Synchro Dimensions
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From: Creede, CO
Synchro Dimensions
I'm rebuilding a 1986 911 transaxle and the installed diameter for the first gear synchro ring is 86.10mm, .1mm smaller than the small end of the specified range. This is with a new engagement dog ring, new brake band, new anchor and energizer blocks and new synchro ring. All the other gears are within specifications with their new synchro rings installed.
I and rebuilding this transaxle because the it would pop out of first gear under light load. The 1st gear synchro, engagement dog ring and 1/2 slider showed signs of significant wear, but no damage when I disassembled the transaxle.
Is there a way to increase the diameter of first gear's synchro ring?
PerryB
I and rebuilding this transaxle because the it would pop out of first gear under light load. The 1st gear synchro, engagement dog ring and 1/2 slider showed signs of significant wear, but no damage when I disassembled the transaxle.
Is there a way to increase the diameter of first gear's synchro ring?
PerryB
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Its the replacement dog teeth. They likely lack the 9 degree backcut that is required because of the curve of the synchro. Its making it too tght. The teeth need to be machined.
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From: Creede, CO
Swell. Is this something I can accomplish on my own? Can I put this 9 degree curve to match the rounded profile of the synchro ring using a high speed grinder and a carbide burr?
Is there a company that makes the dog ring with the correct chamfer?
Thanks!
Perryb
Is there a company that makes the dog ring with the correct chamfer?
Thanks!
Perryb
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Thank you, Mr. Gross and GTgears.
So if I buy a Rauch & Spiegel brand dog ring, it will DEFINITELY have the chamfer needed to let the synchro ring expand to the proper dimension?
The one that I have now is from Vertex and is supposed to be made by the OE supplier.
PerryB
So if I buy a Rauch & Spiegel brand dog ring, it will DEFINITELY have the chamfer needed to let the synchro ring expand to the proper dimension?
The one that I have now is from Vertex and is supposed to be made by the OE supplier.
PerryB
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So, can anyone confirm that the Rauch & Spiegle brand engagement dog rings will have the 9 degree taper that will allow the synchro ring to expand to the proper diameter? Before I buy another I'd like to have some confirmation.
Perry
Perry
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You can be confident in Kevin's and Matt's (GTGears) advice when it comes to these gearboxes. Matt didn't confirm the R&S dog rings are correct now in this thread, but he has elsewhere: https://rennlist.com/forums/911-foru...l#post15114107
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From: Loveland, CO
Measure the replacement with a loaded synchro prior to pressing it in the gear. R&S made no public announcement when they started back cutting them. Someone with old stock on the shelf may still have uncut ones.
I wouldnt try to diy is without a lathe.
I wouldnt try to diy is without a lathe.
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From: Creede, CO
Thanks for the replies.
I didn't mistrust the answers from GTgears or from Kevin Gross nor did I intend to insult any one. It's just incredible to me that a company would go to all the trouble of reproducing an internal transmission part and not have it match the original so that it can work correctly.
I will purchase a new Rauch & Spiegle engagement dog ring.
Thank for the advice.
PerryB
I didn't mistrust the answers from GTgears or from Kevin Gross nor did I intend to insult any one. It's just incredible to me that a company would go to all the trouble of reproducing an internal transmission part and not have it match the original so that it can work correctly.
I will purchase a new Rauch & Spiegle engagement dog ring.
Thank for the advice.
PerryB
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From: Loveland, CO
I saw no insult. I saw someone just trying to understand.
It makes no sense to me. I manufacture new gears using the German oem dogs. We’ve been doing so for a couple decades. They’ve never been backcut. We backcut them to spec after they are on our gear.
I’m glad R&S was listening and did something. I have been publicly unkind to some of their b grade products. In this instance they heard the criticism (through another more gentle messenger who I had discussed it with) and fixed the problem. Originally they had just copied the German part. Copy an unfinished part and you get the same.
Use the German synchros. They are harder than the R&S ones. They are too soft and wear quickly.
It makes no sense to me. I manufacture new gears using the German oem dogs. We’ve been doing so for a couple decades. They’ve never been backcut. We backcut them to spec after they are on our gear.
I’m glad R&S was listening and did something. I have been publicly unkind to some of their b grade products. In this instance they heard the criticism (through another more gentle messenger who I had discussed it with) and fixed the problem. Originally they had just copied the German part. Copy an unfinished part and you get the same.
Use the German synchros. They are harder than the R&S ones. They are too soft and wear quickly.
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From: Creede, CO
I know that everyone was on the edge of their collective seats, so....
I purchased a Rauch and Spiegle dog-tooth 1st gear engagement ring and installed it today. The syncho dimension is now in spec.
Thanks to GTgears and Kevin for their diagnosis and suggested cure.
PerryB
I purchased a Rauch and Spiegle dog-tooth 1st gear engagement ring and installed it today. The syncho dimension is now in spec.
Thanks to GTgears and Kevin for their diagnosis and suggested cure.
PerryB
