Hi. I am looking at buying an 01-02 Duramax and was wondering what kind of mpg can I expect with the Allison, a 3.73 rear axle ratio running empty in the city and on the highway? Also does GM offer a lower rear ratio? Thanks for your help!:help:

I'll start the voting at 15 city, 20 highway. There were no gear ratio options available.

hey giltruck98,

I have an 2001 chevy crew cab short bed 4X4 for sale. It is listed in my signature. PM me and I will discuss details if interested.

The only gear ratio in ALL DMax trucks is 3.73.

After 4-1/2 years and 123,000 miles I've got an overall average of 17.4 mpg

My empty in-town runs 16-18

Empty highway runs 18-20

The only gear ratio in ALL DMax trucks is 3.73.

After 4-1/2 years and 123,000 miles I've got an overall average of 17.4 mpg

My empty in-town runs 16-18

Empty highway runs 18-20

:exactly:

Empty in town 16 Empty highway 19

The only gear ratio in ALL DMax trucks is 3.73.

After 4-1/2 years and 123,000 miles I've got an overall average of 17.4 mpg

My empty in-town runs 16-18

Empty highway runs 18-20

:exactly:

Empty runs combined city/highway 20.5mpg.

Empty in town 16 Empty highway 19

:exactly:

hopefully my will change after Wednesday, when I go straight pipe and cut out the stock muffler....

Have 04 LB7, No Mods yet. Best Hwy: 22 Around Town: Between 18-20.

hopefully my will change after Wednesday, when I go straight pipe and cut out the stock muffler....

That will help your EGTs and allow your turbo to spool up quicker, but I wouldn't expect any great mileage gains. I've had a Magnaflow straight-through 4" spliced into my stock pipes for over 3 years.

That will help your EGTs and allow your turbo to spool up quicker, but I wouldn't expect any great mileage gains. I've had a Magnaflow straight-through 4" spliced into my stock pipes for over 3 years.

Well its worth a try. I hear both sides of that discussion. If I get even a 1 mile its worth it.. Saving up for my 5" exhaust :ro) with a cat delete pipe....

It's sure not gonna hurt. The OEM oval muffler is very restrictive, in addition to being very heavy.:eek: I think your mileage gains might be offset by the desire to put your foot into it and hear the big dog roar.;)

I hear you. I won't be able to compare #'s until after a tank or two of fuel....

Im in about the same MPG range , but most the time Im a mile or two on the low side, but thats due to me using Jet-A, hey if its free I can handle low MPG's .

Around town I've been getting 16-18 during normal driving. On the highway which I don't do much driving on cept for trips I get like 20-22. I have a predator tuner and 5" exhaust.

):h I get about 18.5 on the avg. High 20 low 15 towing about 8000 lbs
George

I get 16-17 around town,18-19 highway.I did keep it at 2000 rpm on a trip and got 21.So goes to show the more your in it the less your going to get.

04 cc sb...2WD... I believe 2wd helps a little. 19around town 21hyw running 70-75. I also have a Banks 4" exhaust, thats only mod. I'm very pleased.

Best I ever got was a little over 20. Mostly get around 15-18. Pulling my 28ft Prowler, 8,000lbs, I get 11-12. Sometimes even 13 if it's flat. I was talking to a guy at the rape station, oh, I mean gas station yesterday with a 2004 GMC, crew cab, long bed, who claimed he gets between 21 and 28 because he switched to synthetics. It was all I could do to not ask him if he made it past the 8th grade.....:lol:

after a 6 inch lift and 35's , i get 10-11 towing and 13-14 mpg around town. but it was worth it! :ro)

2003 4x4 cab and a half 50,000 miles all stock 17 around town 22 highway 70 75 great for a 6,000 pound truck

The only gear ratio in ALL DMax trucks is 3.73.

After 4-1/2 years and 123,000 miles I've got an overall average of 17.4 mpg

My empty in-town runs 16-18

Empty highway runs 18-20

Ditto , hand calculated , best was 21.6 ,NH to MD all interstate in the summer

16mpg city for me and have never calculated highway as I drive too fast to get good mpg.

15-16 in town,16-19 highway(75-80) it really depends on terrain. real flat and I can go over 20 pretty easy, but any ups and downs(even minor ones) and it drops to 17-18. I just put in my new transflerflow30 gallon cross bed so I should be able to go so cal to montana this summer non-stop.

18-19 commuting, mostly highway
15-16 pulling 2500# open trailer, highway 80mph+
16.5 Albq to Denver empty, 85-90 mph, in a rain storm
17.8 Denver to Albq, 85-90 mph

Hand Calced

Gil,
Missed if you were talking 3500 DRW or 2500HD. I have K3500 DRW CC LB, 15.5-16 daily driving, 12 flat towing. I have ~120 K miles. I have a lot of extra weight on truck. I have 60 Gal tank and Reunel frontend replacement with Warn M 15000 winch. I have added 1100 lbs to my truck not counting tool boxes and gear.