Bevel box
In June DAT appeared with a crownwheel & pinion from the ex ex Captian RP thank you. So September 09 took the car back to JB for a another major 'mid' 'back end' rebuild.
He dropped the back end and didnt have to take the axle out.
So the bevel box was out. Lots of metal bits in the oil, so it would seem that this was good Bolzano 09 preventative work!!!
Here is the email information for Nash geeks to enjoy from the 'man that does' in Huddersfield. I have toned the down the expletives and all names changed!
"The countershaft is bent, when I run my dial indicator on it, I get 0.100" TIR. which is more than the amount by which the bevel box bobbed up and down with the engine running(0.023" from memory), but it kind of depends where along the length its bent. Was going to attempt to straighten it, but have done a crack test on it, and its cracked as well, along- side a keyway , no risk of snapping in two, its kind of on ther driven side of a keyway.
This dispite beautifully radius keyway bottoms! It could the one huge jolt it got when 2 gears at once, who knows."
So RP Mr Spares of Sheffield supplied a new countershaft to Huddersfield man at Cadwell park.
"The distances from the location faces on both the crown wheel and pinion were quite different (new shims) to the old one. It meshes good now, with a tiny bit of back lash.
The countershaft keys roll a little, to help gearchangeing.
The scroll seal on the nose-piece (before the spider) is a bit to rusty and tired to fit the right way, so I've fitted the wrong way, as before, but makes virtually no difference especially as I have put grease in the nose piece.
Roll pin in the new 4th gear bush, and press-fit and locktite.
Extra holes drilled in bush to add oil
Lockwire on that bolt that hold the reverse shaft in. New steel bush on other end where it entered casting in the chassis.
Bolted crown wheel. Not a fan of hot rivetting personally as difficult to get right when not in a smithy, and I only have oxy-acetylene heat. Extensively lockwired bolts/nuts.
Check them when you check the b/box oil."
"The new crown wheel and pinion required different sized spacers behind them, as to be expected. I got all the unit assembled and re-fitted the gear selector bell cranks. These were very sloppy and worn, and a difficult call as I didn't want to replace them - all original bits etc.
So I shimmed them a bit with a brass shim (diametrically and shimmed them vertically quite accurately using washers and they were better. But on the selector end which runs in the double dog, the big bush/roller was spinning around as it should, but the whole threaded bolt which carries it was spinning too so the wrong bits were wearing.
If I just tightened the nuts on top then the roller nipped up solid which was no good!
So I had to de-rivet/file off the small roller (which operates in the wriggley monkey slot) to get these bolts out. Then I fettled the bolts to give clearance to the bottom roller, when nipped up, great. Then when it came to re-fit the top bush/roller again, I've already filed off the rivet bit, so had nothing left!
So I made new rollers as the others didn't roll well, were square as a result and did little to prevent a 2 at once gear selection. The new rollers are chain rollers shortened a bit, and for a rivet end I added a blob of mig weld. Little other option really, but now everything rolls which should, and everything is nipped up which should be nipped up.
2 gears at once SHOULD now be impossible (OK lets not talk about reverse)
I then happened to turn the pinion before I was about to fit it in the car and realised there was no back-lash at one point on the crown wheel!!! "
"New crown wheel, new countershaft, impossible!!! Can only be I've got a bit of dirt under the crown wheel as I fitted it. Drat!!!
Pulled it all apart and ran a dial indicator round the back face of the crown wheel and had 0.010 reading!! Yes probably dirt, but I couldn't see any when I stripped it!!!!
Bolted it on again, and it still was 0.010 out!!! Bolted it on 180 degrees out and still 0.010 out!!! But it was always the same point on the countershaft, not the crown wheel, so the new crown wheel was OK. I check the new countershaft for straighteness and it too was good!
How can the crown wheel carrier be bent? Its a disc with a hole in it.
The dial indiator was a smooth climbing reading (like out of true) not a sudden bump, like might be impact damage. All had been press fitted together, with shaft in freezer and carrier in Aga and it took only 2 tonnes to assemble, so couldn't be bent.
So bored out the soft jaws on the lathe, put the countershaft in, dead true, skimmed the face on the carrier (0.080" out which made perfect sense being on a smaller diameter) and skimmed the crown wheel mounting face flat.
Put it all back together again, re-shimming behind the crown wheel of course, and all seems good!"
"2nd and 4th gears needed tapping over to align them (on the rear axle).
Undertray re-fitted.
4th gear bush (on countershaft) is press fitted, loctited then roll pinned and burred up between dogs to absolutely prevent dog/sprocket moving off its bush (famous 2 at once scenario)
Crown wheel now rivetted, not bolted as previous. Had bolts rotated (even though lock-wired) I was afraid they would have hit inside of B/box casing. Rivets are probably better.
Not sure about propshaft balance and clutch disengagement until I test down the road....."
Comments