2002 1 ton van need more power

I have a 2002 Chevy Express 3500 van. I use it as a service truck but would also like to pull a travel trailer we are restoring. The trailer will weigh
around 5000 to 6000 pounds when loaded. The trailer is currently striped of all cabinets, paneling etc.. so it only weighs around 2500 pounds right now. I towed it to northern Arizona to have the exterior painted a few weeks ago and was only able to travel about 35 mph on some of the hills in 2nd gear. The van did not come with the towing package. Is there anything I can do to increase the power, like a larger exhaust, better air cleaner, tweaking the computer, change out the rear end or any combo of these items? You can see pictures of the van and trailer here: http://www.azcraig.us/Show_Low_Adventure.html
Thanks in advance for any and all advice,
Craig
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Does it have an engine and transmission, Craig?
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Yup-----350 v-8, 5.7 liter. I don't know what transmission. Sorry I'm a tad bit absentminded. I had more towing power with a 6 cylinder Isuzu Trooper!
Thanks,
Craig

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Your biggest issue here is the rear end gear ratio, should be at least a 3.73 or 4.10 for the best pulling power.

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Shep,
Do you know if I can just change out the "gear pod" or do I need to switch out the whole rear end. Also do you know what years/vehicles are interchangeable.
THX,
Craig

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I looked at the pumkin and it looks like I would need to buy the whole rear end. Which gives more power 3.73.or 4.10?
Thanks,
Craig

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Neither gives more power than the other, altho' the 4.10 gives more 'pulling power' than the 3.73 for the same reason that it's easier to pull off from a standstill in 1st (lower) gear than 4th (higher) gear. The flip side is that it makes your engine turn faster rpm's for a given mph. Chances are good that your truck has a 4L60E tranny, which has OVERDRIVE, and whose ratio on final drive is 70%. With a 4.10 rear end and this 70% overdrive, you have a final drive equivalent of 4.10 X 0.70 which equals 2.88. Using the 3.73 gives a final drive equivalent of 3.73 X.0.70 2.61. My gut feel is that the 4.10 would be more satisfactory, as it gives much "lower" gears starting off, and still a quite decent final equivalent of 2.88. Many of the 1965-1980 years used much higher gears for cars, like 3.70, 3.55, 3.36, etc. with NO overdrive to help reduce rpm's at highway speeds. (Poor gas mileage?!) The o'drive gives the best of both worlds, so why not use the 4.10 and still have a tall, 2.88, gear for hwy. speeds? (Other posters who are more currently up to date may even suggest using a 4.56, as practical usage has to be considered in addition to theory.) FYI, I had in 1964 a 1955 Chevy with an aftermarket 327 V8, ordinarily a 'gas-user' with customary 3.70 differentials--yielding ~15 mpg. But this one had come from factory with an overdrive, manual 3-speed trans. It also used a 70% reduction gear for overdrive, which along with the 4.10 differential made the final equivalent of 2.88; which, if it were a 2.88 differential would not pull off from a standstill w/out burning & slipping the clutch. But the 4.10 puilled off quick and easy, and by shifting into o'drive at about 40 mph, on hwy. trips the resulting 2.88 yielded ~21 mpg. It pulled off quick and would still cruise at low rpm at hwy. speeds and give unheard-of mpg. Hope all this helps. Actually, if any of it helps , you should become closer a believer in overdrives! Luck to you........s
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rear
The larger the number, the greater the effect. There is somewhat of a tradeoff between gas mileage and gearing.
On GM products, you change the ring gear and pinion to change the ratio. It is somewhat less convenient than the old third member approach.
I have sometimes seen that the effect of gearing on gas mileage is not as severe as one might imagine.
For example, I did a lot of work on my (New, in 1966) Mustang and one of the changes was removing the 2.73 gearing and replacing it with a 3.73 (I believe those numbers are close.) The mileage actually improved, maybe due to the valve work I did, the distributor recontouring, etc. The acceleration darn sure improved.
There are aftermarket two speed gear units that are installed between the tranny and the rear end that can theoretically give you a very versatile gearing system. They are not cheap, if they are still being made. Couple of grand, I believe. Maybe you could pick one up used, but I have no personal experience with them, and do not know how they hold up.
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