Better mileage? nv4500 or 700r4?

[Fubeca]

I would stick with the auto because the costs of changing to manual aren't justified.

However, you can see significant MPG gains in a manual if you modify your driving habits a bit. If you pop it in neutral everytime you are coasting or depress the clutch for short coasts you can save an amazing amount of fuel. It is even more pronounced if you wire up a kill switch for the motor and coast with the engine off (of course, this is a bit radical )

 

[Redwookie]

Yeah that would be a bit radical! I am not against it or anything but I am also a realist. I know it's a Blazer and if I was gonna hypermile and totally obsess over mileage I'd probably be better off with like some crazy modified Metro or something! I mean to each their own of course but I was looking to get the best mileage I can with the ol Blazer but I am not expecting miracles. I just figured ig the manual gave me a couple extra mpg it would be worth the conversion but if once you are driving in the real world, the difference between the nv4500 and the 700r4 is like less than 1/2 mpg or something then it may not be worth the trouble of doing the conversion since I do prefer the laziness of an auto....BUT I would make do with the manual if I'm getting a couple mpg again so what's the real world difference guys? That's my decision maker....real world mileage difference?????

 

[bp71k5]

Most modern cars see a modest 1 mpg gain in all the averages. Whatever difference there is would be seen at non-freeway speeds around town.

 

[Redwookie]

See now that makes the decision a bit tougher again! I mean a mpg adds up eventually! And I do most of my driving in town. Man this is a toughy! Well guys keep sending me opinions and experiences I guess because sheesh I mean a mpg is almost enough, I think if somebody out there saw even a little better than that in their Blazer, I might do it. I mean someone earlier in the thread said they got better mileage switching from a 700 to just a 4 speed w/a low gear so with the 5 speed, hmmm.... yeah anybody see any mileage gains they can report back out there?

 

[bp71k5]

See now that makes the decision a bit tougher again! I mean a mpg adds up eventually!

I was just trying to say that if everything was perfectly equal in terms of driving style and conditions, the absolute best you could hope for would be about the 3% difference modern cars see (1 mpg improvement at 30 mpg average). In my experience that difference is much lower and if you are trying to find some monetary savings to justify an nv4500, that'll be tough.

When I swapped in that trans and fuel injection, my mileage went from 15 mpg down to 8mpg. ( I also swapped in a bigger motor, tires, and axles).

 

[Redwookie]

I appreciate all the help, i do. Ok so really my goal is to get the best mileage I can get out og my Blazer. I am going to switch out the TBI 350 that is in the truck for a 6.2 Diesel so I am obviously not all about savings lol. Presently if I keep my foot out of the gas with the 700r4, 35" KM2s, and 3.73s, I get about 12-14 mpg. I am hoping with the 6.2 to get 17-18 or even more! I am honestly hoping with driving nicely to crack the 20 mpg mark! I have heard of some people I know actually getting that, in the real world some even getting to 25mpg at times! I would love to get there myself! But again really, am I wasting a few grand bothering with the 5 speed that could go somewhere else?????

 

[bp71k5]

I am hoping with the 6.2 to get 17-18 or even more! I am honestly hoping with driving nicely to crack the 20 mpg mark! I have heard of some people I know actually getting that, in the real world some even getting to 25mpg at times!

I am assuming those are freeway miles, and if they are then there's no difference between a 700 and the 4500.

am I wasting a few grand bothering with the 5 speed that could go somewhere else?????

I think so.

 

[Redwookie]

Yeah certainly that was on the freeway! Man if you could get that in a big ol k5 in town why would anybody drive anything else lol! Dang yeah that's kinda what I keep coming back to as bad as I wanna waste my money lol, I keep coming back to getting a solid new or rebuilt 700 to replace my 700 and use that money on other goodies...

 

[Russell]

If you are switching to diesel, run the 700r4. The NV4500's gear ratios are too wide for a 6.2L diesel IMO. I find I am either lugging the engine, or over-revving it all the time in town.

An NV3500 would not be a bad choice behind a naturally aspirated 6.2L however. No weaker than a stock 700r4 (again, in my opinion), and has much better gear ratios. I had one in my old K10 with a NA 6.2L running 3.08s and 35" tires, and though I always wished for better gearing, the gear spacing of the transmisison was really good.

 

[Thunder]

12-14 on the freeway in a 350 tbi? That is pretty bad. there must be something wrong. Most likely the 35" tires with the wrong gear ratio.
I get 15 average city highway.
If i do 65-70 with all terrain tires I can pull 18- 19 easy on the interstate. With my Mts on it drops down to 17.
89 K5 350, 4" lift, 33" tires 3.73, 700r4 I have no complaints about my MPG.
I have ran 35" tires but dont like them. The small increase in height was not worth the hit I took in MPG. But it never dropped below 15 on the highway. Plus towing on 35" sucked with my gear ratio.
Even if you go diesel you will still take a hit on your MPG. With taller tires there is just no getting away from it.
Maybe you should just look into better gears for your tires and work with the TBI.
TBI can be tuned to get good MPG.

 

[tRustyK5]

I appreciate all the help, i do. Ok so really my goal is to get the best mileage I can get out og my Blazer. I am going to switch out the TBI 350 that is in the truck for a 6.2 Diesel so I am obviously not all about savings lol. Presently if I keep my foot out of the gas with the 700r4, 35" KM2s, and 3.73s, I get about 12-14 mpg. I am hoping with the 6.2 to get 17-18 or even more! I am honestly hoping with driving nicely to crack the 20 mpg mark! I have heard of some people I know actually getting that, in the real world some even getting to 25mpg at times! I would love to get there myself! But again really, am I wasting a few grand bothering with the 5 speed that could go somewhere else?????

I don't think you need to spend a boatload on a "custom" NV4500 if you do decide to make the swap. All of those "custom" options are just different factory configurations. Both the early and the later NV4500 have the deep crawler gear...it's just one is a little deeper than the other. The early one is 6.34:1, and the later model is 5.61:1. Pretty hard to tell the difference really.

You want Chev 1 1/8" 10 spline input, 4WD version with the GM 32 spline output. Shifter style is irrelevant...both work just fine and are in the same location.

As for diesel mileage, I do have some experience with that. I also have some experience with a manual tranny behind a 6.2.

I ran a SM 465 behind the 6.2 in my old K5 for 4 or 5 years. 4.56 gears and 39.5" TSL's. My average in city driving was 15 mpg. Rarely any lower. Freeway it'd get 16.5 mpg, but it was revving at 2600 rpm and big bias ply tires hurt mileage a lot. With decent gears I don't feel the gear spread is a problem. Maybe if your gearing is not the best it can be an issue...

I currently DD an '83 GMC pick-up with the 6.2 and 700R-4. it pulls down high teens in town, and regularly gets between 24 and 25 mpg freeway. It really doesn't vary much. I'd be surprised if a NV4500 would gain me more than 1 mpg in that pick-up.

That being said I'll be swapping my NV4500 into my 90 K5 (with TBI 350)soon enough.

Rene

 

[Redwookie]

Well all good stuff guys. I am glad to be getting some opinions for or against the both of the transmissions. Thunder I got about the same outta my truck when I had 33" tires too but that 12-14 is what I get now, in town, with my lead foot driving! I don't think of it as too bad for that ol tired 350 I have plus the 35" tires. I get maybe 16 or 17 on the freeway and used to get maybe even 20+ with the 33"s. See I wanna get like 16-17 in town and 20+ with my 35" tires and the 6.2 turbo! That would make me happy and if I can do better that will kick some serious tail! I know I will need to also start keeping my foot out of the gas a bit more too but again I'm looking for 17+ in the city realistically not bragging numbers but really what I can get driving normally every day. I hope.

 

[Redwookie]

Hey thanks TrustyK5! That's what I wanted to hear! Those numbers sound great! If I can get those kinda numbers on my Radial 35" tires with my 3.73 gears that would be perfect! And if I can do that with the auto then I think I may have a winner!

 

[Thunder]

beings you are thinking about a rattler.....
i got bit by the diesel bug too.
I also have a 6.5 TD K1500 EX cab PU. I just bought it. and have been driving it for about a month now. I am on my 2nd tank of gas errr... diesel. Gotta say i am lovin the fuel mileage. Filled the tank over a week ago and the needle just mooved off the full mark with 120 miles of mostly city driving on it.
Its great driving it day after day and not seeing the fuel needle move much. I have not checked fuel mileage but just by seeing the fuel guage sitting on full day after day. I know i am getting better mileage than my TBI K5.
My new 1/2 ton truck has a 4l80E 14bsf 3.73 gears. More like a 3/4 ton in disguise.

 

[Redwookie]

Yes sir Thunder! Rattler indeed! It's tough to turn your head on the longevity and especially the mileage! I mean we all know gas is gonna go through the roof again it's only a matter of time so might as well be prepared!

 

[Pookster]

I have one in the combination your talking about. I have a 92k2500 ext cab long bed.. with the nv4500 super low first gear ratio, and 4.10 gears.

I actually intentionally upsized the tires. My highway speeds were really high. Optimally, Ive found the best fuel economy in the 1800-2200 rpm range. With the smallish 30-31's stock tire (265? or 275) I was always in the high 2500's on the highway. The OD works well, but I don't tow all that much. And as such, it was not optimal when cruising at 70-75. Its perfect if your cruisng at 55 to 65.

If you stay 3.73's you could probably keep 33's and be happy. I think 35's are kinda sub optimal with 3.73's unless your going 75-80.

 

[Redwookie]

Hmmm..interesting. Somebody told me or I read somewhere that if I was to stick with the gas motor and 35" I may wanna bump the gears to 4.10 or so. And if I was going diesel with 35" I'd see my best mileage and performance with 3.73s. Thanks for the input.