G50 Transmission Repair

[Ian Comerford]

It's amazing the difference that the 1mm distortion has made as the spring loaded pin doesn't seem to have a made a mark where it should have done in the detents.

 

Ian

[coxy]

Tops Matt

[MaxDiesel]

It's amazing the difference that the 1mm distortion has made as the spring loaded pin doesn't seem to have a made a mark where it should have done in the detents.

 

Ian

 

I've just measured the bend in the shaft again and its more like 1.5mm... it must have had been given some abuse at some point to cause this. I don't think the detent pin is meant to run all the way to the bottom of the 1st and 2nd gear grooves - more just sit on the downward slope so it provides a constant tension (if that makes sense !).

 

It looks like I'll have all the bits on Saturday - so time to start putting all back together.....

[REX]

Keep it up Matt, brilliant. Good luck with the rebuild.

[flatsix777]

Fascinating diagnosis Matt. Great work.

 

David

[GaryH]

Great work Matt You don't do 915's do you ?

[MaxDiesel]

Great work Matt You don't do 915's do you ?

Cheers guys - it's going to be a nerve racking first drive once it's back in one piece !

 

There's much more info available on 915's which should help the DIY option... I think there's more that needs "setting up" on a 915 though which sounds like a bit of a black art !

[johndglynn]

The wonder of actual experts, as opposed to the armchair variety!

 

Great job and great pics mate. Thanks for contributing

[MaxDiesel]

Got back onto my gearbox this afternoon - all the new bits arrived yesterday.

 

Checked the new selector shaft against the old, first of all the new one's straight

 

 

Nice clean edges on the detents:

 

 

Assembled the fork onto the selector shaft with two new roll pins, and then refitted onto the gearset. Then assembled the 1st/2nd gear selector sleeve - needed three hands here to hold the three spring load ball bearings in place - managed to shoot them across the workshop several times before I got this far:

 

 

Gearset and selectors fitted back on the diff casing:

 

 

Had my first go a refitting some of the interference fit bearings and sleeves - gave them 30mins at 150 degC in the fan oven and they slipped straight on by hand (welding glove..) - 5 seconds later they're absolutely solid and not going anywhere without a hydraulic puller !

 

 

Its good to see the 1st/2nd gear selector now sits evenly between to two gears rather than biased towards 1st gear.

 

Next step is to refit the main gearcasing - it uses a paper gasket but there were also traces of sealent when I stripped it - especially around the studs so I'm not sure whether just to go with a dry gasket or use a little Loctite 574 as well...

[Tebbs]

Gorgeous work!

One day I'll have the confidence to do a box, there's something so appealing about those mechanisms. Hope it all works when it's back in.

 

Will adding sealant affect preload on anything or increase slop on any of the shafts?

[MaxDiesel]

Will adding sealant affect preload on anything or increase slop on any of the shafts?

Possibly - it's one of the reasons I'm nervous about using anything other than the paper gasket, I think I'll just go for a smear of 574 around the base of each stud

[Dr Rock]

On the Saabs the number and thickness of the metal gaskets between the tripod joint and the 'box housing affects the diff preload..

[MaxDiesel]

More progress on my gearbox this afternoon..... so time for a photo heavy update !

 

Spent a good couple of hours cleaning the two gear cases ready for refitting:

 

 

Also replaced the two output flange oil seals as both were weeping, old seal:

 

 

New seal in (a 50mm socket is just the right size to drift these in):

 

 

Having trawled though a load of Pelican gearbox threads it sounds like the best sealing method it Loctite 574 plus paper gaskets so I went ahead fitted the main casing - its always reassuring to see a even orange bead coming from a joint:

 

 

 

Reassembled 5th /reverse selector sleeve, this time I had my wife help hold all the spring loaded selector dogs in place - much easier but she really doesn't like the smell of transmission oil

 

Final step prior to fitting the nose casing was to torque up the two shaft nuts... so time to make up the locking tool with Andy Young's old friction plate (cheers Andy !). Managed to make the following without destroying the plate so it's still good as a spare:

 

 

Smaller of the two nuts was no problem at 120Nm, the bigger one required 250Nm though which is more than my torque wrench can do so had to resort to basics...

 

35kg son pressing down on a measured metre mark until the old bathroom scales read 10kg (while I sat on the gearbox !) We pre-checked this at 150Nm/15kg and 200Nm/20kg and it was spot on against my torque wrench.

 

 

The main nut ended up on the same mark as tightened by the factory which was reassuring:

 

 

Just need to refit the nose casing and it's all done - I tried shifting through all gears and no problems so far

 

Edited April 8, 2010 by MaxDiesel

[Tebbs]

Nice work. Good engineering, think outside the box!

[coxy]

Hats off to you Matt, I dont think I would have tackled that, ( hummm we'll see about that ). Well done

[semprini27]

Beautiful work - and a family project too !

 

"I had my wife help hold all the spring loaded selector dogs in place - much easier but she really doesn't like the smell of transmission oil"

 

QOTY ?!

[MrPerkles]

brilliant work

[tim s]

Give me a shout when you need a hand putting it back in. Hats off to you!

[Andy Young]

More progress on my gearbox this afternoon..... so time for a photo heavy update !

Final step prior to fitting the nose casing was to torque up the two shaft nuts... so time to make up the locking tool with Andy Young's old friction plate (cheers Andy !). Managed to make the following without destroying the plate so it's still good as a spare:

Just think of it as IB Recycling - fantastic job you must be chuffed.

 

Andy

[Dr Rock]

35kg son pressing down on a measured metre mark until the old bathroom scales read 10kg (while I sat on the gearbox !) We pre-checked this at 150Nm/15kg and 200Nm/20kg and it was spot on against my torque wrench.

The application in the real world of the laws of physics = genius

[MaxDiesel]

Cheers guys - I hope the pics of the G50 bits prove useful

 

Give me a shout when you need a hand putting it back in.

Thanks Tim - it would be great to have some help with the lift back in - will probably be a couple of weeks yet though, the "while I'm there" list keeps getting longer...

- suspension refurb

- CHT sensor

- engine bay sound pad

- tappets

- more underseal

- etc etc!

[MaxDiesel]

Last couple of bits done now so the tranmission's all ready for refit.

 

Nose casing ready to be fitted - the Loctite 274 also does a good job of holding the gasket in place during assembly:

 

 

And on:

 

 

Fitted the last new seal on the input shaft - getting the old seal out was a right pain... had to drill two holes very carefully and use self tappers to pull it out. A length of plastic sink waste pipe works well as a drift for the new seal.

 

All done - just waiting for the oil to arrive from Opie (ordered a week ago....) - looks just the same as when I took it out !

 

 

Time to get the rear suspension back together now.

[World Citizen]

MD, I'm massively impressed you've tackled a G50 disassembly, it all looks quite scary to me, good effort.

 

I hope you can offer me a bit of advice as I have tracked down what appears over the phone and from pictures a manual G50 6-speed box from a 1998 Porsche 993 for not a lot of money.

 

I know your rebuild is on a 5-speed but it it can't be that much of a different layout than a 6-speed.

 

How easy is it to select the gears without all the gear linkage attached and is it possible to detect when the box is in nuetral?

 

Was removing the nose casing anymore work than undoing the bolted joint and sliding it off the selector shaft?

 

Is there anyway of inspecting the main gear cluster without taking the cente casing off ie, inspection cover or borescope through the drain plug?

 

Any advice welcome as the knowledge may stop me from buying a casing full of swarf.

 

Mr. Perkles if I ring Mike at MB Engineering and mention your name will that be a good or bad thing to start the conversation with

[MrPerkles]

Mr. Perkles if I ring Mike at MB Engineering and mention your name will that be a good or bad thing to start the conversation with

he sees that many people and engines he probably wont remember me,just tell him the stupid brummy Andy recommended you to him

I do need to go up there soon so if your in the UK give me a shout

[MaxDiesel]

MD, I'm massively impressed you've tackled a G50 disassembly, it all looks quite scary to me, good effort.

Cheers - it wasn't that hard in the end, just daunting when you first take apart !

 

I know your rebuild is on a 5-speed but it it can't be that much of a different layout than a 6-speed.

Yes I think there's a lot of commonality between the various G50 boxes - I used the 964 workshop manual for mine and all the internals were identical - the gasket set I used was even a 964 one. A 6 speed is going to have a few major differences though (longer overall I expect).

 

How easy is it to select the gears without all the gear linkage attached and is it possible to detect when the box is in nuetral?

Its not too bad - you need to fit a long M8 bolt onto the shaft to give yourself some leverage then just work through the gears logically... neutral is straightforward to fine - just push all the way one way, pull all the other way - then go halfway betwen the two (it feels like neutral also).

 

Was removing the nose casing anymore work than undoing the bolted joint and sliding it off the selector shaft?

No - just unbolt and remove the nose casing - you'll need a new gasket to re-assemble.

 

Is there anyway of inspecting the main gear cluster without taking the cente casing off ie, inspection cover or borescope through the drain plug?

Borescope would be the only option - ideally one with camera attached to take some pics. By going in through the fill plug you should be able to get to the main gears and enagagment teeth.

 

Other than this you could rig up a crude coupling between a power drill and the input shaft (i.e. bit of rubber hose with two jubilee clips) and try spinning the gearbox in each gear.

 

Good luck !