I got Hollis from HP engines building me a nice 400/470 that I'm pretty sure will put out some nice numbers. It has aluminum heads..solid cam..and rpm intake

Now I need help on which direction to go with my transmission and other parts of the drive line. Car is a 68 roadrunner with 23 spline 4 speed and 8 3/4 rear end. My transmission needs rebuilding..so do I stay with the 23 or go 18 spline? Do I need a Dana 60 or will my stock rear end be able to handle some decent power? I don't plan on racing.. Just cruising..and having a little fun every now and then

How deep are your pockets, and what do you really plan to do with the car?

The 23-spline and 8-3/4 will be fine for your intended use. Slicks at the track, and clutch dumps at high RPM - not so much.

Here we go again, another 8-3/4 vs. Dana thread

Which HP outfit are you referring to? The one in Maryville, Tn?

The 8-3/4" should be OK with street tires, sticky tires and hard launches will be hard on the diff. If you start upgrading the driveline, get the larger 1350 U-Joint yokes and driveshaft.
Passion can convert the stock 833 trans into a 4-speed overdrive if that is what you want. Not sure on rebuild costs?
I put a 5-speed OD trans in my car, but it was not a bolt-in, had to do some hacking of the torsen bar cross member.

No it's in North Carolina. He competed in the amsoil engine challenge few years ago. I don't plan on hitting the tracks.. Just want to make sure the rear end and trans will be ok with the amount of torque this engine might put out once it's done. I'm a newbie at this and just want to make sure I spend money where it counts the most since my pockets aren't that deep.

What Dr Charles said, you're fine as is

As was said on street tires the 8-3/4 and 23 spline will be fine. Basically if you launch it on street tires they will just spin and as long as you dont put drag radials or slicks on the car it will hold up on street tires because they wont hook they will just spin. If you ever decide to race it later then I would definetly go to a Dana or you will be breaking driveline parts all over the track. I bracket raced a 340 Dart years ago that ran low 12's and high 11's with a best of 11.94 @ 113 and that car broke alot of parts as I used an 8-3/4 with a stock 4-speed. I broke 2 driveshafts 3 transmissions and 3 rears including shearing all the teeth off the ring gear once. But I was young and had the money to keep upgrading as my 8-3/4 ended up having Strange Axles and a spool in it. And when I launched it the gas pedal went to the floor as the clutch came out. But really on street tires only you should get away with what you have. If you plan on any sticky tires then I would upgrade . You can always build it and drive it and upgrade the driveline later also. Good luck , Ron

You need to spend the money for a sintered iron clutch set up. You don't need the 18 spline box because it will break 3rd gear long before the input.


McLeod Sof-Lok
Advanced Clutches
Black Magic Clutches

You need to spend money now to save it later.