 2000rpm and speed on the 2nd white dot of 100kph which is 62mph......your diff is 3.54.....just looking at the 4.2 maintenance handbook showing roadspeed/rpm data a 3.54 at 60mph top gear is 2789rpm....so with your 5 speed you are showing a saving of 789 rpm.......does this sound about right...with a 3.07 diff 60mph would be 2418rpm

malcolm · Post by **malcolm** » Mon Dec 14, 2015 9:47 am

My speedo needle waves around all over the place, so it's difficult to see what it's indicating anyway. I use the tacho. Does the waving needle mean the cable is knackered?

Gfhug · Post by **Gfhug** » Mon Dec 14, 2015 10:14 am

Malcolm, it could be either or both a faulty cable and speedo.
With the bouncing speedo I replaced my cable and had my Speedo overhauled by Speedograph Richfield and now works very well

288gto · Post by **288gto** » Mon Dec 14, 2015 10:55 am

alfred wrote:nice to see someone else using the kiss principle to correct their spedo. Mine has a yellow dot for 100 km and a red one for 120.

Alfred

And there was me thinking that was what the red marking was for on the other big dial.....

.

chrisfell · Post by **chrisfell** » Mon Dec 14, 2015 12:14 pm

malcolm wrote:My speedo needle waves around all over the place, so it's difficult to see what it's indicating anyway. I use the tacho. Does the waving needle mean the cable is knackered?

My needle waved all over the place as it had been badly routed under the carbs. A new cable and better routing with smoother bends has it reasonably steady at all speeds.

abowie · Post by **abowie** » Tue Dec 15, 2015 6:12 am

mgcjag wrote:Just to try to get this a bit clearer the photo shows 2000rpm and speed on the 2nd white dot of 100kph which is 62mph......your diff is 3.54.....just looking at the 4.2 maintenance handbook showing roadspeed/rpm data a 3.54 at 60mph top gear is 2789rpm....so with your 5 speed you are showing a saving of 789 rpm.......does this sound about right...with a 3.07 diff 60mph would be 2418rpm

Now even I'm confused :D . I think you're right in that my 4.2 with the 3.07 and standard box does about 2400k at 100 kph but I'll have to check next time I drive it.

I tried to buy the 0.63 OD and was correctly talked out of it by Paul C. The tacho has been rebuilt with a new electronic board and is presumably pretty accurate.

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This is why you fit a 5 speed box.

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