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308 Synchros

Discussion in 'Technical Q&A' started by 328KNB, Jul 12, 2004.

  1. 328KNB

    328KNB Karting

    Jun 14, 2004
    59
    I recently acquired a fibreglass 308 GTB - its had quite a hard life and seems to have weak synchros on 2nd, 4th and 5 th gears. The local agent seems to think it could be the clutch that's dragging as the shift quality improves dramatically when shifting at higher revs. Any ideas out there? Is there any way to test this without stripping the 'box? What sort of mileage is reasonable to expect from a 308 'box before it has to be torn down?
     
  2. Rifledriver

    Rifledriver Two Time F1 World Champ

    Apr 29, 2004
    26,949
    Austin TX
    Full Name:
    Brian Crall
    If you are experienced and know what to look for a reasonably good syncro inspection can be done by removing the pan and inspecting it externally. Your local agent however makes a very good point and checking for a dragging clutch (or bad pilot bearing). Should be relatively simple for a qualified mechanic. Considering the expense of an incorrect diagnosis it is worth the expense of paying to have the car looked at by someone qualified.
     
  3. 328KNB

    328KNB Karting

    Jun 14, 2004
    59
    Thanks Rifledriver that's good to know that one can get some sort of indication by dropping the pan. I've worked on Beemers for years but am a little wary of messing with the 308's oily bits. Have you any idea what mileages a gearbox can do? I'm considering a full restoration on the car and would rather tackle all the issues at once...
     
  4. Rifledriver

    Rifledriver Two Time F1 World Champ

    Apr 29, 2004
    26,949
    Austin TX
    Full Name:
    Brian Crall
    It all depends on how it has been treated. There are too many variables. I have seen them go well into the six digits and have also seen them not make it to the first service. If I had to pick a number I'd say 60-75 K miles.
     
  5. 328KNB

    328KNB Karting

    Jun 14, 2004
    59
    Thanks - the car has done that sort of mileage so hopefully the bills won't be too horrific!
     
  6. f355spider

    f355spider F1 World Champ
    Rossa Subscribed Owner

    May 29, 2001
    17,058
    USA
    Full Name:
    Hugh G. Rection
    Also understand that synchros hate the limited slip additives typically found in many gear oils. Using a gear oil with no limited slip additive may temporarily solve the issue...though there may be some vibration from the limited slip in some instances (like making a very tight turn).

    Redline 75w-90 NS (ns means "no slip") might be worth a try.
     
  7. 328KNB

    328KNB Karting

    Jun 14, 2004
    59
    Thanks Dave - I have heard of the lubricant sensitivity issue before. From what I've heard I'm first going to change the trans oil and check out the clutch adjustment before hassling about clutch condition and dropping the trans oil pan to inspect the synchros. Thereafter I'll pay a visit to my friendly local bank manager in need...hopefully he won't have a sense of humour failure on the day!
     
  8. Nuvolari

    Nuvolari F1 Veteran
    Sponsor Owner

    Sep 3, 2002
    5,354
    Toronto / SoCal
    Full Name:
    Rob C.
    Make sure also that the gear selection mechanisim is in proper adjustment. I am no expert in this but there are lots of threads on the subject. Also whle changing the oil, make sure you are draining both the pan and transfer case (there are 2 drain plugs). There are also 2 fill plugs. Fill from the top of the transfer case till it overflows from the gearbox fill plug. Expect to put in just over 4 litres of oil.
     
  9. thecarreaper

    thecarreaper F1 World Champ
    Silver Subscribed

    Sep 30, 2003
    15,962
    Savannah
    Full Name:
    I NEED A JOB
    i am having a problem with 3rd gear, i have 59k miles on my 78 308. i will be dropping the pan later this month and looking to see if the shift plates can be adjusted. there was no metal in the gear oil or on the plug when i drained the gear oil from the trans and diff. i put in 5 quarts of Lucas 75w 90 snyth gear oil. it made a HUGE difference, but 3rd gear is still not " right" if you find someone who can do a minimum overhaul on a 308 trans POST IT HERE!!! they will have plenty of business!!
     
  10. 208 GT4

    208 GT4 Formula 3

    Dec 27, 2003
    1,699
    Brighton (UK)
    Full Name:
    Dan
    My 208 GT4 had new synchro rings last year. It had done 60,000 miles and they were worn out of tolerance. However, I got a much bigger improvement in shift quality by changing from Mineral to Synthetic oil recently.
     

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