Thread: Diagnosis of noises needed

I feel like a Hypochondriac*- would a new 4.6 motor increase the load substantially? Do they have serviceable nipples?

they can be rebuilt with greaseable UJ's

the best ones have fittings for nipples but dont have the nipples fitted they have a hex socket screw fitted in them that when its time to grease them you remove the hex screw, install the nipple, grease it, remove the nipple and re-install the hex screw.

leaving the nipple in place can wind up leading to a damaged nipple that then lets corruption into the joint or that requires dissasembly of the joint to get the old nipple out so you can put a new one in and grease it up.

I've tried to work out, apart from what I know, what the difference betwen a DC and a back to back uni is. I had a new front shaft made for my RRC years back and it had two unis at onw end and the centre was just more or less two flanges weled together (but a machined part). Yet the DC's from the threads seem to have a centre ball which is the expensive, hard to replace part.

Thoughts and opinions?

Originally Posted by clubagreenie

I've tried to work out, apart from what I know, what the difference betwen a DC and a back to back uni is. I had a new front shaft made for my RRC years back and it had two unis at onw end and the centre was just more or less two flanges weled together (but a machined part). Yet the DC's from the threads seem to have a centre ball which is the expensive, hard to replace part.

Thoughts and opinions?

I think you've nailed it.
As usual UP has it covered:
www.discovery2.co.uk / Workshop :- front and Rear propshaft

correct.

a double uni is usually done on a short lenght to correct misalignment on machines. typically its just as you described it 2 UJ flanges welded together, occasionally they might be bolted. they get their slip alignment from having one side running on a sliding spline like the rear output from a rear wheel drive auto and can run at nearly the angle limit for normal UJ's

A Double Carden shaft has an alignment mechanism built into it and forces the 2 universal joints to move through the same range to achive the "angle" they need to achieve (half each so a 30 degree bend is achieve by both UJ's in the joint moving 15 degrees). The Centralising mechanism usually runs out of travel before the UJ's do and most stressed part is the centering mechanism, Once its worn it begins to "wander" and when that happens the UJ's get ever so slightly out of alignment and the process begins to compound.

I've had a quick look at the geometry and you might be able to get a shaft custom made that runs 2 CV joints as opposed to the DC but thats likely to increase the loading on the Tcase font out put.

DO NOT use a CV on it, trust me my RRC front replacement double uni shaft was replacing the original one that had a CV (fitted from "factory" when they did the borg warner 35 auto conversion). On overrun it rattled and clanked something chronic, new CV lasted about 7-8 months, a month or 2 longer than the boot.

Actually I see the difference now. The DC with self centring the TC flange and shaft end are "circular" where as the diff flange is only a U shape and is what is used in the double uni shaft. Mark from All spares made it for me and pretty sure the flange/joint/spline was from a county or similar vintage. Worked a treat and was much easier to overhaul and cheaper too.

Originally Posted by Blknight.aus

it goes without saying that you're checking the whole shaft, not just the DC itself.

I had a similar metallic 'tick' as I pulled away from a standing start. As Blknight has suggested, it was caused by the front uni in the front propshaft.

The joint itself was fine but it was moving in the front flange. Prior to me purchasing the vehicle, the DC joint has let go (evidenced by the dents in the chassis rail and gearbox from it flapping around). This had caused the front flange to spread open so the front uni wasn't being located properly. New flange and uni solved the problem.

you have to CV both sides a CV + UJ on a single shaft will always cause problems...

dunno why it does though, in theory it should work.