1979 3+3 GMC Dually
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Hey everyone. I was on here a while back with a 1980 c10, but the project was too big for me while I was in school and working.
Finally picked up a truck I’ve been trying to find for a long time. It’s a 1979 crew cab dually. It’s rust free from California (I’m in MA, everything is rusty) and it seems to be all or mostly original and unmolested. My plans are pretty simple, being such a nice example I want to leave it mostly alone but clean it up (especially interior), fix the dents, AC, paint the fender etc. then lower it (maybe 6/8?) and put it on 22” semi wheels. I’ll have some questions for sure, but figured it should go in the project section. My first question is how to tell what’s original, what the truck came with, paint code, etc. can that all be accessed somewhere with the VIN? I want to check my rear end gears, make sure I get the right grille, etc. and find out any cool info - like what makes it a camper special and that kind of stuff. On to the pics: |
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Ugh sorry some of them posted sideways. Not sure why lol
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Beautiful! There should be a spid label in your glovebox or on the fender well under the hood that will label all options. If that is missing, then it will be hard to know all the original options. But You might be able to give the GM heritage center your VIN and maybe they can get you a build sheet.
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Looks like a decent start. Check the glove box for the SPID info. The label was there for my dually.
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Dang, no label in the glovebox. Ill see what I can find from the VIN. I'll need the paint code at least to paint the new fender.
What're you guys doing for highway speeds? I assume they all came with 4:10s? 60MPH is pretty high RPM....not great for around here when 80 is normal cruising speed. If I change the gears will it get out of its own way around town? Ordered some interior parts I needed from Brothers. Of course the dash pad I really need is on backorder. Next phone call will be for semi wheels and a drop....anyone to stay away from? I've heard good things about lowboy so far. |
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does anyone sell the fender trim? havent seen it online anywhere.
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3" spindles & drop coil up front get's your 6" drop. The front x-member gusset bars will be creeping in close to the tarmac on decent size dips on the road w/the stock stuff that low. Flip kit for the rear is 8" (+/- depending on the spring-pack count). At 8" drop you'll be bumpin' the bottom side of the bed floor w/the differential (they're porky). Nothing should hang below the rails @ 6/8. They'll high center around town. I think 4.10's is the most common for the HD rears. Mine does around 2800-3k @ 65-70 w/31.7" rear tires. Some guys will do 3.73's & there are also 3.54's available but like you mentioned it could impact the ability to get a load moving. I search C-list weekly for a 4l80e. |
Re: 1979 3+3 GMC Dually
They came with 3.73, 4.10 or 4.56. Tires came as a 215/75r-16 or a 235/85r-16. 235s are preferred as they are 31.5'' tall. Lowered dually in MA will be fun in the winter
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He also set me up with the semi wheels so I'm real excited to get this stuff in and transform this truck! I definitely need to decide on something to make it more highway speed friendly. Whats needed on the 4l80e swap? I would assume swapping gears is easier but maybe not? |
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Lol, this truck is too nice underneath (and 2wd) to be driving around here in the salt and snow....itll be a 3 season truck only. Ill keep my f250 for winter duty. |
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225/75-16 @ 29.3" w/4.10's 1:1 final drive gear @ 65mph = 3056rpm 225/75-16 w/3.73's & th400 1:1 final drive gear @ 65mph = 2780 265/35-22 w/4.10's & th400 1:1 final drive gear @ 65mph = 3056 265/40-22 @ 30.3" w/4.10's 1:1 final drive gear @ 65mph = 2955rpm 265/40-22 w/3.73's & th400 1:1 final drive gear @ 65mph = 2689 265/45-22 @ 31.3" w/4.10's 1:1 final drive gear @ 65mph = 2861rpm 265/45-22 w/3.73's & th400 1:1 final drive gear @ 65mph = 2603 29.3" tire w/4.10's & 4l80e .75 final driver gear @ 65mph = 2292rpm 29.3" tire w/3.73's & 4l80e .75 final driver gear @ 65mph = 2085 30.3" tire w/4.10's & 4l80e .75 final driver gear @ 65mph = 2216rpm 30.3" tire w/3.73's & 4l80e .75 final driver gear @ 65mph = 2016 31.3" tire w/4.10's & 4l80e .75 final driver gear @ 65mph = 2146rpm 31.3" tire w/3.73's & 4l80e .75 final driver gear @ 65mph = 1952 A Gear Vendors OD set-up would be similar gearing behind a Th400 @ .78 vs .75 final drive ratio (the GV would be slightly higher rpm's vs the 4l80e). |
Re: 1979 3+3 GMC Dually
I daily drove my swb with T400 and gear vendors for the better part of a decade. Loved that combo.
Also your dark brown is most likely cordovan brown. Light tan might be Sante fe tan. |
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For the cost of each, I'd do a 4l80e in a CC lowered dually. |
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