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speedo problems and mpg

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Danny78

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rincon ga
hey guys i am brand new to this site and to the k5 lifestyle. the first time i laid eyes on a k5 i was in love and had to have one! well i finally got one, its a 1991 jimmy, i bought with the speedo not working and i was just wondering if anyone could tell me how to fix it... and its also on 37s and it has the 350 so i need to squeeze some better gas mileage out of it because its my dd. if you got any tips or suggestions i will greatly appreciate it!

thanks,
Danny
 
Welcome aboard.

On the speedo you will have to try and figure out where the problem is. i don't have that new of a rig, but I assume it still has a mechanical speedo not electronic.
 
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Gas mileage: If it needs a tune up do it, plugs, wires, air cleaner for starters, check the condition of the distributor cap. It might be getting bad mileage due to the tire size change making your gear ratio way higher, so engine has to work harder to get the rig rolling. Also a new fuel filter might help. is the check engine light on? If it is find out what the code is.

Good luck and I am sure someone with more knowledge than I have on the 91's will chime in shortly.
 
'91 uses an electric speedometer and VSS (Vehicle Speed Sensor). It could be the speedometer itself, but more likely the VSS or wiring.
 
i'm thinking the spedometers went electronic in 1990, could be wrong though.

37's and bad fuel economy? were the gears changed to at least 4.56's?
 
fyi when you get the speedo part figured out and want the speedo correct for axle ratio and tire size. i do modifyed drac = vehhicle speeed buffers. its located in a white plastic box just under the stereo on the back side of the dash.

but i dont know how to fix stuff. just modify the unit.

check to see if the wire is unpluged at the output shaft on the rear of the tcase . then mabye check the basics like fuses. otherwise sorry cant help ya my self.

and 90-91 is electric speedo head.
 
where would i find this vss? and i dont know the exact gear ration but i think its 4:11, if there is a way to check let me know and ill do it. and it gets like 14mpg on the interstate but like 9 on normal road ways and its just killing my wallet.
 
well.....with 4.10's and 37's you're spinning 2427 rpms at 65 at 1:1 ratio, less with overdrive if it stays in it. if a motor is not in the powerband it is wasting fuel. 4.88's would put you at 2880, damn close to stock. 14 really ain't bad at all.....my friend that owned my '90 for 20 years said all he got was 14-15 with OD, 31's and 3.73's. your rig is kinda like 3.08's and 31's, better on the highway and pretty bad in the city. gotta think how much it would cost to regear for what you'll get.

my old 305/700R/4.10/35's got 18-19....with 4.56's got 17. both around 9 in New York City driving.

i also think you just might blow the rear if you beat on it :rolleyes:.
 
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