Rear double cardan propshaft.

[larryowner]

Wanting to fit a double cardan prop to the rear of my D1 based RTV trialer. The phasing of flanges on T/box and diffs is not right any more, at the front I have fitted standard D2 front prop and larger T/box flange. But the rear is not so strait forward, changing to the larger flange would require machining of the hand brake drum etc. So apart from spending around £500. with Gwyn Lewis, is there another way. I see a lot on the forum about front props and double cardan  joints but can't find much on rear's. Although for trialing the set up fine I drive to events some times, but vibration between drive and over run above 30mph is worrying.  

[lo-fi]

Get an adaptor plate made up? Think wheel spacer... I reckon 1/2 - 3/4" thick should do it. It's simple enough, and could easily be made in a home shop if you have access to a lathe and pillar drill, or would be a cheap job at any local engineering firm for cash.

 

[miketomcat]

I had a double carden front prop on the rear of my tomcat. From memory I re-machined the disco front flange to fit inside a td5 hand brake. I re-phased the prop by pulling the end out and re-fitting in a different spline position.

Mike

[Daan]

Are you sure a rear double cardan prop will solve your problems? a picture of rear prop angles would be good.

[larryowner]

As suggested I think the adaptor plate would be the easiest way. On the original donor vehicle the transfer box flange was facing down app 6 degrees and the diff flange up the same amount, so in phase, no vibe's. However the T/box flange is now vertical and so out of phase with diff flange. All 90's and Disco's are out of phase on the front prop, but can be improved by fitting a double cardan to the shaft, which i have done. So want to try same on the rear.

[hurbie]

my 110 is out off phase on the front axle , you have to clock the driveshaft for being out off phase (there are 2 arrows on the driveshaft that need to align, i think there's 45 degrees between flanges)  you can do the same with your rear drive shaft .

undo the rear drive shaft  , pull out the flange and put it back 1 spline apart from what it was , do a testdrive and adjust further if need be, i bet that solves the problem .

 

see this old posting :

Edited October 10, 2019 by hurbie

[miketomcat]

On my tomcat with a standard prop on the rear I used to get vibration on over run. My tomcat had the engine shifted back 10 inches, enough to swap front and rear props on a 100 inch wheel base. When I built it I re-phased the the rear prop to suit the front location and vice versa. I fitted a front double carden prop on the rear (re-phased to suit rear location) this solved the vibration.

Mike

[larryowner]

Update. I tried turning the rear prop one spline at a time as suggested by Hurbie, but made no noticeable difference to vibration, thanks for your idea though. So decided to purchase a ready made shaft. Dunning + Fairbank made me a double cardan shaft with standard L/R flange sizes, fitted it today and happy days, all vibe's and strange noises gone.    

[Carloz]

Strange... I see quite a big angle at the UJ at diff side... About the same angle as on the transfer box. I would expect that this situation would cause vibrations... 🤔

[cackshifter]

Mmm a useful company to know of, thanks for mentioning them

[tuko]

@larryowner

How long is your rear propshaft?
I have an 88" hybrid which has vibrations/horrible noises on overrun but my rear prop is very short so I thought it might be too short for a double joint.  

[larryowner]

Tuko, on level ground the rear prop is 580mm long, and has 50mm movement either side of that as the slip joint is around 100mm long.