Rear wheel bearings (GT6 non rotoflex)

[Rubce]

Hi All

I am in the process of reassembling the rear shafts on our late Mark 3 GT6 (non rotoflex). Both shafts are new and so is one trunnion housing. One asembly has gone together fine but the other side is causing is me problems!

When I came to drift the ball bearing onto the second shaft it became stuck and immoveable. I ended up having to cut it off with a disc cutter! To determine why it became stuck I measured the shaft and bearing. The sizes were as follows:-

new shaft 25.50mm
both old scrap shafts 25.50mm
new bearing cut off  25.40mm
new bearing just purchased today 25.40mm
both old bearings removed 25.40mm

So, all the bearings are 0.1mm smaller than the shaft onto which they fit. This confuses me as I thought the turnnion housing was supposed to slide up and down the shaft as the vertical link moves up and down with the rear spring. For the bearing to slide surely it has to be a transission fit, non an interference fit that the above items give. The driveshaft which has already been reassembled (new bearing, new shaft & reconned trunnion housing) has been refitted to the car and the trunnion slides happily as the spring moves. That ball bearing drifted onto the shaft with just a few taps from a hammer and a piece of wood.

Can someone please explain to me what I am doing wrong? Is my interpretation of how the rear suspension works incorrect?

HELP!

Thanks

Bruce

[thebrookster]

I can't advise on whether the trunnion houseing should slide, but going on my engineering experience I should think it very unlikely that the bearing is supposed to slide on the shaft!! That would entail a lot of wear onn either the shaft or the bearing, and I personally have never come across a bearing designed to slide in such an application (allthough to be fair the majority of bearings I work with are on pumps and motors, which are an interference fit).

I am not certain on the method of fitting bearings in a home setting, as all the car bearings I have fitted have been an interference fit into the hub, as apposed to a shaft, so I usually drift them in gently. Doing this on a ship we have a funky piece of kit that I think uses ultrasound, we balance the bearing onto a rod which sits on two terminals, which heats the inner race up, allowing enough expansion to slide it onto the shaft with a bit of gentle persuasion. However I have yet to find this tool available in the UK at anything other than an extortionate price!!

I hope that this helps!

Cheers,

Phil

[drofgum]

Bruce,
The bearings aren't intended to move on the shaft in service. They should be pressed or drifted onto the shaft the correct distance as shown in a workshop manual, and then stay there. I had a set of axles that apparently were undersized once, and the bearings did move, which led to the axle pushing the brake drum away from the backing plate. Not the sort of thing you want to see.
                                                                   Best of luck,
                                                                   Paul

[junkuser]

"When I came to drift the ball bearing onto the second shaft it became stuck and immoveable"
Sounds as though the bearing was not square on the shaft.
Pressing on is safest but drifting on squarely using a piece of pipe with with a true square end is next best.
Drifting the bearing on by tapping around it is probably the commonest attack but runs the risk of the bearing cutting into the surface of the shaft and raising a lump and then you are in trouble.

Could this be what happened in this case?

[Rubce]

Hi

Thanks for the various postings and sugestions etc. I popped the driveshaft into the freezer for 24 hours and then knocked the bearing on using a piece of hollow tube and a hammer. It went on fine this time.

Thanks

Bruce