Fitting a 5 speed propshaft

[stuartgb100]

I'll soon be installing a 5 speed box into my Sprint.
The prop that came with it has been dis-assembled.
I note that there are uj's and flanges each end, but that one end is adjustable for overall length,
whereas the 4 speed prop has a sliding spline at one end.

Presumably I should install the gearbox and then adjust the prop to suit the distance between
the flanges on the box and the diff.

So, how tight a fit should it be ?

Regards,
Stuart.

[Foxie]

Stuart,

The propshaft should not need "adjustment" It should just bolt up and take its normal design length between flanges. The sliding joint prevents linear forces being transmitted between gb and diff. Check rear propshaft flange and diff flange match, there are 2 diameters possible. Be sure the propshaft u/j axies are parallel when fitting the sliding joint. Access to the forward flange bolts will test your patience

Sean

[CBUEB1771]

whereas the 4 speed prop has a sliding spline at one end.

Sean is correct. The "adjustment" in the propshaft for the Lotus five speed gearbox performs exactly the same function as the one that slides onto the tail shaft of the four speed gearbox. The difference is only in the sequence of the components in the shaft. With the four speed it is sliding spline - Cardan joint - Cardan joint going from front to back. With the five speed it is Cardan joint - sliding spline - Cardan joint. Some axial compliance is needed to handle the small fore-aft movements of the engine and differential. Most of the propshaft parts were originally intended for vehicles with solid rear axles where much more compliance is needed due to motion of the axle.

[Elanintheforest]

I'm assuming that Stuart's propshaft is off a Plus 2 5 speed, and it's going into a Sprint, so will need to be reduced in length...but by how much? If this is the case, it should be the same reduction as the Sprint chassis spine is less than the Plus 2? I'll measure the two chassis tomorrow.

Mark

[Foxie]

I'm assuming that Stuart's propshaft is off a Plus 2 5 speed, and it's going into a Sprint, so will need to be reduced in length...
Mark

Yes, Mark, you're right.

I think only in terms of +2s.

Homer nods

[CBUEB1771]

I'm assuming that Stuart's propshaft is off a Plus 2 5 speed, and it's going into a Sprint, so will need to be reduced in length...but by how much?

Mark, In all likelihood you are correct although Stuart's propshaft could be the right one for installing the Lotus five speed in an Elan, A036 R 0038Z. The difference in length between the +2 and Elan versions has to be essentially the difference in wheelbase, 96 inches for the +2 and 84 for the Elan. The distance from the gearbox mount weld nuts to the front axle centerline is the same for the Elan and +2 and the diff housings are all the same so the propshafts should be different by 12 inches. If Stuart lines up his 5 speed propshaft against the 4 speed version it will be obvious which one he has.

[Elanintheforest]

!2 inches it is, Russ. The only difference between the 2 and 4 seat Elan chassis is the length of the 'spine', and that is 12 inches on my two. It wasn't until I put the two chassis together a couple of years ago that I realised how little difference there was.

Mark

[mikealdren]

Stuart,
Sean's right, it's essential to get the UJs lined up. It's also essential that they are lined up the same way round as they were when the shaft was originally balanced or it will need rebalancing.

Of course, if you're cutting and shutting your shaft it will need rebalancing anyway. Have you thought of getting a custom shaft made up? It may be cheaper to do that and sell the +2 shaft to a +2 owner?

Mike

[stuartgb100]

Thanks for the further interest and the trouble taken.

The 5 speed box and propshaft were bought from a guy who was moving on to a Voight conversion.
It had been fitted and working in either a Sprint or an S4 (can't remember which).

Graham Boulton has rebuilt the box for me. I'm now looking at the propshaft.

I'm part way through changing the uj's (one is part out ) so a bit of slop, but a measurement
overall flanges gives a total propshaft length of 1036mm.

Can you say how that compares please ?

And yes ......... a re-balance will be required.

Regards,
Stuart.

[stuartgb100]

Having re-read the thread, I really ought to have been clearer from the start.
My apologies.

Must have been pre-empting F1 Maclaren !

Sean,

You say the forward flange bolts are a challenge.
Could not the propshaft be bolted to the gearbox part way through the installation, and then
just guide every thing into place?

Regards,
Stuart.

[Foxie]

Sean,

You say the forward flange bolts are a challenge.
Could not the propshaft be bolted to the gearbox part way through the installation, and then
just guide every thing into place?

Regards,
Stuart.

Yes, that might be possible, bolt up the front part of the prop-shaft, install engine/gb, and fit rear propshaft, it would need to be checked out to see if it works. I have a TT exhaust, have to fit it to engine/gb assembly before reinstalling in car. A nuisance

[john.p.clegg]

If you "break-open" the propshaft at the sliding joint will you not have to mark it up for re-assembly...

John