T5 jumps out of second gear

Discussion in 'Classic Mustang Specific Tech' started by zigmont, Jun 11, 2009.


  1. zigmont

    zigmont Member

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    I just put a never installed heavy duty T5Z in my Mustang last month. It seemed fine for the first 600 miles or so. Last week I did a downshift from 3rd to 2nd at about 35 MPH and it jumped out of 2nd. Ever since then It will jump out of 2nd most of the time on a downshift, but only on a downshift. Even if you are pulling back on the shifter handle. When it jumps and you are holding back on the handle it grinds for a second, and seems to find a spot and goes back into second and then it wont jump back out till you downshift again.
    When you shift to second it feels solid like it is going all of the way in on either an up or downshift.
    If you upshift from 1st to 2nd it will stay in second even if you run up to 35 or so and push the clutch in and let the motor go back to idle and let the clutch back out quickly. Not so if you downshift from 3rd or 4th back to second.
    It never jumps out of 2nd on an upshift from 1st.
    It never jumps on a downshift if you apply power. Only if you are decelerating.
    I thought it might be the shift stops on the shifter so I loosened the 2nd gear stop till there was at least a 1/6th inch of clearance when you shift to second. Second and 4th share the same stop, but it wont jump out of 4th. Nothing changed.
    Remember.... this was a new transmission when I put it in a month ago, and was perfectly fine till last week.
    I have never abused the transmission....powershift etc...
    I have a new Pro 5.0 shifter I can put on it, but I don't think will make any difference.
    I am at a complete loss as to why this is happening. If anyone on the forum can help with this I will be very grateful.
    #1
  2. golf4283

    golf4283 Active Member

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    Granted I don't practice downshifting to slow the car but the first thing I would try and do if I were you would be to slow down to like 20 or so in 3rd then downshift to 2nd and see if it sticks. It may just be you're going to fast for it to catch the gear.

    Are you making sure to heel toe shift it as well? It's gonna have a big spike in RPM shifting down at that high a MPH so you want to rev the engine up to match the shift point.
    #2
  3. mtlman22

    mtlman22 New Member

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    what kind of bell housing are you using??
    #3
  4. 68RCodeConv

    68RCodeConv New Member

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    Sometimes the rubber boot will bind up and push the shifter out of gear.
    #4
  5. grainboy

    grainboy Member

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    Mine does the exact same thing. Only Only on downshift to second. I round corners in third now. Mine has done that even when it was freshly rebuilt by a very competent transmission specialist.
    #5
  6. Hack

    Hack Active Member

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    When the tranny jumps out of gear, typically it's because the dog teeth on the gear and/or the slider are worn. Being that the trans is new and you say you haven't abused it, that shouldn't be the cause.

    I've read that a trans can jump out of gear due to the spacing between the gear and slider being incorrect, but I wouldn't think that would be the case on a T5, unless 2nd gear or the slider for second gear was machined incorrectly.

    Possibly the selector lever is bent or something, but you say you don't abuse it, so I would assume you're not shifting overly hard.

    If it were my trans, I would pull it, tear it apart and examine the internals. Something's not right, but without looking at the transmission internal parts there's no way to be sure.

    How much power are you making? Do you have super sticky tires? How heavy is the car? The weak link on a T5 is the case - according to what I've read. I'm not sure how much power a built T5 can really handle. I would think that would break a gear rather than make the trans pop out of gear on decelleration, though.

    My 3550 used to pop out of second sometimes on decelleration, I rebuilt it a couple years ago and that took care of the problem. 2nd gear and the 1-2-reverse slider had worn dog teeth. The trans came out of a car with a blown 331 and the guy raced it. I have no idea if he did something to cause the trans to pop out of gear or if it was a defective part, but when I rebuilt it the problem went away.
    #6
  7. v8only

    v8only Active Member

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    shift levers break, they don't bend on t5's.

    the most common cause, as mentioned is a hanging boot. pull your shift boots off before anything else.

    I rebuilt a t5 that wound up doing the exact same thing. since I had just put new syncro's and a new second gear into it, and the slider was good, I knew that wasn't the issue.

    Since yours is new or rebuilt, I'll "assume" your hardware is good.

    in my case, the input shaft had loosened up to a large enough amount to allow play in the t5. This was causing it to pop out in second gear.

    my suggestion is to pull the t5 down, grab the input shaft and move it in and out of the trans. side to side movement is fine, but you should have no in and out movement.

    if you do have in and out movement, then you need to re shim the throwout retainer. This is an easy job.

    if you don't, then the lid and tail need to come off. you'll be looking for worn syncro's/blocker ring, worn slider teeth, worn dog teeth on the gear itself, and look at the shape of the shaft on the gear to the dog teeth and the bar/shaft on the slider too..make sure it's not worn (when I say bar, I mean to follow the dog teeth down, and you'll see the extended ridges. make sure they're not rounded)
    #7
  8. mtlman22

    mtlman22 New Member

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    V8 is correct. just because the tranny was rebuilt or New doesnt mean it is ok. i had a brand new G-Force T-5 that did the same plus grinded, and i had to send it back because there were issues with the blocker rings! also aftermarket bellhousings sometimes require centering in order to work properly
    #8
  9. garner67

    garner67 New Member

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    I had the same problem with my T5, but the solution turned out to be simple. The rubber shift boot inside the car on the trans tunnel was getting pinched between the shifter and the trans tunne openingl, which pushed the shifter out of gear. I just found a different shift boot, and the problem was solved.
    #9
  10. 67coupestang

    67coupestang Founding Member

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    i vote for the shifter boot binding... it happened to mine. the only reason it happens under decceleration is because under power the gears will kind of pull together

    like mentioned pull the boot off and even check clearances around the shifter hole before you panic and tear into the transmission itself
    #10
  11. zigmont

    zigmont Member

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    T5 jumping out of second

    Thanks many times for all of the great info guys.
    I got a reply from another forum which I think explains my situation pretty well, and may help others. It explains why it only jumps when downshifting, not after shifting into second under load. Here is the quote:

    "Classic T5 problem, the internal shift fork is bent or broke the tabs off it, when you down shift, the gears are reverse loaded and it makes it jump out because the fork isnt putting the gear all the way into its travel. It doesnt do this on up shifts because the counter shaft has forward load on it and grabs the gear into place."

    I think this may explain why it is doing what it is. I am leaning towards the tabs being the problem since the trans only has 600 miles on it

    BTW...... I found if I shift to neutral and rev the motor with the clutch out. Push the clutch in and immediately pull it into second, it stays in gear. I believe that in the day this was called double clutching. This seems to be working for now at least. Maybe this will buy some extra time until I can pull the trans.
    When I find the problem I will post it to the forum.
    #11
  12. v8only

    v8only Active Member

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    shift forks on t5's dont bend, they break. It's unlikely that the tabs b roke after 600 miles.

    Regardless, she's got to come down.
    #12

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