spied 2010 GMc Sieera shows off new perforated grille

[C/K Man]

Originally Posted by chakis24

until its offered with an sfa, it wont be the top seller.

I don't think I agree with that statement. A well-designed IFS is better than a straight axle in every respect. The Ford and Dodge SFA's both seem to have a lot more wheel bearing and ball joint trouble than GM's IFS, and the GM suspension isn't plagued with the notorious 'death wobble'. It is true that a SFA is more popular with the modification crowd, because it is much easier and cheaper to lift a truck with a straight axle.

[Michael_S]

Originally Posted by C/K Man

I don't think I agree with that statement. A well-designed IFS is better than a straight axle in every respect. The Ford and Dodge SFA's both seem to have a lot more wheel bearing and ball joint trouble than GM's IFS, and the GM suspension isn't plagued with the notorious 'death wobble'. It is true that a SFA is more popular with the modification crowd, because it is much easier and cheaper to lift a truck with a straight axle.

Thanks. That's the first time I think I've seen anyone defend the GM IFS with a reasonable argument.

Originally Posted by Johnny P

Maybe so. I really haven't checked....

Either way, if you roll across the scales over 26k around here, you're gonna need a CDL.

Any of the current trucks can pull that kind of weight. Heck, my old 170hp '81 K20 has pulled 30k of grain a few times through the fields.

I wondered about that. If you read about the World War 2 Sherman Tanks, they were 30 tons and had 350 net horsepower gas engines. A HD truck pulling 10 tons has around twice the power-to-weight ratio of the Sherman, so presumably they can pull far more.

Still, pulling 30 tons with 170 horsepower seems crazy. Doesn't that stress the motor and transmission? Were you in first / low gear the whole time?

[Montana Mike]

C/K Man you got it Mike

[Johnny P]

Originally Posted by Michael_S

I wondered about that. If you read about the World War 2 Sherman Tanks, they were 30 tons and had 350 net horsepower gas engines. A HD truck pulling 10 tons has around twice the power-to-weight ratio of the Sherman, so presumably they can pull far more.

Still, pulling 30 tons with 170 horsepower seems crazy. Doesn't that stress the motor and transmission? Were you in first / low gear the whole time?

The answer to both paragraphs is torque multiplication through gear reduction. Those Shermans had a top speed of maybe 15mph?

My truck has a 6.72 low gear with a 2.72 gear through the transfer case.

30,000lbs, not 30tons.

[ollie7777]

Pulling the weight is not the problem with these trucks it is stopping the weight and the load handling. I tow 23,000 pounds all the time with my 2003 duramax 3/4 ton GMC CC and it does fine. I keep my distance at all times to eliminate panic stopping. I do however wish GM would build a truck that would legally tow 24000 pounds. Time to make a HD truck that is worthy of the HD title.

[nailhead425]

Originally Posted by C/K Man

I don't think I agree with that statement. A well-designed IFS is better than a straight axle in every respect. The Ford and Dodge SFA's both seem to have a lot more wheel bearing and ball joint trouble than GM's IFS, and the GM suspension isn't plagued with the notorious 'death wobble'. It is true that a SFA is more popular with the modification crowd, because it is much easier and cheaper to lift a truck with a straight axle.

That is a pretty broad statement to say that a well designed IFS is better in every respect.

Let's consider the linear spring rate of the torsion bar IFS. Not only is the capacity less than the competition, the suspension travel is limited and a fraction of the SFA crowd. By limiting the suspension travel the Engineers were able to minimize fatigue in the torsion bars, at the sacrifice of load capacity. Because the spring rate is not progressive, the compression travel is virtually zero and most GM torsion bar IFS trucks sit on (or very near) the bump stops. The deflection of the bump stop is the additional spring rate before bottoming out. I have 5" of compression travel on my coil-spring SFA truck.

Let's consider ball joints, wheel bearings, and half-shafts. IFS runs best a neutral CV joint angle. With about a 23* max operating angle, the combined max angle would be about 46*. While on paper that is outstanding, the amount of expansion in the joint limits the strength and durability of the joint and shaft assembly. So as the total amount of suspension travel increases, the life of the joints and shafts decreases. Also, in order to compensate for the increased moments about the joints, the corresponding increase in mass of the components to provide additional durability further reduces the effective operating range. Another concept that is often discounted is the tendency for a half-shaft to deflect under torque. The moment about the shaft, especially given a heavy static load at the drive wheel, results in deflection of the shaft. The greater the torque input, combined with a greater static load, the greater the amount of deflection. This is the Achilles’ heel of half-shafts. Ball joints have been and will continue to be a supplier issue, not a flaw in the design concept. While Ford uses a different supplier, GM and Dodge HD trucks use the same supplier for the front-suspension drive system. The comparisons should be done Dodge to GM, SFA to IFS. Unitized wheel bearings will always be an issue, but anecdotal evidence has yet to become scientific fact that one supplier is better than the other.

Let's talk about component strength: GM, 22 years after the debut of their full-size IFS, still hasn't sorted out the component strength issue. Tires larger than 285/75-16 or 285/70-17 aren't supported. Where the competition is using larger, heavier tires on their SFA and IFS rigs, why not GM? Let us investigate the H2 tie rod issues with the stock 315/70-17s to gain a greater understanding.

Let's talk about the "death wobble". GM IFS trucks with wider than stock wheels, especially those with a large amount of offset, generate a substantial amount of wobble. In fact, the independent nature of the GM IFS generates an increasing level of bump-steer, especially as the operating angle of the suspension increases. Larger than stock tires exaggerate this condition, beyond deflection of the stock components. While not to minimize the wobble in SFA trucks, it isn't a SFA only condition. But bumper steer is more pronounced with IFS.

Let's talk about "thermal creep". The GM IFS diff housing is made from aluminum, where the Dodge is cast iron with steel tubes pressed into the center section. Both are made by AAM, both have the same torque rating. Aluminum, under repeated thermal loads, exhibits a condition called thermal creep. With cast iron the tolerances vary much less. It should be noted that due to this condition the H3 Alpha was fitted with a cast iron center section for the IFS. Certainly there are many exotic materials that don't exhibit creep to the same degree as aluminum, but they are cost prohibitive. There is a trade-off with each material. Strength or weight. Take your pick.

I'm not saying that every IFS is evil, there is plenty of room to improve. However, it goes without saying that the GM HD system is long overdue for an update.

[05ChevySilveradoSS]

Originally Posted by C/K Man

I don't think I agree with that statement. A well-designed IFS is better than a straight axle in every respect. The Ford and Dodge SFA's both seem to have a lot more wheel bearing and ball joint trouble than GM's IFS, and the GM suspension isn't plagued with the notorious 'death wobble'. It is true that a SFA is more popular with the modification crowd, because it is much easier and cheaper to lift a truck with a straight axle.

LOL! Let the comments begain. . .

This is a way of getting alot of GM HD guys fired up! LOL

And as someone else has said in a earlyer post, GM NEEDS to get these HD trucks in the same leauge as the Super Duty (as far as looks are concerned), and i can comfortably say this bc i sell these things and im kindve dissappointed on the effort GM puts into the looks of these trucks compared to the Superduty

[Michael_S]

Originally Posted by nailhead425

That is a pretty broad statement to say that a well designed IFS is better in every respect.

Let's consider the linear spring rate of the torsion bar IFS. Not only is the capacity less than the competition, the suspension travel is limited and a fraction of the SFA crowd. By limiting the suspension travel the Engineers were able to minimize fatigue in the torsion bars, at the sacrifice of load capacity. Because the spring rate is not progressive, the compression travel is virtually zero and most GM torsion bar IFS trucks sit on (or very near) the bump stops. The deflection of the bump stop is the additional spring rate before bottoming out. I have 5" of compression travel on my coil-spring SFA truck.

Let's consider ball joints, wheel bearings, and half-shafts. IFS runs best a neutral CV joint angle. With about a 23* max operating angle, the combined max angle would be about 46*. While on paper that is outstanding, the amount of expansion in the joint limits the strength and durability of the joint and shaft assembly. So as the total amount of suspension travel increases, the life of the joints and shafts decreases. Also, in order to compensate for the increased moments about the joints, the corresponding increase in mass of the components to provide additional durability further reduces the effective operating range. Another concept that is often discounted is the tendency for a half-shaft to deflect under torque. The moment about the shaft, especially given a heavy static load at the drive wheel, results in deflection of the shaft. The greater the torque input, combined with a greater static load, the greater the amount of deflection. This is the Achilles’ heel of half-shafts. Ball joints have been and will continue to be a supplier issue, not a flaw in the design concept. While Ford uses a different supplier, GM and Dodge HD trucks use the same supplier for the front-suspension drive system. The comparisons should be done Dodge to GM, SFA to IFS. Unitized wheel bearings will always be an issue, but anecdotal evidence has yet to become scientific fact that one supplier is better than the other.

Let's talk about component strength: GM, 22 years after the debut of their full-size IFS, still hasn't sorted out the component strength issue. Tires larger than 285/75-16 or 285/70-17 aren't supported. Where the competition is using larger, heavier tires on their SFA and IFS rigs, why not GM? Let us investigate the H2 tie rod issues with the stock 315/70-17s to gain a greater understanding.

Let's talk about the "death wobble". GM IFS trucks with wider than stock wheels, especially those with a large amount of offset, generate a substantial amount of wobble. In fact, the independent nature of the GM IFS generates an increasing level of bump-steer, especially as the operating angle of the suspension increases. Larger than stock tires exaggerate this condition, beyond deflection of the stock components. While not to minimize the wobble in SFA trucks, it isn't a SFA only condition. But bumper steer is more pronounced with IFS.

Let's talk about "thermal creep". The GM IFS diff housing is made from aluminum, where the Dodge is cast iron with steel tubes pressed into the center section. Both are made by AAM, both have the same torque rating. Aluminum, under repeated thermal loads, exhibits a condition called thermal creep. With cast iron the tolerances vary much less. It should be noted that due to this condition the H3 Alpha was fitted with a cast iron center section for the IFS. Certainly there are many exotic materials that don't exhibit creep to the same degree as aluminum, but they are cost prohibitive. There is a trade-off with each material. Strength or weight. Take your pick.

I'm not saying that every IFS is evil, there is plenty of room to improve. However, it goes without saying that the GM HD system is long overdue for an update.

If I understand you correctly, a reliable IFS that supports as much weight as the Ford and Dodge HDs is possible, it just isn't what GM sells today. Is that right?

[FanOfDurant]

GM has forgotten perception is a Huge part of sales. They abandoned their truck customers and their rich truck history. Heavy Duty guys want Heavy Duty trucks period. The IFS 'HD' trucks GM has running around on their little baby tires is almost embarrassing...

Even IF (and that's a big if), GM beefed up their IFS to match the durability of a SFA, it will never be PERCEIVED as 'strong' by guys in the market for a heavy duty truck. The contractors and construction guys out there want what they view as the 'real deal'. Solid Front Axles and beefier tires. You know?? Heavy Duty. A truck that Looks the part and Acts the part. You would think somewhere along the line the GM engineers, marketing dept and bean counters alike would have gathered around a Super Duty Ford and took notes on how to build a real HD truck.

[SDRacing]

Originally Posted by FanOfDurant

GM has forgotten perception is a Huge part of sales. They abandoned their truck customers and their rich truck history. Heavy Duty guys want Heavy Duty trucks period. The IFS 'HD' trucks GM has running around on their little baby tires is almost embarrassing...

Even IF (and that's a big if), GM beefed up their IFS to match the durability of a SFA, it will never be PERCEIVED as 'strong' by guys in the market for a heavy duty truck. The contractors and construction guys out there want what they view as the 'real deal'. Solid Front Axles and beefier tires. You know?? Heavy Duty. A truck that Looks the part and Acts the part. You would think somewhere along the line the GM engineers, marketing dept and bean counters alike would have gathered around a Super Duty Ford and took notes on how to build a real HD truck.

Good one. Somebody on here once stated that ford "is making their trucks look like tonka trucks and who wants that". LOL. Who didnt want a tonka truck growing up?!?!? Im just saying, they look like good work trucks to begin with.

[SDRacing]

Originally Posted by nailhead425

That is a pretty broad statement to say that a well designed IFS is better in every respect.

Let's consider the linear spring rate of the torsion bar IFS. Not only is the capacity less than the competition, the suspension travel is limited and a fraction of the SFA crowd. By limiting the suspension travel the Engineers were able to minimize fatigue in the torsion bars, at the sacrifice of load capacity. Because the spring rate is not progressive, the compression travel is virtually zero and most GM torsion bar IFS trucks sit on (or very near) the bump stops. The deflection of the bump stop is the additional spring rate before bottoming out. I have 5" of compression travel on my coil-spring SFA truck.

Let's consider ball joints, wheel bearings, and half-shafts. IFS runs best a neutral CV joint angle. With about a 23* max operating angle, the combined max angle would be about 46*. While on paper that is outstanding, the amount of expansion in the joint limits the strength and durability of the joint and shaft assembly. So as the total amount of suspension travel increases, the life of the joints and shafts decreases. Also, in order to compensate for the increased moments about the joints, the corresponding increase in mass of the components to provide additional durability further reduces the effective operating range. Another concept that is often discounted is the tendency for a half-shaft to deflect under torque. The moment about the shaft, especially given a heavy static load at the drive wheel, results in deflection of the shaft. The greater the torque input, combined with a greater static load, the greater the amount of deflection. This is the Achilles’ heel of half-shafts. Ball joints have been and will continue to be a supplier issue, not a flaw in the design concept. While Ford uses a different supplier, GM and Dodge HD trucks use the same supplier for the front-suspension drive system. The comparisons should be done Dodge to GM, SFA to IFS. Unitized wheel bearings will always be an issue, but anecdotal evidence has yet to become scientific fact that one supplier is better than the other.

Let's talk about component strength: GM, 22 years after the debut of their full-size IFS, still hasn't sorted out the component strength issue. Tires larger than 285/75-16 or 285/70-17 aren't supported. Where the competition is using larger, heavier tires on their SFA and IFS rigs, why not GM? Let us investigate the H2 tie rod issues with the stock 315/70-17s to gain a greater understanding.

Let's talk about the "death wobble". GM IFS trucks with wider than stock wheels, especially those with a large amount of offset, generate a substantial amount of wobble. In fact, the independent nature of the GM IFS generates an increasing level of bump-steer, especially as the operating angle of the suspension increases. Larger than stock tires exaggerate this condition, beyond deflection of the stock components. While not to minimize the wobble in SFA trucks, it isn't a SFA only condition. But bumper steer is more pronounced with IFS.

Let's talk about "thermal creep". The GM IFS diff housing is made from aluminum, where the Dodge is cast iron with steel tubes pressed into the center section. Both are made by AAM, both have the same torque rating. Aluminum, under repeated thermal loads, exhibits a condition called thermal creep. With cast iron the tolerances vary much less. It should be noted that due to this condition the H3 Alpha was fitted with a cast iron center section for the IFS. Certainly there are many exotic materials that don't exhibit creep to the same degree as aluminum, but they are cost prohibitive. There is a trade-off with each material. Strength or weight. Take your pick.

I'm not saying that every IFS is evil, there is plenty of room to improve. However, it goes without saying that the GM HD system is long overdue for an update.

I agree with you. I am shocked though that AAM and fords supplier haven't remedied the ball joint issues.

[Michael_S]

Originally Posted by Johnny P

The answer to both paragraphs is torque multiplication through gear reduction. Those Shermans had a top speed of maybe 15mph?

My truck has a 6.72 low gear with a 2.72 gear through the transfer case.

30,000lbs, not 30tons.

Whoops! I don't know how I read 30,000 pounds as 30 tons. Still, that's incredibly impressive.

[member12]

Originally Posted by ChevyHDGert

I hope that lowest plastic air valance can come off.

All of which will turn white after exactly 10 months.

I won't buy another car or truck with that much black plastic anymore....ever. It looks like crap, and no amount of dressing or polishing will make it look right again.

Is there any chance that it's there to hide a SFA? Not that it matters, I'm not one of those guys that thinks that the GM HDs much have a SFA....the IFS, based on what I've seen and driven, is very impressive. With better wheels and tires, the whole package will look much nicer- hopefully the new suspension can support it. If not, then they just wasted their money.

Those look like 18" wheels at best, with road tires....then again, its' hard to judge. The truck is flipping huge.

When it comes to HD trucks, I'd go in the Ford camp- even though I think GM has the best power train and handling. Hopefully this will one up the new Super Duper "tiny ***** edition" Duty.

[member12]

I'm glad they are keeping this truck updated...but why does it sit so high off the frame?

At least the wheels and tires aren't so small anymore. Hopefully, they've solved the stupid government diesel mandates and figured out how to get better mileage out of it.

[nailhead425]

Originally Posted by Michael_S

If I understand you correctly, a reliable IFS that supports as much weight as the Ford and Dodge HDs is possible, it just isn't what GM sells today. Is that right?

Yes. While it is more difficult, it isn't impossible to build a reliable, robust HD front axle assembly that uses IFS components instead of a SFA.

And that is my point all along. Right now the competitor's SFA is much better than GMs IFS for true HD use. Since GM has long stated that there will be no return of the SFA they certainly have a much greater engineering challenge to improve the IFS to a competitive position.

A couple of key design changes would do wonders.
Torsion bars, Aluminum center section, and half-shafts.

Switching to a coil-over system with a taller spindle will help reduce the camber change through the suspension cycle. Coil overs will facilitate more travel and a progressive rate. The progressive rate will give the car-like ride that many "claim" the IFS posseses and yet allow for an added total capacity. The taller spindle and reduced camber change with the given increased suspension travel will allow the steering components to be moved higher in the chassis without an increase in bump-steer.
Switching to a 3-stage halfshaft with a splined center section to facilitate dive combined with inner and outter tripod joints will help increase the longevity and strength of the IFS components.
Using a Cast Iron diff section will reduce the instances of case cracking and eliminate thermal creep.

However, if the new Scorpion diesel is a hit (and reliable) there may be a much larger impact to GM HD sales.