Ring and Pinion

[Ron Earp]

The GCR states:

"a. Any final drive ratio is permitted provided it fits the stock differential/transaxle housing without modification to the housing."

Now, do we collectively take this to mean any ratio, meaning, any ring and pinion of any shape and size, as long as it fits in the factory housing? So one could use a ring and pinion out of unobtainium, a skeletonized ring and pinion, or one that wasn't based on the factory OEM gears at all but fit into the housing?

[Mseiler]

one would come to that conclusion...the rule, in this case, is clear.

That is to say, it's the size of your pumpkin, not what's in it

[Eagle7]

The 2nd gen RX-7 is a good example of this allowance. The 5.12 gear was never available for this car, and was never manufactured with an input shaft that works with the long housing in this car. To use it, you need to cut the long shaft off a donor gear and the short shaft off the 5.12 and weld the pieces together.

[seckerich]

Keep in mind Ron that it must fit with no changes to bearing race area, etc. No machining to add different bearings, or clearance for larger ring gear. Basically it can be made from scratch to fit the original working area. And yes, we do this for the second gen with 2 pinions cut and welded to make one and they slip into the original bearings with no mods.

Also note that differential is open so you are not limited to ID of ring gear or bolt circle.

[Mseiler]

If the ring and pinion fit, you must acquit :D

[Ron Earp]

Keep in mind Ron that it must fit with no changes to bearing race area, etc. No machining to add different bearings, or clearance for larger ring gear. Basically it can be made from scratch to fit the original working area. And yes, we do this for the second gen with 2 pinions cut and welded to make one and they slip into the original bearings with no mods.

Also note that differential is open so you are not limited to ID of ring gear or bolt circle.

Yep, no changes needed. My question is aimed and making the assembly lighter. The 7.5" axle is light duty in Ford speak, but compared to a ring and pinion out of say a R180 or R200, this thing is monsterous. Ring and pinion bare weighs 18 lbs, more than twice what the same parts weigh from a R180. So, one could do something like this:

http://static.speedwaymotors.com/RS/SR/Product/91600013_R.jpg

[Chip42]

legal. AND if you can find a way to pull out even more material, it's still legal. I'm wondering how far you can/will go with this. you always seem to take it to 11, and it's a lot of fun to watch.

[seckerich]

Yes they could. :rolleyes: Just make sure they know what they are doing and use the proper machines. Otherwise it will warp and the gear will not mesh properly. Ring gears are hardened to rc 58-60 or so I hear.

[JeffYoung]

I'm putting together a new rear end package for next year, and have the LS and the R&P on the way.

These guys backcut the ring gear and REM the R&P for $350:

http://www.innovatorswest.com/REM-gear-polishing.html

Moser and others will do it as well but I've seen mixed results reported on the web.

[Ron Earp]

legal. AND if you can find a way to pull out even more material, it's still legal. I'm wondering how far you can/will go with this. you always seem to take it to 11, and it's a lot of fun to watch.

Sort of like this?

http://www.gt40s.com/images/Mustang/2013/gear.JPG

There are some R&Ps that just don't have much material to remove. The Z R180s don't have a lot of meat. I assume Jeff's does, but I've not seen one. Stangs don't have that problem, the R&P is quite hefty.

[JeffYoung]

Yes, mine looks basically like that (before cutting).

[Ron Earp]

These are done via electrical discharge machine. I have talked to some shops that machine them, but as Steve says, the hardness of these things is pretty high and machining would take a lot of time. Looks like the standard fare is to EDM them for weight reduction, stress relieve them via heating or peening, then to polish them to remove any imperfections.

[seckerich]

Sort of like this?

http://www.gt40s.com/images/Mustang/2013/gear.JPG

There are some R&Ps that just don't have much material to remove. The Z R180s don't have a lot of meat. I assume Jeff's does, but I've not seen one. Stangs don't have that problem, the R&P is quite hefty.


Lightening like this picture is done for mostly drag racing. The webs that stick out will foam the diff oil and burn one down pretty quick in road race conditions.

[Ron Earp]

Lightening like this picture is done for mostly drag racing. The webs that stick out will foam the diff oil and burn one down pretty quick in road race conditions.

I was just talking about that yesterday at the office. I think if it is lightened it should be radially all around with no paddles since the flats won't be doing the oil any favors. On the other hand, the videos with the transparent rear differential cover show a pretty dire situation with oil flying around in the housing.

http://www.moserengineering.com/media/catalog/product/cache/1/image/5e06319eda06f020e43594a9c230972d/l/i/lightened.ring.gear.jpg

This one looks pretty good:

http://www.neilparks.com/chassis/RingGearLightening.jpg

And this one might be a bit extreme:
http://i102.photobucket.com/albums/m108/stage20/DSCN2283.jpg

I also saw some that were castellated around each bolt hole. The oil would run into the castellations and I figured it'd get frothed up quickly. Hmm, Google images is failing me on that one.

[Rabbit07]

I would be lying if I told you I had never done that to a ring and pinion..........:rolleyes:

Tex Racing will perform that service for you. Have them REM it when they are done also.

[Flyinglizard]

One of my old racer buds makes these,
http://www.ebay.com/itm/NASCAR-Gleason-Ford-9-inch-ring-and-pinion-set-4-63-ratio-/350764335397?pt=Race_Car_Parts&hash=item51ab2f0125&vxp=mtr