2500hd Transfer Case Vs. 1500

Ridgerunner30 · August 22, 2010

Do any of you know why the 2500HD trucks do not have the automatic 4X4 function as the 1500's do. The auto function is handy. There must be some logical reason why the 2500's do not have this function.

[email protected] · August 22, 2010

Yeah, it's simple the 2500s don't have the auto-trac transfer case. The 2500s have a much more stout transfer case, which doesn't have the auto feature. Like I have the NP1, which is much stronger than a auto-trac NP8 active transfer case that most 1/2 tons have.

Ridgerunner30 · August 22, 2010

Yeah, it's simple the 2500s don't have the auto-trac transfer case. The 2500s have a much more stout transfer case, which doesn't have the auto feature.

I understand. I guess my question is why don't the transfer cases (the stout models) used in the 2500's have the same funcationality of the light duty transfer cases of the 1500's.

This may be a question of holding down cost. The auto function in a stout case may be too expensive. I don't believe any of the big three offer the automatic function in their HD transfer cases.

[email protected] · August 22, 2010

Well the auto-tracs have clutches in them, like a transmission. I guess they don't want to take the chance of using them in a 3/4 ton because they might not can stand the torque of a diesel without slipping.

markw8 · August 22, 2010

My 2000, 2500 6.0 had the autotrac case.

Mark

[email protected] · August 22, 2010

My 2000, 2500 6.0 had the autotrac case.

Mark

Really, and the auto button would actually light up. Maybe it was cause that wasn't an hd.

Bluedog · August 22, 2010

My 2000, 2500 6.0 had the autotrac case.

In 2000 there were no HD 2500's. That year 2500's were 1500's with an extra spring pack to raise the GWR (a little).

sonjaab · August 22, 2010

2001 to 2004 gmt-800 2500 LDs had the Auto-trac option.

Bluedog · August 22, 2010

2001 to 2004 gmt-800 2500 LDs had the Auto-trac option.

Correct. In 2000 there was only one choice for a 2500. In 2001-2004, GM offered an "HD" model with a significantly higher GVW and IIRC the engine was either a 7.4 gas or the 6.6 Duramax. Both engines had quite a bit more HP and torque, and the NP8 could not keep up.

So the regular 6.0 2500's got the NP8 autorac and the HD's got the NP1's.

HTH

alaska511 · August 22, 2010

2001 to 2004 gmt-800 2500 LDs had the Auto-trac option.

Correct. In 2000 there was only one choice for a 2500. In 2001-2004, GM offered an "HD" model with a significantly higher GVW and IIRC the engine was either a 7.4 gas or the 6.6 Duramax. Both engines had quite a bit more HP and torque, and the NP8 could not keep up.

So the regular 6.0 2500's got the NP8 autorac and the HD's got the NP1's.

HTH

8.1

not 7.4

Bluedog · August 23, 2010

8.1
not 7.4

Doh! you are correct...

markw8 · August 23, 2010

My 2000, 2500 6.0 had the autotrac case.

In 2000 there were no HD 2500's. That year 2500's were 1500's with an extra spring pack to raise the GWR (a little).

It didn't say HD on the fender, but it sure wasn't a 1500 with a bigger spring pack. There were only 2 main differences with the 01 HD's. Bigger frame and full floater axle. Even the brakes are the same.

Mark

Bluedog · August 23, 2010

The 2500 HD's shared some of the other components with those of the "regular" 2500. However the limiting factor was the use of the shared 1500 frame. With a larger spring pack than that of the 1500, the GVW for the "regular" 2500 was 7,200 lbs; only 1,000 lbs more that the 1500. The larger components (axle and brakes - on the Z-71 equipped trucks) did little to raise the GVW to that number, although certainly they helped some.

The payload rating between the 1500 and the 2500 was about 750 lbs.

In comparison, the 2500 HD's used a frame that was shared with the 3500 series trucks, and that, plus the larger rear axle (11.5 vs. 9.5), larger torsion bars and shocks, bigger disc brakes and wider springs raised the GVW to 9,200lbs, and hence the payload rating between the 1500 and the 2500 HD was 1,920 lbs.

There is an extensive discussion about the differences here: Light Duty 2500

So - to the original OP - the autotrac transfer case can't withstand the stress of the higher GVW (and power and torque of the larger engines) of the 2500 HD trucks, and hence why these trucks came with the NP-1.

Hope this clears it up...

[email protected] · August 23, 2010

My 2000, 2500 6.0 had the autotrac case.

In 2000 there were no HD 2500's. That year 2500's were 1500's with an extra spring pack to raise the GWR (a little).

It didn't say HD on the fender, but it sure wasn't a 1500 with a bigger spring pack. There were only 2 main differences with the 01 HD's. Bigger frame and full floater axle. Even the brakes are the same.

Mark

There's a huge difference between a 2000 2500 and an 01' 2500hd, including brakes, exhaust, frame, axles, transfer case, front grille, and hitch.

markw8 · August 23, 2010

My 2000, 2500 6.0 had the autotrac case.

In 2000 there were no HD 2500's. That year 2500's were 1500's with an extra spring pack to raise the GWR (a little).

My trucks gvwr was 8600#.

It didn't say HD on the fender, but it sure wasn't a 1500 with a bigger spring pack. There were only 2 main differences with the 01 HD's. Bigger frame and full floater axle. Even the brakes are the same.

Mark

There's a huge difference between a 2000 2500 and an 01' 2500hd, including brakes, exhaust, frame, axles, transfer case, front grille, and hitch.

The two trucks have the same part#s for frt break rotars, which means they are the same. I know the frame and rear axle changed. Don't know about the hitch, and the grill means nothing to the truck working.

My 2000 was an HD on the window sticker, but not badged. It shared the body but not the frame with the 1500s. It had torsion bars, 1500s had coils. It had the 4/80 the 1500s 4/60 trans.

Even the early 2500LDs with 6 lug wheels, to my knowledge didn't share the frame with 1500s.

Regardless of what you Hd owners think of them my 2000 did a fine job carrying my 3500# truck camper for nine years and 82,000 miles. The truck loaded weighed 9800#s. The only thing I added was airbags and better shocks.

Now that I have a 3500 dually D/A I'll try not to look down on you guys with 2500 6.0s.

Mark.

Just because it doesn't say HD dosen't make it a bad truck.