Bwitched has rebuilt his box to be quiet http://www.talkmorgan.com/ubbthreads.php/topics/267875/Bevel_box_rebuild#Post267875 Another thought on the difference between the BMW and Quaife bevel box is that the bearing arrangement in the Quaife design by virtue of the use of angular contact bearings means the pinion is supported for thrust in both the forward and reverse direction, whilst the BMW box appears to be only supported for thrust in the forward direction.
The pinion thrust on the M3W spiral bevel gear set (l/h pinion, r/h crownwheel) is only outwards from the crownwheel under driving load but reverses with a trailing throttle when car is driving engine, due to helical gear effect (left hand diagrams)
Clearly there is a load point though when the pinion thrust is near zero and possibility of chatter without correct bearing pre-load, as Bwitched found. Referring back to the Guzzi box, note that pinion bearing pre-load is performed (correctly) with solid spacer and varying shims, not a crude crush spacer. Likely this then is cause of what I can best describe as a banshee wail as it happens on very light throttle settings.
Incorrect backlash could also be an explanation. Note this quote from KHK gears:
Is it a problem to use gears with no backlash? Backlash is required so that gears are able to rotate smoothly. Less backlash causes lubrication problem, leading to abrasion. Also, without backlash, excessive noise is produced as gears should contact with both tooth surfaces. Higher precision gears produce fewer problems when backlash is set at a small value, however, no-backlash must be avoided.
Richard
2018 Roadster 3.7 1966 Land Rover S2a 88 2024 Royal Enfield Guerrilla 450 1945 Guzzi Airone
For what it's worth... I replaced the lube in the BB at 1000 miles, using Valvoline full synthetic 80/140 Extreme Pressure. Noise greatly reduced when cold, reduced only somewhat when hot at 70mph, but still noticeable. Added 300ml.
Great to see someone take charge and fix this last link in the drivetrain.
If you have any questions that come up when changing out to the Centa drive, give me a call (561) 441-0199
check my repair thread too.
cheers
JV
A few month ago I have send a PM to Bwitched about this subject but never got a reply on it. I also don't see any new post of Bwitched so not sure if he's still reading the forum. I just have send him again a PM and hoping he gives us his experiences about the refurbishment of his bevelbox.
Can someone tell me how the bevelbox is attached to the frame ?
On the picture it looks that it's attached to the frame with two bolts which going through the detachable bearing housing. Or are there anymore bolts or attachments to the car frame ?
If its only by this two bolts it looks to me that the counterforce from the bevelbox needs to pass via this detachable housing to the frame.
Due to the two bearings in two separate housings it could be that the once set tolerances for the pinion/crown wheel has changed after the driving force has passed the two to each other bolted housings.
Perhaps I'm completely wrong with my simple ideas, but there must be a reason that one box is screaming and the other not even when they are from the same year. As long we don't know the cause we can't find the solution.
