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Thoughts on 308 Transmission/Gearbox Rebuild

Discussion in 'Technical Q&A' started by Mike328, Jan 22, 2004.

  1. Mike328

    Mike328 F1 Rookie
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    Oct 19, 2002
    2,655
    Boulder, CO
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    Mike
    So I was speaking with James at Norwood's about possibly rebuilding my transmission.

    Currently, there's a bad 3rd gear syncro and a tired second syncro. 59k miles on it (verified by records etc).

    So it's an expensive job. James himself would do it. He called it a healthy "medium" job, one that I'm not sure I'm up for. Requires a few special tools. Figure $1000 even in labor.

    Parts are really expensive; figure like $150 to $250 for syncro rings alone depending on for which gear... Then the dog teeth rings or whatever, and then possibly the syncro hubs.

    So that's $1000 in syncros alone. This sounds like a $3k job. Uggh...

    Do I really need to do this? Clearly I'm so far into getting this car up to shape (it WAS really good to begin with, seriosuly!) that I'm pretty much obligated to keep it :).

    If I have to pull then engine, I probably need to rebuilt the whole thing while the engine's out. On the other hand, is there some way I could just get in there and replace the 2nd and 3rd rings with the gearbox still on the car?

    I'm just not really sure I'm ready for a whole gearbox rebuild at this point. And I don't feel like driving the thing for another year with the bad 3rd syncro. Right now, I have a mechanic who I can work closely with who will basically work with me (teach me) with pulling the engine--labor costs will be low, but I'd be doing most of the work (valve adjust, hose replacement).

    At some point, it's going to have to get pulled again for a top end rebuild (new valves etc.).

    Any thoughts on how I should proceed at this point?

    --Mike
     
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  3. Newman

    Newman F1 World Champ
    Professional Ferrari Technician Consultant Owner

    Dec 26, 2001
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    Newman
    Replace the syncros before damage to the dog teeth happens. The dog teeth are part of the gear as is the cone clutch. The syncro ring wears and doesnt cut throught the gear oil on the cone clutch to "syncronize" gear speeds allowing you to shift. Every time you grind, you knock the points down on the dog teeth which when bad enough requires a gear replacement. I would be surprised if you need more than just the 2 rings, first is never an issue and 4th and 5th take a different style of ring and they dont seem to wear like 2nd and 3rd. Mine had 160K on it when I did mine and thats all it needed really.
     
  4. 308GTS

    308GTS Formula 3

    Dec 27, 2001
    2,220
    TN
    How can you tell when they are going bad? Do they grind all of the time or just not go into gear? Any info would be appreciated. Thanks.
     
  5. Mike328

    Mike328 F1 Rookie
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    Paul (Newman), thanks a lot for your response--I know you've done this before and your help means a lot.

    This is a very new condition. I don't grind the gears--I know the gearbox's limits (even with the bad syncro) and shift within them (double clutching into 3rd on the downshift, not to0 fast into 2nd on the upshift).

    So what I'm hearing is, I really don't need to go "too" crazy with this thing replacing everything (just yet). Maybe it makes sense to do just 2nd and 3rd, and wait for the big overhaul when I've got some more mileage on the box.

    Paul, is it at *all* possible to do the job you did (2nd and 3rd syncros) with the engine in (albeit more difficult)?

    Can you list any special tools you had to use?

    --Mike
     
  6. 308GTS

    308GTS Formula 3

    Dec 27, 2001
    2,220
    TN
    If you don't mind may I ask how you know the synchros are going? I just want to know for future reference. I am not familiar with what one feels like when it is going bad.
     
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  8. Mike328

    Mike328 F1 Rookie
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    Sure, sure.

    You'll know when your syncros are getting tired ("worn") or are completely hosed based on how the car shifts.

    Never assume ANYTHING until you've put in a fresh batch of gearbox/transmission fluid in, though.

    When you shift into 2nd quickly and it crunches, that's an early sign of wear. The quicker the shift, the more demand placed upon the syncros (they have less time to do their job). You might say the syncro is getting a bit "tired."

    This is where my 2nd gear syncro is.

    My third gear is toast, i.e. ready for immediate replacemenet. Even shortly after I first got the car, a a 5th to 3rd downshift would crunch. Then 4th to third started to do it. Then I had to be really slow and deliberate with my UPSHIFTS (easier on the syncros--less "matching" for them to do) into third. Currently, an upshift into third takes about three seconds, and a downshift requires a double-clutch (where you "match" the two rotating parts--layshaft and something else, I have to think about it--manually). So third gear syncro is positively worn.

    And there you have it. It's no fun to drive w/o a good third gear, takes the fun out of the car (and makes it really slow, since 3 seconds shift time!). So it's time to do something about it...
     
  9. Newman

    Newman F1 World Champ
    Professional Ferrari Technician Consultant Owner

    Dec 26, 2001
    13,589
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    I have heard of others using different lubricants to solve a single gear shifting concern. It may work but its masking a future problem, it didnt fix it, it only made the dead syncro's job easier for the time being. The syncro rings are the same part for the first 3 gears so if 2nd or 3rd is a problem before a fluid change, then the syncro has issues plain and simple, you are only buying time (which is fine but just remember, it will come back). The trick would be to switch fluid before the symptom popped up.
    You cannot do the job in car, impossible but I did it myself (out of car)and would encourage a mechanically inclinded person to tackle it. You can get alot of input from fchat.
    You need a couple of ring nut sockets but besides that, nothing special.
    Chances are you will only need 2nd and 3rd rings. Change both even if one is the problem because you will be doing it again next year if you dont. i wouldnt say change them all, it gets very expensive and 1st gear is a wanker to get to so dont if its fine.
     

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