Advice

[Rupsol]

My current project is a ratty 72 911T Targa - it has a later 2.7 motor and a dogleg gearbox (so either a 901 or 911) - it needs a rebuild as it whines in 2nd and 4th although the syncro's are not too bad. The spec from Porsche was that it was originally fitted with a 915 gearbox.....here's the quandry

Do I

a) rebuild the current dog leg box? I have spoken to Mike Bainbridge and he reckons £3k should do it and he will sort the ratios to match the higher power output of the 2.7

or

b) find a 915 box from a SC as they were ali and a better box?

Problem is if I buy another gearbox I really have to rely on the seller to tell me it is good - don't want to go to the effort of putting it in and then finding it too needs a rebuild in 12 months...…….you know the score chaps.

[911hillclimber]

In my personal experiences, the alum 915 box is not always good, they can suffer from the main bearings spinning into case and the wear is tricky to fix...
Mike B machined mine in the end and it is good after 4 years so far.
There were some boxes for sale on here very recently.

[murph2309]

With Mike you have a guaranteed (good) result. With an unknown box, you don’t... if I was buying on open market, I would send to Mike anyway (he’s done 2 of mine.... both epic)

I know dogleg isn’t right for your 2.7 (wonder how that happened....?) so maybe sell that, buy a 915 and get that sorted by Mike - then you have both the correct box and peace of mind

[Sam]

Using a dog leg box makes every trip an occasion. Racing cars have dog leg boxes.

The 915 is boring in comparison.

[911hillclimber]

Never driven a dog leg box but can see your point.
My 73T is a bitza too and currently has a 3.2 with an alum 915/Bainbridge built box with electric speedo.

Some 915's are good to use from what I've heard but mine is reluctance going to 2nd especially if you slightly 'rush' the box.
Maybe all the old design boxes are like this?

A friend has a dog leg 911 box in his tweeked 2.2T and loves it.

A dog leg in a bitza sounds perfectly ok to me.

MB Engineering must be the Go-To man for transmissions, he has done hundreds of them, each numbered after he has done them.
I have 2 of his boxes in very different cars.
The parts are not cheap, but he is the best to assemble them.

Before MB I tried 2 other specialists, and they dismally failed for different reasons, one being a big name in classic Porsches.
MB corrected the one's cock-up cleanly and to time and quote.

The Lakes will be very nice this time of the year!

[210bhp]

I have a 1976 915 gearbox available with the electronic pickup. However, I might not be very trustworthy and although the box looks nice outside I can’t see inside but when I lift it up and shake it nothing rattles.


I am traveling south from Scotland on Sunday and might be able to drop it off with Mike if he’s around so no shipping costs.
I’m looking for £3k

Regards
Mike

[Rupsol]

[quote="Sam"]Using a dog leg box makes every trip an occasion. Racing cars have dog leg boxes.

The 915 is boring in comparison.[/quote]

good response Sam thanks

[Rupsol]

[quote="911hillclimber"]Never driven a dog leg box but can see your point.
My 73T is a bitza too and currently has a 3.2 with an alum 915/Bainbridge built box with electric speedo.

Some 915's are good to use from what I've heard but mine is reluctance going to 2nd especially if you slightly 'rush' the box.
Maybe all the old design boxes are like this?

A friend has a dog leg 911 box in his tweeked 2.2T and loves it.

A dog leg in a bitza sounds perfectly ok to me.

MB Engineering must be the Go-To man for transmissions, he has done hundreds of them, each numbered after he has done them.
I have 2 of his boxes in very different cars.
The parts are not cheap, but he is the best to assemble them.

Before MB I tried 2 other specialists, and they dismally failed for different reasons, one being a big name in classic Porsches.
MB corrected the one's cock-up cleanly and to time and quote.

The Lakes will be very nice this time of the year![/quote]

I had a 3.0 SC with a rebuilt box and that was a pain to use - certainly couldn't rush it at all - I quite like the dog leg (apart from the whine)

[Rupsol]

[quote="210bhp"]I have a 1976 915 gearbox available with the electronic pickup. However, I might not be very trustworthy and although the box looks nice outside I can’t see inside but when I lift it up and shake it nothing rattles.


I am traveling south from Scotland on Sunday and might be able to drop it off with Mike if he’s around so no shipping costs.
I’m looking for £3k

Regards
Mike[/quote]


I cant make a decision that quickly - I am old I need time to ponder it. Whats the electronic pick up for? Please enlighten me

[Rupsol]

Thanks for all the responses chaps - another question - what is a dogleg box worth that needs a rebuild?

[911hillclimber]

Ref: Electronic pick-up

The later 915's (mainly aluminium cases) have a sensor in the box that drives the speedo via an electrical wire and not a normal (to the year) speedo cable.

Here is a later 915 box with the sensor/speedo wire :



My 911 has this set up and you need the speedo that matches the 'electronic' gearbox.
This speedo slots straight into the early 911 but the centre boss of the finger in the speedo is black, the early instruments have a silver boss.

The alum case 915's are stronger compared to the mag case 915 and most deem the dog leg box weaker still as the engines had less torque. The torque of the engine kills a box.

Not sure I totally subscribe to this reasoning, and maybe this is why MB is happy to rebuild the dog leg box with the 2.7 engine.
Not sure the dog leg box should whine if ok inside.

Finally, the dog leg box I think is a bit lighter than the mag case 915 and certainly lighter than the alum case 915, every little helps.

I still think the dog leg box with 2nd to 3rd in the same plane would give a good fun drive with those gears being the best on some of our less crowded roads.
Good luck with your decision making!

[Rupsol]

Thanks Hillclimber

[gridgway]

One question is whether it actually needs a rebuild. Is the whine worn bearings or noisy gears? Mine works really well but does have some gear whine. It'll last forever and the noise isn't obtrusive.

Good matched replacement gears are hard to come by.

Graham

[neilbardsley]

Using a dog leg box makes every trip an occasion. Racing cars have dog leg boxes.

The 915 is boring in comparison.

good response Sam thanks

An occasion like the time Mrs B drove the 912 and asked why it made a noise went she tried to select 1st !!

Sent from my Redmi 7 using Tapatalk

[Rupsol]

[quote="gridgway"]One question is whether it actually needs a rebuild. Is the whine worn bearings or noisy gears? Mine works really well but does have some gear whine. It'll last forever and the noise isn't obtrusive.

Good matched replacement gears are hard to come by.

Graham[/quote]

its a significant whine especially in 4th