Ok, I’ll preface this by saying I may never do either unless an original to the vehicle (rear axle or engine) dies prematurely, but I think it’s a fun discussion.
I have an extended cab 4wd GMC Sierra. It has 3.42 gears and a 4.8 liter V8. I’m always interested in more power. A 6.0 V8 will swap in place of the 4.8 rather easily. Custom computer tuning would be required, but isn’t that expensive or hard to get. I have a mechanic acquaintance that has done a 6.0 swap in his own truck (an older truck factory equipped with a 350), and he would probably be the one to do the work if I proceeded. Or, I could install 4.10 gears in place of the factory 3.42’s and keep the 4.8. But I’m curious. Which would be more fun to drive? And which would be more fuel efficient (relatively)? The 4.8 with 4.10’s? Or the 6.0 with 3.42’s?
If you can get a proper 4.10 axle for cheap and get the ECM calibrated for it why not give it a try? And if you can find a C2500 rear axle with 4.10 gears you will have one heck of a 1/2 ton truck, gas mileage being ignored that is.
I’ll need two axles, since it’s 4wd. Otherwise, I believe I would try the lower gears first. The independent front axle would be a pain to swap.
My thoughts, the lower gear, smaller V8 equipped truck might be more responsive in normal driving. The taller gear, larger V8 equipped truck would tow better. I imagine fuel mileage would be a wash.
You’ll probably spend less on gas with the 4.8L. I looked up the EPA gas mileage for a 2006 Silverado with both engines the average mileage for the 4.8 is 15 mpg and the average for the 6L is 14 mpg. The big difference is the 6L uses premium fuel. They estimate the annual gas cost at $2850 for the smaller engine and $3700 for the larger one, given 15,000 miles per year. I’m guessing that they both use something like 3.42 gearing. If you use a ratio of the gearing and multiply by the annual fuel cost, the 4.8L with 4.10 gearing will cost around $3400 annually for gas. A rough guess for sure, if you drive more like 7500 miles each year, the annual gas cost is about the same. Hey, an extra $300 for the bigger engine is pretty much a push too. If you can use regular gas, the 6L will cost less.
If you have the slightest hankering for power it wont be sated with the 4.8 and a ratio swap. Your subconscious mind has already decided on the 6.0…and is waiting for you to catch up.
There were a couple of different variants of the 6.0. I’d most likely use an iron block 6.0 out of a 3/4 ton, which I think would negate needing the higher octane.
I think the 6.0 would probably be the best bet. It would be interesting driving the larger engine taller gear truck and the smaller engine shorter geared truck back to back for comparison.
I’d go w/4.10 gears and keep the 4.8 engine. My 4wd Ford truck is configured similar to that with 4.11 gears & 5.0 L engine. I’ve used it to pull full-grown juniper shrubs and small tree stumps out of the ground with ease in 4WD lo. If you go w/a bigger engine you risk having a problem with the tires not holding traction as well for a job like that. The downside to 4.11 vs 3.5ish gears is the engine tends to rev a little on the high-side on the freeway at 65-70 mph, but that’s a quibble rather than a complaint. I just go a little slower is all. I don’t worry much about MPG’s on a 47 year old truck, but when newer the truck got about 17 mpg on the highway. You probably have fuel injection and get better mpg anyway b/c of that.
I’ve never seen 17 mpg, to be honest. But the speed limit is 70 and I drive 75. If I were to drive 60 or so, I imagine the mileage would be much better. I’m impressed that your 47 year old Ford can hit 17 mpg, though. Must be a pretty good old truck!
Gotcha. More power or torque in a vehicle is more enjoyable or “fun” to me, regardless of the vehicle. Trust me, I have no intentions of driving an extended cab full size 4wd truck “sportingly” or doing any drag racing. If I were, I agree, most any vehicle would be better suited.
I’m not overly concerned with gas mileage either. Just curious if the small V8 with low gears would yield better or worse mileage than the larger V8 with higher gears in this scenario. Generally a smaller engine gives better mileage, but if it’s turning more rpm’s than the larger engine…maybe it’s a wash at some point. Pushing a 2 ton brick around at highway speeds isn’t going to result in great gas mileage either way, of course.
A friend has an old Chevy pickup with a 3-speed auto and tall gearing. First is essentially unusable unless you are pulling stumps; it’s really a two speed. We delivered mulch for a high school fund raiser, and the engine was maxed out around 50. That combination is not something I’d want in a truck.
As for gas mileage, the EPA numbers I showed above were gas cost, not MPG. Both engines in the 2006 configuration got about the same average mileage (14 vs 15). The big difference in cost was the octane change.
The 4.10 axle ratio would give you almost 20% more torque to the ground. The 6.0 is a 25% bigger engine an should give you about that large an increase in torque… Sooo that seems to be the answer, go bigger. @db4690’s point is well taken… the heavier transmission would be a great add and give you some durability in the long run. If you bought the engine (stick with the low compression LQ4) and trans as a package, often sold with the wiring harness and ecu.
With all that work and expense, though, now I am starting to lean towards the 4.10’s. My '04 4WD Avalanche has 4.10’s from the factory with a 5.3 V8. It is pretty peppy but doesn’t get more than 15 mpg highway.