Yukon Gear ring and pinion

[john-9]

i do not know if this has ever come up before but it concerns Yukon Gear ring and pinion sets for the 742 case.
i purchased a set of 3.55's and while trying to set the pinion bearing preload , the shims used were being distorted and the preload would be all over the map.
i noticed that Yukon leaves a small radius at the shim location on the pinion gear -- factory Chrysler gears are undercut at this location so the shims sit flat to the shoulder.
once i corrected for this defect the preload set perfectly ---

i did send a e-mail to Yukon about this --so maybe it will get to their manufacturing people and this defect can be corrected.

 

[yellow rose]

Can you get it in a lathe and just remove the radius? Maybe they make a different shim?

Just throwing stuff out there.

 

[69FBCuda]

Nothing rides there, if the outer bearing is hitting this shoulder you don't have enough pinion shim at the case. All you did was create a little more space for the outer bearing to compress the crush sleeve.

 

[Treblig]

The radius gives the inside corner a lot of extra strength. I would have trimmed the inner diameter of the shim that rests against the small radius. I realize Chrysler didn't have a large radius in that corner but things were built better and stronger back in the day. An undercut allows the manufacturer to get rid of the corner and still have room for a radius in the undercut. I'm a machinist and know how important a radius can be in preventing stress fractures at a critical point. Remember that the threaded shoulder where the bearing mounts has to handle ALL the load of the engine torque when you stomp on the gas pedal! Hope you didn't have the machine shop put a sharp corner in place of the radius because even a 1/32" or a 1/64 radius is stronger than a sharp corner.??? Wishing you luck with your build!!

treblig

 

[yellow rose]

The radius gives the inside corner a lot of extra strength. I would have trimmed the inner diameter of the shim that rests against the small radius. I realize Chrysler didn't have a large radius in that corner but things were built better and stronger back in the day. An undercut allows the manufacturer to get rid of the corner and still have room for a radius in the undercut. I'm a machinist and know how important a radius can be in preventing stress fractures at a critical point. Remember that the threaded shoulder where the bearing mounts has to handle ALL the load of the engine torque when you stomp on the gas pedal! Hope you didn't have the machine shop put a sharp corner in place of the radius because even a 1/32" or a 1/64 radius is stronger than a sharp corner.??? Wishing you luck with your build!!

treblig

I understand a radius is stronger. The question is...is it neseccary. Chrysler cranks were undercut (although that was rolled) and they are reliable.

I've never, ever broken a pinion gear at the radius. The teeth come off first.

Sounds like the radius is overkill to me.

 

[Treblig]

I understand a radius is stronger. The question is...is it neseccary. Chrysler cranks were undercut (although that was rolled) and they are reliable.

I've never, ever broken a pinion gear at the radius. The teeth come off first.

Sounds like the radius is overkill to me.

Yes, the radius is overkill. Most things that are manufactured are designed to withstand much more abuse/force than required...that's why you've never broken one at the radius. In manufacturing a radius is almost always called for except in unique situations. I would be interested to see if the factory pinion has a radius where the "undercut"" meets the input shaft?? I would bet there is, otherwise they would have simply put a sharp corner there without the undercut. The undercut w/radius doesn't weaken the input shaft or the rest of the pinion but a sharp corner would absolutely make it weaker.

Treblig

 

[john-9]

Nothing rides there, if the outer bearing is hitting this shoulder you don't have enough pinion shim at the case. All you did was create a little more space for the outer bearing to compress the crush sleeve.

there is no crush sleeve used in the 742 cases -- shims set the preload

the reason i brought this issue up is make people aware of this so when they try to build their diff they have a idea as to why the preload is giving them trouble.
never had any issues like this with any other major gear makers -- Motive ( Richmond ) , US Gear ,etc.
since US Gear , Motive etc. has stopped making 3.55 gears for the 742 cases , Yukon is becoming the only game in town.

 

[yellow rose]

The radius gives the inside corner a lot of extra strength. I would have trimmed the inner diameter of the shim that rests against the small radius. I realize Chrysler didn't have a large radius in that corner but things were built better and stronger back in the day. An undercut allows the manufacturer to get rid of the corner and still have room for a radius in the undercut. I'm a machinist and know how important a radius can be in preventing stress fractures at a critical point. Remember that the threaded shoulder where the bearing mounts has to handle ALL the load of the engine torque when you stomp on the gas pedal! Hope you didn't have the machine shop put a sharp corner in place of the radius because even a 1/32" or a 1/64 radius is stronger than a sharp corner.??? Wishing you luck with your build!!

treblig

I found a video today and it reminded me of this thread and you. It's on enginelab.com and they show a 5 minute video of some of the operations in making a crank from the raw forging. It is a vomitwagon crank for some super car deal, but what I found interesting is that they undercut both the rod throws and the mains. And they do it with a tool. I was told Chrysler rolled the undercuts on their cranks but this was done with a tool.

As a machinist myself I was interested and thought you may be too. Also I found interesting the induction hardening process. Very cool.

I'm an idiot so I can't post a link, but it should be on the from page of the web site, as it was just posted today.

Check it out. Very cool.

 

[Treblig]

I found a video today and it reminded me of this thread and you. It's on enginelab.com and they show a 5 minute video of some of the operations in making a crank from the raw forging. It is a vomitwagon crank for some super car deal, but what I found interesting is that they undercut both the rod throws and the mains. And they do it with a tool. I was told Chrysler rolled the undercuts on their cranks but this was done with a tool.

As a machinist myself I was interested and thought you may be too. Also I found interesting the induction hardening process. Very cool.

I'm an idiot so I can't post a link, but it should be on the from page of the web site, as it was just posted today.

Check it out. Very cool.

I found it!!....Very cool video especially the induction hardening part. I also used to be a CNC machine programmer, that was a lots of fun and paid really good money!! We would machine 900 lb High pressure wellhead castings for the oil field. After they were completed they only weighed 500 lbs.....lots of cutting with intricate/complex IDs. Treblig

 

[mderoy340]

there is no crush sleeve used in the 742 cases -- shims set the preload

the reason i brought this issue up is make people aware of this so when they try to build their diff they have a idea as to why the preload is giving them trouble.
never had any issues like this with any other major gear makers -- Motive ( Richmond ) , US Gear ,etc.
since US Gear , Motive etc. has stopped making 3.55 gears for the 742 cases , Yukon is becoming the only game in town.

Dr Diff has his Hoosier brand. I recently put a set in and they are nice.