On my truck I want break neck acceleration so what ring and pinion gear do I need.

 

The one that's hooked up to the driveshaft from a 460.

Seriously, if you want to build a super quick truck, you're probably working with the wrong engine. The 300 is a workhorse, not a quarterhorse. It can be improved upon, but the same amount of money sunk into a 302 or 351 will take you a lot further.

A ring and pinion swap may not help much. I swapped the 3.08s in my 96 4.9 for a set of 3.73s. It tows better now, hunts for gears a lot less and uses more fuel at highway speeds, less around town. The difference in performance was ZERO. ETs at 60, 330, 660, 1000 and 1320 were all the same within 0.1 or less. Trap speeds in both the 1/8 and the 1/4 were the same within 1 MPH. I cannot explain it, but I've got the timeslips to prove it. Would a 4.10 or 4.33 have made a huge difference? Maybe, but I doubt it.

 

Opps I meant the differential gears

 

The ring and pinion ARE the "differential gears" unless you mean the spiders which have a 1:1 ratio and zero effect on acceleration.

What exactly are you trying to do?

 

I'm no expert, but I suspect the reason why a gear swap didn't help your performance times any is because most of the power in the 300 is low end. All a gear swap will do is increase your rev's at a given speed, which might take you right out of your power band just a tad sooner. The 300 is kind of like a mini diesel in my book. You don't often see people doing gear swaps in Powerstrokes because peak torque comes at 1600 rpm (peak torque occurs at 2000 rpm in the 4.9) so there's really no reason to do a gear swap, since there's no reason to rev so high. That's my take on it, any ways.

So I agree, if you're looking for breakneck acceleration in a Ford pickup, my suggestion is to purchase a lightning, or take a pickup of the V8 variety and go wild with some heads and a blower-- then do your gear swap.

 

That would make sense except that the original 3.08 gears were so high the poor thing was always struggling to even get into it's power band, with the 3.73s it's working a lot more freely -- just no results. The gears made a huge difference in towing capability and I'd do the swap again in a heartbeat, I'm just perplexed as to why there's no acceleration benefit. I was honestly expecting about 0.2. I'm amassing parts and ideas for some engine mods. I have a friend whose Dakota runs 17.4s, I think I can get my stone to outrun his stone

 

StrangeRanger I was running mid 17's in the 1/4 with my 96 4.9L with only a FIPK as a performance mod pulling my 31' tires....but that's with clogged cat's and a weak fuel pump LOL, new fuel pump will be in this weekend and I'll have new cat's as soon as I can get ahold of a descent credit card to max out since I have to have the dealer replace them.

Can't wait to run it again as soon as everything is fixed.

 

Manual tranny 300s are quite a bit quicker that E4OD versions. The automatic doesn't use up a lot of HP, but the 300 hasn't many to spare.

 

I think my clogged cat's actualy worked to my advantage in the 1/4 also...cuz my off the line response and acceleration have greatly increased I guess from the back pressure but my high end is suffering, I feel the difference every day on the freeway.

 

Back pressure NEVER increases performance, not anywhere in the RPM range. Small diameter pipes keep exhaust gas velocities high at lower RPMs and produce better performance there; that has mistakenly been interpeted as "back pressure helps low RPM performance." It doesn't. Back pressure is the inevitable - and undesired - consequence of the smaller pipes required for high velocities. As RPMs climb pressure goes up to the point where it kills the velocity and larger pipes are required, again to maintain correct velocities. The ideal exhaust system would have a variable diameter which increased as a function of RPM (possible but messy and unreliable) and produces no backpressure (a physical impossibility)

FWIW velocity through a pipe is a function of it's area, i.e. diameter^2 but pressure drop is a function of diameter^4 so small changes in pipe diameter have large effects on exhaust velocity and huge effects on pressure drop.