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Thread: T50 new speedometer driven gear worn out after little use.

  1. #1
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    T50 new speedometer driven gear worn out after little use.

    Hey guys,

    I recently decided to tackle my non-functional speedometer on my AE86 (GT-S). The T50 transmission is a modified unit with close ratio gears that the previous owner bought from Japan way back in the day. The rear diff is a USDM GT-S unit.

    I've tested the speedometer cable and it moves freely. And the speedometer does move when I rotate the transmission side of the cable. I thought the cause was because the gear was worn out.

    The older driven gear I took out was very worn out in the center of gear. I replaced it a month ago. It says 19 5 on the old and the new.


    And probably drove about 2-3 miles on it as this is a project car with more time in the garage than on the road.

    The speedometer worked for a little bit, however now it only goes 4-5mph on deceleration.

    I decided to check on the new driven gear today, and it looks as worn out as the old one.

    I have a couple guesses,

    1) the casing has 1mm slop to it, perhaps that contributed to the driven gear not seated correctly. I didn't notice it the first time I installed the new driven gear. I did attempt to push the casing in a way so that the driven gear is in contact with the drive gear and securing it with the bolt and plate.

    2) the worm drive gear inside the transmission is could be a different toothed gear and thus is causing the fast wear on driven gear. I'm guessing symptoms might be similar to partial conversion between a SR-5 and GT-S. IE, using SR-5 transmission, but using the 19 5 tooth gear (GT-S) instead of the 22 6 (SR-5) to compensate for the new GT-S final drive ratio.

    Any help highly appreciated.
    Last edited by aceforever; 07-31-2015 at 11:41 AM.
    1985 Toyota Corolla GT-S

  2. #2
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    Quote Originally Posted by aceforever View Post

    (2) the worm drive gear inside the transmission is a different toothed gear and thus is causing the fast wear on driven gear. I'm guessing symptoms might be similar to partial conversion between a SR-5 and GT-S. IE, using SR-5 transmission, but using the 19 5 tooth gear (GT-S) instead of the 22 6 (SR-5) to compensate for the new GT-S final drive ratio.
    Are you saying that using an SR5 speedo gear has worn out something? Cause that makes no sense.

  3. #3
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    T50 new speedometer driven gear worn out after little use.

    Sorry, I'm trying to figure out what is causing the excessive wear. By that sentence I meant that perhaps I have an SR5 drive worm gear and it's causing the wear on a GT-S driven gear. And maybe people who performed SR5 to GTS conversions ran into this issue too.

    I'm just brainstorming why the new GTS driven gear got worn out so fast.
    1985 Toyota Corolla GT-S

  4. #4
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    Casing should not have slop. From my experience they fit in super tight.
    I think...it's been a while.


    RETIRED

  5. #5
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    Quote Originally Posted by JungleMatic View Post
    Casing should not have slop. From my experience they fit in super tight.
    I think...it's been a while.
    That's interesting, my casing goes in really tight, but after you push it in all the way. The casing has a little jiggle about 1 mm or so at an angle. Perhaps that's why the toyota engineers decided to include a plate + bolt that could push against the casing so it is in the right angle when it slops? I'm thinking of buying a new casing if there are any and order the same GT-S driven gear if the wear is caused by scenario 1 above. But my dilemma is if it's scenario 2, where the wear is because of mismatched drive gear to the driven gear then I would waste the time and money once again.

    Unless anyone else know of any other causes. I'm thinking of jacking up the rear and drain the transmission oil enough so that I can see how many teeth the drive gear has by rotating the rear wheels and counting how many starting teeth the worm gear has on one side. This way I can verify if scenario 2 is the case or not.

  6. #6
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    Today I jacked up the car from the rear for the first time. The aftermarket exhaust forces me to jack it up by the rear diff housing instead of the side otherwise the rear axles would hit it.

    I asked around for the safest way I could do this since I'm terribly afraid that the car might fall on me as there are no ebrakes for the front wheels. I bought myself some wheel chocks. In addition to the jack stands, I felt more at ease.



    I pulled out the speedometer casing and gear all together and had something to catch the transmission oil dripping out.



    You can definitely see where the starts of the teeth are. It was kind of hard to see where starting position was, however luckily there was a strand of hair or nylon (from the plastic driven gear) on one of the teeth starts. So I used that as my reference point.

    I count 6, how about you?
    https://www.youtube.com/watch?v=viHeodKxY60

    Looks like I'll need a special 22 or 23 6 driven gear. But at this point any gear that was made for the 6 teeth worm drive gear would work for me. Maybe I'll just get the 20 6 that the SR-5 comes with and call it a day.
    1985 Toyota Corolla GT-S

  7. #7
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    As a last resort, you could use a GPS speedo instead.

    The ones from Speedhut have 0-100kmph time and 400m time features (0-60mph and 1/4 mile). The only thing i didn't like was the odometer went haywire on mine. I don't think they tested them in the southern hemisphere.

  8. #8
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    Quote Originally Posted by aceforever View Post

    Looks like I'll need a special 22 or 23 6 driven gear. But at this point any gear that was made for the 6 teeth worm drive gear would work for me. Maybe I'll just get the 20 6 that the SR-5 comes with and call it a day.
    What matters is the pitch of the gear, not just the number of teeth. You can change number of teeth only if the pitch matches. ToyoDIY says original NA GTS is 19 driven teeth.... and NA SR5 has 20 teeth... and there are some JDM models with 22... That 22 may have a totally different pitch. I don't know anything about T50 speedo drives, but I do know that gear pitches have to match.

    I see that there are two different DRIVE gears in JDM T50s... N=5 and N=6. Are they the same pitch?

    1985 JDM AE86 trans parts list here: http://www.toyodiy.com/parts/p_J_198...CMQF_3305.html

    Maybe you need a JDM driven gear? http://www.toyodiy.com/parts/p_J_198...CMQF_3304.html
    Last edited by b-rock; 08-01-2015 at 11:53 AM.
    $28 Bronze T50 shifter bushings HERE

  9. #9
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    Quote Originally Posted by andrewzuku View Post
    As a last resort, you could use a GPS speedo instead.

    The ones from Speedhut have 0-100kmph time and 400m time features (0-60mph and 1/4 mile). The only thing i didn't like was the odometer went haywire on mine. I don't think they tested them in the southern hemisphere.
    Thanks for the tip! I'm trying to keep the look as stock as I can. But I'll definitely keep it in mind if all my other ideas fail.

    Quote Originally Posted by b-rock View Post
    What matters is the pitch of the gear, not just the number of teeth. You can change number of teeth only if the pitch matches. ToyoDIY says original NA GTS is 19 driven teeth.... and NA SR5 has 20 teeth... and there are some JDM models with 22... That 22 may have a totally different pitch. I don't know anything about T50 speedo drives, but I do know that gear pitches have to match.

    I see that there are two different DRIVE gears in JDM T50s... N=5 and N=6. Are they the same pitch?

    1985 JDM AE86 trans parts list here: http://www.toyodiy.com/parts/p_J_198...CMQF_3305.html

    Maybe you need a JDM driven gear? http://www.toyodiy.com/parts/p_J_198...CMQF_3304.html
    Thanks for the help. I came to the same conclusion while looking at toyodiy as well.

    The two drive gears in JDM T50 are the same as the SR5 (6 tooth drive) and GT-S (5 tooth drive) in the USDM. I've cross checked the part numbers.

    I assume the 19 tooth driven goes with the 5 tooth drive, and 22 tooth driven goes with the 6 tooth drive. Which is kind of odd. Since 5/19 = 0.263 and 6/22 = 0.2727. They're a little bit different. Maybe for different tire sizes or something? Since there is only one final drive ratio (4.3) on JDM AE86s.

    I've ordered a part number 33403-19175, the 22 tooth gear. Let's see if they have it in stock. Wish me luck!
    1985 Toyota Corolla GT-S

  10. #10
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    I'm using a 5/22 because I have a 4.8 Final Gear.

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    Quote Originally Posted by Serendipity View Post
    I'm using a 5/22 because I have a 4.8 Final Gear.
    Do you remember the part number for this? Hopefully the part number I ordered is a 6/22.

    Thanks!
    1985 Toyota Corolla GT-S

  12. #12
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    Quote Originally Posted by aceforever View Post
    Do you remember the part number for this? Hopefully the part number I ordered is a 6/22.

    Thanks!
    Click image for larger version. 

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  13. #13
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    Damn, I ordered 33403-19175. Hope it works with a 6 tooth SR-5 gear.
    1985 Toyota Corolla GT-S

  14. #14
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    Today my gear finally arrived. Seems like part number 33403-19175 is actually a 22 tooth driven gear made for the 6 tooth drive gear.

    1985 Toyota Corolla GT-S

  15. #15
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    This thread really has me on the edge of my seat.
    1JZ 1984 Celica GTS
    1UZ 1981 Corolla sedan
    ? 1972 Celica race car

  16. #16
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    Quote Originally Posted by clay72 View Post
    This thread really has me on the edge of my seat.
    Haha, are you also in the same situation?
    1985 Toyota Corolla GT-S

  17. #17
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    33403-19135 5/19 GT-S

    33403-19175 5/22 JDM GT-S


    sr5 is 6/20? part no?

    Did JDM 86 come with a 4.8 final?

    By the sounds of it your sr5 trans is just going to eat the gear....maybe? Can someone check part numbers for drive gears for gts and sr5 tranny? Also, how do you tell a gts and sr5 tranny apart?
    Last edited by JungleMatic; 08-14-2015 at 08:23 AM.


    RETIRED

  18. #18
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    Quote Originally Posted by JungleMatic View Post
    33403-19135 5/19 GT-S

    33403-19175 5/22 JDM GT-S


    sr5 is 6/20? part no?

    Did JDM 86 come with a 4.8 final?

    By the sounds of it your sr5 trans is just going to eat the gear....maybe? Can someone check part numbers for drive gears for gts and sr5 tranny? Also, how do you tell a gts and sr5 tranny apart?
    Seems like you're confusing some of the parts.

    33403-19175 is a 6/22 JDM speedometer driven gear. Not 5/22. Look at my picture in a couple posts earlier. The gear is colored green with markings 6 and 22.

    From ToyoDIY.com:
    JDM AE86 has only 4.3 final (Part #: 41201-29207)
    JDM AE86 T50 transmissions speedometer drive gears can have 5 tooth OR 6 tooth

    The 5 tooth is the same as the GT-S speedometer drive gear in the T50 (Part #: 33481-12030)
    The 6 tooth is the same as the SR-5 speedometer drive gear in the T50 (Part #: 33481-14040)

    USDM SR-5 driven gear is 6/20 (Part #: 33481-14040)
    USDM SR-5 final diff is 43:11(3.9) (Part #: 41201-19188)

    My transmission is not SR-5 or GT-S. It is a JDM unit, so calling it that seems kind of odd. It does have the same speedometer drive gear as an USDM SR-5 though.

    So any driven gear made for SR-5 like the 6/20 would work. However it would read too fast with a 4.3 final diff.

    The only way to tell a GT-S and a SR-5 transmission apart that I know of is to check how many teeth the speedometer drive gear has. But even then, the T50 could be from Japan, or the drive gear can be switched out.

    I have a video of myself counting the "starts" of teeth on the right side of the worm gear a few posts before. If you're curious on how to check.

    Hope this clarifies everything.
    Last edited by aceforever; 08-14-2015 at 09:33 AM.
    1985 Toyota Corolla GT-S

  19. #19
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    That said, I still have not actually tested to see if the gear will wear out or not.

    If it works well, anyone can follow this procedure in the future when converting from SR-5 to GT-S rear ends. Instead of buying a new drive gear and driven gear (currently $50-60 total) and time taking the transmission apart. They can just swap out the speedometer driven gear to the JDM one. This way you save time and money.
    Last edited by aceforever; 08-14-2015 at 09:43 AM.
    1985 Toyota Corolla GT-S

  20. #20
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    Took the time to swap out the gear today.

    This is prior moving the clip from the old to the new. You can see how worn out the 1 month old speedometer driven gear is. No wonder it wasn't working. I also got a new sleeve/casing for the gear as I wasn't sure if it was the slight play in the casing that was causing the wear.


    I'll report back in a month.
    1985 Toyota Corolla GT-S

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