5 speed conversion and propshaft

[ventadorn]

Hi I have a LWB twin wheeler mk1 with a 2.5 di, MT75 and mk3 propshaft, in the middle of a conversion. Apparently I have an unusual flange on the diff, it's quite small (bolt spacings are 2" x 2 3/8".) The end of the prop has a flange that is 2 3/8" x 2 5/8". So the easiest thing to do would be to swap the diff flange for the larger size. Anyone know if this larger size flange is fairly common for the mk1 as I need one quite urgently. Or does a mk3 one fit the earlier axle?
cheers

[DougT]

The Mk1 twin wheel diff flange is quite small although I don't have the measurements to hand.

The Mk1 and Mk2 have the same diameter spline on the pinion shaft but from the Mk3 onwards the pinion spline diameter was larger. So the Mk3 flange will be too loose on the Mk1 spline.

You can fit the Mk3 onward Crown wheel and Pinion into the Mk1/2casing which is a good option if you want to change the diff ratio (ie to 4.63) as the later CW&Ps are easier to find although not that easy or cheap these days. See Ken B's post

viewtopic.php?f=3&t=111158

Doug

[dumper]

Take both you prop-shafts to a specialist they will be able to remove the ends and swop them and rebalance it try
D&F prop shafts Bradford

[ventadorn]

The Mk1 twin wheel diff flange is quite small although I don't have the measurements to hand.

The Mk1 and Mk2 have the same diameter spline on the pinion shaft but from the Mk3 onwards the pinion spline diameter was larger. So the Mk3 flange will be too loose on the Mk1 spline.

You can fit the Mk3 onward Crown wheel and Pinion into the Mk1/2casing which is a good option if you want to change the diff ratio (ie to 4.63) as the later CW&Ps are easier to find although not that easy or cheap these days. See Ken B's post

viewtopic.php?f=3&t=111158

Doug

many thanks for the info, so no use me looking for a mk3 flange unless I want to go the whole hog and swap crown wheel and pinion as well, something I would prefer not to do just yet. I think I would like to get the truck up and running and then see how I get on with the 5.14 diff before changing anything.
So.....I am wondering what the dimensions are of various mk1 or mk2 flanges and if anything out there will match up?

[DougT]

Not sure if bolt heads fouling against the joint lugs etc would allow you to do this, but have you looked at drilling new holes in the larger propshaft flange offset slightly from the original holes to allow you to bolt them together?

Basically it is the reverse of doing what Ken did to bolt the smaller prop flange to the larger pinion flange. Might just be worth checking if you have not already done so.

Only other suggestion would be an adapter plate but the thickness would mean you will need to shorten the shaft so you might as well get the propshaft end changed as dumper suggests.

Doug

[ventadorn]

Not sure if bolt heads fouling against the joint lugs etc would allow you to do this, but have you looked at drilling new holes in the larger propshaft flange offset slightly from the original holes to allow you to bolt them together?

Basically it is the reverse of doing what Ken did to bolt the smaller prop flange to the larger pinion flange. Might just be worth checking if you have not already done so.

Only other suggestion would be an adapter plate but the thickness would mean you will need to shorten the shaft so you might as well get the propshaft end changed as dumper suggests.

Doug

Thanks Doug but as you can see from the photos the rear of the prop has not got a "proper" flange so not really able to drill anything in that. If it were only the other way round and the diff flange was bigger.....
I have been told that my diff flange is unusually small so I am holding out hope that there might be a bigger one out there that will fit?

[DougT]

Photos can be deceptive, but I am afraid that to me that looks like the standard Mk1 and Mk2 twin wheel pinion flange. If someone is not used to them, they can seem unusually small but they are what was fitted. So I don't think you will find a different flange with a Mk1 & Mk2 twin wheel axle pinion spline diameter.

The only other thing to wonder about is whether you can find another propshaft of same length with a full flange then. Would that be easier ?

Doug

[Neil]

bottom pic is standard,, why have you a mk 3 prop ?

[ventadorn]

Photos can be deceptive, but I am afraid that to me that looks like the standard Mk1 and Mk2 twin wheel pinion flange. If someone is not used to them, they can seem unusually small but they are what was fitted. So I don't think you will find a different flange with a Mk1 & Mk2 twin wheel axle pinion spline diameter.

The only other thing to wonder about is whether you can find another propshaft of same length with a full flange then. Would that be easier ?

Doug

Ah right I was holding out hope that there was something different available if nothing can be found then it's either join a mk1 rear prop section to the mk3 prop or go the whole hog and do the 4.63 conversion with later pinion crown wheel and flange