Stock C3500 Rear Leafs on a C2500

[Westieterrier]

Hi Forum Members, my first post here about tow hitches resulted in a PRECISE answer along with MANY helpful comments. This site is really awesome! My 1999 C2500 Long Bed 2wd Classic with 10.5 corporate 14-bolt rear and 8 lug wheels is new to me (bought from the widow of the original owner). I will be carrying a heavy Lance Camper of 3500 lbs and want to swap my 5/1 springs for C3500 6/1 or 7/1 springs, preferably new ones. Is this a simple bolt-on job? Any drilling or welding required? Does anyone have a suggestion for USA-made springs?

Also, second question, I have the angled front frame, along with an RPO Code of C6P. Do I have an HD model? I can't tell after quite a bit of research (getting contradictory information). I have the full 7 pages of all my RPO Codes printed out by a super-nice parts guy at the local dealership (love Oregon!), but can't decipher them. Pics below. Any help on all this would be GREATLY appreciated. P

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[PlayingWithTBI]

FWIU 8 lug is HD and 6 lug is LD, as mentioned in your other thread. Also, 4+1 leafs are LD and 5+1 is HD. Here's a link to some springs, you'll need new U-Bolts and I suggest you get shackle bolts too.

www.sdtrucksprings.com/index.php?main_page=advanced_search_result&inc_subcat=1&categories_id=1&year_select=1999&make_select=616&model_select=8919&x=104&y=18

 

[tpass]

Yes I would say new u-bolts as well due to thicker spring and inspect the bottom u-bolt plates for rust as they hold water like a dish.

You may have some troubles getting the spring eye bolts out, they tend to seize into the bushings. I had to burn the rubber out of mine then cut the shell to get the bushing out of the spring. Bear in mind I am in the rust belt, so you may not have that issue, you have a very clean looking truck.

You could also go the airbag route, SD truck springs link has those as well.

 

[GMCTruck]

Beautiful truck. Those stock springs look to be in good shape. You could consider adding a leaf or two to the existing spring pack. I had a spring shop add 3 leafs to my K1500 when I used to carry a camper. Rides like a wagon now. ha ha.
3500 lbs is a lot of weight. Take it easy.

 

[Supercharged111]

6/1 and 7/1 was not factory. 5/1 and 5/1 plus upper overload was factory. The latter would handily deal with a 3500# camper.

 

[stutaeng]

What is your GVWR on the door sticker?

I "think" the 2500 with the RPO code CP6 was in fact sort of like 2500HD model, as it was the same as the 3500 SRW of 9200 lbs. The 2500 was 8600 lbs. This is before GM started using the "HD" in the 2500 series truck, of course.

If what I said is true, I think your leafs are the same as a C/K 3500 single rear wheel.

I'd say get the 6 leaf pack with overload, which came on the duallies. It's a direct swap. I think you are still within your GVWR. Double check...

 

[Westieterrier]

6/1 and 7/1 was not factory. 5/1 and 5/1 plus upper overload was factory. The latter would handily deal with a 3500# camper.

A continuing thank you Supercharged! I'm gonna owe you a few Oregon IPAs after all this. I'm not sure what "plus upper overload" is and I'm not getting any results from my Google search. What is an upper overload? This may be the way I go. Thanks. P

 

[Westieterrier]

What is your GVWR on the door sticker?

I "think" the 2500 with the RPO code CP6 was in fact sort of like 2500HD model, as it was the same as the 3500 SRW of 9200 lbs. The 2500 was 8600 lbs. This is before GM started using the "HD" in the 2500 series truck, of course.

If what I said is true, I think your leafs are the same as a C/K 3500 single rear wheel.

I'd say get the 6 leaf pack with overload, which came on the duallies. It's a direct swap. I think you are still within your GVWR. Double check...

Hi Stutaeng, thanks so much for the helpful reply! The sticker and title both say 8,600 lbs, so the good news is I have an "HD-esque" model. When did Chevy start using that actual designation, with the Silverado name in 1999 or later? Adding a leaf sounds like the way to go, or perhaps a 6/1 pack, but what is this "upper overload" term you guys are using? I'm not finding anything on it. I really appreciate your insights. P

 

[stutaeng]

Hi Stutaeng, thanks so much for the helpful reply! The sticker and title both say 8,600 lbs, so the good news is I have an "HD-esque" model. When did Chevy start using that actual designation, with the Silverado name in 1999 or later? Adding a leaf sounds like the way to go, or perhaps a 6/1 pack, but what is this "upper overload" term you guys are using? I'm not finding anything on it. I really appreciate your insights. P

Um, I was hoping your model would be 9200 lbs. I wonder how much your truck weighs empty?

The GVWR minus the "curb weight" is your payload. I'm not sure how they figure out that yellow sticker that was weights listed on some trucks?

The HD models came out in 2001. For a while they made 2500HD and 2500 models. The 2500HD had larger frames and front torsion bar suspension (even on 2wd models.) The GVWR were higher than on the GMT 400 production.

 

[GMCTruck]

Which brake RPO code do you have? JB7 or JB8 (if vacuum boost) or JD7 or JD8 (if hydroboost)
JB7/JD7 = 8400 lbs
JB8/JD8 = 10,000 lbs

I imagine, since you have the 10.5 full float rear axle, it is JB8 or JD8. That would be good.

"overload" springs, which are also referred to as "auxiliary" springs sit on top of the regular spring pack. They are more curved. There are brackets bolted to the frame (2 on each side). as weight in the back of the truck increases, the truck will sag and the overload springs come into contact with the brackets on the frame which then adds the weight carrying ability of the overload springs to the regular spring pack.
Your frame will already have the holes drilled for the brackets.
I will try to find a picture as it is much easier to understand by simply seeing it.
Generally, only the dual wheel trucks have them although some SRW 3500 trucks did.