I need help, i have an LH SLR 5000, original engine, but four speed ford toploader and 2.82 ford 9 inch with 14 inch rims fitted, the speedo is way out, 85km/hr on the speedo is about 110km/hr. Our local mechanic told me that i have to change the cog on the gear box end of the speedo cable. Does any one know what part i would need and where i may be able to buy it.
Tahnk You
Speedo Reading
Started by
_Lime SLR_
, Mar 12 2007 12:47 PM
11 replies to this topic
#2
_SLRMike_
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Posted 12 March 2007 - 01:10 PM
Hi Lime SLR.
Firstly check that the speedo cog in the gearbox is matched to your diff ratio eg 2.82. Holdens colour code the speedo drives so you know what ratio you have, eg red is 3.08? white is 2.78. perhaps consult a ford man for the ford equiv. this may fix your problem straight up.
If that is right and the problem persists then is comes down to wheels and tyres. the speedo is grossly effected by the overall tyre/wheel diameter, simply changing tyres will throw everything out, eg standard 195x70x13 give correct speedo reading with stock holden running gear change the tyres to 185x60x13 and the speedo goes out about 10km/h from memory. If you go say 185x60x14 problems start again because the diameter of the tyre has increased by 1" with me so far?
There is a calculation that you can do and I have a formula somewhere, I'll dig it up for you.
Sort this out and if you still have a problem then it could be the speedo head itself. Maybe a recalibration is in order.
hope that helps a little.
cheers
Mike
Firstly check that the speedo cog in the gearbox is matched to your diff ratio eg 2.82. Holdens colour code the speedo drives so you know what ratio you have, eg red is 3.08? white is 2.78. perhaps consult a ford man for the ford equiv. this may fix your problem straight up.
If that is right and the problem persists then is comes down to wheels and tyres. the speedo is grossly effected by the overall tyre/wheel diameter, simply changing tyres will throw everything out, eg standard 195x70x13 give correct speedo reading with stock holden running gear change the tyres to 185x60x13 and the speedo goes out about 10km/h from memory. If you go say 185x60x14 problems start again because the diameter of the tyre has increased by 1" with me so far?
There is a calculation that you can do and I have a formula somewhere, I'll dig it up for you.
Sort this out and if you still have a problem then it could be the speedo head itself. Maybe a recalibration is in order.
hope that helps a little.
cheers
Mike
#3
arrimar
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Posted 12 March 2007 - 01:33 PM
driven gear for holden four speed(yes i know yours is top loader)are:
v8 four speed
19teeth for 2.78 ratio
21 teeth for 3.08
L34 (14 inch wheel)
20 teeth for 2.78
22teeth for 3.08
going by the way holden has done it,going 14 inch wheels you need one more tooth on the gear.but the internal drive gear of the box is same for 6 and 8 but not for L34.
my bet would be the appropriate top loader gear that has 20 or 21 teeth.providing the internal drive gear is the same as a holden box.
now even i'm confused.
if you know some of the details of your components there is a free computer here.
speedo calc
as a matter of interest other holden drives for speedo are:
6cyl 4 speed/13 inch wheel
23 teeth/red/3.36
21 teeth/green/3.08
4cyl 4 speed/13 inch wheel
23 teeth/red/3.90
24 teeth /yellow/3.55
v8 four speed
19teeth for 2.78 ratio
21 teeth for 3.08
L34 (14 inch wheel)
20 teeth for 2.78
22teeth for 3.08
going by the way holden has done it,going 14 inch wheels you need one more tooth on the gear.but the internal drive gear of the box is same for 6 and 8 but not for L34.
my bet would be the appropriate top loader gear that has 20 or 21 teeth.providing the internal drive gear is the same as a holden box.
now even i'm confused.
if you know some of the details of your components there is a free computer here.
speedo calc
as a matter of interest other holden drives for speedo are:
6cyl 4 speed/13 inch wheel
23 teeth/red/3.36
21 teeth/green/3.08
4cyl 4 speed/13 inch wheel
23 teeth/red/3.90
24 teeth /yellow/3.55
#4
_Lime SLR_
_Lime SLR_
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Posted 12 March 2007 - 02:45 PM
Cheers for the replys, now i have something to go on, i thought that maybe someone else had the same problem and they may have know what holden or ford part i needed, but now with the info i should be able to work it out.
Thank You
Thank You
#5
arrimar
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Posted 12 March 2007 - 04:23 PM
some additonal info taken from the old holden wiki.
Speedo Driven Gears (The plastic gears driven by the gearbox and which the speedo cable connects to) (Speedo Driving gears have similar colours but fewer teeth and are fitted to the gearbox tailshaft.)
For 13" wheels:
2.60 diff Pink 19 teeth
2.78 diff White 20 teeth
3.08 diff Dark Blue 22 teeth
3.36 diff Red 23 teeth
3.55 diff Yellow 24 teeth
3.89 diff Light blue 25 teeth
--------------------------------------------------------------------------------
For 14" wheels:
2.78 diff Pink 19 teeth
3.08 diff White 20 teeth
3.36 diff Green 21 teeth
3.55 diff Red 23 teeth
3.89 diff Yellow 24 teeth
--------------------------------------------------------------------------------
The above are all varied again by tyre and wheel sizes.
A 205/60/13 tyre with a 2.78 diff is about the same overall gearing as a 275/55/17 tyre with a 3.55 diff.
A 2.78 diff in a Torana with standard 13" wheels and tyres (say 185/75 SR 13) will show 3080 rpm at exactly 100kph in top gear (1:1) (Note, the next lowest diff, 3.08).
A 3.08 diff in a Torana with standard 13" wheels and tyres (say 185/75 SR 13) will show 3360 rpm at exactly 100kph in top gear (1:1) (Note, the next lowest diff, 3.36).
Retrieved from "http://www.oldholden...atio_selection"
Speedo Driven Gears (The plastic gears driven by the gearbox and which the speedo cable connects to) (Speedo Driving gears have similar colours but fewer teeth and are fitted to the gearbox tailshaft.)
For 13" wheels:
2.60 diff Pink 19 teeth
2.78 diff White 20 teeth
3.08 diff Dark Blue 22 teeth
3.36 diff Red 23 teeth
3.55 diff Yellow 24 teeth
3.89 diff Light blue 25 teeth
--------------------------------------------------------------------------------
For 14" wheels:
2.78 diff Pink 19 teeth
3.08 diff White 20 teeth
3.36 diff Green 21 teeth
3.55 diff Red 23 teeth
3.89 diff Yellow 24 teeth
--------------------------------------------------------------------------------
The above are all varied again by tyre and wheel sizes.
A 205/60/13 tyre with a 2.78 diff is about the same overall gearing as a 275/55/17 tyre with a 3.55 diff.
A 2.78 diff in a Torana with standard 13" wheels and tyres (say 185/75 SR 13) will show 3080 rpm at exactly 100kph in top gear (1:1) (Note, the next lowest diff, 3.08).
A 3.08 diff in a Torana with standard 13" wheels and tyres (say 185/75 SR 13) will show 3360 rpm at exactly 100kph in top gear (1:1) (Note, the next lowest diff, 3.36).
Retrieved from "http://www.oldholden...atio_selection"
#6
_CHOPPER_
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Posted 12 March 2007 - 05:37 PM
What you need to realise is that the Toploader speedo drive gear may have a different number of teeth than a Trimatic or M20. Give me that number and I'll have an answer in a couple of seconds after I see it.
#7
_Holdenmad_
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Posted 12 March 2007 - 08:09 PM
Now I can see why my speedo is so far outta whack too.
173 with M20 and a 3.08 banjo diff. Then some new wheels to add more difficulty: 225/50/15.
No wonder everyone says I drive like a nanna
173 with M20 and a 3.08 banjo diff. Then some new wheels to add more difficulty: 225/50/15.
No wonder everyone says I drive like a nanna
#8
V-SLR5000-P
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Posted 12 March 2007 - 08:59 PM
If you speedo is reading too slowly you need to either:
� Increase the number of teeth on the main shaft gear, or
� Reduce the number of teeth on the gear that drives the speedo cable
Your speedo error is probably too great to fix by changing one or other of the gears alone.
I think you need to change both gears in order to increase the speedo reading by 30%. To fix this problem you will need to know what the tooth count of both gears you have is and the range of available gears for a Toploader. The ratio between the two gears needs to be stepped up by 30%
� Increase the number of teeth on the main shaft gear, or
� Reduce the number of teeth on the gear that drives the speedo cable
Your speedo error is probably too great to fix by changing one or other of the gears alone.
I think you need to change both gears in order to increase the speedo reading by 30%. To fix this problem you will need to know what the tooth count of both gears you have is and the range of available gears for a Toploader. The ratio between the two gears needs to be stepped up by 30%
#9
_CHOPPER_
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Posted 12 March 2007 - 10:43 PM
Use a 21 tooth gear.Now I can see why my speedo is so far outta whack too.
173 with M20 and a 3.08 banjo diff. Then some new wheels to add more difficulty: 225/50/15.
No wonder everyone says I drive like a nanna
#11
Statler
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Posted 02 April 2007 - 06:09 PM
Somebody PLEASE make arrimar's post a sticky!!!!!
That info is gold!
Oh, ring Dellow for the corect part!
I think you will need to know what speed you are really doing at 80k's to get the right bit.
That info is gold!
Oh, ring Dellow for the corect part!
I think you will need to know what speed you are really doing at 80k's to get the right bit.
#12
_CHOPPER_
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Posted 02 April 2007 - 10:23 PM
Look in Driveline, there is a more comprehensive sticky there.Somebody PLEASE make arrimar's post a sticky!!!!!
That info is gold!
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