Incorrect Speedo Reading Options

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Guest		#1 Posted : Sunday, 1 July 2007 10:24:02 PM(UTC)
Rank: Guest Groups: Guests Joined: 2/09/2015(UTC) Posts: 43,977 Was thanked: 5 time(s) in 5 post(s)		Can anyone assist with explaining why the speedo in my HJ GTS is reading about 20km/hr below what it should. It also shakes a tiny bit. Do I need to replace the cable or are there adjustments that can be made? Thanks Kev

HK1837		#2 Posted : Monday, 2 July 2007 2:05:24 AM(UTC)
Rank: Veteran Reputation: Groups: Moderator, Registered, Veteran Joined: 1/03/2005(UTC) Posts: 14,898 Thanks: 1 times Was thanked: 558 time(s) in 533 post(s)		Pull the cable out of the box and look at the colour and count the teeth on the driven gear. Report what diff ratio is in it and what size tyres and which gearbox it has. If it's a TH400 you'll have to pull the carrier out to see which gear it has. ___
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HK1837		#3 Posted : Monday, 2 July 2007 2:05:24 AM(UTC)
Rank: Veteran Reputation: Groups: Moderator, Registered, Veteran Joined: 1/03/2005(UTC) Posts: 14,898 Thanks: 1 times Was thanked: 558 time(s) in 533 post(s)		Pull the cable out of the box and look at the colour and count the teeth on the driven gear. Report what diff ratio is in it and what size tyres and which gearbox it has. If its a TH400 youll have to pull the carrier out to see which gear it has. _____
		_______________________________________________________ If we all had the same (good) taste, who would buy all the Fords?
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Guest		#4 Posted : Monday, 2 July 2007 2:53:25 AM(UTC)
Rank: Guest Groups: Guests Joined: 2/09/2015(UTC) Posts: 43,977 Was thanked: 5 time(s) in 5 post(s)		Thanks Byron, I will give that a go. It is a 3 speed auto and the tyres are P215/65R14. Im not sure what the diff ratio would be but I do know that it has never been changed. Kev

Guest		#5 Posted : Monday, 2 July 2007 2:53:25 AM(UTC)
Rank: Guest Groups: Guests Joined: 2/09/2015(UTC) Posts: 43,977 Was thanked: 5 time(s) in 5 post(s)		Thanks Byron, I will give that a go. It is a 3 speed auto and the tyres are P215/65R14. I'm not sure what the diff ratio would be but I do know that it has never been changed. Kev

musksell		#6 Posted : Monday, 2 July 2007 3:45:17 AM(UTC)
Rank: Member Reputation: Groups: Registered Joined: 29/08/2005(UTC) Posts: 243		Jack the back end up put a mark on drive shaft and mark at botom of wheel.......turn wheel around one revolution....count how many times drive shaft turns....3 and half times=3.55 etc etc
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jabba		#7 Posted : Thursday, 19 July 2007 10:37:39 PM(UTC)
Rank: Member Reputation: Groups: Registered Joined: 17/04/2005(UTC) Posts: 465		What colour gear would indicate 100kph at 2500 rpm? I suspect that it is going to be an awkward cuss of a job getting to the speedo gear, so an idea of the right one to acquire before I start would be helpful. Running 350 SBC, Turbo 400, GU4 coded d
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jabba		#8 Posted : Thursday, 26 July 2007 6:31:23 PM(UTC)
Rank: Member Reputation: Groups: Registered Joined: 17/04/2005(UTC) Posts: 465		Going to a swap meet this weekend, hoping to pick up a 2.78 diff and the right speedo gears. What should I be looking for for T400, 2.78 diff and 235/60/14 tyres? __________________________________________ Keep the shiny side up, and the greasy sid
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HK1837		#9 Posted : Thursday, 26 July 2007 10:17:48 PM(UTC)
Rank: Veteran Reputation: Groups: Moderator, Registered, Veteran Joined: 1/03/2005(UTC) Posts: 14,898 Thanks: 1 times Was thanked: 558 time(s) in 533 post(s)		Work it out - it's simple. Just work out your kM/h in metres per minute (100kM/h = 1666.6666 M/min). Then work out the circumference of your tyres in m = pi x (235 x 0.6 x 2 + 14 x 25.4)/1000 = 2.0031m. Then divide the m/min figure by the tyre circu
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HK1837		#10 Posted : Thursday, 26 July 2007 10:17:48 PM(UTC)
Rank: Veteran Reputation: Groups: Moderator, Registered, Veteran Joined: 1/03/2005(UTC) Posts: 14,898 Thanks: 1 times Was thanked: 558 time(s) in 533 post(s)		Work it out - its simple. Just work out your kM/h in metres per minute (100kM/h = 1666.6666 M/min). Then work out the circumference of your tyres in m = pi x (235 x 0.6 x 2 + 14 x 25.4)/1000 = 2.0031m. Then divide the m/min figure by the tyre circum
		_______________________________________________________ If we all had the same (good) taste, who would buy all the Fords?
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jabba		#11 Posted : Friday, 27 July 2007 2:53:49 PM(UTC)
Rank: Member Reputation: Groups: Registered Joined: 17/04/2005(UTC) Posts: 465		Wow. I had thought of working it out, but then realised the having the engine rpm only told 1/2 the story. the other half is how many speedo rpm = what indicated speed. From that, I could work out the driving gears and driven gears to get the right r
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jabba		#12 Posted : Monday, 30 July 2007 4:31:15 PM(UTC)
Rank: Member Reputation: Groups: Registered Joined: 17/04/2005(UTC) Posts: 465		Did the old "leg in the air" and confirm that I do indeed already have a 2.78 diff. The book says that for the 3.08 it would be running a 17 tooth steel driving gear into a 43 tooth driven gear. What would be the best driving / driven gear combo for
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