Need advice with rear suspension

[turdmagnet]

I am going to use my '74 K5 for some hauling. I figure about 1600 lbs. max. It won't be subject to this kind of load all the time, but I don't want to have to worry about collapsing the suspension when I want to haul a bunch of stuff. I already plan to replace the rear leaf springs with new leaf springs. I am debating what to do next: overload springs, coil springs, or air bags? What's your best advice for this? Also, do I need to worry about breaking the axles? These are the 6 bolt, 1/2 ton axles that the truck came with, how much weight can they bear up to before giving up the ghost?

 

[bigblazer87]

What size tires will you be running? If it's going to stay fairly stock, you should be able to haul that around fine on your 1/2 tons. Now, pretty much everyone else on here will tell you to swap in a 14BFF because it is all that is holy to Chevy truck enthusiasts, although it shouldn't be necessary, but this all depends on what size tire you're gonna be running. For the suspension, I'd throw in some helper bags, that way, when you're not hauling, the suspension isn't as harsh.

 

[turdmagnet]

BigBlazer: Thanks...just one other question though: I am concerned about the helper bags because I have heard that they have a tendency to develop leaks, usually at the worst possible time. If I don't mind a harsh ride, should I install the coil springs or overload springs? I plan on running the Maxxis Mudder M-754 in the 235/85R16/E. It's about 31.5" in total diameter. I think that the K5 came with 29" tires stock. Do you think there will be any problems with this tire size?

 

[bigblazer87]

Nope, you should be fine with that tire on your axles. My dad's F-350 has helper bags and it tows around anything from enclosed trailers to camper trailers and boats, and it's never developed a leak. Firestone makes some of the best air bags on the market, so look into them for reliability and quality. And remember, you won't always need 100% air in the bags; a lot of times 10-30% of pressure will get the job done with lighter loads.

 

[cbbr]

You guys might also consider how far you are hauling and what the conditions will be. I don't give a rats ass if you get a "holy" axle or not, if you are going to haul 1600lbs in the bed of a truck times to be concerned, and you are going to do it on public roads in Co, you might want to look into another truck.

 

[4X4HIGH]

Just as was said lots of people are going to say throw a 14ff under your rig. Here i will be the first person to say it and let you know why. With a semi float axle the axleshaft itself it supporting the weight of your rig and any payload you are carrying. Obviously the full float axle, the axle housing is supporting the weight of your rig and also any payload. It would be a bad thing to have an axle break because there was too much weight being exerted on it. With that being said go with a 14ff axle.

 

[ntsqd]

What is the rated rear axle capacity ?

How much weight is actually on the rear axle now?

If the difference is 1600 lbs or more then I wouldn't worry about it beyond the normal considerations.

Know that the closer you get to the axle's max weight rating the more that you're going to be working the wheel bearings. In the case of the 1/2t axles that likely means that the axle shafts themselves will also suffer since the bearing rollers ride directly on the axle shaft.

If you are at or over the max with that 1600lbs in the back then either a 14bff or a 3/4t truck are your best options.

 

[vortec]

i know i'll get flamed for this one.....i think all of the "big 3" underestimate their tow/haul ratings, for CYA purposes. 1600lbs should be no problem for a 1/2ton chevy, in good shape. about 6 years ago, i hauled about 3000lbs in the bed of my '94 c1500 for about 25 miles. no problem. i used to do 300 mile trips with 500-1500lbs in the bed of the '94 every few months. to this day, i have absolutely no rear-end or suspension problems, and it's been my dd since 1998. i think it's more about how you drive with the weight than how much weight there is. careful on the bumps and go easy on all the pedals.

i realize it's not the k5 i was dealing with, but they're both gm half-tons with 10 bolt rears. most i've done in my k5 is about 800lbs. felt fine, except for i really missed the separate bed of a pickup when i thought the load was shifting . i had it tied down pretty well, but i needed more anchor points.

 

[gmc4cw]

the cheapest advice I can give is if you are going to haul a lot of weight try to keep it as far froward in the bed as possible. that way both axles help carry the load. sometimes thats easy. if you are hauling a skid of bricks. other times its not. if you were hauling loose dirt.

what are you planning on hauling? how far? and what did you base your estimated weight on?

I had 1752 lbs of scrap steel in the bed of my 2000 a couple of weeks ago. The newer ones have a better curb weight to GVWR ratio. Mine is registered at 6400 lbs and weighs 4800 with me in it. I was overweight just slightly(so was the truck).

 

[cbbr]

My issue with the question is safety. Just because the axle does not break does not mean that the rest of the 25 year old truck (brakes, steering, etc.) are up to the task. You put a Dana 80 in the thing and you still have major concerns with the fact that it was never designed to safely haul loads in excess of 1/2 ton.

The fact is that people ask questions and sometimes forget that there may be concerns beyond their immediate concern.

 

[diesel4me]

Underated...

The older trucks can carry far in excess of their rated capacity--I dont condone it,just saying they can DO it!..I have hauled many loads in my 1/2 and 3/4 ton trucks that should have crushed them,yet they survived just fine..I'm talking 87 and older trucks,not the new IFS ones..

I had a diesel engine from an allis-chamler bull dozer that weighed over 2 tons in my 74 K20,I drove it only a few miles to the scrap place though..I was worried my 14 bolt SF axle would pop a wheel right off,but it did it without a problem!..truck weighed in at 10,560 lbs with the load,and empty it weighed a tad over 6,000 lbs..

The truck had a heavy flatbed made of 4" channel and a crane on it,and I abused the hell out of that thing hauling junk,firewood,and I plowed with it for 16 years..it's frame was so rusty I poked a screwdriver right through it,just before I junked it!..yet it still carried that weight with no sweat..

I would not have driven it much further than 10 miles with 2 tons on it though,or I'm sure it would have had a problem..stopping was the biggest one!..(my steering rag joint did fail on my way home from that scrap run,but that was due to rust , the weight I carried might have helped it rip apart though..truck was a real rotbox!)..

I had 1500lb. coil type overloads on top of the leaf springs in that K20,and all of my 1/2 tons and K5's..they stiffen the ride some,but add "bounce" too,they dont just make it feel like dead axles..I always had a lot of stuff in my trucks as far as tools, and I often carried riding mowers ,firewood,and ATV's in them..

While I'd be wary of hauling too much weight on a 10 bolt axle,it has been done many times without incident..Chevy Vans use the same 10 bolt axle only a bit wider,and I have seen them stuffed to the roof with motors and trannys at the junkyard ,when they were towed in behind a tow truck,with ALL the weight on the rear axle, to be scrapped--none of them ever broke an axle..not to say they never would,but I wouldn't be afraid of 1500-1600 lbs in a half ton truck,with beefy enough springs..

I often filled my 71 GMC 8' fleetside K10 bed right to the top of the bed rails with sand when I plowed,and I never hurt the axle..it had 10 leafs in each rear spring...I'd guess 3-4 tons is what you'd need to have an axle fail,especially if you hit a pothole with it..I beat mine pretty bad and never had a failure..but yes,a bigger truck IS a good idea if you plan on hauling that much quite often..a few times once in a while wont hurt it,IMO..

Air bags are nice,but I see many dry rot here in a few years time..coil springs rust fast around here too..Air shocks suck,don't put those on!..I'd say good leafs with some "jelly bags" would be a good option..we used them on my brothers E-350 cube van we made into a ramp truck--they look like air bags,but have a gel inside them,and only work when its loaded heavy enough for them to touch the frame brackets..work slick,and you retain a good ride when empty..

 

[chris walker]

12-bolt chevy rear is rated at 3500lbs gawr just get a 14-bolt SF the axle is 1.70" at the wheel bearings and that axle I believe is rated at 4800-5200lbs