Press for gearbox bearings...

[tunnelrider]

Hi all,

I'm just about to get into my 5 speed gearbox and replace the bearings (hopefully that's all it needs...) for the first time.  I have access to a 1.5 ton manual press - not hydraulic.  Can anyone advise please whether this will crack the mustard - be enough pressure to take off and press on new gearbox shaft bearings?

Thanks for any input.
Dan

[Tony Smith]

Hi all,

I'm just about to get into my 5 speed gearbox and replace the bearings (hopefully that's all it needs...) for the first time.  I have access to a 1.5 ton manual press - not hydraulic.  Can anyone advise please whether this will crack the mustard - be enough pressure to take off and press on new gearbox shaft bearings?


When I did mine I used hand held bearing pullers and a drill press, so I reckon you will be just fine.

I do have a question though. The shimming of the shafts is a trick, I was able to borrow a trepanned rear cover from a (then) local workshop, without that, or a specially made steel jig i do not believe the job can be done with a guarantee of a satisfactory outcome. What are you going to use?

[mrclubike]

A three jaw puller and a heat gun or propane torch will do the trick.
But without a shim plate to set up the end play of the shafts after you replace the bearing is the hard part.
You will also need a out put flange puller
I have been doing this kind of stuff a long time and I got to tell you  setting up one of these gears boxes defied all logic.
Even though Bearings are made to very high  tolerances and  one would  think all you have to do is replace the bearing and use the same shims.
Not so When I did that the box was tight.
I had to buy a shim plate and start all over with the shim packs.
A big issue is that the bearings are a press fit into the case and you have to heat the case just to get it apart and it is made of thin aluminum.  
I would not use the crush the solder method to calculate the shim pack.
You will also want to replace the springs and clips and the plastic roller.
You will need  these 2  special tools a depth Mic and a 1 inch mic to measure the shims  http://www.cycleworks.net/index.php?main_page=product_info&cPath=29_33_52&products_id=39
http://www.cycleworks.net/index.php?main_page=product_info&cPath=29_33_52&products_id=321
I made my own flange puller
Read everything you can find on the internet about it before you start.    

[tunnelrider]

Thanks for the tips Tony and Mrclubike,
As I don't have an output flange tool my plan is to get a shop to remove the output flange for me, which they did today.  They also had to make a flange tool as he couldn't budge the flange nut - reckoned he had to take it past 700Nm!.  He's a BMW trained mechanic.  There was no lockwasher under the flange nut from a previous effort (not mine!), so I'm guessing the nut must've jammed on the flange.  Anyway, glad I didn't bother without a flange tool.
Good to see you both want me to do the job properly, re the shimming of the shafts on install!  Since I don't have the jig either I was going to take it back to the shop to shim and close up.  He does have the shimming jig already.

The 1985 gearbox (170 000km) is in good shape gear wise, the worst bearing was the output shaft cover bearing, followed by the large output shaft bearing at the other end.  There is no cirlclip in front of the large bearing.   The housing cover was removed easily without heating, if the new bearings fit in their receptacles too easily, I guess it means the cover should be replaced?...  I imagine that'd be expensive or hard to find a 2nd hand one!

[Tony Smith]

Re output flange puller.

There is no magic in this. I went to a motorcycle shop I frequented at the time that I knew machined up semi-finished sprockets for lesser machines. I scrounged a "centre" that had been cut from a blank sprocket that was big enough to fit over the output flange, the advantage being that already had a substantial centre hole.

I then drilled four holes so I could bolt my piece of steel to the flange and then used a (big) 3-jaw puller to pull the flange.

In regards to your other comment about loose bearings, you could try seating them in a hard epoxy - if it were mine I'd try Devcon, otherwise, yes you are looking for a good 2nd hand case.