Community Forums

evan0810 · 04-17-2008, 04:08 PM

Having recently traded a standard box, Duramax, 4x4 2500HD Chevy for a K3500, I noticed in the new brochure that the tow rating for the 2500HD is 1,100 lbs less than the '06. In an era where the manufacturers are in a tow rating contest for 1/2 ton trucks, I find this curious. Does anyone know why? I'm wondering if the '06s were overrated.

evan0810 · 04-17-2008, 04:08 PM

Having recently traded a standard box, Duramax, 4x4 2500HD Chevy for a K3500, I noticed in the new brochure that the tow rating for the 2500HD is 1,100 lbs less than the '06. In an era where the manufacturers are in a tow rating contest for 1/2 ton trucks, I find this curious. Does anyone know why? I'm wondering if the '06s were overrated.

John66 · 04-18-2008, 04:32 PM

Make sure you are comparing 4x4 to 4x4. This is a very heavy option which sucks several hundred pounds from your towing capacity.

Also make sure that the engines are the same, the gear ratios are the same, and the towing packages are the same.

evan0810 · 04-18-2008, 04:42 PM

I was comparing identical trucks. Duramax, Xtended Cab. 4x4, Standard (6 1/2') bed. My '06 was rated for 15,400 lbs and the '08 is rated for 14,300 lbs.

Ray,IN · 04-19-2008, 08:19 AM

Phone GM's 800 customer service number and inquire. Misprints seem to be common in owner's manuals, my old 96 Dodge BR 2500HD, CTD, was rated (in owner's manual) exactly the same as the 3500 dually in their charts?????? We all know that was not accurate.

Tugboat · 04-19-2008, 07:57 PM

The tow rating of the same truck will change if the gear ratio is different.

LindaH · 04-20-2008, 05:50 AM

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Tugboat:
The tow rating of the same truck will change if the gear ratio is different. </div></BLOCKQUOTE>
While I know that's true, can you explain WHY that's true? WHY can a 4.x gear ratio pull more than a 3.x gear ratio?

Stanbnv · 04-20-2008, 07:24 AM

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">While I know that's true, can you explain WHY that's true? WHY can a 4.x gear ratio pull more than a 3.x gear ratio? </div></BLOCKQUOTE>
While explaining that, Can you also explain why a manual transmission is rated LESS than an Automatic?

evan0810 · 04-20-2008, 12:10 PM

Dodge used to rate their trucks w/ manual transmission higher than trucks w/ auto.
Sometimes I wish GM would offer a 4.10 w/ the Duramax. The reason Fords have a higher rating is the fact that you can get up to a 4.30 in an F350. Higher ratings have something to do with lower gears transferring more torque to the rear wheels. But don't quote me on it.

LindaH · 04-20-2008, 04:03 PM

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by evan0810:
Higher ratings have something to do with lower gears transferring more torque to the rear wheels. </div></BLOCKQUOTE>

Sorry, I quoted you!

I understand the "more torque." And I can see where more torque would make it easier to get the load moving. What I don't understand is why it also translates into being able to pull a heavier load.

Ray,IN · 04-20-2008, 05:42 PM

LindaH, manufacturers set weight ratings to insure their product outlives the warranty. With time and history, they can establish that point more accurately. Higher gear ratios( more engine revolutions for the same distance traveled) place less stress on the engine and transmission. Keep in mind few of the manufacturer's weight rating have any basis in law.

Suburbbus · 04-21-2008, 11:04 AM

LindaH,
Let me see if I can answer your questions.
First off, I think that an auto can tow more due to the multiple clutches inside it verses the one disc on a manual.

Secondly, on the gear ratio. The higher the number, ie. 4.10 vs 3.42 for example, the driveshaft on the 4.10 will turn 4.10 times for each rotation of the rear wheels and your engine will rev slightly higher producing more power and torque than it would with the 3.42 gear which would turn 3.42 times for each rotation of the rear wheels and run slightly lower rpms.
You can have two identical vehicles with the same engines, but if one has the 4.10 and the other has the 3.42, the 4.10 will be rated higher. For example, my 01 suburban has a 3.73 rear gear and is rated at 10,900lbs. If I had the 4.10, it would be rated at 12000+.

Did not mean to ramble so long.

Hope this helps,

Rodney

RustyJC · 04-21-2008, 11:17 AM

Typically, the manufacturers who rated the manual transmissions lower than the automatics were worried about drivers abusing the clutch when starting off or spotting the rig with a manual transmission. The torque converter in the automatic made this easier, although it has heat problems of its own. Many truck configurations, however, are rated higher with the manual than the automatic.

Manufacturers increase ratings with lower (higher numerical) gear ratios on the premise that (1) the lower axle gearing reduces stress on driveline components upstream of the axle for a given axle load and (2) maximum wheel torque is higher since torque can be multiplied through gearing, even though horsepower can't.

Rusty

JIMNLIN · 04-25-2008, 06:10 PM

one point to keep in mind when the manufactor gives a lower power rating to their manual tranny is a big auto such as the Allison takes 45-50 hp to operate as compared to 15-20 hp for the manual tranny. Actual power the rear wheels are putting out is the bottom line. Looking at dyno numbers with a stock DMAX/A vs a DMAX/ZF6 shows the ZF6 puttting out more power on the dyno. Parasitic loss.

Jim