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Axle ratings...

SlimJim Z71

PlowSite.com Addict
Location
Cary, IL
Okay... on GM pickups with IFS, how exactly is the axle weight rating calculated? The actual weight is not really on the axle, more so on the torsion bars and control arms. How do they get their figures? I know that brakes, springs (torsion bars), axle, and control arms are all part of the final figure. Theoretically, if you upgrade to 3/4-ton torsion bars on a 1/2-ton, you'd probably be better off. I've heard of guys doing this, but I was wondering exactly how much the truck would benefit from that.

-Tim
 

DaveO

PlowSite.com Veteran
Location
Ma.
FAWR

Tim,

I believe the weight rating is determined by several factors. Thses would include bearing capacity, brakes, spring, and tire/rim capacity. Whichever is the weakest would determine the rating.

Dave
 
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SlimJim Z71

SlimJim Z71

PlowSite.com Addict
Location
Cary, IL
Weakest part huh...

I believe that would be the torsion bars. I like the way my truck rides, but it does get a little sloppy with the plow on there. MAN AM I PICKY!!!

-Tim
 

Chuck Smith

2000 Club Member
Location
NJ
Dave is correct. There is also the gears in the differential to consider. If the resistance at the wheels is too much, the pinion gear will knock teeth off the ring gear. Once a tooth gets knocked off, many more will follow!!

This is evident to me, by a friend who overloaded his 1/2 ton Silverado all the time. He went through 3 GM 10 bolt rear axles in 100,000 miles. He constantly carried a 3000#+ "cube" of bricks, or concrete blocks.

Another time, he had me put a new hitch on his truck so he could tow a bobcat on a trailer with a pintle hook. Talk about scarry! He left the rental yard, got about a mile up the road, and there was a long steep hill. About 1/2 way up the hill, his clutch started slipping until he started going back down the hill, while in 2nd gear!

He had to call the rental yard to come get their machine and deliver it to the job site for him.

Ironically, he had better luck with the front end. He ran a Western 7.5' Pro Plow on the truck for 2 seasons. The suspension was bottomed out 90% of the time, but the front end held up ok.

He finally wised up and bought a truck that suits his needs better. A 1999 F-350 Superduty PSD. That truck has handled all he could dish out with ease.

I think the term GAWR is a little out dated, as far as IFS trucks go. Yes there is still an axle in the front, but it handles weight differently than a straight axle.

Straight axles are sometimes "trussed" to help them handle added stress. This is to help prevent the axle tubes from getting tweaked or cracking.

For instance, my 77 Chevy K/20 has a GAWR for the rear, of 5,500# respectively. I know for a fact, that the axle itself is rated to carry 7,000# max.

The same axle is in my 80 GMC K/25, and it's GAWR for the rear is 3,980#. The difference? Brake drums and shoes, and the number of leaves in the springs. Also the tire sizes.

Typically, on a front IFS system, the weakest parts are the drag link, center link, pitman arm, and idler arms. They will wear out first along with bushings.

When I put 35" tires on my 77 Chevy, the first thing I noticed is the drag link began to wear out fast. Then again, no faster than my 80 GMC during a winter with a lot of plowing events.

~Chuck
 

DaveO

PlowSite.com Veteran
Location
Ma.
Chuck,

I know of 3 guys who blew their 10 bolts last year. All were around 1990's, two blazers, one pickup. None of them worked their trucks. But all had oversize tires on them.

I actually saw one of the Blazers blow his. Had 33's on it. He pulled out into traffic, got on it. The rear tires chirped...then BANG, clunk, clunk, clunk. Took out the ring/pinion gear, like you said. Has a heavier setup in it now. I didn't realize they were THAT weak.

Dave
 

TLS

PlowSite.com Addict
Slim Jim,

The 1/2 ton and 3/4 & 1 tons had different front Ring gears(pumpkin cases too) 8 1/4" and 9 1/4" They also have larger brakes and bearings. The frame is beefier and yes the torsion bars are different. They used a lot of different rate and indexed bars depending on what was ordered (1/2, 3/4, 1T , extended cab, crew cab, reg cab, short and long beds, Z71, towing package, snow plow prep, etc.) I think that you may be on the right track with replacing your torsion bars. If I can remember correctly, the Z71's used a spongier, softer bar, that was more forgiving for off roading. Order a pair from a 3/4 T with a HD front end.
 

Chuck Smith

2000 Club Member
Location
NJ
Dave,

The 10 bolt has been weak from day one. I have no idea why GM started using the 10 bolt in place of the 12 bolt older models had. I had 2 friends also, who blew 10 bolts, and both had stock tires on the trucks with less than 10,000 miles on the odometers. One was an 85 K/5 Blazer, the other was an 86 K/10 pick up. Interestingly, a third friend bought a new 87 K/20, and blew the 14 bolt rear in less than 5,000 miles. All three of these guys had stock tires, and babied their trucks since they were still new.

Now, just try and find a 12 bolt rear axle for one of these trucks, talk about hard to get! We called all around here after my friend blew his second rear in that 93 Silverado. None to be found. I tried to talk him into a 14 bolt, but he didn't want different size tires and rims on the rear.


~Chuck
 

DaveO

PlowSite.com Veteran
Location
Ma.
Chuck,

Your right. We looked for a 12 bolt to replace the 10. Forget it. Even a good used 10 bolt was hard to find, and expensive too. Like $900... We ended up replacing it with a setup made by Richmond Gear if I remember right. A limited slip unit.

Dave
 

cowboy

Member
Well I won't say GM 10 Bolts are the beefiest axle, but I will say my 81 C10 has 331,000 and has been used for towing, tree business, etc, and has never been touched

but I have friends with Dana 60's that blew just over 100,000 mi.

of course my truck has a 250 I6 but it is a good motor,

anyone ever seen a late 70's Chevy or GMC with the 292 I6? I have been looking for one for a while and haven't been able to find one, this is what I would like for plowing, if not a 250 I6 but they are hard to find in 4x4's.

anyway, my two cents :)

Adam
 

diggerman

Senior Member
Location
Ames
Whoa there Cowboy,talk like that is treason around here.Your likely to be banned,if you don't know the truck you are talking about could never plow snow.There just is'nt enough horse power and it's far to old.So please try not to bring it up again you are really disturbing the 400hp new 1 ton truck gods.
 

cowboy

Member
lol hehe was waiting to be ousted from the industry <G>

hey it could do it, I think people forget what people used in the 50's, they had way less horespower and they were used to tow things we have today. I'm shure a I6 could do it.

not too old, more reliable than these new things with 20 computers that quit because their cold, think of it this way, what can break on older trucks?

And I will let you know my 250 I-6 has almost the torque of a 318 in my old 74 Dodge 3/4 ton, not too mention the reliability of a inline 6. Plus your drivetrain will last longer as well

Ford 300 six, has same torque as 302. wouldn't mind one of those either.

and as far as new truck, 30,000$+ what happened to trucks supposed to be for work, cheap and durable? older trucks are the only way to go!
:)

*boy this should be a good war starter*

Adam
 

Lazer

Senior Member
Cowboy, you're right on.

I've got almost $100,000 into these 2 new Fords. But I'll tell you this: I'm taking care of the old Dodges. (Even got me a 1978 Chevy this week)
 

GeoffD

PlowSite.com Veteran
It comes down to two things reliablity and looks.

I work in the utility construction biz. I my service area is just about the whole state of Maine, and have been to NH before for jobs.

I send guys to jobs 2,3 even 4 hours away. They don't want a beater truck, and I don't blame them. We have contract jobs with major utilities, and do jobs for other private contractors. When a gas maine breaks at 3 am in the morning, guess what my guys have to get up and fix it. I don't need to hear at 3 am that a truck won't start and they can't get to the job or something like that. My trucks need to run every day, they need to leave the shop every day, and ya know what if they don't i have lost big time money. If they have to call someone else, if they can find someone else, because we can't get there. We have to pay for the other company to do the job, as well as a "fine" to the company. If we are doing a contract job, and we have 15 days to do the job, and we take 17 days we, could be paying the a fine for as much as 5K a day. If it takes 2 days longer, because we have a truck in the shop for 2 days, where does that leave us?

It sometimes sounds like I have trucks just sitting around, but when the ground isn't frozen, and there isn't any snow. We are working very hard, when we are done with installs and under ground work, we change modes. We park the backhoes, and exevators, the loaders go to do snow, and the tri axels may sit around. However the pick ups and 1-tons and even the F 650s are out doing service up-grades, where exevation isn't required.

If I had a service radius of 20 miles, you bet I would run trucks longer. I look at it this way, bigger service area, more money, at the same time more expenses, trucks need to be replaced more often.

Could you tell your employees get in that 1985 F 250 with 400,000 miles on it, and drive to Fort Kent, almost to Canada, about a 4 hour ride from my shope, where you can drive 50 miles and not pass a car, or a town?


Granted I keep a truck till it has 150K on it at least. Then it is either replaced, or kept in a more local service area.

I am just tired of being "picked on" for having to use new truck, to keep the biz on track.

I will tell you, that if all I did was plow snow, I would be running older trucks, and keeping new ones much longer. I have nothing against useing older trucks, their is nothing wrong with it, when you have a small service area.

However for me Time is money, I can't afford to have a truck in the shop for days on end waiting for parts. I don't have time or enough to keep fixing trucks all the time, my Mechanic is busy enough as it is. It's plain and simple an old truck will spend more time in the shop, and thats fine for most work.

Geoff

[Edited by GeoffDiamond on 11-29-2000 at 12:28 AM]
 

cowboy

Member
I can understand that, I'm just saying because it is old and has a lot of miles doesn't mean it is a beater, my truck still looks great, has a new floor-matt and the seat has been overhauled, the interior looks like it is new. No dents, bed still in good condition, warms up like a new truck. Old trucks can be just as nice and sometimes nicer than a new truck, and the usually look better style wise too.

LMC truck has every single trim piece for a 73-87 Chevy truck, you paint it good all dents/rust fixed and refurbish it and for around 5,000 you could probably take a pretty beat up truck and give it life for another 150,000.

better stop my self before I get to wrapped up about it :)

Adam
 
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SlimJim Z71

SlimJim Z71

PlowSite.com Addict
Location
Cary, IL
Okay... here's my thought's on my "Pretty Boy Truck." I'm thinking if I upgrade to 3/4-ton torsion bars, and put an axle truss on the back axle, I should be a LOT better off. Like I said, I've got the air bags on the back end, and I don't haul more than 400-lbs. of salt around at a time. Think this would work out okay? I've invested a lot of money and time into this truck (even though I know a 3/4 or 1-ton would be better) and I want to keep it for a long time. By the way... where can I find a truss for the rear axle? Thanks guys!

-Tim
 

GeoffD

PlowSite.com Veteran
Adam, it's nothing against you. Older trucks work fine, for lots of companies. You have to trust me on this one, I have run the numbers and the cost is about the same either way, if not a little less the way I do things now.

If I ran older trucks, they would need more upkeep, which would equal back up trucks, and a second if not third mechanic.

If I had a 20 mile service radius I would run older trucks. However in maine it's not had to drive 50 miles, and not pass a sole. If I ran older trucks had and had one break down, I would have to find a truck to go help them, if it wasn't a simple fix. So now I am behind on two jobs, not just one because a truck broke down. I don't expect my guys to play Mechanic, they have enough utility stuff to learn, before they have time to be a mechanic.

I am just tired of being know as the 400 HP 1 ton new truck god. I have good business reasons, for useing the trucks I do, that is the only point I am trying to make.

Geoff
 

Alan

PlowSite.com Addict
Geoff wrote::, I can't afford to have a truck in the shop for days on end waiting for parts. I don't have time or enough to keep fixing trucks all the time, my Mechanic is busy enough as it is.::

Sounds like a Ford man for sure! :)
 

GeoffD

PlowSite.com Veteran
Alan, it's not the Fords that break down.

My Mechanic has a lot of stuff to maintain.

He has to maintain/fix, exevators, loaders, backhoes, tractors, snowblowers, tri -axel dumps, tandem axel dumps, compactors, generators, trailers, pick-ups, 1-tons, and just about every other thing you can think of with a motor on it.

I am very lucky I have found someone that can fix all that stuff. I don't want to add to his load, by constantly maintaining an older truck.

Geoff
 
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