Triumph 5TA Gearbox Bush

[Bri]

Hello Everyone!

Does anyone have experience of fitting one of these bronze bushes? - It's for a '66 Triumph 5TA gearbox.
I've read about using a long bolt and piece of oversize tubing to push the new one in / old one out - and I've 'Googled' for any tips on this and have turned up absolutely nothing!
I'm guessing I will probably need to heat the gear up, but not sure by how much - and obviously how I'm going to handle it after!?!

Any ideas?
Thanks!
Bri

[52t-bird]

HelloBri, It is not the easiest bush to replace as it is so thin walled and easy to distort . I do not heat the gear especially not with a flame as it could damage the hardening and as you say it makes for difficult handling.BEFORE REMOVING THE BUSH make sure you look carefully at the spirals inside and fit the new bush the same way.I have seen more than one bush fitted the wrong way around with damaged main shafts as a result.I use a vice and appropriate bar to first press out the old bush.I then use the vice and spacer to push in the new bush but make sure you get it in true or it will distort!Depending on the quality of the new bush it is quite likely you will have to ream it after fitting.regards David

[Bri]

Thanks for your reply, 52t-bird  

Now you mention the direction of the spiral inside the bush, I'm wondering if the one already fitted is correct or not?!
 - The gear would be spinning clockwise, (as viewed from the angle in the picture) but the spiral appears as though it would be driving oil back towards the camera rather along the shaft towards the clutch end of the mainshaft - So am I right in thinking it's already the wrong way round??

Thanks again.

[TBS]

The spiral is correct as fitted. When you look at it, it doesn't go all the wayto the end, if it did it would take the oil out of the gearbox into the clutch.

[Bruce]

Putting the bush in the frezzer and warming up the steel will help but as said do not over heat the steel, try the oven if your wife will let you.

[Bri]

The spiral is correct as fitted. When you look at it, it doesn't go all the wayto the end, if it did it would take the oil out of the gearbox into the clutch.

...Of course!....... Thanks for that  

Thanks guys for all your replies  

[Rex]

It doesn't matter which way in the new bush goes, as the spirals will still "rotate" the same way. A right-hand threaded stud (for instance) doesn't become a left-hand threaded stud if you turn it around.....

Anyway, bush in freezer, gear in oven, and press in CAREFULLY in a vice (if you haven't got access to a fly-press).
You may wish to slightly taper the end of the new bush and clean and polish the outside too, and make sure the gear has no burr around the lip to impede fitting.

[33d6]

For final precise sizing after fitting the bush my personal preference is to hone rather than ream. I find honing to be more precise and gives a better finish than reaming.
Also, on the gloom and doom side, how much wear is there on the mainshaft? Usually, if a bronze bush is worn to that extent the underlying shaft is badly worn also. There isn't much point renovating one without the other.
Again, I have refurbished mainshafts using an electroless nickel system. This is not electroplating but instead uses a chemical bath where the plating medium can be precisely controlled so a very accurate repair can be made that is ready to fit as soon as the job is removed from the bath.
A sweet gearbox is a thing of joy. I appreciate why you want to get it right.
Good luck,

[Bri]

For final precise sizing after fitting the bush my personal preference is to hone rather than ream. I find honing to be more precise and gives a better finish than reaming.
Also, on the gloom and doom side, how much wear is there on the mainshaft? Usually, if a bronze bush is worn to that extent the underlying shaft is badly worn also. There isn't much point renovating one without the other.
Again, I have refurbished mainshafts using an electroless nickel system. This is not electroplating but instead uses a chemical bath where the plating medium can be precisely controlled so a very accurate repair can be made that is ready to fit as soon as the job is removed from the bath.
A sweet gearbox is a thing of joy. I appreciate why you want to get it right.
Good luck,

There is actually a section of the main shaft that is worn - at the cog end of the pictured gear, directly under the cog. When I measure the area with a digital vernier it appears to be worn about .006" undersize to the rest of the shaft - I fully expected it would need replacing at some point, and wasn't sure if a repair was even a possibility. I was hoping that replacing the bushes might buy me some time!  :-/
The gear box always worked fine last time I rode the bike - never had any noticeable problems at all. The main reason I took the box out was to replace the drive side oil seal - and at that point I decided to take the clusters out and check / replace the bearings at the same time - I'm only an amateur 'mechanic', and was hoping to get it back on the road quickly!  :-[
So where is it possible to get the main shaft repaired? And what sort of cost are we talking about?

Thanks!

[33d6]

I can only tell you about where I get my stuff done in my home town in Australia. Can't help with any other part of the world, sorry.
I can tell you what the process involves so you can ask the right questions but thats about it.
Essentially the repair requires the worn part to be first ground concentric again and then built up again by submerging it in a chemical bath containing various nickel compounds. Those parts you don't want built up are coated in wax. Because the part is  submerged in the bath the coating builds up at an even rate all over the exposed area. Teflon can also be added so you have a nickel/teflon coating to further reduce friction when the part is in use.
The bloke who does my parts swears using the nickel/teflon process is worth 2 seconds a lap to him on our local track.
Just Google "electroless nickel" and you'll find out a lot about it.
Its a very useful process to know about.

[TBS]

Rex, you are completely missing the point. The bush is not spiralled all the way through , only about 3/4 of the way, so that the shaft is lubricated as the spiral cutting picks up the gearbox oil. If you fitted it the other way round the gearbox side would not pick up the oil so easily as :
a: the bush is stepped at the end of the spiral  
b: the bush is a smaller diameter at the unspiralled end and is therefore a closer fit on the shaft
c: Workshop manual states "The new bush must be pressed in with the oil groove in the bore of the bush at the teeth end"

[Rex]

Must be more than one design of pattern part going around then, as the last two I've had the misfortune to have to fit were basically a constant diameter (id and od) bush with a spiral machined the entire length.
Incidentally the spiral is not for shaft/bush lubrication, but to reduce gearbox oil migration along the mainshaft.

[Blue]

speaking of diameters and reaming/honing etc it would pay to check the outside diameter of the new bush to ensure it will fit properly in the first place.  It's very unlikely it isn't the right size, but I buy bronze main-bearing bushes from Draganfly which are made oversize on the outer and undersize on the inner diameters.
10 seconds with a vernier gauge can prevent a headache later.