Does Heavy Half mean my truck is fat?

[79gmcsierragrande]

Hi, new here, had a couple of questions about my truck if you don’t mind. I bought a 1979 2X4 short bed GMC Sierra Grande about a year and a half ago for $500. The guy I bought it from said it was a Heavy Half, but I was told by someone else that it would have a ¾ ton rear axle making it a 6 lug instead of a 5on5 lug. That didn’t make a lot of sense to me so I looked it up on Wikipidia and a few other sites and it looked like the heavy half was something different from a Sierra Grande. It dose have the 350 with the 4bbl carb, the heavier breaks, a 3.73 rear axle and the card in the glove box says Heavy Duty Chassis in the options box if that helps. Also if anyone knows what Heavy Half means I would like to know?


The trans is a 4 speed manual with a low gear (meaning you start in 2nd). Highway speeds out here (Grand Junction CO) are 75 mph and I’m out of gears at 30. I can almost watch the gas gage go down over 3 miles on the hwy. I would like to get better gas mileage without sacrificing towing capacity, is there anything I can do? Also I WON”T drive an automatic, I bought this truck because it was a stick so please don’t suggest a turbo 350 or 400 I know they are out there.


The other thing I was wondering about is, the truck has a drifting problem. My philosophy is if something breaks replace it and everything attached to it. So I’m replacing the ball joints (shot), tie rod ends (shot), shocks (shot, on the way), idler arm, gear box, adding a stabilizer, and replacing all the bushings. The power steering pump was supposedly replaced just before I got it but he must have gotten it from a junk yard because it’s old. I’m not going to raise or lower the truck, I did put on some 31 10.50 R15 Toyo Open Country A/T tires with 15”X8” rims, but that’s as far as I’m going with it I like the stock height. I was wondering if there is anything I’m missing and if anyone has heard of Energy Suspension? I found a site that has the full bushing kit for $192.57 http://www.energysuspensionparts.com...s.asp?cat=2330 but I don’t want garbage. If anyone has bought from them or knows about them I would appreciate the feedback.


This is the first truck I’ve tried to restore. I’m a welder by trade and I’ve always done all my own work on my cars but I’ve never taken on something this big before, I’m looking forward to it. When I bought the truck the breaks didn’t work and the clutch pedal popped in and out making the truck jump. I spent about $300 replacing everything accept the break lines and the vacuum assist (master cylinder, calipers, wheel cylinders, shoes, pads, and drum and rotor turn) and the clutch was a simple tightening of two nuts on the pedal. The body is in good shape accept for a dent on the tailgate, the driver door (my wife did, I could have killed her), and two on the hood, the paint is faded and there is minimal surface rust, and the interior is also shot but that just means I can do WHATEVER I WANT TO IT. I’ll post some pictures when I figure out how….



Sorry about the essay I don’t normally type this much...

[jsbgump]

A heavy half or a big ten is a 5/8 ton which means it has a 3/4 ton suspension as in the rear leaf springs and the front coils but will have the 5 lug bolt pattern. It has 1/2 ton axles with 3/4 ton springs is all it is

[old Rusty C10]

welcome to the board.. JSB answered your question but how about some pics of your truck?

[79gmcsierragrande]

Ok now that makes sence. That explains why I have 9 leaf springs. Now lets see if these pictures work....

[SBTork]

WELCOME. Wow, you can't go wrong with $500 for that truck. It seems like you have a good handle on what to do with it too. I have not gotten anything from energy suspension, but I have heard nothing but good about them. Good luck on the build, and post progress and pics along the way.

[79gmcsierragrande]

I was going to ask if that means I need 3/4 ton shocks but it looks like (from checking amazon) it's the same shock all the way up to the 1 ton. That's good because I just got in my Rancho 5000 shocks delivered when I had that thought.




Yeah $500 for the truck and one of the first things I did was spend $600 on tires. Oh well, the spending has just begun. I'm triing to keep a running tally, and I'm cutting myself off at $10,000

[dan42]

Yeah, but at that number, you should have a really nice truck, that would cost you a lot more if you bought it new. That's a good budget, and if you're starting with something solid, it's a good investment. Welcome to the board!

[Ivan D.]

Originally Posted by 79gmcsierragrande

The trans is a 4 speed manual with a low gear (meaning you start in 2nd). Highway speeds out here (Grand Junction CO) are 75 mph and I’m out of gears at 30. I can almost watch the gas gage go down over 3 miles on the hwy. I would like to get better gas mileage without sacrificing towing capacity, is there anything I can do? Also I WON”T drive an automatic, I bought this truck because it was a stick so please don’t suggest a turbo 350 or 400 I know they are out there.

I'd suggest that you install a set of numerically lower gears in the rear axle - for a tranny with a 1:1 final ratio (no overdrive) I think 3.08 gears will work out good, I had them in my old '79 halfton with a TH350 slushbox and with my 33" tires at 65mph my engine speed was a bit around 2200 rpms, which is still well before the opening point for the carburetor's secondary barrels so you should be getting decent fuel economy (I was getting 18-19mpg freeway at 2000 rpms). Also, you having a bolt-action tranny means there will be no torque converter losses, so more of what your engine makes will go to the rear wheels, and your engine speed will be a bit lower as well.

The other thing I was wondering about is, the truck has a drifting problem. My philosophy is if something breaks replace it and everything attached to it. So I’m replacing the ball joints (shot), tie rod ends (shot), shocks (shot, on the way), idler arm, gear box, adding a stabilizer, and replacing all the bushings. The power steering pump was supposedly replaced just before I got it but he must have gotten it from a junk yard because it’s old. I’m not going to raise or lower the truck, I did put on some 31 10.50 R15 Toyo Open Country A/T tires with 15”X8” rims, but that’s as far as I’m going with it I like the stock height. I was wondering if there is anything I’m missing and if anyone has heard of Energy Suspension? I found a site that has the full bushing kit for $192.57 http://www.energysuspensionparts.com...s.asp?cat=2330 but I don’t want garbage. If anyone has bought from them or knows about them I would appreciate the feedback.

Energy Suspension (aka ENS) are well known for their polyurethane suspension components, I got a set of bushings in my Lincoln Town car and with the stiffer springs and road race shocks that 4500lb landyacht handles scarey good - I think you will like the ENS bushings on your truck as well, as a matter of fact that's what I was planning on using on my '79 c10.

This is the first truck I’ve tried to restore. I’m a welder by trade and I’ve always done all my own work on my cars but I’ve never taken on something this big before, I’m looking forward to it. When I bought the truck the breaks didn’t work and the clutch pedal popped in and out making the truck jump. I spent about $300 replacing everything accept the break lines and the vacuum assist (master cylinder, calipers, wheel cylinders, shoes, pads, and drum and rotor turn) and the clutch was a simple tightening of two nuts on the pedal. The body is in good shape accept for a dent on the tailgate, the driver door (my wife did, I could have killed her), and two on the hood, the paint is faded and there is minimal surface rust, and the interior is also shot but that just means I can do WHATEVER I WANT TO IT. I’ll post some pictures when I figure out how….

I would replace the brake lines as well as rust gets to them eventually, and hoses like to collapse internally and cause a caliper to freeze and overheat the brake. Also, if you want to be able to out-brake good 50% of what's out there on the roads, think about swapping the vacuum assist with a hydroboost unit from a diesel or 1-ton truck, those use the power steering pump to run the brakes and are able to achieve much higher line pressure and work especially good on halftons - now that pretty much requires that you replace the steel lines, I blew first the front then the rear on my halfton when I was testing my hydroboost in the carport.

[84 400]

Energy suspention is a good company. In dealings that I have heard nothing but good things. Nice truck you got there and 500.00 seems like a deal to me.

Welcome to the boards from NH Lotta good people on here who are very willing to help out

[Pyrotechnic]

Heavy Half trucks also got bigger rear brakes, a 2 piece drive shaft, and a double hump crossmember. The bigger weight rating moves the truck out of emissions requirements so emissions equipment is very minimal.

[78BO]

Originally Posted by Pyrotechnic

Heavy Half trucks also got bigger rear brakes, a 2 piece drive shaft, and a double hump crossmember. The bigger weight rating moves the truck out of emissions requirements so emissions equipment is very minimal.

Can you give a little more info on this? I just looked up my VIN and it says
ccl448s161365, so that would make it a Heavy Half according to http://www.chuckschevytruckpages.com/73-87specs.html. I've seen the trucks with the logo BIG 10, but never asked and my doesn't have the decal.

I'll have to go home and check to see what gears it has. It would be cool as hell if it has 373's. But I bet with the auto it wont.

[78BO]

Also, that link shows that the 373's for my truck only cam with the I6, that sucks for me.

[Pyrotechnic]

I have a Heavy Half that came with 3.42's. It really just depends how it was ordered.

[79gmcsierragrande]

Originally Posted by Ivan D.

I'd suggest that you install a set of numerically lower gears in the rear axle - for a tranny with a 1:1 final ratio (no overdrive) I think 3.08 gears will work out good, I had them in my old '79 halfton with a TH350 slushbox and with my 33" tires at 65mph my engine speed was a bit around 2200 rpms, which is still well before the opening point for the carburetor's secondary barrels so you should be getting decent fuel economy (I was getting 18-19mpg freeway at 2000 rpms). Also, you having a bolt-action tranny means there will be no torque converter losses, so more of what your engine makes will go to the rear wheels, and your engine speed will be a bit lower as well.


Energy Suspension (aka ENS) are well known for their polyurethane suspension components, I got a set of bushings in my Lincoln Town car and with the stiffer springs and road race shocks that 4500lb landyacht handles scarey good - I think you will like the ENS bushings on your truck as well, as a matter of fact that's what I was planning on using on my '79 c10.


I would replace the brake lines as well as rust gets to them eventually, and hoses like to collapse internally and cause a caliper to freeze and overheat the brake. Also, if you want to be able to out-brake good 50% of what's out there on the roads, think about swapping the vacuum assist with a hydroboost unit from a diesel or 1-ton truck, those use the power steering pump to run the brakes and are able to achieve much higher line pressure and work especially good on halftons - now that pretty much requires that you replace the steel lines, I blew first the front then the rear on my halfton when I was testing my hydroboost in the carport.

What about putting in an overdrive, or are they just for automatics? I don't want to lose power at the wheels if I can avoid it. I bought this truck for hauling.


Good to know thank you.



Yeah Break lines are on the list. I was just replacing the rear shocks and I checked out the lines, they looked good but I figure on replacing just about everything. I don't think I'll get the hydroboost though. It stops just fine and I have a trailer break for when I hall so I'm not going to worry about it for now.

[67_C-30]

This is what my brother did with his Heavy Half! it runs 11.90's (7.60's in the 1/8) on motor.

[Ivan D.]

Originally Posted by 79gmcsierragrande

What about putting in an overdrive, or are they just for automatics? I don't want to lose power at the wheels if I can avoid it. I bought this truck for hauling.

Well didn't you say your 1st gear is so low that you gotta start straight in 2nd? Generally you should be able to get an aftermarket overdrive unit, if you gonna tow with that truck tis actually a good idea cause it will give you another 4 gears so you can do splits and have gears between the gears and put less stress on the drivetrain while you accelerate with that trailer.

[Pyrotechnic]

Originally Posted by 79gmcsierragrande

What about putting in an overdrive, or are they just for automatics? I don't want to lose power at the wheels if I can avoid it. I bought this truck for hauling.

Overdrive units are just too expensive unless you got more money than you know what to do with.

I would never run 3.08's, 2.73's, or any other super tall gear with a manual transmission in a truck. I can't stand having to ride the clutch like crazy to get going. 3.73's and an overdrive trans are what you want.

If you want to stay manual transmission, a NV4500 5 speed overdrive, or a Getrag 5 speed from a 88-98 truck would be a good swap. The NV4500 is extremely tough and is much like the transmission you have now, but with an overdrive. The Getrag is lighter duty but it's still a good transmission for the purpose of overdrive.

[Ivan D.]

Pyro, he has granny 1st, so tall rear gears shouldn't be of much issue to him?

[Walts_restoration]

He has granny gear, so its L 2 3 4, hence why he starts in second. No problem with rear gears, he just has a granny trans, isnt a bad trans, never had a problem with my dads 73, and its got 190k or so miles on it, we got it at 30k, lol.

[Pyrotechnic]

1st=6.54
2nd=3.57
3rd=1.57
4th=1.00

Man that is a HUGE jump between 1st and 2nd to have to make between every stop light though. I don't think they really ever intended that 1st gear to actually be used as first except when heavily loaded.

True, taller gears wouldn't be too much of an issue as far as riding the clutch, except that huge jump between first and second. With a first gear that low I would go with 2.73's in back. It would make first gear more usable, and the effective overdrive deeper.

I still vote for a NV4500 5 speed since that takes exactly what he has and adds overdrive with no sacrifices except the cost.

First Gear 6.34
Second Gear 3.44
Third Gear 1.71
Fourth Gear 1.00
Fifth Gear 0.73

[killthewabbit]

Heavy Wabbit would imply that I was fat.

Sorry, I know that wasn't very helpful...

[Walts_restoration]

no, L or "1st" was never supposed to be a every time startup gear, its to help get a heavy load going, or start on a hill. I always start in 2nd

[79gmcsierragrande]

I like the sound of the NV4500 5 speed. Is there any modifications I would need to make or would it bolt right up? I'm a welder and I've cut and swapped bell housings for a trans shop before so that wouldn't be a problem I'm just wondering. If it cost more to do it that way but it's the better way to do it I'm all for it. I don't like temporary fixes and I'm not good about maintenance or tuning. Also I priced out the truck I “Want” for the need I have and it was around $35,000 for the base model that’s 4 years old, so I figure $10,000 for a fully customized (by the time I’m done) older truck sounds about right.

[autologic]

Is the 4th digit in your VIN a 4?

If so, then it is a heavy half.

[xtreme80]

That's a sweet truck! In arizona, a heavy half is emissions exempt because it's technically considered a 3/4 ton, and that's cool because you can just put half ton parts on it and still be exempt!

I wish I could get my hands on one!