UJ installation direction


I am putting a T3 back together. I have stripped and services the swing arm and bevel box (Bearings and seals)

I have noticed that some new or recon UJs have a red direction dot. When I took mine apart there was no sign of any marking. My UJ is tight and does not need replacing but:

is there a wrong way to put the UJ back. Does it matter if I get it the “wrong” way round and is there anything other than the dot that might show me the "right " way round.


I thought the 2 ends had different diameters, so will only go one way round? From memory that’s how mine was, but if it’s spun in the bearing I read somewhere that the big end can be turned down and the UJ swapped round, so presumably doesn’t matter.


Yes in my experience only one end fits in the bearing.

As mike says one end is machined to be a tight fit in the support bearing


The reason I asked was that one end was a sliding fit and the other would be an interference fit if I had used a sledge hammer.

The carrier bearing was seized solid, you can work the rest out for yourselves… :frowning:

Ho hum. When rebuilding a Guzzi, work out the cost of the parts and add a 0 :unamused:

Thanks for your help.

If the machined end is less than tight in the bearing, the favoured fix is to use some Loctite bearing fit.

Thanks Duffo

The UJ had obviously been spinning inside the carrier bearing for a long time. There was about 0.27 mm difference in the ID of the bearing and the OD of the shaft. The shaft could be rocked in the carrier bearing. Probably a bit too worn for Loctite.

I have taken some advice that I found on a blog somewhere, which was to knurl the end that goes into the bearing. I thoroughly dot punched the machined end and inserted it into the old bearing. This was seized but could now be rotated with the UJ shaft with a lot of effort. So I dot punched it some more and inserted it into the new bearing. Seems to work. It was an “interference fit” Took a few blows from a plastic mallet to get it to seat in the new bearing !

I will take it apart after a few miles and see if there are any witness marks suggesting that the shaft is turning in the bearing. Great if it works, nothing lost if it doesn’t.

They always go loose with use. Personally I think it’s because of sideways forces. Your raised punch marks may not last long before they’re flattened out. I’d have replaced the lot but of course depends whether you can get all the bits…

It’s a poor design. E.g. BMW R-series have a SINGLE UJ at the gearbox end and a ‘bendy’ spline coupling at the FD pinion end, so the shaft swings through a small arc relative to the tunnel. This takes a lot of stress off the UJ. AND it sits in its own oil bath.

I will probably go for new UJ. The bearing is new.

I just want the thing back in one bit now. Once it is rebuilt, the rest is ongoing maintenance. The UJ will be a priority and not much hassle to replace.

It does strike me as a bad design. The oil seal on the bearing was split and the bearing was dry and seized. Probably because the gaiter had split, Once things start going wrong, dirt and water get in, heat builds up, the whole system is compromised.

Gotta work with what you got though.


I stuck the UJ in the freezer for 24 hours which made it easier to fit.
I then left the whole lot in the freezer to make it easier to fit into the swinging arm.