Chevy Silverado/GMC Sierra's w 8100/Allison



  • n75v111n75v111 Member Posts: 243
    8.1 alli 3.73 at 1500 mi and running good == no knock!

    If your getting the knock with the Syn. I think it would be worth while changing oil again back to non-syn. At least you would have a comparison!!

    Mobil falsified data on their Aviation Syn. product and had to get out of that market. Personally I don't trust Mobil for any thing.

    Just a thought!!

  • elderdog1elderdog1 Member Posts: 10
    just checked milage again today overall driving not towing anything ,last tank 10.94, also just purchased 7 qts mobil one and new filter, haven't changed yet , and don't have any knocks, do i want to switch or not ?
  • khbushkhbush Member Posts: 19
    Read your post re slider brackets. Mine the front bracket rear edge is about 2" forward of the seam you mention. Installer didn't have to drop the tank to do it that way. The bracket is on the outer side of the frame with the top "L" pointed to the center of the truck. I think this position gets you a little ahead of the axle.
  • tomh12tomh12 Member Posts: 240
    The Mobile one is not causing the knocks. Switch when you get about 5000-7500 miles on the engine.
  • n75v111n75v111 Member Posts: 243
    Thks for that position confirmation. Wasn't sure how far ahead i could move the front 'L's and still not drop the tank.

    2" forward of the weld seam - if all my measurements were close - would put you about 1 & 1/16" ahead of the axel (if Reese K/S).

    What Hitch do you have? 15K Reese kwik slide?? What is your towing position 'Pin' measurement from the rear window glass or front of box??

    Wonder if you could also confirm your measurement of the front rail front row of sq. holes from the rear of the bed floor - you know-(right where the tail gate closes next to).
    If my measurements are close your measurement should be about 52&1/8".

    Top of 'L' will point in as you said and will use the outer two front rail holes (40 3/4" C to C) & the front centered slot of the 'L's. (Truck frame rails at that area are 44" apart outside to outside.)]

    Thanks for any trouble but nice to have comparison (measure twice/cut once type of a deal)

    Thanks - 75v
  • khbushkhbush Member Posts: 19
    Measurements as follows: 2 inch from weld was eyeballed. Is actually 2.5 inches. 3/4 inch back from tubular cross member at front of bracket.

    I have 14k slider. From rear window on ext cab to centerline of hitchpin hole is 40". From front bed floor is 25.5" back to leading edge of front bed rail of hitch mount.

    From rear of bed floor to front rail square hole is 52.5"

    I remember the installer measureing in the bed with the assembled hitch in place and marking holes. I'm pretty certain after setting hitch in bed he drilled bed holes and then put the brackets on the frame where they fell based on bed holes. Front rail the 2 bolts on each end of rail are in first holes. The rear rail the bolts are in second hole from the end on each side.
    Hitch sets centered from side to side.

    If you need any more measure. let me know.
  • ryanbabryanbab Member Posts: 7,240
    Did you remove your fender flares?

  • blackchevyblackchevy Member Posts: 12
    I was just told my truck that I ordered in late January (LT 2500HD 8.1 Allison) was built and would be here in 2 weeks. I got it with a 3.73 axle ratio. I pull a 8,000 pound trailer for the five vacation weeks I get at work, the rest of the time I would use it to drive back and forth to work(five miles). I was told you get better mileage with the 3.73 but sacrifice the pulling power by not getting the 4.10. I wish I could find out the difference in mileage between the two. I know the 3.73 will tow my trailer without a problem but if I was only saving 1 mile a gallon I wonder if I should have got the 4.10. Any help from people with the 3.73 or the 4.10 would be appreciated. I have a 5.7 chev silverado now and it has problems on steep hills pulling that trailer. Also comparing the HD2500 to my old 95 5.7 1/2 ton I noticed the HD2500 was alot higher to where I need steps or running boards anybody find some that look good wihtout spending a fortune? I am also wondering if anyone who has a trailer noticed a big difference in the ride since using the 1/2 ton was a roller coaster on some of the highways? My trailer is a travel trailer and not a 5th wheel. I also had a problem with my trailer swaying to where it rolled onto it side,and had to be almost totaled,but was fixed by the insurance company. The trailer company couldn't figure out why it happened. It wasn't windy and it had already gone almost a 100 miles without a problem. This is why I moved up to the 2500HD for fear it would happen again. Any help would be appreciated
  • jackson43jackson43 Member Posts: 15
    Response to #259

    BlackChevy, I pull a 30 foot,8000 lb travel trailer (~950 hitch weight) with my 1989 350 G20 Chevy Conversion van with 3:73 gears with no problems. I took a 10,000 mile trip from Florida to Washington State through many mountains. I've done all the right things to this tow vehicle to handle the load (ventilated rotors, new front springs/gas shocks, 4 transmission coolers, engine oil cooler, rear air shocks, added spring in the rear, rear anti-sway bar, posi-traction, etc)

    I use 1000 lb weigh distribution bars and two (2) anti-sway bars...this is important.

    In my opinion the 3:73 gears you ordered are fine for what you are towing, and you wouldn't have needed the 8.1 to do the job.

    I'm seriously considering a 2002 2500HD Extended cab sb to pull a 11,000 5th wheel, and based on my experience with the 350 and 3/4 ton chevy van, I may very well go with the 6.0 rather than the 8.1.

    Hope this helps, John
  • n75v111n75v111 Member Posts: 243
    Yep! Sure did. Dealer had them off before I picked it up. laying down in the basement collecting dust.

    Boards --
    HD 4x4 8100 alli SB does set too high (guess its the Ford/Dodge thing i could have done without) to not have boards for us.
    Went with single piece front to rear wheel (really strugled with that decission)that have three L shaped frame mounted brackets with rubber splash guards each end (super strong to stand on) to take care of any flex issues - installed about $360.00. Extruded Alum w/anodized black step area and chrome looking outer edge. Really matches up well with the LT chrome body side stripe and the Access Tonnue cover with chrome rails -(Indigo Blu).
    Note the HD cab does not have a flange to mount to so if you don't get a design that keys off the frame the hangars have to be about 2' long up to the floor pan area-- didn't like that idea!!

  • ryanbabryanbab Member Posts: 7,240

    You should try and sell them im sure someone would buy them
  • elderdog1elderdog1 Member Posts: 10
    thanks tomh12, i'll wait awhile before i switch to mobil one ,only have 2600 miles as of this date' i will also be installing a fifth wheel hitch , i have 35 foot yelloestone dry weight of 10,700 lbs. i have the 3.73 rear end,love the truck so far ,almost bought a ford v 10 , caught myself just in time
  • blackchevyblackchevy Member Posts: 12
    Jackson43, My 1/2 ton Chevy Silverado with the 5.7 has the trailer package on it with the heavy duty shocks, transmission cooler,etc. When I bought the trailer they said the 5.7 could pull it but most trailer people suggested getting a 3/4 ton because I was getting close to, in pounds ,to its capacity for towing. I also had two anti sway bars and a weight distribution bar which looked like prezels after the roll. The only reason I could think of for the roll was I did't have the hitch fully engaged on the ball, but why after 100 miles did it become engaged because I had pins on it to keep it from coming undone. The trailer just started swaying from side to side farther and farther until it rolled on its side.It sounds to me like you really had that van ready to pull that 30 footer. I have a 26 foot Sierra and when I pull it up a steep hill(For example we have a hill out here in California called the Grapevine) it starts pinging and slows to where I have to shift it into Low 1 and crawl over the mountain. You have 3 transmission coolers well I hope I don't need to add one to this HD2500,but I figure it has a transmission temp gauge so if its hot I will know it and can pull over to let it cool. I also had a problem with the trucks headlights going up with the trailer in the back so I added the Monroe Mussels. They are like little rubber shocks that replace the rubber piece where you bed hits the axle when it has a load. Thanks for your help
  • gmcgtgmcgt Member Posts: 15
    Any idea how I can track the delivery of my PU knowing the VIN#.

  • msbergermsberger Member Posts: 1
    Ordered my C3500CC on 1/27 from local dealer. Can't obtain a build date for any time soon. Customer relations no help. Told there is a similar vehicle in Ohio, or Texas, or CA on the lot, not sold. Does this make sense to anyone?? Similar problems out there, sure would like to know how you handled this.
  • loyalgmcguyloyalgmcguy Member Posts: 64
    I have a 2000 5800# Prowler 26H trailer that I pulled with my 97 GMC K1500 4x4. Despite a proper sized equilizer I have almost lost the trailer twice traveling down the Interstate at 60 MPH. Worse, my 97 would really heat up on the high Montana passes despite slowing to 30-35 MPH. This was my main reason for purchasing a 2500 HD. You should be able to get by with the 6.0 and save a little gas....but only a little. My 8.1, Allison, 3.73 crew consistently delivered 10.5 MPG around town and 13.4 on the highway until I moved up to 265 tires and lost .5 MPG at both ends. If I had it to do over, I'd still order the 8.1 with the Allison. It's a nice package.

    Note to Ryan and n75. I've had my black fender flares in my local newspaper classifieds for over a month for $150 for the four flare set and haven't had a nibble. I'll take best offer if you know anyone interested..
  • ryanbabryanbab Member Posts: 7,240
    Sorry man i already have a set on my truck


    In their forum section they have a place where you can place ads.

    Try that i have heard a few people asking for fender flares.

  • cowboyjohn1cowboyjohn1 Member Posts: 125
    I sure wish I could get that kind of gas mileage out of my 8.1, allison, 2500HD. I only get 9.5 to 10. But I will be in Montana soon and maybe the high country will boost it. Where do you live in Montana? I used to live in Nye.
  • n75v111n75v111 Member Posts: 243
    For what ever reason, I have alway experienced 3 to 5 mpg increase with every vehicle (that has been fuel injected) when driving in the Western States HIGH COUNTRY. Buick PA V-6, Chev 5.0 PU, F150 5.8, Seville North Star-- So hope 8.1 alli also.

  • owenm1owenm1 Member Posts: 29

    What can I do with this VIN? I know that some of you were able to track shipment.


  • noobie1noobie1 Member Posts: 326
    Re: #233 and #235
    2001 Chev Silv 2500HD 4dr Ext Cab LT 4WD w/Onstar

    There is apparently some confusion by Edmunds about the LS and LT equipment groups for this truck, the LT being more expensive, differing in price by almost $4000. Both list the same price for the Allison option: $1974 (inv.), $2295 (MSRP). However, given that the LS comes standard with a 5 spd. man. trans., the 4 spd. auto standard in the LT should offset the cost of the Allison by about $1000, the approximate amount of the error. I just ordered this truck yesterday and will pay $1032 (inv.) for the option. With all due respect to our host, and considering the monumental task of keeping all this *@%## straight, buyers entering the arena armed with this (Edmunds) price are gonna get carried out on a pole. I just emailed Edmunds about it. Hopefully, correction follows.

    - Dave
  • loyalgmcguyloyalgmcguy Member Posts: 64
    I live in Butte. It's a nice place to live.
  • n75v111n75v111 Member Posts: 243
    Boy! Thanks alot for getting those Dim. Confirmations so quick to last week.

    After a thousand times of measuring everything I drilled my floor using a very precisly measured cardboard template and used 52.8125" dim from the back
    (I didn't want to use the hitch because its too heavy for me to move around and didn't want to scratch up the floor in the process plus with the template everything was square without X measuring process on the hitch it's self).
    I kept getting about a 5/16" discrepency between what I was measureing and the 52.5" when I plumb-lined up over the bed sides and down to the frame for the front L's. Those front L's have to be exactly where you said. You got about +/- a 1/4" because of that access slot in the side of the frame.

    Anyway, really appreciate it. (was able to 'measure twice and cut once' -- You must have had to go out and measure things the same nite I asked.


  • gmcgtgmcgt Member Posts: 15
    Owen, Try use the last 8 digits on your vin
  • woolybackwoolyback Member Posts: 45
    Just got back from my first trip towing with my 2001 Sierra, I didn't have any problems with the gears and the check engine light didn't come on so maybe that bug has been dealt with.
    For (blackchevy) I have the 2500 with the 3.73 gear ratio and I was getting between 8 and 10 mpg towing and averaging 60 mph with the AC on most of the time. Took about a 1500 mile round trip to Las Vegas over the Tehachapi which I think is around 4000 feet.
    Regarding the question about the placement of the hitch. I have used the same RBW Lil Rocker hitch in my last 3 shortbed trucks. A 91 Silverado, 2000 Sierra and this 2001 Sierra, I installed it in the last 2 trucks myself and placed in the middle of the bed right over the axle. I pull a 26 foot Nash and have been able to do a 90 degree turn without any problems with each truck.
    I wasn't aware of the 5 minute idling time in drive I guess I should read the owners manual sometime.
    I have noticed that my trans. temp. reading goes up when I am driving solo in stop and go traffic... is that normal for this trans.
    It would actually go higher in those situations than it would towing on the highway.
    Thanks guys I appreciate all opinions.
  • woolybackwoolyback Member Posts: 45
    I am having a problem deciding which type of step to get for my 2001 2500 ext. cab Sierra,
    Does anyone know if the nerf bars extend past the second door to the edge of the wheel well. I've seen some steps that do that but not a bar. I want to be able to stand on the bar or step to reach over to the middle of the truck bed. I have a Roll-N-Lock cover and can't reach the lock from the ground with this truck.
    Also do they custom make the bars and steps to fit the 8.1 trucks or do you have to do some fitting yourself.
  • mugwhump1mugwhump1 Member Posts: 1
    I have had my 8.1 2500HD for about two months now and all I can say is WOW! I towed my 26' Nash travel trailer with a 1/2ton Z71 (2000) for a few months and I had to do something. I have always liked GMC's and this one is no exception. I average about 9.75 mpg towing the trailer (5520#). I do have a question though. A couple of times when the trailer was hooked up, I noticed a sound upon acceleration from a standstill. It was almost like the sound you feel and hear when you get off the edge of the roadway and you hit the "wake up grooves". Kind of a vibration I guess. It seemed to happen right around the shift from 3rd to 4th. I am wondering if I might have lifte my foot slightly off the gas and the tranny got confused. Anyone else experience this? Thanks. I have learned a lot from all of your posts.
  • mgdvhmanmgdvhman Member Posts: 4,157
    These have worked good for me..all stainless..made by Putco.

     - Tim

  • khbushkhbush Member Posts: 19
    Hope it worked out o k for you. I was only giving the benefit of what I learned from having it installed on our HD. I was afraid to try it myself. You are a better man than I.
    Good luck!
  • n75v111n75v111 Member Posts: 243
    My dealer happened to call me today about replacing my Extra CD player so i mentioned your lock-up situation.

    He said the Computer in the regular Automatic (4???) has a Default mode where if the computer senses (or thinks) there is a trany problem it will lock the trany in a low gear where if can run high pressure fluid (he said 2nd gear but maybe he didn't remember that correctly) to prevent transmission damage etc.

    So it may be that the Allison has a similar Default condition and if the computer has some sort of a glitch it could cause the trany to lock down.

    Maybe thats what happened to yours????

  • woolybackwoolyback Member Posts: 45
    Thanks for thinking of me (n75v111) and mentioning my problem to your dealer. I got a letter in the mail yesterday from the dealer saying that my part had come in and to call for an appointment. It turned out they had ordered a module for the trans. that they are going to install so maybe that will eliminate any repercussion of my lock up problem.
    Do any of you guys have a problem with one side of the truck being higher than the other. I noticed that when I look at the tailgate of my truck from the rear, the right side is about an inch higher than the left. I thought at first it was the ground that was not level but I measured it on level ground and it is higher. When I mentioned it to the service dept. I was told that they sometimes come that way because of the way the body is assembled on the chassis. What do you guys think ??
    If any of you guys that tow are using CIPA slide on mirrors take a good look at the plastic insert that fits inside of them.
    I scratched up the chrome on my mirrors because of a rough finish on those inserts. I've used 000 steel wool on mine now to get rid of the burrs and glued some rubber patch material over the curved end.
  • n75v111n75v111 Member Posts: 243
    Yeah- Mine is the same way and I've noticed it in almost all my new vehicles over the years. I recall there was a lot of discussion on this and people getting all upset going in and changing tortion bars etc to make it level.

    Anyway I sure would not start messing with the tortion bars to make it level.

    I was told years ago that is required because of the normal crown in the road way and has to do with alignments so it tracks straight going down the 'standard crown' in the 'standard road way'.

    Maybe cowboyjohn will comment.

  • cowboyjohn1cowboyjohn1 Member Posts: 125
    For Wooly and Loop Silverado - I am 1/2 owner in a front end alignment/brake shop in Bellflower CA. We get all kinds of crunched cars, custom pickups, and lowered vehicles. You can tighten up your torsion bars and expect a stiffened ride - kind of like riding a draught horse. If you do so, this will change the geometrics of the front end, although this does not mean it puts it out of factory spec - but it may. We charge $12.50 for an alignment check, which would be worth it for my piece of mind. If the alignment is out, and you want it aligned, the 12.50 is applied to the alignment charges.

    Now on to the road crown. A good shop will ask you what type of driving you do and on what kind of roads. The shop can then set your alignment for that type of road crown. The vehicle should go straight down the road - hands off - Don't count on this for a 5 mile nap. All of our customers vehicles - if it is driveable when we get it - gets two test drives, one before the work to see what a good mechanic may detect that a customer may not, then again after the work is done to assure that it drives right and the problem has been solved.
    For what ever all the above is worth. cowboyjohn
  • gordo13gordo13 Member Posts: 20
    Can you give the name and address of your shop? Also, how's your MPG been and what gears do you have? I remember seeing some rather high MPG numbers coming from some other 8.1 owners while yours seemed to be a little lower.
  • cowboyjohn1cowboyjohn1 Member Posts: 125
    Corner of Lakewood and Alondra
    25 foot Bear sign out in front
    15812 Lakewood Blvd
    Bellflower, CA
    Ask for Jerry

  • cowboyjohn1cowboyjohn1 Member Posts: 125
    Sorry, but I forgot to answer the other part of your question on Post 285. I have a 2001 2500HD, LT, Long bed, 4X4, 8.1 with Allison, and 3.73 gears with locker. I have been running 9.5 to 9.9 miles per gallon. The last tank I got slightly over 10. Yes I have noted others who seem to be getting better gas mileage, but I am not complaining when I compare it to me 1988 F250 that got an average of 7.3 in 1999, 8.3 in 2000, so I think 10 is wonderful.
  • n75v111n75v111 Member Posts: 243
    Anyone With the UY2 option that is coiled up underneath behind the cab in front of the box on the left side ----

    How did you run it inside the box??

    I need it inside as i have an Access tonnue cover that i keep closed when unhooked from the camper.

    Don't see any knock out plugs in the front box pannel or the floor so assume have to make my own hole??

  • khbushkhbush Member Posts: 19
    I don't have that option. I made a 4 foot extension cable so my 5th wheel hooks up at the receiver under the bumper. I've wondered where option comes into the bed.

  • woolybackwoolyback Member Posts: 45
    n75v111 & khbush... I asked for that option on my truck. The wire is coiled up and tied to the chassis on the driver side of the truck bed near the cab.
    I have a Roll-N-lock cover so I drilled my hole into the sidewall just in front and above the wheel well on that side. They don't give you a lot of wire so you can't go too far down the bed to drill you hole. I bought a 7 pin towing socket you will find there are 9 conductors in the cable but you only need the 7 in most cases. When I'm towing I can close my cover part way and cover the plug. I made a divider so that when the cover is partially closed it reaches the divider and locks there making a secure compartment for all of my junk I carry when I am towing.
  • n75v111n75v111 Member Posts: 243
    Need to find power source to wire into for Radar Detector.

    Any place under dash available or wiring to 'piggy back' onto??

  • hunter98hunter98 Member Posts: 273
    Just use your cigarette lighter. Your truck can sit with the detector on for weeks without draining the battery down. This is what I do, just leave her plugged in and on. When I get to school though, I usually unplug and HIDE it to keep it from getting stolen.

  • n75v111n75v111 Member Posts: 243
    Thats what i'm doing temperarily (have had battery drain in Seville when forgot it though)

    Don't really want to have the wire strung from 'RD' to the plug on a permanent basis plus when on trip all three are spoken for.

    #1- Appolo Precedus GPS to drive --
    #2- Lap top with moving map driven from the GPS-
    #3- TV for Grand Kids for 6hrs to Oshkosh --

    Hoping someone knows an easy wire to glum on to.

    I wonder if there is an empty spot in the fuse box?
    Power only when ingnition is on.
    Really don't want to have to go thru the firewall though!!

  • 1i2cu1i2cu Member Posts: 32
    TPW has been changed once again, now its 04/16/01.
    This waiting is like going to the dentist for root canal. ANTICIPATION! ANTICIPATION! ANTICIPATION!
    This is the longest I've ever had to wait for an ordered vehicle.
  • woolybackwoolyback Member Posts: 45
    Sorry(mgdvhman) didn't notice your post on the Nerf bar question. I wish I had seen those pictures of your steps earlier, I just order Nerf Bars from Go Rhino. Yours look really nice better than any other steps I've seen.
  • sf0383sf0383 Member Posts: 204
    Now if you could just wire the radar detector to the GPS you could have the moving map on the laptop pinpoint the exact location of the speed trap. And my wife gives ME grief about all my 'stuff'. What we need now is the heads up display with the night vision built in like they were advertising on the Cadillacs and Bonnie SLE's
  • hunter98hunter98 Member Posts: 273
    They were running run this morning in southern IL on route 57 around mile marker 75. They pulled alot of people over, just not me ;) They are getting more and more aggressive on the road down to school. Must of seen 20 cops this morning on one 60 mile streatch.

  • cowboyjohn1cowboyjohn1 Member Posts: 125
    As a bit of information, our shop had its first 2500HD. However, it had been modified to the tune of and additional $30,000 according to the owner. Had lift kits both front and back - the door sills were 3 feet above the ground. However, not to worry for the little woman, when the doors open the stairs were extended, then retracted after the doors were closed. TV and I am not sure what else. The fellow came in for an alignment after his custom work was done. He also said there was an occassional clunk underneath. We told him it was a control arm hitting the frame and would cost an additional $68 to fix. He said "I don't care what it costs - fix it." My kind of man. I would like to try that a while. I am told the 2500HD has an easy front end to work on.

    We also had a new Ford Explorer in. The front ends have definitely been modified from previous years. Apparently it is somewhat on the order of the slipper and slider front ends used on some of the older Dodges.
  • gordo13gordo13 Member Posts: 20
    From reading here and on the 2500/3500 discussion, it seems like there's only a slight MPG difference between the 8.1 and the 6.0. I realize there's still the price
    difference and the difference in driving characteristics, any comments? I also posted this on the other post.
  • n75v111n75v111 Member Posts: 243
    Or if ya don't mind the foul CB language by the truckers, you just scan ahead to the mile marker on the moving map to see which bend in the road smoky's at.


    really tough isn't it??

    But I still need that Ignition Off wire (:-(

  • mgdvhmanmgdvhman Member Posts: 4,157

    I really like them

    - Tim
This discussion has been closed.