I'm interested in purchasing a 5th wheel, but it will put me 500 to 1000 lbs over the GVWR (9200) of my 2500HD CC SB D/A. The GVWR always seems to be the week link-- I'm within axle ratings, and easily with GCWR (22000). I would have bought a 3500HD to start with, but wanted a short bed, which is not (or was not) available with 3500HD (SB barely fits in the garage as it is).

My ASSUMPTION is that converting a 2500HD to a 3500HD (effectually) can be done by simply upgrading the rear axle, and adding some leaf springs. IF correct, this would *seem* more cost effective than having to replace the entire vehicle.

My QUESTION is... What would this cost in parts and labor? If there is anything else involved (other differences between 2500HD and 3500HD), I'd like to know....

Thanks,
Paul.

Here is what I'm dealing with (weighed with wife/I, and 65 gallons of fuel):

GCWR:22000
GCW: 7560
GCW Left: 14440

GVWR: 9200
GVW: 7560
GVW Left: 1640

RAWR: 6080
RAW: 3220
RAW Left: 2860

FAWR: 4670
FAW: 4340
FAW Left: 330

I'm pretty sure the only difference are the leaf springs... I think the 3500 has one or two more heavy duty helper springs.

Dan

The 3500 also has Steel wheels and 265's if I am not mistaking.

The GMC brochures says that the 2500HD has "two-stage multileaf springs" whereas the 3500HD has "three-stage multileaf springs". And yes, I believe the tires are also rated higher, marginally.

What about the rear axle, which is rated MUCH higher in the 3500HD??? Is the 3500HD rear axle ACTUALLY DIFFERENT than the 2500HD rear axle, or is the RAWR higher because of the heavier leaf springs? Or... is the 2500HD rear axle IDENTICAL to the 3500HD rear axle, and GMC just rated it lower to harmonize with some state's laws, when in actuality it's the SAME as the 3500HD (someone mentioned this somewhere)...?

There are also overload springs, which on a short bed would be hard to put the brackets in I think, because of the bed mount welded to the frame in the area the bracket normally would be on the long bed. I did put a set of the 3500 rear springs on my truck and removed the overload spring from the pack.

If you are talking the SRW3500 I believe it is only rated at about 300 more lbs of carrying capacity or so (lawyer rating only). Correct me if I'm wrong. Can't quite remember. You can add air bags to help and some higher ply tires for safty, other wise I think your getting into a can of worms with the conversion. Add some Rancho 9000 adjustable shocks and your ready to go.

-Alcoa 16" by 7" Classic Rims with a load rating of 3750 LBS - < $700 including shipping.
-Michelin 265/75/16E tires rated for 3415 lbs, (instead of 245/75/16 at 3042 lbs), $750
Air Lift Super Duty Bags $250

The factory rubber limits the rear axle to 6082 lbs. The 265's with a higher weight rating and Alcoa Classics will increase rear axle capacity to 6830 lbs.

-Alcoa 16" by 7" Classic Rims with a load rating of 3750 LBS - < $700 including shipping.
-Michelin 265/75/16E tires rated for 3415 lbs, (instead of 245/75/16 at 3042 lbs), $750
Air Lift Super Duty Bags $250

The factory rubber limits the rear axle to 6082 lbs. The 265's with a higher weight rating and Alcoa Classics will increase rear axle capacity to 6830 lbs.

I like the idea of the 265's (later), will be ordering the airlift bags shortly, and have already ordered Bilstiens.

QUESTION: What is the load rating of the OEM Rims (i.e. do I NEED bigger rims)?

QUESTION: Does the statement about rubber/rim limitation imply that the 2500HD rear axle is IDENTICAL to the 3500HD rear axle, and that it is merely the rim and rubber that increase the RAWR???

Answers are greatly appreciated!!!
Thanks,

Paul.

QUESTION: What is the load rating of the OEM Rims (i.e. do I NEED bigger rims)?

This question has been asked many times, and I don’t recall anyone with a positive answer. The far majority of one piece forged aluminum rims are rated for 3200 lbs or less. The new 3500 SRW trucks only come with steel rims and 265 tires, which tells me their PYO’s are not rated for the 10K GVW.
All tire manufactures recommend mounting the 265/75/16 tire on a 7-8 inch wide rim. The stock aluminum PYO’s are 6.5 inch wide.


QUESTION: Does the statement about rubber/rim limitation imply that the 2500HD rear axle is IDENTICAL to the 3500HD rear axle, and that it is merely the rim and rubber that increase the RAWR???

The AAM 11.5 Inch rear axle is rated at 4950 kg, (10,915 lbs). Not sure how this applies to the 2500HD, the 3500 SRW, and the 3500 DRW. A friend was told by a Dealer that the 3500 DRW bearings were bigger than the 2500HD’s, (different part number).
http://www.aam.com/technology/tech_prod_dl_rearaxle.html

As stated in last post, I don’t think the 6084 lbs RAWR and two 245/75/16 wheels rated at 3042 lbs each is a coincidence.

I belive the 3500 rear axle is an 11.5" ring gear as opposed to our 2500's 10.5" the studs are longer to account for the two wheels stacked, both trucks come with load range E tires. 2500 has 245/75/16 while the 3500 has 215/85/16's