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Old 02-02-2006, 02:45 AM
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spedo

change trany from 3 speed manual to 4 speed manual now spedo is off by 10 mph how do i correct this

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Old 02-02-2006, 05:08 AM
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Remove the original drive gear from the tailshaft of the 3 speed and install it on the 4 speed. Or, count the number of teeth on your driven gear (on the speedo cable) and figure it out. You didn't say if it was too fast or too slow.

Vince
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Old 02-02-2006, 11:14 AM
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its going to fast when u go 60 it reads 70
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Old 02-05-2006, 09:39 AM
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would it help if i got a cable for 4 speed
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Old 02-05-2006, 10:04 AM
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The cable has nothing to do with changing the speed indication, that is handled by the driven gear (on the speedo cable). The small driven gear is color coded per the number of teeth it has. By changing the driven gear up or down in teeth count will increase or decrease your speedo indication. For too fast an indication you need to increase the number of teeth on the driven gear. Pull the speedometer cable assembly from the transmission and see what color your existing gear is and count the teeth. Go to a GM dealer and tell the parts counter man what you have and what you are after. Offhand I do not know how many gear teeth you need to increase to make a 10mph slower change.

Vince
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Old 02-05-2006, 12:09 PM
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Quote:
Originally Posted by 302/Z28
Remove the original drive gear from the tailshaft of the 3 speed and install it on the 4 speed. Or, count the number of teeth on your driven gear (on the speedo cable) and figure it out. You didn't say if it was too fast or too slow.

Vince



You need to change the large gear on the end of the speedometer cable and the gear on the output shaft to the ones on the donor transmission.....and then it will be correct.......IF IT WAS before ...
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Old 02-05-2006, 12:56 PM
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Here is a link to a on-line site that will help.......

http://www.tciauto.com/tech_info/speedo_gears.htm

It shows automatics but the principal is the same.......
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Old 02-05-2006, 03:38 PM
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You could also look for my Speedometer Information thread.

Or have a search through the Knowledge Base, it's been covered many times before.

You are better off changing BOTH drive AND driven gears when swapping them out.

The main things you will need to know when figuring out your speed for the gears of the speedometer to be correct are:
1. axle gear ratio.
2. tire size.
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