1. #1
    Enzo16's Avatar
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    Every since I had a lift installed on my jeep 1991 YJ a 7" lift.
    my speedometer does not read accurate?
    what is suggested to fix this problem?
    I saw a device called "tru speed" but it is too expensive?
    help me

  2. #2
    Bounty__Hunter's Avatar
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    Not sure on a '91, but newer YJ's have a gear on the end of the speedo wire in the tailshaft of the transfer case. You change the size of the gear for the appropriate speedo reading. It's plastic gear and is easy to swap.

    Or do like many and borrow a GPS with a speedo on it, and determine just how far off the speedo is. Then adjust your speed accordingly, and live with it

  3. #3
    jps4jeep's Avatar
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    I just guess how fast I am going, But if I get pulled over and the officer asks how fast I was going I simple reply "it is a lifted jeep, it can't speed, you got the wrong man"

    Works everytime

    Johnny

    (the sererio you just read has never accually happened hehe)
    It used to be a jeep Thing,
    But all that stuff broke

    -Johnny-


  4. #4
    Tug-n-pull's Avatar
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    Ask a friend to drive along side of you and let you know when you hit 65 mph look at your speedo and keep a mental note of how far off it is. Adjust your speed accordingly.

    The USA spent over 2.5 million dollars in the research of an ink pen that would wringh t in a gravity free space capsule. The USSR used a pincel! Think about it! hehehehehehe Tug

  5. #5
    Greywolf's Avatar
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    It's a lifted Jeep and can't speed? They actually buy that? Dang, what kind of cops ya'll got up that way?

    One thing to remember though... if ya ever DO get written up, if you elect to go to court many times a modified vehicle will lose because the owner knowlingly changed it... take this from experience, I wrote all kinds of modified vehicles when I was a cop and it was pretty easy to get convictions.

    As to getting the speedo right, it would be best in the long run to just get the right gear and install it so you don't have to worry about it any more.

    Again the main reason being... if you KNOW it's wrong, and you are "guess-timating" as to what your speed is, they can zap ya if you get caught and have to go to court on that too. Their premise is you're relying on something that you know to be wrong so it's your problem.

    All the ideas offered so far were good ones, don't get me wrong... I just wanted to offer some insight as to how the officer and court might be thinking should you ever get written up.

    Later,

    Chris

  6. #6
    Bounty__Hunter's Avatar
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    I wouldn't rely on another vehicle's speedo, they are too often inaccurate themselves. I've found the GPS to be most accurate, and most on the market today have a speedo. I put mine in a cell-phone mount and I'm always sure of my speed, the satellites don't lie :P

    Knowing you're speedometer is inaccurate cuz larger tires were installed has never worked as an excuse given to me but then again very few excuses do work

  7. #7
    jps4jeep's Avatar
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    I was just joking, If you read the PS you would have seen that. I know that the fine men and women of our law enforcement are knowledgable enough to know when a vehicle is speeding, whether it is lifted lowered or stock.

    My theory is, if you get a violation (which I never have) you deserve it.

    There is no excuse for breaking the law, except that cushion tag removal one, I love ripping tha tags off of the couch cushions, makes feel like bill bad a$$!
    It used to be a jeep Thing,
    But all that stuff broke

    -Johnny-


  8. #8
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    Sorry if this is OT, but I have to do it. Did everyone know that jeeps are notorious for getting pulled over and their occupants accused of "holding." That happened to me and my cousin one night after we went to the movies. The cop pulled us over at 10:45 and slung the bull for 20 minutes until it was after 11 and I couldn't drive anymore(I had a junior license and they have an 11:00 curfew). He made my cousin who couldn't drive stick drive my jeep home. My transmission has never been the same since.

    TARSI

  9. #9
    jeepinstien's Avatar
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    Try rotating the speedometer gear a little (clock wise) and see if this changes anything. The gear is offset and you might not be making full contact with the gear in the transfercase.
    Still under construction. 38\'s,LT1/700r4,waggy axels.

  10. #10
    Snitty's Avatar
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    Harley for sale or trade !!!!!!!!!!!!!!!!

    Just purposely speed, and when a cop pulls you over, he'll tell you exactly how fast you were going
    93 YJ 4.0
    Spring Over, 33x12.50 Mastercraft Courser M/T, High Flow Exhaust, Diamondplate Rear Bumper, Trimmed Flares, 6\" spotters


    We, the Sovereign People of the Universe, wish to live in peace. We live among you, but we are not of you.

  11. #11
    Bounty__Hunter's Avatar
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    Don't rotate the speedo gear housing, it has a precise location depending on the tooth count of the speedo gear.

    I'm not sure the electronic gizmo that corrects the speed will work on the mechanical speedo of the older YJ's. It's for newer Jeeps with an electronic speedo.

  12. #12
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    When I lifted my XJ and put the 32" tires on it my parts store did not have the right gear for me to drop in to get my speedo right. I stayed slow and went slower than the flow of traffic for a couple days until it came in. Once I got it in and installed I drove straight to my local police station and asked for help from the desk sergant. He got a car to come back to the station. He had me drive 30, 45, 55, and 75 at least on my speedo. At 75 I was off by 3 mph (actually doing 72). After we got done doing this he said thank you to me for getting it checked. He was very helpfull and really cool about it. Those guys in blue will help you out if you ask. Better to find out before you are in trouble.

    Like Tug said, the housing cover that holds the gear in is offset and should be marked for the amount of teeth on the gear. If you take it out and don't put it back in right it will jump around all over the place if it works at all. Mine has 4 positions and depending on the number of teeth on the gear it needs to go in a differnt way. I had to turn mine 90 degrees when I got the 32 tooth gear.
    Sound_Man
    '04 Rubi some stuff done to it
    '88 XJ, 5.5" lift 32" tires, it needs a motor

  13. #13
    Tug-n-pull's Avatar
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    I wouldn't rely on another vehicle's speedo, they are too often inaccurate themselves. I've found the GPS to be most accurate
    Man you are so right but not everyone has a GPS. So if you get a late modle auto non modified I am sure you are going to be able toat least get a close idea of how fast you are going! jeeeeez take it ez tug

  14. #14
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    I agree with Tug, if you don't have a GPS, the friend way is alot better than trying to guestimate. At least you'll have a ballpark idea.



    Rob :P :)

  15. #15
    Sully's Avatar
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    How much will 31 inch tires affect the speedo?

  16. #16
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    I rotated mine. After the SYE was installed. The teeth weren't making contact. Called JB conversions and they told me to loosen the hold down and rotate the gear. Works fine now.
    Still under construction. 38\'s,LT1/700r4,waggy axels.

  17. #17
    jackal's Avatar
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    I have a really cool fix for mine. I figured the tire size and the gear ratio. I then laminated a card with the rpm and corresponding speed.
    30 mph=1151 rpm
    down to
    70mph=2686rpm.

    I have this attached to my dash, and I check it every now and then.

    It is pretty close because I went through a construction site on the interstate, and the light flashes and the sign tells you how fast you are going.

    My speedometer quits working and jumps around at 45 mph. Now that I have a new fuel injected 350 , my wife asks me how do I know when I am going too fast. I tell her the windshield wipers start flapping when I reach 80.HAHAHAHAHAHAHAHA




    Later,
    Jackal.

    Let me know if you need the math formula??????

  18. #18
    Snitty's Avatar
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    you can also make a speedometer gauge overlay with the correct positions.... as i think back... tommyjeep had an interesting calculator for this.... you put in the equipment you have, then the calculator will tell you what your highway speed in top gear is at any given rpm... if you change the rpm in the highway speed calculator, it will give you the speed at which you should be moving

    http://www.tommyjeep.com/apps/ratio/index.htm
    93 YJ 4.0
    Spring Over, 33x12.50 Mastercraft Courser M/T, High Flow Exhaust, Diamondplate Rear Bumper, Trimmed Flares, 6\" spotters


    We, the Sovereign People of the Universe, wish to live in peace. We live among you, but we are not of you.

  19. #19
    TwistedCU's Avatar
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    Here's a site I came across recently, It wont fix your problem, but it will give you an idea how fast you are going.

    FYI: For the purpose of using these tables, the stock jeep tires (215-75-15) translate to 27.696850393700785 inches.

    Let us know if/when you get it corrected, I need to do the same.

  20. #20
    TwistedCU's Avatar
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    ooops, here's the link:

    http://www.4lo.com/4LoCalc.htm

    FYI: For the purpose of using these tables, the stock jeep tires (215-75-15) translate to 27.696850393700785 inches.

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