We picked up a spare IRS trans the other day. It is a AH code, the kind with two side covers. Looking up the spec's it shows to have a 4.12 ring and pinion as stock, similar to the 67 and later Swing axle trans.

I know that our current trans is an AT code with the correct 3.88 ring and pinion.

Question, Score speces call for the 3.88 ring and pinion. Does everyone change out and run the 3.88's in the swing axle trans and early IRS boxes? Does anyone care? Would you challenge us with the 4.12 in it?

It would seem that the 4.12 would be a real advantage, at least for us to get into third gear more often.

Hi Jeff
the 3.88 is a toller gear then both of them. you dont want a 3.88. you want to use a 4.12 it would be better if we could use a 4.37 becouse its a lower gear. and you would be able to use all the gears. you can use the IRS trans and put the SWING guts in it.

if you count the teeth they go like this.

35 devide by 8 = 4.37
33 devide by 8 = 4.12

hope this helps. Dennis

Is the 4.37 legal? I thought the highest legal ratio was 4.12???? I know you want to get the late model first/second since the teeth are sturdier right? and that changes the first gear ratio a tiny bit.

La Rana used to let you use the 4.37.

Hi Dennis, FYI, I have your shocks and they are in the best of care. I just tucked them in. We will see you guys in July. If you need them sooner, let me know and I can run them out to you no problem.

CEO of pump gas racing.
no problem on the shocks we will get them at the next race. we want to pit togather. talk soon Dennis

The SCORE rule book on page 117 reads ring and pinon must be 3.88 (actually a typo 8.33) So, is everyone OK with us have the spare trans with 4.12 ring and pinion?

The only RP you can use in class 11 is the 4/12 for all year cars. 4/37 is illegal to use in all class 11 cars, it is as simple as that. also the gears have got to go with the 4/12 RP It would be nice to run the 4/37 but we cannot and never have been except when the class was running everything stock to the year car then early swingaxel cars could run the 4/37 but that has not been since 1979 when 4/12 was mandated for all cars. Anybody tells you different they are WRONG!!! The 3.88 is just that, a 3.88 rp which is illegal for any class 11 also!!!!! 8.33 is 4/12 period. So i guess I would say YES, I dont mind if you use the 4/12 in your spare, any other I do

DaveCo11 wrote:


I am even more confused now...

8.33 is not a typo then?? 8.33 = 4.12

\"Type 1 bug 4 speed transaxle only. Heavy duty side plate and differential
allowed. 8.33 ring and pinion only stock gears only no close ratio gears allowed.\"

8.33 is the final drive with a 4/12 RP and drive gears just like out of a 69 bug from the factory. I hope this takes any confusion away. I have read on here that you take this and put that well, that is fine, untell they tear you down like they have me and read these things when they do. Dont be creative, it is what it is 4/12 only, no other ring and pinions allowed in class 11 ANYWERE. Class 9 allows both 4/12 and 4/37,but not class 11. Thats as clear as I can make it and no other way to interprit it!!! good luck