Shortening a jackshaft

Hi All,
Got to the stage with this auxilliary transmission where once I measure the distance between the two (transmissions), where I want to make up a jackshaft as short as possible.
I'm using common mid-size Ford/Dodge Spicer uni-joints. Think they are 1350 series.
Have all the components here, couple of spare tailshafts with the right fittings on them. Thinking along the lines of a jackshaft similar to an "island" transfer case as in 4WD application. Just how critical is the balance on such a short shaft? Got a mate who's pretty good with a MIG, also has a lathe. Thought if I could weld the male spline directly to the circular section of the uni plate, remove a couple of inches off the male end, would end up with something close to required length. They will be as close and level as possible, so as long as the yokes are in correct alignment, is balance going to be a real issue on such a short shaft? Way I figure it, only need enough travel in the splined section to remove the jackshaft (if ever necessary) to clear the yokes without having to remove the transmission(s). Obviously will retain as much splined area as possible for strength. Just the balance I'm not sure about.
Realise the actual tailshaft to be used will have to be both shortened and balanced, can send that away to be done.
Dave_64

I'd say you would want the balance pretty spot on other wise it could transfer vibration through the rest of the driveline components. As for level, don't get it absolutely perfect otherwise the unis don't rotate as designed and the rollers stay in one place and will wear out in no time. Have you got a Hardy Spicer near you? You could do the work and take it in to them for balancing maybe?

Thanks, 600Dodge,
Got a tailshaft contact over in Bendigo, another in Geelong, both a couple of hours away. May be the go, get the mate to set it up in his lathe for correct alignment and send it out to be balanced, or just mark up the lengths and get a tailshaft bloke to do the lot.
Cheers, Dave

Dave,

I had a 1 meter-ish shaft made for the bus. It was about $400 ish for the (all new) shaft, flanges, unis and balance.
I supplied the old flanges (so they could match the bolt pattern) and the distance I wanted. They did the rest.

If you get anything balanced, it's going to cost about $200 min. (1-2 hours plus 'on costs')

last shaft I got made was at least 10 years ago
There was a place in Cambellfeild just off the Hume and I would just drop the shaft off when I went to the city and pick it up at the end of the day and I dont reckon they ever cost any more than a couple of hundred balanced and all
I stood and yacked top him when he did one for me once and it didnt even take a hour to make a whole shaft

Paul

Cogz
Gudday M8
Balance B critical
Normally U supply the unis also so the hole lot can B evenly balanced
then they try to sell U new unis if yours aint 100%
:woohoo:

cya

§

I've shortened a couple of car tailshafts, so smaller diameter but higher revs compared to trucks. I machined up the ends so they were a tap in fit to the tube, then welded shaft to yoke end with low hydrogen rod, stitch welded.

Used behind big block Fords, no vibration issues noticed even at high revs.

I have seen back in production racing days, put car on hoist, have driver run top gear and watch tailshaft from underneath, mark each end of shaft with chalk if vibrating then balance by using 2 large wormdrive hoseclamps changing phasing between the two to improve balance.

I am not recommending this procedure as professional practice, just saying how we did it.
Paul

Just having a bit of a think about this, how would I go with a double cardan shaft setup, similar to what they use on lifted 4WD's ?? That way I could maybe even keep it shorter still, but would probably have to change from a yoke type coupling to a flange?? Dave

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.dave ........ if I was just going to use something on the farm , may be . just do it your self...........
but for on road use not good..........
If you make it, then take it to get it balanced , you can bet your life .they will say we have to do it
and balance it for you...........with any supplied parts deemed serviceable by us.........
Tailshaft vibration can chop out bearings in things that it is attached to...so.....
Yep.... balance is critical.....of corse, the longer the shaft the more critical it is to use the proper
propeller shaft tubing that is made to a strict criteria,, because ( or used to be ) only the ends
of a tail shaft can be balanced, not the centre area...........
Yep, all boxes, diffs, etc should have working angles so the unis are not stationary and wear from
brinelling, (rollers embedding into the cross and caps ), as well the correct over all angles from eng to
boxes to diff (or diffs) to alleviate any drive line vibrations ...........
wow ....did I say all that..............a bit like Ripley.............
I guess a phone call or 2 will sort that out...........
.........................Billy..............................

If you are going super short do you even need a tail shaft ?????
perhaps a tyre coupling ???




Paul