So I'm starting to regret the 3.90 rear

[kmccabe56]

Swapped out the stock 2.76 open 741 case for a 489 Posi with richmond 3.90 gears.
Ita actually fun as hell but not really being able to get on and cruise on the highway is become a pain in the ***. I should have tracked down a 3.23 Center section.
Anyway I wanna swap out the gears to 3.23.
How difficult is this and should I just take it to a shop to be done correctly.

If you want your cake and be able to eat it too, do what Kip did, and put a gear vendors overdrive unit on the back of the 727. Point 7 (0.7) overdrive will allow even those 3.90s to be palatable on the freeways.

 

[Snotty]

If you want your cake and be able to eat it too, do what Kip did, and put a gear vendors overdrive unit on the back of the 727. Point 7 (0.7) overdrive will allow even those 3.90s to be palatable on the freeways.

That's true, but is it worth the cost? Last time I looked such a unit was over $2500. That's a lot of cash for a little gas mileage.

 

[Andysfury]

Just get taller rear tires. Like a 255/70-15. Near 29" it'll get ya closer to where you wanna be faster than a gear swap. Those tires with a 3.91 rear will get you an effective gear ratio of 3.39. Still be fun, but be able to cruise with a slightly raised rpm.

I'm running that tire with 3.23's and my effective ratio is 2.81. I'm on the hunt for 3.73's to get me where I want to be.

 

[Andysfury]

This is exactly what I did with my '66 Fury. Stuffed in 3.73 ring and pinion and went to a 275/60/15 tire. Great kick in the pants with a warmed over 440 and not terrible rpm at 75 mph. I think it's around 2800 going 75