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Chevy Silverado/GMC Sierra's w 8100/Allison



  • falknorfalknor Member Posts: 27
    Took delivery of my LT Excab 2500HD 8.1/Allison 4.10 loaded Wed. Its great to have it. The first tank of gas I got 11.8 MPG on the dealer,s fill up and on the second fill up got 12.86 mixed 40 city and 60 Highway not a big foot driver. The power is just awesome. Had Lounere SS nerf bars installed today. Its looks so good. Just hard to believe that I have such a truck. Happy trails to you. Dave
  • loyalgmcguyloyalgmcguy Member Posts: 64
    As promised, here is a gas mileage update on my 8.1, Allison, CC, 3.73. Around town (stop and go, no highway miles, etc) I had been averaging about 10.5 mpg with my standard 245 treads. Two weeks ago I upgraded to 265/75 BFG All Terrrain T/A's. I checked mileage twice over the past week on my daily work drive and found it had fallen about .5 to .6 MPG. Latest tank was 9.7 MPG. Tank before that was 9.9 MPG. I am curious of the experience of the 4.10 guys who have increased tire sizes. Did you witness a drop in MPG?
  • smart99smart99 Member Posts: 48
    I've got the same combo that you have on order. It should be here either this month or next. On the 4.10 query I had this in my 5.3 and I swapped to 285's. I lost about 1.5 mpg. However please note that I never recalibrated the speedo. I checked it with a GPS unit and it was so close that I didn't think it was worth the trouble.
  • jumpinjjumpinj Member Posts: 1
    I'm thinking about getting a 2500 HD 4x4 LS. I'm wondering what is a good price Can anyone help?
  • mdirvinmdirvin Member Posts: 8
    I'm interested in hearing if anyone has pulled a 14000# 5th wheel over a high mountain pass, Say 12000 to 14000 ft. I have ordered a 8.1/Allison/4.10 2500HD with extended cab. I am hopping that it will be able to handle the load OK.
  • redi2retireredi2retire Member Posts: 2
    My wife and I will be purchasing a 2002 GMC 3500 dually, 2WD, Ext. cab, Vortec 8100 (or 6600 Duromax), SLT for a firm delivery date of Jan 12, 2002. We will be towing a 15,000# fifth wheel about 25% of the time all over the United States, Canada, and Mexico during the following five years as full timing RVer's.
    This is our initial contact at Edmunds forum and would appreciate any assistance in the way of:
    1. Price negotiating & expectations (our last vehicle purchase was in 1987).
    2. Options, ordering, & delivering.
    3. Gas vs. diesel (performance and cost factors).
    4. Surprises (good and bad).
    5. Any other areas for assistance.

    We thank you for your assistance and input.
  • mgdvhmanmgdvhman Member Posts: 4,157
    to become a full time RV'er....for 5 years...I'd have a Duramax over an 8.1.

    ..every day stuff and a few trips here and there..I'd get an 8.1

    - Tim
  • bigred17bigred17 Member Posts: 12
    Just received my 8.1 I I 3.73 two wheel drive extended cab and here is the mileage so far.

    1st tank 80% city 20 % highway = 11.2 mpg
    2nd tank 95% highway 5% city = 14.0 mpg at 65 MPH
    Had tough time holding it to 65 MPH. Truck does not work at 65 and wants to go faster.

    Truck ride is better as I put on more miles.

    For the person who asked about the increase wheel size and the impact on mileage. Dealer warned me that when you increase the size of the tire, you could lose up to 2 miles per gallon. You then have the problem of towing heavy trailers as there are no tires larger the 245/16 that have an I rating that the dealer was aware of. The I rated tire is necessary for the heavy loads.

    For the person who asked what is a good deal on the truck. I bought mine for 500 over dealer's invoice but I had to order it and could not take one off the lot. I knew the owner and that helped. No other dealer would even talk to me about 500 over and I went to alot of them.
  • bigred17bigred17 Member Posts: 12
    Everytime I used the letter E, the message used I. The e rated tire is the one that gives the HD the towing capacity. According to the dealer, he is not aware of any tire larger than the standard tire that comes with the truck that has a E rating. If you chose to use a bigger tire, you lose the towing capacity.
  • falknorfalknor Member Posts: 27
    I got my LT 2500HD 8.1 allison 4.10 loaded at invoice price at Huffines Lewisville Tx.972-221-8686 Paul Morse started at $500.00 and came down to invoice price. Love that truck. Happy trails to you. Dave
  • n75v111n75v111 Member Posts: 243
    Been installing rear splash guards and because there is NO SPLASH protection around the rear wheel section been enclosing that area down to fendor splash guards and the spring level all way around. Don't like the wheels throwing crap back against the rear bumper area etc.

    Question - I have noticed that I can look into the right side dash aircondition outlet and see the floor courtesy light. Haven't take a mirror to investigate but assume some AC hoses are disconnected. ANYONE CONFIRM THIS FROM YOUR UNIT.

    LT ExCab 4x4 SB


  • davidj6davidj6 Member Posts: 1
    will 285/75/R16 fit on the stock 2500 HD wheels? also is there any rubbing of the fenders? Or will the 265/75's BFG MT's work better, anybody have any updates on 8.1/alli/ 3.73 or 4.10, 4wd mileage with 285/75's? email me with results please [email protected] thank you
  • jgmilbergjgmilberg Member Posts: 872
    Did you have your speedo/odometer re-calibrated after you had the tires changed? If not this is why your mileage is changing. You can got to the dealer and tell them to re program the speedo with the Tech 2 computer. Takes about 5-10 min and your speedo/odometer will read correct again.
  • obyoneobyone Member Posts: 7,841
    While that's true, they cannot reprogram for non stock sizes like 285/75R16 or 305's.
  • markbuckmarkbuck Member Posts: 1,021
    Load Range E = 80psi. Typically around 3,000 lbs per tire on sizes 245/75-16 or 235/75-16. Goes to 3,250lbs or so on 265/75-16 which Michelin and Firestone make and are OEM on the F350SDs....

    Load Range D = 65psi. Typically around 3,000 lbs per tire on sizes 265/75-16 or 285/85-16. Almost everybody makes these tires.

    All that matter is load carrying capacity. And for towing, that's usually not too important. Load carrying capacity is more important when you go lots of stuff in the bed (or a heavey 5th wheel).
  • sf0383sf0383 Member Posts: 204
    I read your post and thought "What the hell is he talking about?" Then as luck would have it I needed to walk next door so I got a flashlight and stopped in the parking lot to take a peek. Well I'll be damned if I didn't seem the light bulb when I first looked. Upon closer inspection I see that there is actually a slot cut in the air duct that part of the mechanism that opens and closes the vent rides in. That's how we can see the light. It looks like the air duct comes from in from the center of the dash.
  • n75v111n75v111 Member Posts: 243
    I thought for sure Pontiac Assembly had probably left half of my AC plenium out or something and the dealer was going to have to tare my whole dash appart to fix it.

    Thanks for the quick look see.

  • loyalgmcguyloyalgmcguy Member Posts: 64
    Thanks for the speedo recalibration advice. I'll try it and let you know if it affects my MPG calculations.
  • gulfguygulfguy Member Posts: 30
    What are you using for splash guards in the rear wheel wells? Its a maze of nooks and crannies for dirt and mud. Do the plastic liners from Suburbans/Yukons fit or what?

    I'm still looking for some functional and non obtrusive boards for my crew cab HD short bed. Owens products has GlaStep with functional box boards but the are over $800 PLUS tax. Ideas?
  • eric2001eric2001 Member Posts: 482
    Hey anbody waiting still on orders? Any word on hold-ups? Just curious, if people still waiting, will order from 2/20 make it in?
  • falknorfalknor Member Posts: 27
    If anyone is interested Covert Chev in Bastrap Tx Harry Green (800-938-7076) will have a LT 25HD LB with 8.1/allison 3.73 pewter loaded in about 4-6 wks. I ordered this truck Nov 22 and gave up on them and found another truck and bought it. Two days later GM picked-up the order. Harry will work with you on this truck. When I ordered it he priced it to me for $500. over invoice. If you have any questions e-mail me [email protected] Happy trails to you. Dave
  • n75v111n75v111 Member Posts: 243
    I installed the Molded Style of Splash Guard off the fender flange as normal (Found them at Wallmart to fit the 'ado & Sierra's without Flairs - I removed the 'Ugly Black Flairs'- Style F - $17.95 fit perfect --I know Ryan found Huskys to fit the Flairs).

    Note there is a flange extending down from the formed wheel well cavity (that goes up into the box)- all the way around it-front, inside & rear--(look over the top of the wheel to see it--

    I made a template that started approx. from the center of the formed wheel well (just above the axel) and rapped it around behind the wheel out to the inside of the fendor flange where the SG attaches also. After I got the template to a shape to fit from the upper flange down to just above the springs, I cut the final molding from a flat sheet of black poly platic (actually i used those Kid's 'mini-bogon flat sheet -18"x48"- things they use to go sliding on that I found at WM before X-mas - Takes total of Four) and pop-rivited it to the flange and down level with bottom of the body fenders and to the molded splash guard itself so it kinda all becomes one piece assembly after installed.

    I will do the same with the front half.

    This forms a totally enclosed inner fender so to speak that at the rear is almost level with the very bottom of the molded flair so almost no crap can be thrown back into the spare tire or bumper areas. And the same for the front half.

    Know this is kinda rough discription so if i'm not too clear i'll give it another try if you like.
    Just picture that when you look inside that wheel area it is totally enclosed level with the bottom of the front and rear fender on all three sides and is a couple inches above the Leaf-Spring Pack.

  • gmcgtgmcgt Member Posts: 15
    Eric, I've been waiting on my order since 9/21/00 when I placed it with the dealer. Yesterday 3/6/01 I learned that the build date is the week of 3/26/01 and I should take delivery of my GMC3500, 4x4, SLT, 8100, Alli, around 4/13/01. Good luck on your PU.
  • 1i2cu1i2cu Member Posts: 32
    Now its March 26. Something about they (GMC) want to do it right. Third change to TPW.
  • eric2001eric2001 Member Posts: 482
    Sorry to hear about your long wait. But on the other hand, from what everyone is saying, it seems worth it. I am wondering if I should talk to the dealership yet. Alot of you guys got GM acceptance dates for the order (not build dates). When do the dealers know this?
  • loyalgmcguyloyalgmcguy Member Posts: 64
    You caught my interest with your splash guards and flair removal. Any photos?
  • 1i2cu1i2cu Member Posts: 32
    I knew two days after I ordered the HD. The truck manager from the dealer called to let me know that the order was acceptance and the first TPW.
    With the price of gas going up to about $2.50 a gallon this summer, there will be a number of BIG BLOCK HD's available. What, me worry ?
  • gordo13gordo13 Member Posts: 20
    Where did you hear that and did they say what's driving the price up?
  • eric2001eric2001 Member Posts: 482
    Thanks for the reply. Ignoring my ignorance, what is "TPW"?
  • 1i2cu1i2cu Member Posts: 32
    'TPW' To Production Week. Gas prices are going up due to the summer additives required by law.
    I heard this on the news.
  • redi2retireredi2retire Member Posts: 2
    How do I find the messages I have posted and any responses to them? I can't seem to get anywhere in this message posing forum. If anyone knows how to do this would they please email me directly (since I can't find anything in here, I certainly wouldn't be able to ferret out any response).

    Thank you

    [email protected]
  • n75v111n75v111 Member Posts: 243
    8100/3.73 ---- First two half a tanks 10.3mpg -- driveing mixed town/hwy - but still 'lightfooten' it.

    Have pictures with 'Ugly Black Flairs' removed, Stones replaced with Cooper WL 245 'E's A/T's today
    (Tire dealer orderd in Michlen 245 'E's but turned out NA w/White Letters so said to heck with and put on the Coops - They look good and better warrenty-- what the heck!!!)

    Also got Boards on -- God!! It's been a Pain in the *** just getting in to the dard thing and my wife kinda has bad knees so we had to do something.

    I'm going to do a follow up post to see if i can just drag the pics into it and post em that way but if it don't work send me your e-mail address. ([email protected])

    Holding my breath - Here goes Nothing.

  • n75v111n75v111 Member Posts: 243
    Post some very very easy to follow step by step A, B, C posting instructions or send me an email

    Sorry!! 75v
  • falknorfalknor Member Posts: 27
    We went to see our son this week-end. 642 miles aout 95 percent Hwy and 5 percent town driving, and averaged 12.29 MPG. Ran about 75 most of the time. I let my son drive while we were there and he took it on the Highway and ran it up to 90 MPH for a short period. Truck runs and rides great. I have the LT 8.1 w/allison 4.1 2500HD loaded. Happy trails to you. Dave
  • n75v111n75v111 Member Posts: 243
    Have 'ado 8100/4x4 HD SB & getting ready to mount my Reese 15000.

    Starting to determine how much rear window clearance vrs Axel to window space to decide just how far aft of the Axel to position the PIN pivot location.

    Talked to Hitchhiker dealer today and he said that Reese has and Slider Adoptor Devise that allows you to mount the 'A' Frame and Hitch tilting platform support assembly directly to which inturn allows approx. 9" slide back when parking. Reese dealer catalog show a price of about $330 but can't tell how it works in combo with current 'A' Frame hitch unit.

    Can't seem to get into the Reeseproducts web page but don't think they do a very good jop of showing detail anyway.

    Anyone know the 'nitty gritty' details on this??


  • loyalgmcguyloyalgmcguy Member Posts: 64
    I always heard TPW stood for Target Production Week rather than To Production Week. My "target week" was bumped several times. I checked my mileage again. It is holding at 10 MPG with a combination of 70%city/ 30%highway driving. Without question I lost .5 to .7 MPG moving up to 265 tires. n75, thanks for the address. I'll be in touch.
  • eric2001eric2001 Member Posts: 482
    Saw TPW on another sight. Guy sounded like someone in authority @ Pontiac plant in Flint. He said it was Truck Projected Week.

    On another note, if you had it to do all over again, would you still go with the 265's, or something else?
  • bsilerbsiler Member Posts: 30
    having Allison problems yet. I would like to hear about the goods and the bads!

  • hunter98hunter98 Member Posts: 273
    People that want to change out to a taller tire for looks, really ought to look at a premium 235x85R16. They are the same height as a premium brand 265, are about the same width as the factory, and may actually increase milage because of the 4% more distance traveled per engine revolution. The only possible decrease would be from increased air flow below the truck.

  • markbuckmarkbuck Member Posts: 1,021
    Agree 100% with you on the LT235/85-16 E choice for the HD line...
  • khbushkhbush Member Posts: 19
    I have the reese quick slide you are talking about. You use the same bed rail insatll kit but evrything above that is different. The whole apparatus slides rearward 9 inches to give the necessary clearance. I have been told that mounting a hitch back of the axle severely affects handling. If you have the installation kit the hitch is about $500 at
    If you need any more info email me at [email protected]
  • eric2001eric2001 Member Posts: 482
    For all of you that have ordered these wonderful trucks, how long did it take the dealer to give you any information? I ordered mine 2/24 and the dealer has no information as of yet. They claim the computer doesn't show anything, yet other people stated the received the TPW & SON (truck projected? week & sales order number) within days of ordering. Could my dealer be holding out? Maybe he didn't have the allocation? HELP!
  • sf0383sf0383 Member Posts: 204
    It probably has to do with allocation. I waited 8 or 9 weeks after placing the order to get the TPW ( Targeted Production Week )Once you get that things start to happen pretty fast. Supposedly Chevrolet "pulls" the orders once a week. Your dealer should be able to tell you which day. Then it is a matter of calling them once a week or so to see if your order has been pulled and assigned a TPW.
  • falknorfalknor Member Posts: 27
    You are most likely right about not having an allocation. I placed an order on Nov 22 and ended up cancelling it on Feb 28 as I found a LT 2500HD LB at another dealer and bought it. Two days after I canceled my order the dealer received a TPW. He said that he will go ahead and get it in and sell it. Coverts Chevy in Bastrap Tx has this truck coming in.(Harry Green 1-800-937-7076) Happy trails to you. Dave
  • nelson22nelson22 Member Posts: 3
    I'm new here and would have noticed that there seems to be some very knowledgable people here. I see that with the diesel or 8.1L, the four-speed auto tranny is not an option. That tells me that it must not be beefy enough. According to edmunds though, a manual five-speed or manual six-speed is available. Does anyone have experience with these transmissions. I drive a stick now and don't mind one bit. It looks like it would save a chunk of money also. Thanks.

  • n75v111n75v111 Member Posts: 243
    everone for the info on the Slider for 8100/3.73 LT 4x4 SB

    THIS TRUCK IS AWESOME!!!! Quality looks to be excellent. All you guys waiting hang in there.
    Ordered Sept. 05 delivered March 1st.

    But Get Rid of the Firestones.
    My Cooper/Michlien tire dealer exchanged (4) for Coop 245 WL A/T E's for $198.00 on road (they looks great).
    Mich's were going to be over $400.00 and they don't even make em in WL's plus NO road hazzard.

    I have the 15000 w/o the slider - Ordered today the Slider unit to switch my 15K over (which i have not mounted in truck yet) -- Use my rails and upper yoke/tilting head assy etc.

    Kwik Slide conversion $245.00 plus 32.25 UPS shipping from Discount [email protected] San Jose--(local best price was at list $330.35 w/no certain on hand date)-should have end of week.

  • eric2001eric2001 Member Posts: 482
    The 8.1 or the 6.6 Duramax are both available with the 5-speed automatic, or the six speed standard (not in LT/SLT flavors). The 4 speed auto is for 6.0 only. The bigger motors have the Allison auto trans with many nice features. Pick your flavor.
  • eric2001eric2001 Member Posts: 482
    According to my dealer, he had the allocations, and was given an extra window for another the weekend I ordered. Or maybe they are just salesmen, yanking my chain...
  • sf0383sf0383 Member Posts: 204
    Another place you can look is at They have a section there that will show what cars and trucks are on hold for whatever reason at the different manufacturers. It could be that some particular option you have ordered is on constraint. From my own experience and others that I have read here you can expect to wait 12-16 weeks for the truck. Anything faster than that consider yourself lucky. But they are worth the wait

    Good Luck
  • n75v111n75v111 Member Posts: 243
    Well, Obviously it's taking me awhile to get totally use to this 8100 LT.

    I just noticed that my 'REMOTE Cassette Tape Player' is a 'REMOTE CD Player' instead. (AND NO it does not function other than to fill in the hole)

    Just when I had been braging about GM Quality (:-)

This discussion has been closed.