Does anyone know why there is a listed increase in 2005 for MPG? I'm considering buying a used 2003, 2004, or 2005 Sierra and all the used car websites show in 2005 the MPG went up to 19 on the highway.

Cananyone tell methe differences from 2003 to 2005 on the engines to increase power and fuel economy?

Thanks!

 

Electric fans and increased horse power as far as I know was the only difference in the year models from 2004 to 2005. In 2005 the horse power was increased, but I think it was only due to the electric fans.

 

Cool thanks. Do you know if they did the same thing on the tahoe/yukons?

 

On my 05 i have a extra air dam over the 03s and 04s and rear drum breaks and electric fans like said. I do know that i get better gas mileage then the 03s and 04s thats all i know.

 

the only major difference betweent he 04's and 05's was the switch to electric fans and the standard 3.42 gear ratio vs the standard 3.73 from the past years. in ext cab models, 3.73 wasnt an option anymore, just 3.42 or optional 4.10. crew cabs could have all 3.

 

TIMBER74WOLF BEAT ME TO THE DRAW,YES ELECTRIC FANS WAS THE DIFFERENCE.
JB2004 HAS A 2004 THAT HAD CLUTCH FAN,I PUT STOCK 2005 ELECTRIC FAN WITH
A NELSON HARNESS. OPEN THE HOOD LOOKS JUST LIKE STOCK. 2004 5.3 295 H/P
2005 310 H/P THE FANS WERE THE DIFFERENCE IN H/P AND F/M. AND BY THE WAY
2005 WAS THE YEAR THAT THE CHANGE OVER TOOK OVER. THE CLUTCH FAN ASSEMBLY
WEIGHTS A TON.

 

not correct. the fans were not the cause of the hp increase in the 05's to 310. 310hp was a HO version of the 5.3 and it was an all aluminum motor (block/heads) whereas the normal 5.3 was an iron block. the aluminum block (code L33) was and still is rare for the 05-07 classics. the more common 5.3's are the iron blocks.

 

WELL THEN WOULD PLEASE TELL US HOW THE 2005 GOT MORE H/P
THAN THE 2004.

 

The 310hp 5.3 got 15hp more due to the all aluminum design. my 2006 5.3 was an iron block 5.3 (L59)and rated at 295hp. The L33 was considered a High output verison of the 5.3. the HO verison was also only available in the ext cab, 6.5' bed trucks. the reg cabs and crew cabs got either the LM7 or the L59. the L33 was a rare motor.

the print out i have from the chevy website from 2006 lists the differences:

LM7/L59: cast iron block, cast aluminum heads with 9.5:1 compression
L59: flex fuel version of the LM7

L33: cast aluminum block and heads with 9.9:1 compression, everything else is the same.

from what i have read the only difference between the 2003 and 2004 models which in 2004 got a 10hp bump to 295 from 285 was a simple tuning reclaibration.

i have driven both the 2003 (285hp)5.3, my 2006(295) 5.3, and a HO 2006(310) 5.3, and there isnt much difference between them.

in 2005 3.42 became the predominent gear ratio over the better 3.73 gears, mainly for mileage. 3.73 were not an option on ext cab 4x4 verisons.Electric fans also became standard in 2005 or 2006. rear drum brakes replaced rear disc brakes in 2005.

 

bad2006, have you driven the 2003 and the 2006 enough to comment on the difference in gas milage? Is it noticable?

BTW I have a 97 GMC 2-door Yukon with 153k miles. Full Banks exhaust from the headers,K&N Intake, Custom Wester's Tune, etc. It's been a great truck mechanically. I just recently had a baby boy and its kind of a pain to get him in the back seat. On the other hand it still runs well, no car payment, and still 18 mpg on the highway...Just been looking at newer trucks and seeing if it's worth my while.

I would think there would be a huge drop-off in performance by going with the 3.42 gear ratio vs. the 3.73, or at least that's what I've heard with the older trucks.

Any comments or experiences are greatly appreciated.