extending gearbox input shaft

[adamwatson]

I'm building an MGB with an RX8 gearbox and Saab turbo engine. I have an adaptor plate but the gearbox input shaft doesn't seem to go more than a few mm into the crank bearing. I'm thinking as the end of the shaft just supports its in the bearing and doesn't really take any load I could weld an extra section on and turn it down so its all the same thickness. Obviously I'll remove it from the box and grind a big V in the shaft ends so its strong. If I use another piece of input shaft as material can anyone think of a reason to not do it? I know I could have the bell housing skimmed down but I'm concerned if I take too much off it'll be too weak

Thanks
Adam

[froggy]

Just get a slip over extension turned for it ,job done . The kit I got to put a bm zf onto a Volvo whiteblock came with an extension.

[welshpug]

how much is a few mm?

most bellhousings are quite overbuilt so taking a couple of mil off to get the shaft into the bearing would be much better than trying to weld a shaft.

[vitesseefi]

If the input shaft spline fully engages with the clutch plate and it's just that the tip doesn't quite reach the pilot bearing I'd look ways to move the bearing nearer to it rather than messing with the input shaft.

For example, my Triumph Vitesse is fitted with a W58 Supra gearbox. The problem there was that the original box has a long tip for the pilot bearing but the Supra box has a little stumpy one and couldn't reach the pilot bearing in the crankshaft.

My first solution for this was to modify an easily available top-hat section Oilite bush so that it sat in the bore in the centre of the flywheel. This moved it about 20mm nearer and was enough. This worked fine for about 20k miles but when I had it all apart to swap the engine a year or so back the bush had been spinning in the flywheel and rather than make another I had the flywheel machined (simple job) to take a suitable sealed ball bearing race (which is what is used in the Supra).



If this doesn't win you enough it would also be possible to have a stepped extension tube made to tap into either the back of the crankshaft at one end and carry a suitable bush or bearing at the other.

Nick

[adamwatson]

Feb 23, 2017 19:50:36 GMT froggy said:

Just get a slip over extension turned for it ,job done . The kit I got to put a bm zf onto a Volvo whiteblock came with an extension.

what is a slip over extension? can you link to an example or stick a picture up?

[froggy]

With the Saab engine your better off with something oilite pressed into the crank to take the input shaft

[MrSpeedy]

Get an extended phosphor bronze bush made to fit into the flywheel and project further out to carry the shaft.
It only carries load when the clutch is disengaged

[curryracer]

My two-penneth. .

One option is to make an extension to the input shaft. Think of a short 3/8" ratchet extension to give you the idea.

The more popular option for the RX8 converters (including me) is to have the appropriate amount machined off the bell housing.

Have you seen the threads on the turbosport forum? They have covered most of the different fitment methods. There is plenty of material on the BH just be careful of the counter sunk bolts!

Good luck 😉

[adamwatson]

thanks guys. Will check out the turbosport forums as well

[dodgerover]

Can someone tell me what trick I'm missing here? His input shaft engages a few mm in the existing bearing, how can he extend the shaft without causing problems with the bearing? Anything that slips over to extend it is going to need to be bigger? I'm assuming needle roller in the end if the crank so you couldn't go bigger there?

[slater]

Just need an extended bronze bush in the crank. Easier than extending the shaft unless you have the box to bits and a cyl grinder to hand.