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  1. #26
    FEP Super Member mmb617's Avatar
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    Quote Originally Posted by erratic50 View Post
    Wonder if its something to do with the output shaft on the transmission. AFAIK the newer shafts don't have provisions for a speedometer gear to be installed.

    The older shafts that have provisions are getting more expensive and harder to find. The transmission guy I had build the T5 in my 86GT said he's been messing with using roll-pins. He started with epoxy and JB-Welded but didn't like that those made it near impossible to remove the gear without heating the output shaft to release the glue and he was worried about ruining it.

    Also if the T5 gets particularly hot a some point the epoxy or JB-Weld may let go.
    When I bought my car the speedometer didn't work. Like the OP, when I looked in the transmission hole that the cable goes into I could see the drive gear on the output shaft and the teeth didn't look to be damaged. Everything I checked seemed to be ok, so I finally pulled the transmission from the car and took off the tailshaft. I know this can be done with the trans in the car but it's a whole lot easier with the trans out and it isn't hard at all to pull the trans, so that's the way I went.

    So that was when I found the problem. I was able to slip the drive gear off the output shaft with very little resistance.





    The T5 in my car must have originally been from a later model that used an electronic speedo. See that square toothed "gear"on the output shaft? That's used to trigger the sensor for an electronic speedo and isn't present on older T5's that use a mechanical speedo. Since my T5 wasn't setup for a mechanical speedo it had no hole in the output shaft for the speedo drive gear retainer. Someone had simply slid the drive gear onto the output shaft without a retainer and it had slid back on the shaft just enough that it didn't engage the gear on the end of the speedo cable. And that's why the speedo didn't work.

    As the poster above mentioned I was afraid to attempt drilling a hole in the shaft for fear of ruining it. What I did was smear some red loctite on the drive gear retainer, then slid the gear and retainer into their proper position, making sure I forced the gear far enough forward into the retainer so that the little tang on the top side of the retainer snapped over the drive gear holding it firmly to the retainer.

    Of course the tang on the bottom side of the retainer was meant to drop into a hole in the output shaft that wasn't there so it kind of bent back when I forced the gear on. I let the whole assembly setup overnight and reinstalled everything the next day. The speedo now worked! Red loctite is supposed to be good to 500* F and you better hope your transmission fluid never gets that hot.

    Here's a pic of the drive gear in it's proper position after my repair.




    I ran the car that way for several years and when I had to tear down the T5 later I was able to knock the drive gear off with a couple sharp blows and no damage was done to the shaft. When I re-assembled it I again used the red loctite method and it's been working fine to this day.

    Since the OP has checked everything else I'm thinking he may be having the same problem I did and if so I can verify this method will fix it.
    408/T5/3.73's

    We're not fast racers, we're more what's known as half fast racers.

  2. #27
    FEP Power Member Broncojunkie's Avatar
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    I've heard of others doing the same thing and even using a pair of hose clamps (one on each side) to help keep it in place. I just drill a hole in them...about 1/8" deep. A small diamond bit in a dremel cuts right through the hardened steel and costs about $5. I've done 4 or 5 with the same bit. I think it's about worn out now, so I may need a new one for the next time.

  3. #28

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    Quote Originally Posted by homer302 View Post
    That cable is a true PITA to properly connect to the speedo. Are you SURE it is all the way in? If you can just pull it out of the back of the speedo without depressing that tab on the side, it's not properly connected. The drive gear looks fine and you said if someone spins it at the bottom of the car it spins at the top of the cable so the cable at least "appears" to be good. Bouncing speedos are usually caused by a cable that has run dry of graphite lubricant but this one is new. Of course, new doesn't not necessarily suggest that it is GOOD, it's just new. I have utmost confidence it was assembled by a 12 year old child laborer in a sweat shop in who knows what country. You don't have to properly route it and secure it but I wonder what happens if you put the old cable back in with the new LMR gear. At this point, what do you have to lose? Also please post a picture of the new driven gear you installed on the cable.

    EDIT: also need some confirmation on your comment that you "ran the speedo with the drill and it worked" did you just put a drill on the speedo or did you put one on the end of the speedo cable under the car at the transmission and spin it?
    The old cable was shredded and split so it was trashed.

    The speedometer cable was connected to the gauge (correctly) tight locked in. I had to use the side of pliers to push it and hear that click. I unhooked the cable end at the tranny and hooked the drill to it from there while the other end was connected and video’d it working.

    today side note - I hit a bump and it started working. It was showing 10mph faster than real gps speed via app on My phone. Later in the day that changed to 10mph slower than actual speed then it went ka-put again to zero not working

  4. #29
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    Do you have a standard transmission speedometer driven gear and not an automatic one? The auto gear is longer. Show a picture of the one you have.

  5. #30

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    Quote Originally Posted by dynodon64 View Post
    Do you have a standard transmission speedometer driven gear and not an automatic one? The auto gear is longer. Show a picture of the one you have.

    Its the correct one. I did the LMR calculator as well and got the 17 tooth gear as it suggested Name:  14DB1628-8EB0-4CB1-BE1A-BA5F762B2135.jpg
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  6. #31
    FEP Senior Member
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    Yes that's the correct type. It sounds like your having a gear meshing problem. Sounds like the two are not coming together correctly.

  7. #32

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    Quote Originally Posted by dynodon64 View Post
    Yes that's the correct type. It sounds like your having a gear meshing problem. Sounds like the two are not coming together correctly.
    I agree. Otherwise why would a bump randomly make it work and then show 10 more over then 10 more less.

    I assume it’s all inside the transmission seeing I’ve checked the cluster and have gotten all new cables and gears up to the transmission

  8. #33

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    Wonder if it's possible for the drive gear inside the tranny to still be clipped in the correct spot but somehow the inside of it is worn where it stops spinning or spins erratically on the transmission shaft? Just throwing it out there. I've never seen this one. It's also possible that a drill turns the speedo head okay but maybe something inside of it is goofy when it is turned slower by the cable. I live nowhere near there or I would loan you an old speedo head and see how it behaves. Doesn't matter what it's from.

  9. #34

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    My speed-o-meter went south a few years ago. Erratic readings and jumps then finally one day it just went to zero and stayed there. If I recall it made some noise as well. Sounds like the problem is in the speedometer and I had to replace mine. Getting the cable on and off was fun but my car has dealer added cruise. And I replaced the cable just to be safe. Now all is good and quiet.
    Hope you get it fixed.

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