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6.2L/6.5L Tech Tech forum containing the best technical information about these engines. Please post in the related 6.2L & 6.5L forums. We'll transfer the best topic threads to this forum.

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  #101  
Old 05-15-2013, 07:55 AM
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Robyn Robyn is offline
Missy Good Wench ( Moderator)
 
Join Date: Apr 2001
Location: Newberg Oregon
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Your Tahoe is very similar in size to a K5 Blazer and they would do 25 mpg hwy with the 6.2 n/a engine.

The 6.5 td has never been a miser on fuel.

Our 94 Burb got 20 mpg once on a trip, but usually it get 17

Missy
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  #102  
Old 06-16-2013, 04:58 AM
greatwhite greatwhite is offline
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Quote:
Originally Posted by dragonriot View Post
So this thread was necro'd about a year ago, but after reading everything I thought I would chime in with my situation as well.

My truck is very stock on the outside... no Chicken Lights, stock mirrors, no bug shield, and nothing else that would increase the Aerodrag on the truck. I have fairly large tires, about 32x10x16.5 in US measurements, and hardly ever tow anything larger than a 150lb boat on a Sunfish Trailer. (speaking of which, I need a new sunfish trailer, if anyone has one laying around) My mods include a Turbo-Master set to Heath Specs, a performance chip from Heath Diesel, newer glowplugs, new PMD on a FSDCooler, removed Air Intake Ring, and don't have anything blocking the radiator or bumper holes in the winter (though I know I should.)

At 65mph in Overdrive, I'm running at ~1950RPM, and in Summer I get about 21mpg highway and 18 in the city. In Winter, with Primrose Winter Power fuel additive, the best I've seen is 17MPG on the highway and 15 in the city. I don't know my final gear ratio, but I think it calculates out to about a 3.42 rear end, as I got a 3.10 calculation from my Overdrive RPM. When I checked it without overdrive, I was hitting about 2400RPM at 65 in third gear, and it just didn't sound very nice so I have only run that way once for the purpose of testing.

I would like to get up to 24mpg without spending a crapton of money on the mods, as the truck already has 221,000 miles on it. I still have thoughts of doing a Cummins 4BT swap eventually for the magical 35MPH they are advertised to get in these trucks, but I'm pretty sure it would be cheaper in the long run - even with increased repair costs - to buy an older mercedes 300D or VW TDI when my engine decides to go the way of the dodo. I know that's blasphemous to say in here... but our trucks are becoming more rare, and harder to find parts and replace big ticket items.

Actually, if you`re getting 21 MPG right now, you`re probably getting better than 75% of the people running a similar truck.

Most are somewhere in the 14-17 mpg range.

Looking at your specs about all I can suggest is giving Bill a call and see what can be done to your tune. Most calibrations are for performance and mileage is often a happy byproduct. Bill might be able to squeeze a few more MPG out of your truck, but I would be skeptical of a 220,000K 6.5 TD getting to much closer to 24.

Good luck with your quest.

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  #103  
Old 06-17-2013, 12:38 PM
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TDSECK TDSECK is offline
1999 Suburban LS 6.5 4x4
 
Join Date: Oct 2011
Location: Collingswood NJ
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Default 1999 2500 Suburban 4x4 mpg

I just had my 4:10 ratio axle replaced with 3:42 after much reading and thought about it. I also had the factory posi replaced with an Eton unit.

Thanksgiving of 2011 I towed my old 91 Montero 4x4 to Maine on a U Haul trailer and got around 15 mpg from NJ. I didn’t go past 55 mph for the trip.
On the trip home I got 18 mpg but had to keep the speed under 60 mph as I didn’t want to go past 2000 rpm for my 6.5. It was tuff having every one pass me for the whole trip home! So it was bitter sweet, good mpg but a very slow drive.

This Sub was very well taken care of by the pervious owner. It has 1149000 miles on the clock and runs and starts well.
The only mod I can see is the FSD has been replaced and relocated in the front bumper. Also the exhaust system is 4”. I replaced the straight through type muffler with a 4” reveres flow muff to lower the noise level inside.

I am planning another trip to Maine in July and will let you know what mpg I get with the new gearing.

So far I like the 3:42 gearing MUCH better than the 4:10
I have no plans to do any heavy hauling with my Burb. I bought it for long trips and hauling big stuff inside with the 3rd seat removed. (a 4x8 sheet of dry wall or plywood fits right in!
So far:
Less engine and exhaust noise (no one talks about that)
Less engine wear per mile
Hopefully better mpg

Some one said the having 3:42 gearing makes your truck or Sub a dog! I disagree! It’s a diesel and now the rpm’s are 1200 to 1500 for everyday driving around my NJ suburbs right where it should be, in my opinion.

The Trany Shop offered to recalibrate the vehicle speed sensor buffer but I felt I could do it after reading about it in the Vol 1 Book about the 6.5.
Has any one out there done that mod them selves and or installed the 7-position dip switch instead of the jumper settings?

PS: FYI I wanted to install a overdrive unit but found out from the mfg that the “Auto” type transfer case that is in my Burb is a one piece unit and can not be split apart for the install, other wise I would have gone with the overdrive unit…
The manual transfer case will work with the overdrive unit I looked at.
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  #104  
Old 06-22-2013, 11:38 AM
DennisG01 DennisG01 is offline
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VSSB re-cal... yes, have done it. I bought a DIP switch (after I did the recal) with the anticipation of soldering it in for future use but never did. Either way, it's a pretty easy-peasy thing.
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  #105  
Old 06-25-2013, 10:49 AM
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TDSECK TDSECK is offline
1999 Suburban LS 6.5 4x4
 
Join Date: Oct 2011
Location: Collingswood NJ
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Default Vssb

Can you tell me where you bought the dip switch?
Radio Shack no longer sells the one shown in the Article written in the Turbo Diesel Vol 1 Page 51
Also I can not fig out how you translate the divide code into ones and zeros.
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  #106  
Old 08-31-2013, 02:09 PM
greatwhite greatwhite is offline
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1998 K2500, ECLB, Auto, 4:10, 265 75 16.

Latest results are 18 MPG combined.

Combined is roughly 60% highway, 40% city. Highway speeds not above 100 Kph, windows up, AC on.

Just switched rims to a set of PY0's from a later 2500HD. Requires far less throttle for same rate of acceleration and lighter touch highway to maintain speed.

Weights:
steel wheels scaled at 34 lbs each
PY0's scaled at 17 lbs each

That's 50% savings at each wheel in rolling mass.

Hoping for a small return on the less rolling mass. Would be overjoyed with even 1 mpg increase.
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  #107  
Old 09-16-2013, 06:26 AM
DieselDavy DieselDavy is offline
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Wow,
While 68 lbs are a lot to haul down the road, I'd be surprised if you gained 1 mpg.
Let us know how it works out!
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'97 2 Dr Tahoe, Intercooled,
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  #108  
Old 09-16-2013, 06:28 AM
DieselDavy DieselDavy is offline
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Wow!
While 68 lbs are a lot go haul down the road, I'd be surprised if you gained 1 mpg.
Keep us updated on how much you gain!
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Dave's Diesels:
Sold June, 07 '82 1/2 ton 4X4;340k miles
'97 2 Dr Tahoe, Intercooled,
Kennedy ECM, 4" Exhaust
'02 GMC
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