Interchangeability of gearboxes?

The Simps · Aug 8, 2009

Hi, I'm new to the porsche world and know very little. I have acquired a 924 2.0 8v W reg torque tube & gearbox which is to run on a different space framed car.

How much power can these boxes take and what are my options for future? Do all the boxes easily mate up to the torque tube housing? Is there an upgrade with a LSD?

I'm not concerned about gearbox mounts being different etc, thats not a problem, its more about compatability.

Any help appreciated.

Simps.

geoff Ives · Aug 8, 2009

If you are fitting it to a different chassis have you concidered the 924 Turbo box. This was designed to cope with 270 bhp in the 924 Carrera GT and has better balance with the gearbox behind the differential. It was also available with limited slip diff.

tref · Aug 8, 2009

I am guessing you want cheap, and use what you have, in which case the "cheap" option for LSD will be a 944 box with LSD in it already...
The 924 Turbo/944 boxes/bell housing/torque tube are different in length... not sure how the basic 924 compares... how-ever I am sure 924nutter will be along shortly - and he'll know!

The Simps · Aug 8, 2009

Firstly, thank you for the speedy replies!

I originally wanted a turbo box as it makes sense that they would take more power. However I was offered a 924 complete for free so took the opportunity. I was aware that the layout was different. The turbo box the diff is at the back and the torque tube doesn't go into another bellhousing. I assumed however that the gearboxes would all share the same mounting points on the chassis? ie if I wanted to swap to a turbo box later on I'd just need the box, torque tube and maybe linkage rod and it would all bolt up the same?

Also, are the splines different at the clutch end on different boxes?

Maybe it would help if I tell you what I'm doing....

I'm more of a vauxhall nut and love doing trackdays. I've had a 300bhp 2ltr 16v turbo nova for 8 yrs and wanted to do something different and rwd with it. The car is a 2dr saloon model and the dimensions compared to the 924 are VERY close! I'm talking 40mm out. The thought of a track prepped rwd 50/50 balanced nova got me wet and I've been head scratching ever since! I found out today that the vauxhall clutch I will be using actually fits the torque tube so that was a result. I've just got a lot of work now adapting the bellhousing to suit the vauxhall engine. I will only be running a 185bhp NA lump intially but want the ability to upgrade later on and want a box that can cope with 300lbft all day long and track abuse!

mr brightside · Aug 9, 2009

You may want to consider that the bearings in the gearboxes you are dealing with are prone to wearing out and whining horrendously like mine, it's been the subject of many a thread on here. If you fit a second hand un-rebuilt box personally i'd expect it to be a whiner within a few thousand miles considering the beating you'll be giving it. You may get lucky and get one that's been well treated but in terms of probability my personal opinoin would be that the odds aren't in your favour.

There was some discussion about the subject in the 944 forum some months ago and the concensus seemed to be that whatever the sellers say, be them breakers or otherwise, it's very difficult to get hold of a good non whining second hand box. Some people will charge up for what they claim to be low mileage boxes but the truth is most of them will be whining within 5k and it's a complete waste of cash.

http://www.porscheclubgbforum.com/tm.asp?m=464641

I think this link will help you.

The Simps · Aug 9, 2009

Thanks for the reply.

Interesting reading that thread. It seems that whining is quite normal then?

As I acquired the car for nowt and am in profit from just selling the mint front seats and there are still some more stuff to sell I might aswell fit and try this box. If it blows up then get another.

Anyone got a pic of the layout of the 924 turbo or even 944 turbo from underneath so I can see the difference?

geoff Ives · Aug 9, 2009

ORIGINAL: The Simps

Thanks for the reply.

Interesting reading that thread. It seems that whining is quite normal then?

I just turn the radio up.[

]

If you are fitting a replacement box it is as well to replace the bearings.

.

The Simps · Aug 11, 2009

I won't bother pulling the box apart. Its of unknown condition so I'll just run it and see what its like. Its no problem for me to change it.

tref · Aug 11, 2009

I know that not all boxes use the same mounting points... I don't know which ones use which, but My S2 has four threaded holes under the front of the back seat that are unused, not so on my 924 Turbo, or 944 - not sure which now.

The Simps · Aug 11, 2009

I'm not massively concerned about the mounting points as long as they're in and around the same region as it will all be mounted off the roll cage etc so can be changed quite easily.

I suppose really it just knowing what boxes are a good upgrade (preferably with LSD) and I'm aware I'll need the specific torque tube but is the length going to change considerably and I'm also guessing the main shaft is going to be larger on the more tougher boxes (hence another reason why the torque tube will have to be changed)?

Mike_Pollock · Aug 11, 2009

Hi

Early (pre '85) 944 boxes have 2 mounts approx 400mm apart the later ones have a single mount in the centre.

Mike

The Simps · Aug 11, 2009

This is my box...

I'm assuming thats the same as the early 944?

924nutter · Aug 15, 2009

924 gear box 20 mm torque tube drive shaft and clamping sleeve./
924 turbo 25mm coupling but torque tube is abot 600 mm shorter and does not have the dummy engine backplate shape
1982 944 25mm clamping sleeve so no, a 944 box will not fit a 924

I am having a clear out, so for £300 you can by an old wreck of a 924 that is sat in my garage. The engine runs and the gearbox is a non-whiner. The car is tatty on the inside and the drivers side sill is rotten, but then I got it very cheaply, to run it for a year while my 924 turbo was off the road. Just before I laid this car up I had the Le Mans wheel s refurbished but they have been sat for nearly four years now.Effectively you would be getting a bloody good gearbox, and an engine with good oil pressure but of indeterminate mileage, and some half decent Le Mans wheels for three hundred notes.

On further investigstion on PET the engine bell housing has a different part number, and so does the torque tube.

input shaft- different part number suffix
4th gear - differenet part number suffix

Most tellingly of all the case part numbers again vary by suffix, i.e.;
924 ) 016 301 103 J

944 ) 016 301 103 R

So may physically fit but wont join up.

Changing torque tubes wont help as the clutch centre plate has a smaller dia splined hole on the 924, not withstanding removing the rear axle housing to swap it. This is all from a text dook and drawings, if anyone has actually done the swap then let us know because in theory it is does not seem possible without changing numerous other things

Mike_Pollock · Aug 15, 2009

I have an early ('83) box outside.

Input shaft is 25mm and protrudes approx 45mm forward of the housing.

So can confirm above.

Mike

The Simps · Aug 16, 2009

Thanks for the further info and thanks for the offer of the car. I'm going to try this box and if its funked fit turbo or 944 stuff with an LSD.

I would imagine to change it all over You would need obviously the box and torque tube. As I'm running a vaux engine & custom bellhousing I can make the torque tube fit. Basically I'm running a 150mm Vaux to ford gearbox bellhousing adapter and will chop the end plate off the torque tube and weld a new one on to suit the bellhousing.

As far as clutches go the smaller 924 shaft fits my vaux clutch nicely. Vaux also have a 6 speed gearbox that runs a larger shaft and the suitable clutch, fly & pressure plate all bolts straight on to my engine. It would be handy again if the turbo box shaft is the smae fitment as this larger vaux clutch.

ChasR · Aug 20, 2009

Regarding the comments about no 944 box fitting a 924, that is not strictly true. A friend on mine had a 1983 944 Lux with an iffy gearbox. He fitted in a gearbox from a 924S with no issues. I doubt this would have been possible with a 924 2.0 'box thought mind you.

The Simps · Aug 21, 2009

Thought I would add this quick Paint drawing I done of the engine end of the torque tube on my W reg 924. Forgot to measure the shaft diameter tho :doh: