I'm looking for input here from people who have actually used these gears in their cars.

My next big project with the car will be to build up the 3.23 pegleg rearend thats in it right now.

I was wanting to do an Eaton LSD with moser forged axles and a TA support girdle, but need a bit of input. Since I am running a 700R4 (built) with the notoriously low 3.06 first gear, I would love to have the neck snapping tire scorching performance of a 4.10 rear, but afraid it might be a bit too much stress on a 7.5" 10 bolt when paired with the low first gear of a 700R4, even with forged axles and a support girdle. I am also concerned that a 4.10 rear will net ridiculous gas mileage and hinder my top speed a bit much. If it is just a marginal change, then that's fine. But if It's something to write home about, then it becomes a concern.

I don't want to go with a 4.10 ring and pinion and realize I drastically overkilled the whole idea, but don't want to go with a 3.73 and potentially be disappointed either. Also, what spline count would be a good choice for axles?

Thanks in advance.

 

With the 3.06 first gear in the 700R4 It's my opinion that a 4.10 would be over kill. The 3.73 shoudl be more than enough to impress you and still be all right on the highway. As for axle splines, 28 is as high as you can go in the 7.5 rear end. Don't forget to get a good installation kit when you get the other parts. Don't buy a cheap kit from Ratech, Summit or Jeg's. Get a good kit. It will make the gear set up a lot easier.

 

Right now I have a 4.10 rear and a 700r. Personally I 'hate' it. I am replacing it with a 3.42 as soon as possible. First gear is un-useable. It will light up the tires "at any rpm". I do most of my driving at 70 mph. I installed the 4.10 when I lived in the city and raced on an 1/8 mile drag strip (with a 305).
Now i live in the country and ALL of my driving is at 70 mph. That comes up to approx 2600 rpm with 25 inch tires. I really need another gear. With a tpi engine; I need to shift into overdrive to get through the quarter. NOT good.
The tpi wont make power over 4500 rpm or so and with 4.1 rear you will run outta rpm before the end of the quarter. First gear is horrendous with the torque of a tpi. ZERO traction. You 'will' have to short shift the trans to get into second,,,and the,,,it will still spin a good bit. First gear is 'useless'. Please take my advice and dont get a 4.1. I would really like to have a first gear again. In my opinion; after years of experience, you wont be happy at all.
I will be willing to bet that my car will go "faster" with a 3.42. I would love to have a first gear that can go over 15 mph or so. When i raced it with drag radials (and a 406 tpi) I still could not use first gear. When I raced it with a 305 and 4.10 I still had to short shift. Although not with drag radials.
See a trend here,,,
I'm not happy with the 4.10.
I hope that this will help you make your decision.
I have no experience with the 3.7 rear. Although; it would 'have' to be better than the 4.1,,,,but not by a bunch.