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57_BN4
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Just a little note on my experience with repro sychro cones for a BN4 transmission.
The first lot I got from AH4H looked to be well made so I dutifully assembled the transmission with them. A quick test on the dyno stand showed they have almost no baulking action at all so I stripped down the trans again to find out why. The issue is the lack of care when machining the braking face which mates to the cone shape on the gear.
Pic one is the AH4H supplied synchro after lapping it on the gear for about half an hour then colouring it black with a permanent marker pen and rubbing it a few times on the mating gear.
Pic two is a 'Welch' CGBS140 synchro after the marker pen treatment but with no lapping.
Pic three is the original 55 year old cone.
You can plainly see the differences- the cheapy replacement ones have very little contact area (light colour = contact) due to poor machining when compared to the original and properly made reproduction. They are going straight back to AH4H [edit]
Conclusion: avoid reproduction synchro cones like the plague unless they are properly made. If you are about to assemble a gearbox with repro cones, colour in the brake face and see how much contact it makes with the mating gear.
Andy.
The first lot I got from AH4H looked to be well made so I dutifully assembled the transmission with them. A quick test on the dyno stand showed they have almost no baulking action at all so I stripped down the trans again to find out why. The issue is the lack of care when machining the braking face which mates to the cone shape on the gear.
Pic one is the AH4H supplied synchro after lapping it on the gear for about half an hour then colouring it black with a permanent marker pen and rubbing it a few times on the mating gear.
Pic two is a 'Welch' CGBS140 synchro after the marker pen treatment but with no lapping.
Pic three is the original 55 year old cone.
You can plainly see the differences- the cheapy replacement ones have very little contact area (light colour = contact) due to poor machining when compared to the original and properly made reproduction. They are going straight back to AH4H [edit]
Conclusion: avoid reproduction synchro cones like the plague unless they are properly made. If you are about to assemble a gearbox with repro cones, colour in the brake face and see how much contact it makes with the mating gear.
Andy.
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