speedometer...1990 Grand Marquis
my fiance's 1990 Grand Marq has an issue with the speedometer... the speedometer is off in the car... i go speed limit in mine and hers is WAY OFF!!! say speed limit is 70 or 75 she has to have her speedometer saying 85... is there a way to calibrate, or is it due to the speedometer gear in the transmission? i thought i would post here since the speedometer is electrical and NOT cable...
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Addicted to 86-87 Panthers -
Could be the wrong gear in the trans. Its electrical, but it uses the same gear and whatnot in the trans that the cable drive cars use. If someone replaced the trans with one that has a different number of driven teeth, or the rear was replaced with a different ratio, or the tires are significantly differently sized that would explain it.86 Lincoln Town Car (Galactica).
5.0 HO, CompCams XE258,Scorpion 1.72 roller rockers, 3.55 K code rear, tow package, BHPerformance ported E7 heads, Tmoss Explorer intake, 65mm throttle body, Hedman 1 5/8" headers, 2.5" dual exhaust, ASP underdrive pulley
91 Lincoln Mark VII LSC grandpa spec white and cranberry
1984 Lincoln Continental TurboDiesel - rolls coal
Originally posted by phayzer5
I drive a Lincoln. I can't be bothered to shift like the peasants and rabble rousers -
mine was like this when I got it. The speedo would always read 10 fast. When I pulled the tranny it was an aamco tranny. I replaced it with a fox mustang transmission and it read the same. So I think maybe the tooth count was for a car with the 3.27 gear and not a 3.08 or somthing.
'90 LX 5.0 mustang
Big plansComment
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her car door sticker says it has a 2.73 open... the car only has 98,xxx miles on it ... guess i will have to try to find a speedo gear someplace... all i know is to do 60mph you have to push 70mph in the car and to do 70-75 needle has to show 85mph ... tires on it are 205/70R15 Addicted to 86-87 PanthersComment
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Is it accurate below that speed?Comment
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if it's off by the same difference at low speed as well... there could be a needle misalignment in the speedo (if it's like the older styles and you can wiggle it off pretty easily). My 88 MGM was off by 10 across the board when I got it. speedo would read 35 and I'm doing 45.... 10... doing 20. 60, doing 70. pulled the needle off the shaft, held the works behind the face down to zero and put the needle back on at zero. speedo has been dead on since.
if it's not the same gap across the board... then yeah... speedo gear. If the trans was replaced with one that has a 7 spline output shaft instead of 8... that could be your issue... or if someone changed out the rear gears... etc
Only two things are infinite, the universe and human stupidity, and I'm not sure about the former. -- Albert Einstein
rides: 93 Crown Vic LX (The Red Velvet Cake), 2000 Crown Vic base model (Sandy), 2003 Expedition (the vacation beast)
Originally posted by gadget73
... and it should all work like magic and unicorns and stuff.
Originally posted by dmccaig
Overhead, some poor bastards are flying in airplanes.Comment
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i am guessing the speedo gear... the faster you go, the more its off by... i have no clue of telling if the rear is swapped unless i do a gear oil change... my 1986 supposedly has 3.08 open, but when on gas in gravel or wot, both tires light up... did a burn out in parking lot and driver side was lit up too... Addicted to 86-87 PanthersComment
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could be several things.. the most likely are the speedometer head is not calibrated correctly, the other is it has the wrong speedo driven gear installed. AODs for that year range had either a 7 tooth or 8 tooth speedo drive gear machined on the output shaft. My guess would be some one put a used or reman trans in that had a different gear than what the car came with from the factory.
If you have a speedo shop near you, take the speedo out and have them calibrate it. I had an issue on my 89 CV where the speedo needle wasnt calibrated to 0 and was reading 6 mph fast, even after I had the correct speedo driven gear installed in the transmission.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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the 90 is an electric speedo... so there's no calibration needed (supposedly)
Only two things are infinite, the universe and human stupidity, and I'm not sure about the former. -- Albert Einstein
rides: 93 Crown Vic LX (The Red Velvet Cake), 2000 Crown Vic base model (Sandy), 2003 Expedition (the vacation beast)
Originally posted by gadget73
... and it should all work like magic and unicorns and stuff.
Originally posted by dmccaig
Overhead, some poor bastards are flying in airplanes.Comment
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i had the same problem on my '90 MGM. but it comes after changing the cluster to '91 police speedo. the stock speedo runs ok.'85 Colony Park LSComment
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