MTFCA Forum

Has anyone had experience with running 12 tooth pinon with 40 tooth ring ?
Langs website says NOT FOR USE WITH 40 tooth ring gear.
Thanks in advance.

Yes. I am sure they are saying a 40 T from a 11:40 set. That's correct. 12T gear is large diameter & has to be used with an offset hi speed gear. 39 or 40T rux gear. This does require a tall shim to raise the ring gear, about 1/8" Now you risk shearing gear bolts. Running this now. time will tell.
The best answer has to be some creative shifting of the carrier(non rux) A stock 40 T gear is certainly possible with machining the bell(rux), but not simple.

Can I run a 12 tooth pinion with a 39 tooth ring gear in a Ruckstell axle. I have run the ring gear with a 13 tooth pinion but it is too highly geared and I want to bring the ration close to 3.25:1.
Thanks in advance.
Nigel Hugo.

nigel_hugo wrote: ↑

Wed Nov 03, 2021 3:43 pm

Can I run a 12 tooth pinion with a 39 tooth ring gear in a Ruckstell axle. I have run the ring gear with a 13 tooth pinion but it is too highly geared and I want to bring the ration close to 3.25:1.
Thanks in advance.
Nigel Hugo.

YES.
This my set up (Above post) Did require me to make a special thick spacer for proper gear mesh.

Nigel, I have just that setup in my 25 roadster, with no extra spacers or shims. I set all my rear ends up making adjustments to gear mesh by varying the thickness of the standard Ford thrust plates and the bronze thrust washers supplied by the vendors.

Hope this helps.
Allan from down under.

Are all 39 tooth ring gears offset?
Thanks for the replays .

I used a a 39 tooth ring gear with 12 tooth pinion, no special spacers. Ring gear came from one of the vendors. I have a Jumbo Planator under drive in front of it, works great.

RichJ wrote: ↑

Thu Nov 04, 2021 8:05 am

Are all 39 tooth ring gears offset?
Thanks for the replays .

The hi speed 13:39 gear sets have material removed under the ring gear to allow for the larger diameter pinion gear.

Jsteele wrote: ↑

Thu Nov 04, 2021 8:43 am

I used a a 39 tooth ring gear with 12 tooth pinion, no special spacers. Ring gear came from one of the vendors. I have a Jumbo Planator under drive in front of it, works great.

I found the need for a spacer to raise this gear in a RUX. Other wise the mesh was to loose. Moving the carrier would take serious, unnecessary, re-engineering.
If I do another rux with a 12t gear, I will likely try to use a standard 40t ring & trim the carrier bell considering:
1) Will it mesh well? 2) Can I successfully shorten the correct ring gear bolts.(enough extra thread length.)

Just a note, ring and pinion sets should have one odd number. If there is two even numbers then there is a regular repition in the teeth contact and can cause undesirable wear patterns over time.
Craig.

Allan wrote: ↑

Wed Nov 03, 2021 11:43 pm

Nigel, I have just that setup in my 25 roadster, with no extra spacers or shims. I set all my rear ends up making adjustments to gear mesh by varying the thickness of the standard Ford thrust plates and the bronze thrust washers supplied by the vendors.

Hope this helps.
Allan from down under.

Allan is spot on for both the 39 and Ruckstell 40.

"Are all 39 tooth ring gears offset?"

Yes they are.

40 Tooth Ruckstell ring gears are also offset.

40 Tooth Ford Ring gears are NOT offset.

THANKS to all for there information.!!!
Is there a remote possibility any one would have a 39 tooth they would part with ?