So, as you all know I have a 91 mgm, electronic speedo. My speedo has been 10 fast since I got the car, ( speedo says 65 im actually going 55 ). Its the stock rear gears, and it has done this with 2 diff trannys with 2 diff speedo sensors. So what could make an electric speedo read fast? I haven't really cared up until now, but im getting ready to install 4.30 gears and that will make it even farther off. So ideas on how to correct this. I also know they dont make a speed gear for 4.30's just the 4.10's so I know it will be a lil off anyway. But any ideas anyone had similar prob?
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'90 LX 5.0 mustang
Big plans -
you probably have the wrong gear on the speed sensor.Builder/Owner of Badass Panther Wagons
Busy maintaining a fleet of Fords -
It did it when the stock transmission and speedo gear was on there. Then was exactly the same after I put the mustang trans in there with the mustang speed sensor.
'90 LX 5.0 mustang
Big plansComment
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does it read the same amount off at each speed (20 indicated at 10, 30 indicated at 20, 40 indicated at 50, etc) or is it proportional, reading a certain percentage too high (10 high at 50, 20 high at 100, etc)?
85 4 door 351 Civi Crown Victoria - Summer daily driver, sleeper in the making, and wildly inappropriate autocross machine
160KMs 600cfm holley, shorty headers, 2.5" catted exhaust, 255/295 tires, cop shocks, cop swaybars, underdrive pulley, 2.73L gears.
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06 Mazda 3 hatch 2.3L 5AT (winter beater that cost more than my summer car)Comment
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proportional, its right at 10 off at 75 indicated 65 actual then 85 indicated is only 70 actual. So the faster you go the more it is off.
'90 LX 5.0 mustang
Big plansComment
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Hmm. Wierd.
MAYBE IT'S THE WRONG GEAR ON THE SPEED SENSOR!!!!Builder/Owner of Badass Panther Wagons
Busy maintaining a fleet of FordsComment
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I had similar problems with my 89 car after the 3.55 gear swap.
even wtih the correct speedo gear installed, the speedometer read about 6-7 mph slow.
I found a speedometer shop and had them calibrate the speedo correctly. there is a hair spring inside that you can tighten or loosen to adjust the speed, also found out the needle wasnt on ZERO. speedo is now calibrated and dead on the money.
shop did all this for $35... I pulled the cluster myself in his parking lot.2003 Town Car Signature - 3.27 RAR, Dual exhaust and J-mod - SOLD 9/2011
89 Crown Victoria LX HPP -- SOLD 9/2010
88 Grand Marquis LS - The Original -- Totaled 5/2006
I rebuild AOD/AODE/4R70W/4R75E transmissions....Check out my Facebook page: https://www.facebook.com/pages/North...48414635312478Comment
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yeah man, i have an 89 which the speedo is off by 5, reads 55 when going 60. I thought I was just nutz, lolOriginally posted by 88grandmarq View Post
ps I put a trans out of a Lincoln, that is why it made the reading off.sigpic 1994 Lincoln TC executiveComment
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why was it off with the stock transmission, stock speedo gear, stock tire size, and stock gears, when I first got the car then ?Originally posted by mrltd View Post
Anywho maybe I should just get a JY speedo and put it in there and see if it does the same
'90 LX 5.0 mustang
Big plansComment
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Easy. It doesn't have the ORIGINAL stock parts.
The AOD's came with either a 7 or 8 tooth drive gear on the output shaft. If the trans was swapped at some point, then that could be the problem. It could have had a JY rear, or JY speed sensor, or a JY trans put in it. (Yours had the glued in speed sensor right??)
You cannot assume an old ass car is all original.Builder/Owner of Badass Panther Wagons
Busy maintaining a fleet of FordsComment
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I suppose you make a good point, So I guess I will just buy a 23T speedo gear after I put my 4.30's in and see if that helps.Originally posted by mrltd View Post
'90 LX 5.0 mustang
Big plansComment
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