A couple of months ago there was a mention of bevel box gear lapping done in Australia.
This interested me greatly as my bevel box is both noisy and a screamer, at most speeds.
I made contact with Three Point Classics in Melbourne. They advised they had done two bevel boxes, one 100% and second say 60% improvement. Encouraging i thought.
This was done by getting gears lapped.
So, out with the box. I had done this a couple times before as my box has been "fiddled" with by diff and gear companies. Neither made much difference, possibly worse.
The whole box is quite damn heavy, so being a cheapskate, i decided to just send the gears which was ok by TPC.
The breaking down of the box required assistance from our mechanic friend to remove the sprocket (this is very tight and resisted my attempts with a gear puller) and to undo the pinion and sprocket nuts.
Next issue was the pinion bearing which i left on the shaft to send away.
Courier cost to Oz was 100 NZD. Weight approx 9 kg
Lapping was done and gears returned about a week later
Pinion bearing was removed for the lapping. New one required
Next, Superfinishing. The ring gear and pinion gear done. Really shiny finish, mirrorlike.
This should reduce friction to very low levels and assist in running cooler and quiter, hopefully.
Right, moving closer to the final straight. Time to rebuild
This mean repetitive closing and checking contact patterns. Due to design of box its impossible measure backlash properly so its down to feel.
First job was to get new pinion bearing and press onto shaft (got help on this). Made sure to put old shim on shaft before bearing!
Second, tighten pinion sub-assembly to check preset load. With the fixed shims I managed to get 5-6 inch lbs. Turning gear felt "right"
First assembly highlighted that it wasnt possible to see the marks on the pinion or ring gears to make sure they lined up. So undo and use Sharpie pen to make the pinion tooth and the two ring teeth which need to mesh
Paint ring gear with poster paint ( i didnt have marking blue!), reassemble and turn gear forward and backward a couple of times.
I didnt like the contact position so spoke to the Lapping company direct. Sent pictures.
Was advised to move pinion in towards ring by 5 thou. Didnt want to ruin pinion bearing by removing it to place shimm behind. Was advised it was simpler to pop out the bearing cup and put shim behind the cup. Did this with a bit of judicious drifting
Repeated paint, close, turn, open and inspect. Looked like an even contact over most of the teeth. Checked by sending pictures and got OK.
Now, final reassemble. Only tricky bit being the sprocket. Plenty of oil on splines, wooden block and judicious hammering slowly did the job. Make sure it gies right to the collar on the shaft. Why? Well if you think its a good idea to leave a bit further out for better belt alignment, dont do it! There is so little room between flange screw heads and swinging arm they hit!
Final act, fill with 300 ml gear oil as its easier on the bench. I decided to use a lesser EP 90 for first fill and to run for say 50km to allow settling in etc
If all is well will change to 100% Lucas gear oil stabiliser
Whilst keen to try a run, have spent a bit of time aligning drive belt and retensioning. Besides its very wet st present.
With the car ready to run just had to wait for a break in the weather.
So the climax!
A very short run was very promising. Belt stayed on sprocket too! So , cajole the wife to be a witness and set off for the motorway to see if we still scream.
To cut to the chase
No screaming! Wife happy as refused to ride at speed due to screaming (cars not hers!)
I can only pick a noise at approx 60kph which is quite muted. Similar to loudness of urban cooling fan
Okay, its not so warm here at present at 16 oC and we only did 20 km BUT there is a vast improvement! Yes !
Time will tell
Apologies for the long ramble but its worth the explanation!
Some pix in next post
