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Lowering combined with an air dam should help. I'd say more like 6", but it is a 4wd truck after all.
My dad put a JCWhiteny air dam on the front of our '94 3/4ton van back in the day... it actually made a significant difference. 1.5ish mpg on the highway IIRC.
Biggest difference I imagine would be ditching that cap, or replacing it with a reverse-sloped cap. A few examples on ecomodder where people are reporting 15% more mileage.
ProDarwin wrote:Biggest difference I imagine would be ditching that cap, or replacing it with a reverse-sloped cap. A few examples on ecomodder where people are reporting 15% more mileage.
O'rly? That makes me sad, as the cap would be really useful with it's size, but in the end I am more worried about mpg than space. MPG will kill me, especially if I start towing out east/down to the states. Are you saying a reversed slope cap increased mpg by 15%? 
The reason I ask is there is actually a "deal" with this cap. Basically, the original owner was going to sell it but never got around to it. He told me to sell it, and give him half of the sale. I figured if I paid him his "half" (at a fair price) that I would just keep it. But, caps don't really depreciate, so I could sell it for a pretty penny and put my half towards a reverse slope cap.
As for dropping it, as someone else noted, the truck actually sits level now. Since I'll be towing with 800-1000lbs of tongue weight, I wanted to keep the rear an inch higher to take that into account. A 3" drop all around is also only $130, anything lower also starts to make geometry get out of whack. I most definitely will be experimenting with a front air dam!
I recall reading someone getting better results than this, maybe I just wanted to believe it was better.
Aerodynamic pickup truck caps are a popular topic on EcoModder. That's not surprising when you consider that improving the efficiency of a thirsty vehicle has the potential for a bigger financial payback. Forum member Fubeca has documented the construction and testing of his clean looking prototype that revealed a respectable 4% improvement in MPG at 55 mph.
http://ecomodder.com/forum/showthread.php/silverado-aerocap-build-thread-11611.html
http://ecomodder.com/forum/showthread.php/commercially-produced-aerodynamic-pickup...
There are a few threads on there discussing truck front air dams as well. A couple guys are getting like 30mpg out of pickup trucks, which is pretty impressive.
around here caps depreciate to $50-150 as soon as it is clamped to the truck the first time.
what are you towing? the cap may provide a much smoother transition from truck to towed ( insert whatever you are towing here) as far as air flow is concerned, and work to your mpg benefit while towing. kinda like drafting.
HiTempguy wrote: Edit- And I also found out it has the G80 rear end (locker, I'd have liked a posi with clutches but oh well) and the GU4 (or GT4, I forget) rear axle ratio code = 3.73's.
I didn't know GM had actual lockers. Are you sure it isn't a Gov-lock, which is a clutch style with a crappy governor setup that is about as strong as glass. Searching google it appears the G80 is the gov-lock diff. some info here: http://www.355nation.net/forum/i4-i5-engine-drivetrain/30154-eaton-g80-locker-ques...
Image of gov-lock http://carphotos.cardomain.com/ride_images/2/4106/681/22762840019_large.jpg
just what in the flipping E36 M3 is that piece of crap? Who thought it was a good idea to have a 'centrifugal advance' limited slip?
The idea is that below 20mph (or 20km/h), you have a locked diff. Typically in situations where you need both wheels to turn at the same rate (mud, snow, stuck, starting off etc) you'd be going that speed.
The problem with a true LSD (and I take argument with this, but this is the claim) in a vehicle that is so light in the rear, you could cause sudden sideways action when it is slippy out (like if you hit a patch of ice, instead of one wheel simply unloading, both wheels would spin, causing the rear to move sideways at speed). My dad always says this, and I always roll my eyes at him because IMO it's the dumbest thing I've ever heard.
I am following this with interest. Please keep us updated once the cam is in.
Vigo wrote:just what in the flipping E36 M3 is that piece of crap? Who thought it was a good idea to have a 'centrifugal advance' limited slip?
GM and Eaton.
IF you are serious about building a true stump puller of a TBI engine here is what I have personally done and have seen done before:
5.7L Vortec long block assembly
Comp Cams 08-409-8 cam
LT4 springs
GMPP Vortec TBI intake
454 throttle valve (repinned)
MSD ignition module
MSD coil
Custom chip (TBIchips.com)
Shorty headers
2 1/2" cats
X-pipe
dual 2 1/2" inlet single 3" outlet Flowmaster muffler
I will be honest, we never put the combo on a dyno but it was a night and day difference compared to the 5.0L TBI that the truck had in it.
The problem with a true LSD (and I take argument with this, but this is the claim) in a vehicle that is so light in the rear, you could cause sudden sideways action when it is slippy out (like if you hit a patch of ice, instead of one wheel simply unloading, both wheels would spin, causing the rear to move sideways at speed). My dad always says this, and I always roll my eyes at him because IMO it's the dumbest thing I've ever heard.
Funny you should say that.. ever tried driving a truck with a limited slip? Or dozens of them (worked in a trans shop..)?
Induce wheelspin on a truck with a limited slip and it WILL move the back end sideways more than the same situation with an open diff, every time. Ive tested this on dozens of other people's trucks. Will it NECESSARILY go sideways if you are going perfectly straight? Not unless it's torque biasing. But it still could.
Trucks with limited slips are a lot easier to get into oversteer-related trouble with. You really have to manhandle an open diff truck to get the back end moving sideways very fast.
^ +1 a Foxbody Mustang is another good example. Snap oversteer is no joke, especially on the rock-hard tires my old 92 GT came with. New ones were ordered quickly!
Oh believe me, I'm not saying it "doesn't" happen, I am just more in the camp of blaming the operator than the equipment. Having driven rwd cars down stages before, I know that I'd rather have predictable control/grip then not (in my opinion).
The transmission was pulled out of the truck, the torque converter apparently exploded and took a lot with it. $1500 later and I'll have a rebuilt tranny prepped for hauling (including an extra tranny cooler). I don't want to have to put my search for more torques on hold tooooo long, but with the cost of the tranny rebuild we probably won't be seeing the initial dyno runs until the end of March, cam install and exhaust + dyno runs until the end of April. I'm hoping to get all three trucks together and piggyback on a dyno day (typically $50-$75 for 3 pulls including wideband).
I look forward to the results of the dyno. Here's what Car Craft did with their project.
http://www.carcraft.com/featuredvehicles/ccrp_0408_1993_gmc_350_pickup/viewall.html
From 140hp / 200 tq to 184hp / 268tq with just a tune up, headers, salad bowl, injector spacer, and tune.
The hard part is I can get a 4.8 or 5.3 for $250-$500 around here. I would imagine I could probably do the whole swap for around $1000 net.
If I could get the time and money, I would definitely look into a 5.3L. I would THINK with the right cam it could make similiar torques to a 5.7L. For myself up in canuckland, a $500 5.3L burns oil/is miled out. A good condition one (and let's be real here, I'd want one with an aluminum block) would be approaching $2k not including the wiring/ecu
Thanks for the link to the Car Craft article, I see no reason why I can't make 300tq's at the rear wheels (close to 400 atc) considering they didn't even stab a cam into their truck, AND supposedly those "off the shelf tunes" are pretty craptacular. Add on that I can't tell if they replaced the y-pipe (they said headers, new cat, and after cat exhaust, which would lead me to believe they used an OEM style y-pipe, so they missed out on a lot there).
I'm a big fan of simplicity and OEM engineering, they typically have done stuff right from the factory. While I know that you "can" get everything needed to swap a 5.3L, it is a lot of your own personal man-hours to do the swap if you've never done it before. And the 5.3L is going to need some additional torques down low via tuning/cam to get it to pull stumps. Of course, the 5.3L is silky smooth up to 6000rpm compared to even a vortec 5.7L, so yea...
Dont buy into the driveline losses bullE36 M3. At no point does it take 100lbft of torque to turn your driveline.
Im still optimistic about the results you will get.. but 300 rwtq does not = 400 at the crank..
Vigo wrote:Im still optimistic about the results you will get.. but 300 rwtq does not = 400 at the crank..
Realistically, 300rwtq doesn't equal anything as it's kind of an imaginary number. For E36 M3s and giggles AND to keep this simple, I stick the accepted driveline losses etc. It makes bench racing THAT much easier.
In the end, the number doesn't matter, just that it moves better ;)
In reply to HiTempguy:
I believe the y-pipe used by CarCraft was from Edelbrock or SLP and not nearly as garbage as the stock unit. That said, I'm not sure why they didn't do something like what John Brown posted about; pair of headers, pair of cats, X-pipe, decent flowing muffler or mufflers (I don't really care for Flowmasters but they offer some useful solutions fo sho).
Bringing this back from the dead, I finally have possession of the truck (in a drivable state) 
Runs great! Doesn't burn oil, makes great oil pressure for having 160,000miles on it (25psi cruising on the highway at 2000rpm, 40psi at 4500rpm), starts with a short twist of the key (found out it has command start and remote locks this morning, bitchin'!), rides almost new, very little slop in the steering, brand new Bilsteins all around.
April 14th it should hit the dyno. It's crazy how well it runs though, I mean, it won't win any drag races, but the bottom end feels stout. I really want to hook a 7000 pound trailer up to it just to see how well it tows 
But I don't get any warranty on the tranny until I've installed an additional tranny cooler, and I won't be towing with it for quite a while since I have access to a new truck with free fuel...
Anyways, super stoked!
Sounds good, keep us updated.
