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Gearbox out: rear main seal, selector adjustment, ....

Discussion in '348/355' started by Rupp3r, May 26, 2020.

  1. Rupp3r

    Rupp3r Karting

    Aug 26, 2016
    151
    France
    Hello

    Well here is the gearbox out again and I have a few questions:

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    -I removed it because of an oil leak between the engine and the gearbox.
    It appears to comes from the small holes drilled at the bottom of the front of gearbox, right under the rear main seal.
    Will put pics if needed.
    It feels engine oil and not gearbox oil and it came after I first removed the gearbox last time. I remember that I removed lots of silicone paste all around the rear engine cover since I tought it was useless here...
    I removed the oil pan last year for the major and took care of the sealing but didn't improved the situation.

    I was thinking it was the rear main seal but when looking at it, I don't see a leaky rear main seal could leak oil to the bottom. I have the feeling it could only leak between the gearbox and the engine?
    The gearbox O ring is fine and is not leaking,
    Can it only be a leak between the engine and its rear cover?


    -I would also like to solve a hard shifting issue in fifth gear: my fifth gear is quite hard to engage, kind of same wall feeling than the cold second, but it comes earlier in the shifting movement. I have to play with the shifter to be able to engage it properly.
    Otherwise, no problem to shift the others gear, but got a few crunch when downshifting 5=>4 when cold lately.

    Last time I removed the transmission (oil pump side bearing change and clutch shaft bearing/inspection), I remember that the two upper selector rods fork were not perfectly aligned and when I put back the gearbox cover, I was feeling an offset between when moving the control level between the forks.
    I would then like to align the forks as best as I can.
    Is there a good way of doing it without having the reference tools?
    Maybe I can take reference of the center fork and align the others wrt to this one?


    -When removing the clutch, I noticed that the end of the input shaft (after the triple seals) was slightly oily.
    Is it normal or should it by perfectly dry?
    I replaced my triple seals last time I did the gearbox (maybe 300 miles since then..!) and I put viton seals..

    Thanks!
     
  2. kenneyd

    kenneyd Formula 3
    Silver Subscribed

    Sep 30, 2014
    1,176
    NE FL
    Full Name:
    Ken
    Generally a slight oil leak is only really visible when dirt sticks to the 'misted' oil. If the rear main seal was leaking, it's almost in a sealed environment. So it really wouldn't look that dirty, until it drips out the seep holes at the bottom.
    You should definately be able to tell the difference between gear oil, and engine oil by smell.
    Since you got the gearbox out, and seals are relatively cheap, it might be wise just to reseal everything.
    Well it's possible to leak from anywhere, I found that the front timing gears tend to start oozing first. And the wind will blow that oil on everything.

    As for the clutch, did it ever drip from the clutch housing?

    Can't really help you much on the transmission forks. But I would imagine if 6th gear was aligned, 5th gear would also be aligned. What fluid are you running? And how long has it been since you changed the fluid?
     
  3. jjtjr

    jjtjr Formula Junior

    Aug 29, 2016
    383
    Vermont
    Full Name:
    john truskowski
    I think his car may be a 348 by the looks of the trans case. I would reseal the oil seal cover too. My car (355) is part # 154640 and the 348 is part # 139699. I agree with your statement about resealing as much as possible while its apart.
     
  4. Rupp3r

    Rupp3r Karting

    Aug 26, 2016
    151
    France
    Hello

    Thanks for your replies.

    It is indeed a Mondial T so same gearbox as the 348.

    -Yes it is dripping from the seep holes at the bottom and it is engine oil, not gearbox oil.
    I removed the rear engine cover and it looks to be the sealing between this and the engine block/oil pan that is the problem.
    The gasket shaped to the form of the rear cover is missing and paste has been put at the place, so maybe when I removed some of them it started to leak..
    I will indeed replace the rear main seal while I am here.

    -As for the triple seals, no it has never been dripping from the clutch housing. I only noticed that is was slight oily on the back of the input shaft, so don't know it is usual or if it is a sign that they are stating to leak?

    -For the 5th issue well indeed the fork is common with the 4th, but I don't know what else to look for. When the gearbox was out I checked that I was able to engage each gear without issue, so don't know why it is causing problem with the gear stick.
    I haven't removed yet the gearbox intermediate casing but I will look at this again.

    I read that the forks are bolted into a detent on their shaft and that they can't be mis aligned..?

    Could it be the synchronizerc fork not bolted in the middle of the two gears?

    The only other see I see is the initial position of the control rod before bolting it to the translater, even if I think it wouldn't engage several gears if it was out.
    I wasn't particularly sure of its position but placed it to what I think was the neutral, could someone tell me how to position it properly?

    Thanks
     
  5. ernie

    ernie Two Time F1 World Champ
    Owner Lifetime Rossa

    Nov 19, 2001
    22,001
    The Brickyard
    Full Name:
    The Bad Guy
    Your rear main seal on the back of the engine block probably needs to get replaced. You’ll also want to replace the O-ring that is on the inner diameter for the front of the gearbox cover plate, which mates to the back of the engine. The two weep holes on the bottom of the gearbox are to let you know that seal has gone bad.
     
    3stradale likes this.
  6. Rupp3r

    Rupp3r Karting

    Aug 26, 2016
    151
    France
    Hello Ernie,

    I think my O ring on the gearbox is fine, no leaks around but will replace it obviously.

    Any thought about my 5th gear shifting issue and the selector/forks check to do?
     
  7. ernie

    ernie Two Time F1 World Champ
    Owner Lifetime Rossa

    Nov 19, 2001
    22,001
    The Brickyard
    Full Name:
    The Bad Guy
    While the gearbox is our of the car, may as well change all the outer bearings for the main & layshaft + new ring-nuts. Make sure the new ring-nuts are staked properly after you install them. The ball bearing cages on the old bearings have a tendency to go bad = allowing play in the main/layshaft, which allows it to walk. Over time the cage will get destroyed and the wreck the gearbox because broken off bits it will go through the gears and ruin them. You will also want to make sure your shift cables are adjusted properly, and that the shift linkage is properly attached to the selector shaft (coming our of the gearbox).
     
  8. Rupp3r

    Rupp3r Karting

    Aug 26, 2016
    151
    France
    Yes I already replaced them last time I removed the gearbox, their were not too bad.

    WIll adjust the shift cables indeed when I put it back and my selector was fine.

    Nothing to adjust then inside the gearbox, regarding the forks?
    Maybe checking the synchronizer is well centered?
     
    ernie likes this.
  9. Rupp3r

    Rupp3r Karting

    Aug 26, 2016
    151
    France
    Hello

    I have no update on these problems but I forgot to ask about an another problem I have seen:

    the speed indicated by the speedo looks to have a gain (greater than one) compared to the real speed: at slow speed both are close but at around 60pmh indicated my GPS is reading 70mph and I have never seen a speedo underestimating the speed.

    Can something be wrong on the gearbox regarding the impulse sensor?
     
  10. KevZep

    KevZep Karting

    Feb 17, 2020
    101
    New Zealand
    Full Name:
    Kevin Bennett
    What size are you wheels and what aspect ratio are the tyres? If you have a greater rolling circumference than stock, then the speedo will read under actual speed.
     
  11. Rupp3r

    Rupp3r Karting

    Aug 26, 2016
    151
    France
    Hello

    I haven't even think about it!
    I don't have access to my car now but I am pretty sure my tires are the original sizes, everything is original and I got my french MOT where they are very precise on this. And I would need to have at least a 10% difference which is really huge!

    Could something be wrong in the sensor in the gearbox?
     
  12. KevZep

    KevZep Karting

    Feb 17, 2020
    101
    New Zealand
    Full Name:
    Kevin Bennett
    Okay, yes possibly a sensor fault, or a fault with the actual speedo itself.
    Car manufacturers speedos almost always over-read, IE; they read faster than your actual speed.
    My speedo reads 106kph when I am doing 100kph on GPS, this is the same as my Toyota Blade (2007) it over-reads the same as the 348.

    So, given that, it would be safe to say you definitely have a fault there.
    I would start with the sensor in the gearbox...
     

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