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Can these claims be true

J

jamacee

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Ok so I am a long time toyota owner but....

With my growing family + dogs + gear there has been no other grocery getter I have found better than the GMC suburban. So I went out and bought one. We love it. However I am still a noob and have been lurking around for awhile and about to make the jump to pay it forward to this forum.

I am now looking at another suburban b/c I believe I found a great deal but I NEEDED to ask you all what you thought.

Currently I have a 89 GMC 1500 burb 350,700r4,np241 and 10bolts bone stock on 30.5 x 9.50 tires ((getting 500+ miles on 33gal tank which is the same as 2 tanks of gas in my 95 4RUNNER both my trucks are getting 15-17mpg)) - fairly new (95k) motor from jasper engines and tranny and rear axel gone over before I purchased from orig. owner. I came across another one that I really would want but....not sure the claims are true. This is the guys add:

"1990 gmc suburban, rear barn doors, tow package with trailer brakes, skyjacker 4in. lift with all 4 springs, very nice aluminum wheels with 35s, tinted windows, roof rack, throttle body fuel injection, 15 mpg. 410 gears front and rear, rear positrac, drives great, bucket seats with console, paint is very nice, $3400" - I'd post the pic but I can't

is this shenaninigans could he be serious that a 350 w/ 4.10 gears and 35" tires could be getting 15mpg?

If so or I could get that droppind down to 33's I seriously would like to pick it up. I could live with around 15 just can't do 8mpg yet.

If anyone could drop some wisdom on this it would be awesome.
 
wow thats a sweet truck. good job man. so your running 38's and 44/14ff axels and 12-13?So it maybe possible then? Man I so want a sm 465 or nv4500 in mine I miss havin a manual tranny.
 
I'm getting around 12-13 as well in mine. 350tbi, 700r4, np241, 4.88's to the 37's

Later,
Buddy

BTW - my 350 has about 160,000 on it.
 
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Thanks man. yeah it gets pretty good on the highway but that's since I converted it to a manual. Of course a suburbans heavier, but it's got over drive, and 4.10s so it's within the realm of possibility. Maybe some burbon guys will chime in. I love my truck since I converted it to a manual
 
While not impossible, 15MPG is on the freakishly high end of the scale for a rig like that. 4.10 gearing is actually a decent choice for fuel economy with 35" tires. Obviously he is talking about highway driving and not in-town or expressway. Most gas Suburbans will be in the single digits running stoplight to stoplight.

Before people start throwing in their "amazing" mpg numbers, keep in mind that there is a big difference between the calculation from one tank where conditions were ideal (and you probably didn't have the same amount of gas in the tank before and after) and the average for dozens of fill-ups (which is the only thing that really means anything).

I'm interested why you need two Suburbans? (other than the basic reason why we all need more rigs...)
 
ask if he calibrated the speedo with the 35s on? burbs are heavy bishes and i wouldnt see one getting 15 on the reg.
 
Blue85-

I don't need 2 lol I'd rather have a k5 and a burb. Truth of the matter is my wife lost her job couple days ago and we were talking tonight about which truck to sell and looks like the 4runner was going to be it. However a buddy of mine wanted to buy my burb for his family hunting rig and well when I saw this other one I got to thinking.

It is mildly set up they way I'd like it. It has the factory options mine doesn't have. 1) being the rear heat/air 2)the barn doors vs. tailgate 3) springs all around no blocks) gearing is done 4) It would be almost a trade out for me if my friend purchased mine

Naturally I needed to check it out 1st and look it over but I'm real interested in it but I wasn't sure how accurate his claims were on the mpg.

Thanks guys for your input so far
 
I will bet the speedo was not recalibered for the tires and gears. I have never had one that got that good of milage around town. Maybe on a good day on the highway.
My wifes 2wd 07 subarban gets 10 to 12 in town and 16 to 18 on the highway,mostly on the lower side the way we drive.
 
Generally if someone moves to larger tires and there is speedometer error it makes the speedo slower and the mileage "appearing" worse. If he re-geared to a lower gear but kept the same tires the speedo would be faster and it would 'appear' he got better mileage.

15 is unlikely, but low teens is reasonably common. My best with a 350 in my K5 was 13.7 to the US gallon. Straight up freeway, 65 mph, SM 465, 3.73's and 35's. This was averaged over 3 tanks.

Rene
 
I've got three Burbs. The two half tons are the DD's with the 3/4 ton being the project truck so it doesnt get driven right now.

My 90 4x4 has a 350TBI/465/205 with 3.73's in 10b's front and rear with 33's. As long as I keep it under 60mph on the highway, I've gotten as high as 20mpg. Average is close to 15, but in town I think it's closer to 10. I try to be light on the skinny pedal, makes the tank last longer.

The 88 2wd has a modded 350TBI/Ranger OD/465 with 3.73 in the 10b rear with stock diameter, but slightly wider tires. On the highway, running around 70-80 mph, I can still manage 15mpg. If I keep it below 65mph, I think that might creep to 18mpg. In town this truck guzzles gas if its stop and go but it wasnt nearly as bad when it had the 700R4 in it.

I think the 15mpg is on the high side, but not unattainable if you drive easy. If your heavy on the skinny, dont expect anything higher than single digit fuel economy (or lack there of)
 
So is there much of a gain going down to saya 33 AT w/ the 4:10's? Would it be noticeable? Regardless it is going to be as good as a Toyota Sequoia or a Landcruiser. Like I said earlier there isn't another vehicle thats as good for taking your family and your crap around town and the woods.

I had thought about a 6.5 diesel swap since it is less involved than cummins once. Then I thought of the cost of diesel vs. gas.
 
Diesel fuel is more spendy, but my '83 C1500 pick-up pulls down an honest 25 mpg all day long on the highway with the 6.2, 700R-4, 3.42's and ~28" tall tires...

I had an '81 K5 with a 6.2, SM465, 4.56's and 39.5" TSL's that got an honest 16.5 on the highway, and a regular 14-15 in town.

It just comes down to how much you're gonna drive this thing. Diesel made sense for me at the time because the K5 was my DD. The pick-up is my DD now.

My Crewcab project will be gas engine for a couple of reasons. First it is an FI truck, so no carb to deal with, second is it's not gonna be a DD...so I really don't care if it gets 10 mpg.

Rene
 
I had an 89, almost exact same specs as that one. I averaged 15ish on the highway no problems.
 
jamacee said:
So is there much of a gain going down to saya 33 AT w/ the 4:10's?
Click to expand...

No, because you'd now be making the truck low geared for the tires and spinning the motor faster as you drove down the road. You'd likely get the same or worse gas mileage.
 
AJMBLAZER said:
No, because you'd now be making the truck low geared for the tires and spinning the motor faster as you drove down the road. You'd likely get the same or worse gas mileage.
Click to expand...

ok so gearing always confused me a tas bit. So if the 3.73 were stock on trucks w/ 30" whats the optimum tire size for 4:10

I thought most guys runnin 35"+ went w/ the 4.56 or 4.88?
 
4.10's are sort of the "highway gear" choice for 35's with a gas motor. You're sacrificing a bit of low end power for lower rpm's at higher speeds.

3.73's plus 30" tires is well...the towing package or something. GM did some weird things. The polar opposite was 31's and 3.08 gears.
Hell, my DIESEL Blazer has 3.73 gears and came from the factory with 235/75R15's...I still think it's a bit low geared now with 32's so lord only knows what it was like with the original 29" tires.
 
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