GMC / Chevy Project Dual Sport ; 1998 GMC Sierra

STAG

Well-Known Member
I'm working on the beard... :rofl: I know just what you're saying, no worries.
okay I do fit Ito that category more haha. Steve's stereotype sounded more like a biker gang rather than a redneck :) and I have been called redneck before, so in a Chevy I must stay :D
 
Last edited:

Greg

I run a tight ship... wreck
Admin
So I spend much of Thursday and the morning of Friday doing a last minute thrash to get the truck ready for a trip to Moab! I did a better job bleeding the brakes (had my wife Catherine pumping the pedal), did a quick tape measure alignment, tightening all the TRE's and jam nuts, installing cotter pins, etc, etc, etc. I loaded up the RTT, camping gear and the dirt bike and headed down the freeway to Moab! Probably not the best way to break in new gears, but the truck did great! I'm really happy with the 4.88 gear ratio... the suspension is soft and smooth on the big freeway rollers and the truck has no problem running 75+.

After talking to some good guys at a local wrecking yard about the hydroboost brakes, I decided to keep the vacuum brakes. One of the guy runs hydroboost on his fullsize 'crawler and says he had problems steering when he's on the brakes. I'm not sure if he has bigger issues, but after fiddling with mis-matching hydroboost parts, I wanted to run the vaccum brakes first and see how well they worked with the huge Ford calipers. The brakes seem great! I may have some hydroboost parts for sale!

I do find that the truck needs a steering stabilizer and as mentioned before, a good anti-sway bar would be very nice and I need proper bumpstops for the front axle. Those items are on the list. The tires aren't balanced (tire shop couldn't do 37's) and I have a slight driveline vibration, but it's not that bad. Again, more minor tweaks. The exhaust is patched up temporary and I have a bad leak due to that, but it works for now. I will need to have a new exhaust built after I get a front driveshaft in there... as the truck sits, the exhaust is RIGHT in the way of the front driveshaft.

I do love the truck, I think it will do just want I want to! Here's a pic from today, headed back home after riding in Moab for the weekend. -

175518_10151135420827746_1233406179_o.jpg
 

lewis

Fight Till You Die
Location
Hairyman
nice, just what I am looking for. its it for sale yet? I am in the market for a truck like this. let me know.......
 

Greg

I run a tight ship... wreck
Admin
Looks like you had fun. I hope you didn't get a ticket for not having a front bumper?:D

Yeah, I passed a UHP sitting in the median of I-70 by Thompson, Utah and I figured he was coming after me! No front bumper, no mud flaps, etc... I thought I was busted! I got lucky, he let me go. ;)


Hey, that's something I could join in on :D

Greg, the truck looks great. You have an eye for great looking (and functional) builds. The RME TJ is still probably one of my most favorite TJs to date.

Thanks Caleb, it's kind of a sickness... I enjoy building rigs and seeing how well they can turn out. I need to get past that and be happy with what I have! I still miss the TJ, had I not been laid off and needed cash, I would probably still have it. :(


nice, just what I am looking for. its it for sale yet? I am in the market for a truck like this. let me know.......

Nope. :p


I often wonder how/if sales would have changed for GM had they left the D60 in the K3500's.

Good question! GM's IFS sucks, but I suppose for 98% of the people out there it does the job.
 

Greg

I run a tight ship... wreck
Admin
I love it. Makes me miss my Tahoe.

I bet, the Tahoe was a winner!


Any mpg #'s on this yet?

Nothing official, but mileage sucks. :D

Stock the truck had 3.42 gears, an overdrive ratio of .69 and 285's... it was pulling down 18-19 MPG no problem. That gearing combo just allowed the engine to spin at low RPM's everywhere. It had enough torque to pull it off.

Now with 4.88's and 37's I'd be surprised to see more than 12 MPG... more than likely 10-11 MPG average. I haven't driven it enough to get some actual numbers, so that's a guesstimate.

At freeway speeds (75+ MPH) truck has a hard time staying in OD on anything but flat ground, which is killing the mileage. I would like to rebuild both the engine & transmission and hope I'll gain a good deal more torque with a 383, helping the truck stay in OD.

I realize the 6.5l diesel engine is a turd from a towing/performance standpoint, but I wonder how a 6.5 equipped GM truck would do with the same build and gearing that worked with the diesel.
 

lewis

Fight Till You Die
Location
Hairyman
I realize the 6.5l diesel engine is a turd from a towing/performance standpoint, but I wonder how a 6.5 equipped GM truck would do with the same build and gearing that worked with the diesel.

Don't do it. I don't want a diesel in my future truck. Think at least an Ls1.
 

Rot Box

Diesel and Dust
Supporting Member
Location
Smithfield Utah
I realize the 6.5l diesel engine is a turd from a towing/performance standpoint, but I wonder how a 6.5 equipped GM truck would do with the same build and gearing that worked with the diesel.


With a few simple modifications my old 6.5 pulled a load very well and provided similar fuel mileage and power as the stock 12v and 24v Cummins I've owned. I know numbers on paper don't mean much in the real world... but rated at 215hp/440ft/lbs the later 6.5's are in the same ball park as any of the other 90's diesel pickups. Too bad you can't easily add 100+ hp like the others :-\ Its a bit outdated but have you read this article? http://www.thedieselpage.com/finale.htm

I wouldn't hesitate putting a 6.5 in anything (especially if it was replacing a gasser LOL) but I'd rather have a 12valve Cummins or IDI :p
 

LT.

Well-Known Member
With the truck being built with dual use i guess i would look for a solution to the poor mileage problem as well. Everything is a compermise with a multi use vehicle. I think swapping a diesel would be more trouble than it would be worth. But, i do lile your idea of a stroker motor. More power means the truck may hold high gear longer. And all it may take is a simple computer re flash to make it all work together. But, honestly, i think a goal of mid teens for mileage maybe the best you could manage no matter what you do. Even with a stroker motor you may only be in the low to mid teens. Diesel or not. Take any modern turbo diesel, pep it up, and install larger tires and they may all struggle to maintain mid teens for mileage. Especially if they are honest with their figures. 37" tires is a big, heavy tire. The truck has a much larger frontal area and it is aerodynamically challenged. I just dont see anything you can do to get it over the 15 mpg mark and stay within any kind of a working budget.

I love the truck, and i think it is a home run, bottom of the ninth, score tied kind of build. One of the most impressive builds i have seen. You kept with the theme and had a clear vision of the build from start to finish. Something most of us lack.

LT.
 

sixstringsteve

Well-Known Member
Location
UT
...honestly, i think a goal of mid teens for mileage maybe the best you could manage no matter what you do. Even with a stroker motor you may only be in the low to mid teens. Diesel or not. Take any modern turbo diesel, pep it up, and install larger tires and they may all struggle to maintain mid teens for mileage. Especially if they are honest with their figures. 37" tires is a big, heavy tire. The truck has a much larger frontal area and it is aerodynamically challenged. I just dont see anything you can do to get it over the 15 mpg mark and stay within any kind of a working budget.

I love the truck, and i think it is a home run, bottom of the ninth, score tied kind of build. One of the most impressive builds i have seen. You kept with the theme and had a clear vision of the build from start to finish. Something most of us lack.

LT.

x2. One of the reasons you got this truck was for the motor. I'd stay away from a motor swap. If you're going that route, sell it to Lewis and build something else up. :D
 
Last edited:

I Lean

Mbryson's hairdresser
Vendor
Location
Utah
You would have been better off mileage-wise with 5.13 or 5.38 with that tall overdrive. BUT, since you got the 14b for a good deal with 4.88's, it certainly wouldn't have been worth swapping. (just for future reference or whatever....)
 

Greg

I run a tight ship... wreck
Admin
Go 6BD1 Greg! I even know where you can score one...

It it weren't such a huge project, I'd consider it!



With a few simple modifications my old 6.5 pulled a load very well and provided similar fuel mileage and power as the stock 12v and 24v Cummins I've owned. I know numbers on paper don't mean much in the real world... but rated at 215hp/440ft/lbs the later 6.5's are in the same ball park as any of the other 90's diesel pickups. Too bad you can't easily add 100+ hp like the others :-\ Its a bit outdated but have you read this article? http://www.thedieselpage.com/finale.htm

I wouldn't hesitate putting a 6.5 in anything (especially if it was replacing a gasser LOL) but I'd rather have a 12valve Cummins or IDI :p

Totally agree, I was saying that if one started with a 6.5l truck it could be pretty cool. No way would I swap one in, for the time & money one would be better off with one of the Cummins or Isuzu offerings. IMO the 6BT is overkill for a 1/2 ton GM. ;)

I have read that article, they make the 6.5 (after mods) like a pretty viable option! I don't know about that IDI remark though... :p


With the truck being built with dual use i guess i would look for a solution to the poor mileage problem as well. Everything is a compermise with a multi use vehicle. I think swapping a diesel would be more trouble than it would be worth. But, i do lile your idea of a stroker motor. More power means the truck may hold high gear longer. And all it may take is a simple computer re flash to make it all work together. But, honestly, i think a goal of mid teens for mileage maybe the best you could manage no matter what you do. Even with a stroker motor you may only be in the low to mid teens. Diesel or not. Take any modern turbo diesel, pep it up, and install larger tires and they may all struggle to maintain mid teens for mileage. Especially if they are honest with their figures. 37" tires is a big, heavy tire. The truck has a much larger frontal area and it is aerodynamically challenged. I just dont see anything you can do to get it over the 15 mpg mark and stay within any kind of a working budget.

I love the truck, and i think it is a home run, bottom of the ninth, score tied kind of build. One of the most impressive builds i have seen. You kept with the theme and had a clear vision of the build from start to finish. Something most of us lack.

LT.

You are absolutely correct, I did not expect great mileage with this build and the talk of a diesel swap is just that.... talk. While I would LOVE a powerful turbo diesel under the hood, it's just not a realistic option. I do want to retain factory reliability and that's a huge reason to stick with a smallblock Vortec engine.

I like the Vortec 350 and my plans are to build a 383 stroker with 6" rods and a slightly more aggressive roller cam. 6" rods will let me run low octane and keep the compression ratio decently high. If I can get 420-430 ft/lbs out of the engine, I'd be very happy. I think it would pull the overdrive ratio at freeway speeds just fine at that point. If I could also manage 13-14 MPG, I would be very pleased... but if not... I'd still have 420+ ft/lbs... I can deal with poor MPG's if I have some power.

I've played with the idea of a Vortec 454, but that would require a transmission upgrade to a 4L80E ($$$) and rebuilding the engine would be $$$. An ever more amazing idea is a Vortec 8.1l... probably one of the most badass GM big blocks (other than the 502 ;) ), but that would require a fair amount of wiring, etc, etc. Not something I want to deal with. I think a 383 built right will suite me just fine.

Thanks for the other props on the build, it's been a fun one! Not too complicated, but a very big change in capability. I realize my plans were a little loose at the start, but I knew what I really wanted... just had to make sure my check book agreed. ;)



x2. One of the reasons you got this truck was for the motor. I'd stay away from a motor swap. If you're going that route, sell it to Lewis and build something else up. :D

As mentioned above, a big diesel swap isn't in the works... just talk. Factory reliability is something I want to keep. I don't need/want another big project, I want to get out and hit the trail!

:rofl: Lewis couldn't afford it... at least not what I'd need to get out of it! :D



You would have been better off mileage-wise with 5.13 or 5.38 with that tall overdrive. BUT, since you got the 14b for a good deal with 4.88's, it certainly wouldn't have been worth swapping. (just for future reference or whatever....)

One of the big factors for going with the 4.88's was towing... 4L60E's don't like towing in OD, so I'll be towing in 3rd gear. 37's and 4.88's in 3rd = 3300 RPM at 75 MPH... which IMO is a good place to be. I can use the big OD ratio when I'm not towing and hopefully get half-decent mileage. I like the deep 1st gear ratio and the big OD ratio of the 4L60E, so I'd like to keep it.

Since we're talking about transmissions, my plan is to buy a rebuilt 4L60E Monster Transmission... probably around the same time the 383 gets installed. ;)



^ditto^

but I do have a soft spot for the 6.5TD

Like I said... IMO starting with a 6.5L TD truck would a half decent option.
 
Top