Even though I don't have an auto, I'll toss in my $. 02. My truck came with 3. 54's from the factory. I loved 'em. When the rear end blew apart, the only replacement axle I could find was in a drw truck with 4. 10's. (Me and a buddy bought the whole truck to part out, but thats a whole nother story. I just wanted the axle) I drove my truck with the new 4. 10 rear and hated it. 6 months later I called Randy's Ring and Pinion and ordered a new 3. 54 gear set and had it installed. I occasionaly tow up to and including 12k hauling scrap and pulling a race trailer in the summer. For as much as I tow, there is NO way I would ever go back to the 4. 10's. Let me put it to you tihs way: With the 4. 10's, I actually entertained selling the truck since I wasn't that happy with it ( I didn't exactly realize the gears as the problem though). Once I put the 3. 54's back in it, I realized how stupid of an idea that was. I have had no trouble pulling with the 3. 54's ever, and the 4. 10's sucked the fuel down alot quicker.
Don't give up your gears. Do some transmission work and a gov spring first and give that a shot.