Gearbox repair

[craig001]

I have a 4 speed 915 box that needs some repair. 1st and 2nd gears are very crunchy and selection is sloppy. I have replaced the shifter bushings (gearstick and coupler) which made a massive improvement but still the box has a problem.
Can anyone suggest any other adjustments/easy fixes for this problem or is it a box out, strip down repair?

Any recommendations for reasonably priced specialists in the Reading and surrounding area's and does anyone know a rough cost to fix a problem like this, I’m guessing its 1st and 2nd syncros that need replacing plus whatever else is found.

How easy is it to strip and repair these transaxle boxes yourself? I am a competent DIY mechanic that will tackle almost anything but have not touched gearboxes other than to replace them. Would like to have a go myself but if the cost of special tools etc is too much, I may aswell let someone else do it.

Any help/advice/recommendations/guides appreciated!

Ta
Craig

[hot66]

Mike Bainbridge http://www.mbporsche-engineering.co.uk/

[Gary71]

Hi Craig,

All you need to know about doing your 915 box yourself...

http://www.ddk-online.com/phpBB2/viewtopic.php?t=5052

...any other questions just ask

[johnM]

Hi

I looked into repairing my 911 box myself and decided that the cost of the parts compared to the cost of labour meant that getting a pro to do it was the best option. The parts are expensive and making a mistake could ruin your expensive bits or worse. I had my gearbox repaired by mike Bainbridge and its now a joy to use, I have also had the opportunity to look at quite a number of boxes that have been repaired by experts and they have destroyed all manner of parts. Also you need a number of special tools to dismantle and more importantly reassemble the box. My advice, do it once and get a proper Porsche gearbox mechanic to do it.

Regards

[davidppp]

Hello, Craig.

The price of repair parts is now such that, like engines, good running boxes are much better value than rebuilding unless you really want perfection.

And a 5-speed would be a nice upgrade..

Kind regards
David

[craig001]

A mixed bag of opinions!

David, If I could source a 5speed box, is it a straight forward swap or would the selector and linkage need to be replaced?, any idea on rough cost?

John and Hot66, Mike bainbridge appears to be the man, trouble is hes bloody miles away from me!. I would have to look in to cost of getting the box to him aswell, Any rough ideas on price of an overhaul by him?


Gary- I still am very tempted to do it myself, after all how hard can an old gearbox be!. Where did you get the parts from? and were the special tools you listed (36mm deep socket and 41mm spanner) all that is needed (well not all the tools you need but the only special tools you need, if you know what I mean!)

ta
Craig.

[johnM]

Hi

it would be a good upgrade to go with a five speed box but unless you can find one with a proven history the chances are that it would require some work.
you also need special tools to set the diff up and if this is not done correctly then you will turn the crown wheel and pinion into scrap. These are really expensive. As for the deep socket this needs to be about 18 inches deep and the nut on the input shaft you are undoing should be very tight you need a wrecking bar on it and unless you have the tool for holding the other end of the shaft your stuck.
Not trying to put you off, but make sure you have all the gear before you start.

regards

[hot66]

Have a holiday in the Lakes & drop off the gearbox whilst you are there


Shipping on a pallet isn't that much. I got an engine sent to the outer hebrides for about £60. Can't remember the company that hauled it though

[Mike]

Hi Craig, Mike Bainbridge's brother Neil runs BS Motorsport in Westcott Near Aylesbury in Buckinghamshire, and is a 915 expert! Much closer to you so won't need your passport, inoculations and a visa to go oop north.

He's got about 3 on the go at the moment including an RSR 915 with oil pump He's just done Dyno soar's on a budget, and comes highly recommended

Number is 01296 658422, mention Mike and DDK!

[Gary71]

Hi Craig,

how hard can an old gearbox be

My thoughts exactly! As long as you know your limits and don't go playing in areas that don't need to be touched then pretty simple is the answer.

Other than the tools I mentioned in the write up it was just a normal, but pretty comprehensive, tool kit.

As JohnM mentioned forget trying to set up the diff yourself, but it sounds like your problems are just a couple of syncros, and probably the gear slider as I guess the lack of decent syncromesh will have wiped the dog teeth off by now. Hopefully the dog rings on the gears are still servicable, although these can be replaced as the gears cost £££££ even if you can find them.

I'll disagree with JohnM on the need for a super deep socket and tool for holding then input shaft The input shaft nut is VERY tight, but you can hold the input shaft in a big soft jaw vice and use a big ring spanner. You will have to fit a gear on the splines and clamp that, as you'll never get enough clamp load to react the torque by clamping just the shaft. I had the luxury of 5th gear nicely positioned on the end, but I'm sure there is a way with the 4 speed box.



The tools are only this special




Don't disturb the shift forks on the rods, then you don't need to set them up again using the special jig you don't have

Parts wise I used Type 911, Mittelmotor, Porsche, Powerhaus and my local bearing stockist in equal measure. I just shopped around. The single most expensive part was third gear pair at over £300, other than that it's just lots of £45 items that eventually added up to £800... I did all the syncros and all the bearings expect the pinion bearing (to avoid reseting the diff). You don't have to go this far, but you will suffer from 'whilst I have it apart' syndrome, which can get expensive.

For the ultimate economy and assuming the dog teeth are still sharp, you could always turn the syncros around and put it back together!! (ducks as the purists start to foam at the mouth and use the 'bodge' word... ). Mine looked to have already been turned round about 5 times so it really was time to replace!

Having said all that a 5 speed box would be nice, but then you'll have to rebuild whatever you buy anyway! Around £1500 is the going rate for a rebuilt 5 speed, or at least it was when I did my box.

What ever you choose just get out and enjoy the car, learn to accurately double declutch then who needs syncro anyway!

[craig001]

Mike, Thanks for a more local contact to try,

Gary, thanks for the advice and pictures,

I need to decorate the kitchen, stick the windscreen back in the car after sorting the small amount of rust under the seal, and take the car for a spin, that way I can get a better idea of what might be worn, I cant rememeber if selection into 3rd, 4th and reverse is bad or if its just 1st and 2nd. Also I need to listen for any worn bearing noises, I seem to remember a noise when rolling forward slowly. The car has been in the garage since the MOT in November and Im struggling to recall what I was thinking when I last drove it!!

Once I have a better idea I can decide what the best options are


Any further suggestions welcome!!

[johnM]

Hi

this shaft has just come out of a running gearbox, and this is what happens if you dont tighten your input shaft to the correct torque, it chews up your input shaft because the gaers float around on the shaft and turns your shaft to scrap.


regards