Automotive Gearbox tolerances

[geesamand]

I'm looking for standards that provide guidance on housing accuracy, particularly parallel shafted gearing and interchangeable housing halves with dowel pins.

In the industrial realm, we have only ISO 10064-3 and its DIN equivalent, which specify tight tolerances assuming the housing halves are machined together.

Does SAE or another automotive reference have a standard that applies?

Thanks,

David

 

[Tmoose]

"interchangeable housing halves with dowel pins."

If a bearing bore is partially in both housings that sounds like a really tough assignment to me.

 

[MikeHalloran]

I don't think anyone has ever done _interchangeable_ housing halves with bearing bores split by the split line.

Mike Halloran
Pembroke Pines, FL, USA

 

[geesamand]

A bit of clarification: I'm thinking about the typical front wheel drive transaxle, where the bearing bores are not in the split plane. So the shaft axes are normal to the split plane, and the key question is the required true position accuracy of the bearing bores vs. the dowel pins.

David

 

[MikeHalloran]

I have no direct knowledge of the actual tooling used, but I should hope that the dowel holes are drilled and reamed and all the bearing bores are finished while the housing halves are clamped together (and maybe bolted together) in a single fixture, so the issue of bearing bore location tolerances relative to the dowel holes and of the dowel holes to each other is moot.

Even 'just' locating two pair of dowel holes relative to each other well enough so simple plates can be interchangeable is jig borer territory.

I should note that some Japanese CNC mills are routinely capable of jig borer accuracy, but mass produced gearbox housings are not normal workpieces for them.



Mike Halloran
Pembroke Pines, FL, USA

 

[geesamand]

I've worked with a number of Nissan, Mazda, and Honda FWD transmissions and all of them use dowel pins to connect the housing halves. They are interchangeable, not match-drilled. The dowel holes are blind and you can buy either housing half as a spare part with no qualifications.

David

 

[MikeHalloran]

Well, dip me in ... used food.
I'd sure like to know how they do that.


Mike Halloran
Pembroke Pines, FL, USA

 

[CoryPad]

I think we are talking about something that looks like this image (see attachment). The dowel pins are in the upper left and lower right corners, and the bearing bore is the one surrounded by ATF lubricant.

If so, I know of no industry standards, but position tolerance within 50 micrometers has been used in the automotive industry.

 

[geesamand]

Thank you for that - that is the exact arrangement I'm referring to.

I appreciate the anecdote of .05mm positional, this is roughly what was expected.

It occurred to me after the last post that Japanese automotive standards might cover it instead of SAE, but it's just as possible that it's proprietary tolerances only.

David

 

[CoryPad]

I should have answered Mike's question - manufactured using Vertical Machining Center, Hardinge's Bridgeport GX series or similar.