8 lug conversion on 88 1500?

[SalahHH83]

So I have researched this as much as possible but need some advice.

I have an 88 C1500 with a 3.08 10 bolt rear (positraction is the only plus it has). I want to swap to a 14 bolt rear and have found some FF 14 bolts out of late 90s 2500s for good prices locally. One has 4.10s and one has 3.73s. I think i'd prob go with the 3.73 one as I have a 5 speed and am using the truck for towing. 4.10 seems a little too low for stock height tires.

The FF 14s are 8 lug. I don't mine switching to 8 lug, but if I do so, I'd want the front to match. My question is a 2500 brake upgrade for the front. Can I swap over 3/4 ton spindles and brakes or will these not bolt up?

BTW, I have the 5 lug bolt pattern, so finding a 6 bolt SF 14 bolt wouldn't help me much either.

Just looking at what my options are. Any advice would be much appreciated!

 

[someotherguy]

Any particular reason you want a FF in there? Lots of better gearset 10 bolts out there, typical is 3.42, there are even a few 3.73's. Not sure how the 14 bolt SF doesn't help you, it's very easy to change the front to 6 lug as well, just need rotors from the same C2500LD the 14 bolt SF came from - though if your 88 is a regular cab you'll need to change spindles too, to accommodate the thicker rotor.

Anyway if you still want to go FF then you can install the 8 lug rotors & calipers up front IF you change the spindles, which will also require you change the upper control arms as the ball joint is different. 2WD 3/4 & 1 ton forged uppers will bolt right into your frame. You'll want the master cylinder and brake combination valve from the donor truck too.

Richard

 

[SalahHH83]

Thanks for the reply, Richard! A SF would be fine and I wouldn't mind the weight savings over the FF. The info I was really looking for was the info on the front brakes. Are the 2500LD significantly better than the 1500 brakes? (I'm single cab so I don't have the HD brakes). Are they 2 piston vs 1 piston?

One more dumb question... Is the way to identify a 2500LD vs 2500HD the SF 14 bolt on the LD and the FF 14 bolt on the HD?

Thanks again.

 

[GMC Burbalade]

I believe the 8600 GVWR 2500s were 8 lug and optioned with both the SF and FF 14 bolts, where as the 7200 GVWR 2500s were 6 lug and only available with the SF 14 bolt. So the easiest way to tell should be lug count.

 

[someotherguy]

What he said ^^^ on ID'ing them.

C2500LD -front- brakes are the same as a C1500 with HD brakes, or in other words, the brakes that came on any C1500 extended cab. Nothing special about them other than the rotor is a little thicker than your current ones on the 88 reg cab - 1.25" vs. 1" - same diameter. The back brakes on that 14 SF are bigger though, and you probably want to grab the stouter leaf spring pack too.

Richard

 

[SalahHH83]

Okay that's where I was getting confused in my research.... So they're just thicker rotors? Not a bigger piston in the caliper or dual piston? I definitely want the bigger drums, which is part of the reason I want to go to the 14 bolt. What other options are there for improving the front brakes (and getting the lugs to match front and back)? The NBS front brake swap? I understand that adds dual piston calipers and requires some modification to make it work. Any other options?

Thanks again.

 

[SalahHH83]

One more dumb question... On the rear, I have found a 14 bolt off of a 2002 2500 with disc brakes. The MC and prop valve aside, can this NBS rear axle be swapped onto an OBS? Do the spring perches need to be moved? Anything else?

Thanks again

 

[polar]

There are no dumb questions. But yes I'm almost certain the spring perches need to be moved. A bunch of people have swapped nbs rear ends in


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[SalahHH83]

Thanks a bunch, Polar! I'm going to search for a NBS rear then so I can get the disc brakes as well. I've cut off and rewelded spring perches before on my CJ5 Project when I swapped on Scout Dana 44 axles, so I'm not too worried about having to grind off the old ones.

Thanks again

 

[someotherguy]

The drums on a 9.5" or 10.5" 14 bolt are probably better performers and will leave you with a functional parking brake, vs. those NBS discs. Just my opinion. You might read up a little on them, many of the newer trucks with disc rears are notorious for parking brake problems. The 2009 3500"HD" I drive for work is no exception, and even at only 42K had totally non-functional parking brakes, pedal to the floor, you can push it by hand on level ground in neutral. Our shop just shrugs about it...

Richard