3rd member chunk ??? ?

[Gary_gtx67]

Ok I have a ? Will the 741 casting hold up to a 430 to 456 gear? Or do I really need the 489 casting??

 

[daredevil]

it aint the gear its the horsepower and initial shock and tire type. 450 or under and an auto no slicks i wouldnt worry. by initial shock i mean the hit like a trans brake and slicks are a big shock on a rear.

 

[69HEMICORONETR/TCONV]

it aint the gear its the horsepower and initial shock and tire type. 450 or under and an auto no slicks i wouldnt worry. by initial shock i mean the hit like a trans brake and slicks are a big shock on a rear.

:yes:

 

[Gary_gtx67]

I do not plan on running a trans brake but i will be putting in a line lock and i will be running slicks. My car has a 383 pushing 475 to the flywheel. What do yall think about that type of setup?

 

[Meep-Meep]

My buddy back in the 80's had a 67 383 Formula S Barracuda (full body) and he used to run an auto with a 3.91 741 case on N2O. The first pass he made at Fremont was an 11.84 @ 120 MPH - on 14 x 6 street tires!! His sequence of events with 8" slicks were foot to the floor and immediately followed with the button (100 HP kit). At Sears Point the car slowed down (usually the case) but it was still a regular low 12 sec car with slicks. Not even the trans was rebuilt. It was the original unit with God knows how many miles and a B&M manual pack and a 318 converter. Nothing ever broke.

It's the torque input that will damage things. Since the pinion is stepped there needs to be a nice smooth radius at the step or it will become a stress riser and break at that point. My thought is the tapered pinion makes it easier to put in a good radius at that transition, so it's effectively stronger. The spline size (coarse or fine) are about the same diameter I'm pretty sure and that's the smallest diameter of the pinion. I don't think anyone has ever twisted a pinion shaft. I've seen broken teeth and pinions broke in half at the step, but never a twist. If it did twist it was probably a material selection issue or heat treating problem - cheap Chinese gears perhaps?

I got a set of gears a long time ago from Summit for a 9" Ford and the first thing I looked at was the radius at the step. it was very rough and inconsistent compared to the factory set. Those went back immediately! I have no idea who made them but they weren't going in my car!!

 

[Gary_gtx67]

What is the biggiest gear I can go up to with a 742 casing?

 

[daredevil]

5.13 ,more than ya need. is this a drag car?

 

[daredevil]

i,ve got a 4.88 and a 4.57 i,d trade for a good 4.10

 

[Gary_gtx67]

I want a good 1/8 mile gear for when I do go to the track and I want another set for the street so I was looking for a 4.88 gear with a spool. Then use a 323 limited slip for the street.