1994 GMC Sierra 4X4

In the fall of 2009 I needed a new vehicle to replace the '78 320i that was on it's last legs. I decided it was time to own a pick up again and started searching for a '67-'72 Chevy/GMC short bed truck. I found some nice ones but most in my price range were projects and I needed something to drive right away. I decided to search for an early to mid '90s truck in good drivable condition as they were in my price range and MUCH better looking than the '83-'89 trucks. I was focusing on 2wd trucks but stumbled on to a decent looking 4X4 on Craigslist and decided to check it out. This is what I brought home for just over $2500.

It was actually a Mendocino County Sheriff's truck in it's former life. It's got a 305ci with throttle body injection and the 4l60E overdrive automatic. The engine runs well, the trans shifts well, the 4wd works fine and the tires were in good enough condition to last through the winter. The interior is a little worn and the factory radio is absolutely the worst radio ever installed in a vehicle.

Interior:

I drove it on my daily commute of 60 miles for a few months and decided it was time for some improvements. First change was the steering wheel. I spend a couple hours a day in this truck and I wanted something better to hang on to than the OEM plastic piece so I ordered this from Summit Racing:



It came as plain wood so I spent a couple days sanding it and applying some of my rifle stock finish, it turned out quite stunning.

Next up was some new tunes. The original radio in the dash is just a small head unit, the actual tuner is located deep under the dash. There is no room in the head unit spot for a REAL tuner, the solution was found on ebay in the form of a replacement piece that allows a normal tuner to go in the little sun glasses cubby hole in the center of the dash below the A/C vent. The kit even came with a wiring harness adapter to make it easy to interface an aftermarket tuner to the OEM harness.



The cubby hole above the climate controls came with the radio piece to get rid of the OEM radio head. There were some blown out 6x9 speakers in boxes behind the seat and a Kenwood amp that was not wired up any more. I pulled the amp out and installed the 6x9 speakers I removed from the '78 320i before selling it. The tuner/CD player is also from the '78.

I tried a seat cover from the local Pep Boys store and it totally sucked. I needed something better and ordered a cover from Exact Fit Seat Covers in TX. They sell model specific seat covers on the web and on Ebay. They do good work- it fits nicely, it's easy to install and didn't cost a ton.

I will eventually replace the blown out rubber floor covering but until then I'll just live with some aftermarket mats I tossed in. I haven't decided if I want to go with carpet or rubber when I get around to doing that job. Rubber makes sense because it's easy to clean when it gets muddy but carpet gives the interior a more comfortable feel.

I need to find a new drivers side arm rest and install a momentary horn switch after I figure out why it won't work to start with.

Engine:

I've been getting about 14.5mpg after a good tune up. My driving is a mixture of highway and around town driving, I don't take it easy on the throttle. I think it can do a little better with some old fashioned hot rodding so I added a little spacer to the throttle body that moves the injectors 3/16" or so higher allowing more air flow, this little modification will likely be totally undetected by the local smog Nazi unless they have been specifically trained to look for that spacer. I have a CARB legal Transdap throttle body spacer to install as well as some shorty headers from Summit Racing that are also CARB legal:

I have a new "Y" pipe on order to go from the headers to the factory cat which will then flow into this GIMOUNGUS Magnaflow 6x30 muffler with 3" inlet and outlet. This is the largest "glasspack" I have ever seen in person:



I think with these upgrades I might pick up 2mpg which will pay for the modifications in a year or so. The trick to getting better mileage on my commute is to keep the transmission from down shifting on the hills which dumps a bunch of fuel and kills the mileage. Adding some torque should help the engine pull the hills in 4th gear and save some fuel. I made a quick 200 mi trip last weekend to pick up a '95 BMW M3 drive shaft for my BMW project and got 15.5mpg with the A/C on but there were no hills on that drive so I think 16.5mpg is possible, maybe more. I might try an electric fan in the future also.

Running gear:

The PO had cranked up the front suspension torsion bars to raise the truck a little. This is easy and pretty common on these trucks but the down side is the front suspension is not designed to go that high and you end up with several degrees of POSITIVE camber which wears the outside of the front tires rapidly and makes the truck drive a little strangely and ride excessively rough.

I lowered the suspension nearly 1 inch and lost most of the positive camber and the truck drives and rides much better. I will lower it another 1/2"-3/4" soon. As you can see in the original picture the rear end sits too high so the truck has an excessive rake. I will be lowering the rear 2.5" with a longer rear swing shackle set from Summit Racing.

LOWERING a 4x4?? What's up with that? Aren't you supposed to RAISE a 4x4 to be cool?? Well, I'm too old to care about being cool and I don't want to drop a ton of $$ into this truck. I don't plan on doing any serious off roading, just driving some Forest Service roads and getting around in the snow so extra ground clearance isn't necessary at all.

I ordered a set of these from Treadwright.com a couple days ago:



I like the idea of retread tires for this purpose. They are good for the enviroment because you don't build an entirely new tire = less resources used, they are cheaper by 30% and with the advances in technology they are just as good as new tires - unlike the retreads from back in the day which didn't last as long, had ballance problems and were just plain ugly.

In the next update I'll post up my thoughts once these are mounted and run a while as well as progress on the quest for better mileage and an updated profile pic once the suspension is lowered with the new tires on.

18 Mar 2010:

I installed the lowering shackles today. Here's a shot of the stock shackle in place:



The difference is quite obvious:



Here's the lowering shackle in place:

12 Oct 2010:

I installed the throttle body spacer in July. There is much debate on the web as to how effective these spacers are. I don't know or care about peak HP gains but I can say that it helped the low and mid range power noticeably. The truck had a slightly easier time climbing the hills on my commute and pick up .2 mpg. I installed the headers, "Y" pipe, muffler and new tail pipe in Aug. I did NOT keep the OEM catylitic converter but will install an aftermarket unit soon. The new exhaust from the heads to the bumper helped the power more than expcted-maybe 20 lbft of torque- and 1.2 mpg on my commute. I did a 2500 mi. road trip the end of Sep. and averaged 17mpg on the highway. I usually see 15.7 mpg or so on my commute now.

Here's the old stock exhaust that was about to rot off.



Here's the new exhaust:

You can see the 3" stainless tail pipe after the Magnaflow muffler. It sounds great!

4 March 2011:

I forgot to update on my opinion of the Treadwright.com tires. They've been on the truck for nearly a year now and I like them a lot other than the fact that I ordered load class E tires thinking they would be appropriate for this truck while towing a 20-22' travel trailer but when I mounted them I found that the factory steel wheels are load rated at 2400 lbs. I could have ordered load range D tires and gained a slightly better ride. These tires have such stiff side walls that I could probably run them without any air at all and not know the difference. They are very harsh over sharp edged bumps and pot holes at any speed but a crawl.

They are wearing well and are fantastic on the highway at speed, in the wet (we get REALLY wet here in NorCal) and in the snow. They were fine on the gravel and rock Forest Service roads Shadow and I went on this past fall. We never got a chance to do any real 4 wheeling but I expect they will be fine for my limited use off road. When these wear out I'll replace them with D load rated tires in a size closer to stock so the engine runs at a slightly higher RPM where it makes better torque - freeway cruise RPM is about 500 RPM too low.

Future Projects:

1. DIY bed liner

2. Fabricated rear bumper


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