915 slider teeth: how worn are they (pic)

[Alan.UK]

Hi,

I stripped my 72 915 box today to change the input shaft seal and whilst there check the dog and slider teeth. Everthing looks fine but the slider teeth on 1st do look a little rounded. The problem is knowing how bad they are. The dog teeth are fine, the slider teeth still have their shape but the ends are "blunt" ish (if you know what I mean).

Here is a pic, I hope you can see what I mean.

Any advice is much appreciated.

If the slider does have to come off what the easiest way to get the gears off. I have just tapped them off using a flat metal surface but I can't do that as these early ones have the speedo drive on the end. Can I hold it in press using the the edges of the 2nd gear and then press?

Thanks
Alan

PS. Can someone also quickly confirm the new seal is put in with the spring side facing the gearbox ie) is facing the oil?





PPS. I have never driven with this box in a car so do not know how it changed gear

[1972_911T]

Hi Alan the spring side of the seal should face the oil, as for the slider teeth its hard to tell in the pic but they dont look brilliant possibly not too bad though could do with better pic, strangely the dogs an that gear seem quite good.

Steve

[1972_911T]

Heres some really worn dogs on a 915 box I once owned.





These were shot.

Steve

[Alan.UK]

Thanks Steve,

I will try and get some better pics.

Alan

[MBEngineering]

HI Alan ring me about the gearbox,

regards mike

[Alan.UK]

Calling you now Mike

[Alan.UK]

Just in case anyone reads this thread whom is also working on a early 72 box, the intermediate shaft seal is inserted with the spring facing outwards not towards the oil.

Thanks

Alan

PS. Cheers for all the info Mike

[Elombard]

Uhhh... what are we looking at on the worn dogs. I am a rookie. The points worn off the teeth?

[MBEngineering]

HI Elombard at 2917 postings i would assume you should have picked up some info from this site on gearbox's, as this is not the first post of the internals of a 915 box, and yes it is the pointy bits, the small pointy bits, not the gear teeth, if you com-pear the 2 sets of photos you will see the difference.

regards mike

[john walker's workshop]

the way i look at it, is do you want a shift that's 80% good or 100% good? the sleeves may work fairly well, but they ARE worn. the insides wear larger because they are always rubbing on the syncro ring in normal use and the tips get blunted from grinding on the dog teeth because the syncro and inner sleeve are worn and don't properly match the speed of the free gear to the driven shaft for a nice shift. as for the pressed on dog teeth, 1st and 2nd teeth are famous for shedding teeth, so they both should be replaced when you have it apart. same goes for the 3/4 sleeve. they are easier to see the wear on the inner face of the teeth. one side is usually wider looking than the other.

[Elombard]

Sorry Trannies scare me... I mostly post fluff and bling anyway ;-) Seriosuly maybe its my computer the difference in teeth is subtle. I remember somebody posted pictures of brand new ones once, I will go look for that.

[Jim Sims]

915 Trans rebuild-internal diagnosis

[Alan.UK]

Thanks all. I will be replacing the 1st/2nd slider and will also flip the syncro rings. The rest of the box is in very good condition. It came out of a 70k mile car.

Alan

[john walker's workshop]

flip syncro rings? there's that 80% thing i mentioned. they get polished and chunks of the friction surface are often missing. polished things decrease friction, and that's what these syncros are all about.

[Alan.UK]

Thanks for the advice John, I understand what you mean but I do not want to start changing items which do not really need it. The rings look fine (will take a closer look when they are off) and based the comment on the basis they are good, if not, in the bin they go.

Alan