What gears for pulling
 

I have a 70 GMC swb 4x4 4 sp trans and I beleive it to have 273 gears. What gears to Pull a camper, I have a 19 ft Travel trailer about 4000 pounds or so. I have pulled it twice and can only seem to go about 60 mph at about 2300 rpm in 4th gear. I currently am running 31's but plan to go to 33 in tires.
What gear ratio would work best 410's or even 373"s?
Would 73-87 axles bolt right in?
Thanks for any help.
Ron

Re: What gears for pulling
 

2300 at 60 mph with 31" tires would be about 3.54 gears. If you go to 33" tires, 3.73 would only keep you about even with where you are now. If you aren't satisfied with the present performance, you would probably want at least a 4.10 rear.

Ray

Re: What gears for pulling
 

3.54 to 3.73 isn't worth the change. I'd go 4.10 or 4.56. 4.56 would have it winding out at interstate speeds, but you'd never be short of power.

Its always good to slow down when towing anyways.

4,000lbs isn't much at all for an old truck, but I'm sure that camper has quite a bit of drag.

Re: What gears for pulling
 

I found a cool site that calculates tire sizes and gear ratios and some other things thought I would share it http://www.4lo.com/calc/geartire.htm

Re: What gears for pulling
 

It has 308 gears now I stated the 2300 rpm it is more like 2000 which would put it closer to 3.08 gears. I was thinking about 4.10's. The truck has plenty of power and it handles the trailer fine except when about 2000 rpm or around 60 it is sluggish.
I was hoping to swap entire axles out to save a little money.
Would newer Chevy/GMC truck axles bolt in without major modifications?
Thanks for the help.
Ron

Re: What gears for pulling
 

I would go to 4:10 gear

Re: What gears for pulling
 

4:10's will kill any mileage you might think of getting with 31's so make sure you do get those 33's.

Re: What gears for pulling
 

Would later model axles be a direct bolt in?
Thanks for the input
Ron

Re: What gears for pulling
 

Almost. The rear perches and shock mounts will need moved, but it's going to be tough to find 1/2 ton axles with 4.10 gearing.

Re: What gears for pulling
 

4.10 was an option but not many people ordered it. You can get aftermarket gears, of course, but that's gonna co$t.

Ray

Re: What gears for pulling
 

My 68 K20 burb with an SM465 trans with axles set up with 4.57's, pulled a 25' trailer along with a truck load of people and stuff for many years with ease.

Right now, I am running it with 33" tall tires and it cruises at 70 mph on the hwy nice. Gas mileage? fuhgetabout it. But then I don't commute with my burb, so I don't care.