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I have question about a GMC 1500 Series Plow Truck

Discussion in 'Chevy Trucks' started by ConnorExum, Jan 4, 2010.

  1. ConnorExum

    ConnorExum Senior Member
    Messages: 282

    My father bought a GMC 1500 series Sierra pickup truck with a western snowplow and uni-mount quick mount on it a couple of years ago and I have questions about it. This is the first time I've used it I was away at College when it was first purchased and I have just recently moved back home after finishing college.

    1) This plow has an electric powered hydraulic pump and recently when I've plowed with it the truck has shown a serious voltage drop when raising, lowering or changing the angle of the plow. I'm curious if anyone knows why this would happen. This is a used truck and I have very little information on the equipment. My best guess is the alternator is too small, but shouldn't this type of system had an upgraded alternator installed with the plow?

    2) Also would anyone by any chance know the actual correct oil-pressure range for the GMC Sierra 1500 Series 5.7L engines. I've not been able to really get any reliable information on it and my father's mechanic seems uninterested in really diagnosing this problem correctly.

    3) Does anyone know of common issues with snowplowing using this sized truck. Too me it is too small, I would have purchased an Oshkosh or at least a 1ton truck but my father is not of the same mind as I am on this issue.

  2. Rubicon 327

    Rubicon 327 Senior Member
    Messages: 108

    From what little I know and seeing no one else has answered I will give it a shot!:D

    1. Most all experience a drop in voltage when using the plow like you are.An upgraded Alt may help, but I believe a dual battery set up is more along the lines of what you may need.

    2. I don't know the correct oil pressure, is it knocking or making lower engine noise? Maybe worn main and rod bearings and crankshaft journals just for starters.....it could be other problems though.How many miles on the engine?

    3. You don't say what exactly he uses it for....personal/commercial/business, if he is only doing light plow work....a few drive ways and such it should be fine if he knows how to plow and is easy on his equipment. Many people on here plow with well equipped 1500s and do way more than just driveways with them, so it depends on what he is doing with it, the size of plow he has on the truck and how careful he is with it.

    You may not be of the same mind set as your father and like ME you can always go with the "It's better to have it and not need it, than need it and not have it" mind set:eek: but that can be expensive and overkill for what he may be doing.

    A little more info on all of your questions and I think we can help you better.:nod:

  3. X2
    More info would be a great help. What year truck? What kind of plow?
  4. cmo18

    cmo18 Senior Member
    Messages: 815

    if you need an Oshkosh and instead you bought a half-ton, you are going to have some huge problems!!

    1) voltage drop is normal, but if the truck is going to die then something is wrong
    2) remember its normal for oil pressure to go up and down but more info would be great
    3) This is my year with my own 3/4ton, all the rest of my truck were half tons.. I did fine with my half tons for small parking lots and driveways but when we got 1ft plus is when I was in trouble for parking lots.
  5. ConnorExum

    ConnorExum Senior Member
    Messages: 282

    Okay so here is some information:

    The Truck is a 1995 GMC Seirra 1500 with 5.7L engine four speed automatic trans, Z71 package, extended cab and is pretty much stock.

    1) the plow is a Western ( model not sure) it was with the truck and we got zero manuals with this purchase of a used vehicle. However, this is what is happening when we use it: voltage will drop from 16v down to 8-9v and hold that for 3-10 seconds after moving the plow. It is a single battery set up but before this weekend it would dip down to 10-12v on the meter and immediately recover back to 16v. So I'm thinking that this extra draw is problem either the meter is dead or the alternator is going. But I first wanted to know if it was typical to swap out the factory Alternator for a more powerful aftermarket one.

    2) The oil-pressure is real mystery because I cannot get any info on the actual oil pressure range from anywhere I've tried. Even a dealer I called told me that it was okay idling around 20psi. It sounds fine when you drive it. But according to the gauge the truck as 40psi-42psi at start up and for the first 30 minutes, then it drops down to 18-20psi and holds that for about 30-40 minutes. However, if you drive it for about 1-2 hrs you'll see it hovering at 5psi just barely above the little red danger mark. So you stop it for a while and you let it rest for 10-20 minutes and it is back up to 20psi. I cannot figure out a) what is the proper operating range of the truck and b) what is causing it. I mean it could be a sender issue but you expect to see this type of regularity usually it if were damaged. It could be the gauge but the mechanic didn't test it. It could be the pump, rings, main-journal bearings and so on but not tested and I would expect the truck to overheat and die eventually... Doesn't seem to be doing that either.

    3) We really don't need an Oshkosh... I just want one. I drive M35A2 2.5ton 6x6 around as a daily driver so I'm always a fan of bigger is better. The truck itself is used for non-commercial use. We do our own driveway and our cousins up the street and that is about it. I was just curious if people noticed any part that broke more often than others actually

    I'm still pushing for an oshkosh actually because a P2427 with wing and plow makes quick work of a driveway and is just fun to drive around.
  6. Evanbrendel

    Evanbrendel Senior Member
    Messages: 181

    sounds like the oil pressure guage is going bad
  7. ConnorExum

    ConnorExum Senior Member
    Messages: 282

    that's what my brother thinks too.. I want it to be something else so I push for the Oshkosh... thanks for the help.
  8. ConnorExum

    ConnorExum Senior Member
    Messages: 282

    I'm really curious as to the voltage problem. I would have guessed that a larger alternator would have been put in the truck if the use of plow would cause this much drain on the batteries. So are their kits for the dual battery set ups?

    As for the oil pressure, that one really baffles me because it has been going on now for 2 years. The mechanic is not helping out with the fix.

    As for the use of the truck one or two drive ways. We do treat it well but, it does have to push a lot of snow at times. As for the Oshkosh I just love them and I need to go with my M35A2 so I have set of unrealistic trucks to drive around.
  9. Thermos017

    Thermos017 Member
    Messages: 59

    here is the answer to your oil pressure question: if it is reading on the guage at any point you are within range for the 5.7L. no bull$#!t. the normal startup can go as high as 60 psi, and the safe low range is 8-10psi. the hotter the oil gets the lower the pressure will be.

    thats the case with any high volume/low pressure pump, which is what they put in those 5.7's for decades. if you are worried about the pressure being too low you could try a thicker oil, but your start up pressure is going to jump by more psi than your high temp pressure. my van (77 chevy, 350) and company plow truck (97 k1500, 5.7L) are the exact same way. it starts at 60 psi and when its hot it bounces from 5 to 15 psi. it's basic physics. the hotter the oil, the free-er it flows, the free-er it flows, the lower the pressure. you don't have to have high pressure if you are getting a high enough volume of oil circulated through the block.

    if putting an oil pressure sender or guage on it gives you peace of mind go for it, but i promise you'll be throwing away your money. when the guage stops moving, then you know its dead, or the oil pump is shot.

    i assume you are runnign 5w30 (called for on most oil fill caps) if you are getting that low of a pressure. check gm's suggestions for oil in the owners manual. you can run anything from 5w20 up to 10w40 depending on the air temperatures the truck will be operating in.
  10. Rubicon 327

    Rubicon 327 Senior Member
    Messages: 108

    Sounds like good information from Thermos017 there about the oil pressure!:nod:

    As for the electrical issue,There is a sticky at the top of this Chevy section on how to do it. Not sure if it pertains to you model but it gives you the basics on what you need to do.

    Biggest problem is probably finding a spot to put the 2nd battery tray....and even then I don't think should be that hard on that model truck if I remember correctly.
  11. ConnorExum

    ConnorExum Senior Member
    Messages: 282

    thanks for the information... I still want to see why the truck is acting so wonky, I've seen a lot 5.7l Chevy V8's and I've never seen one run so low even under a load.
  12. ConnorExum

    ConnorExum Senior Member
    Messages: 282

    Thanks for the help. I'll have the mechanic who's looking at it tomorrow see what he thinks about adding a bigger alternator and/or second battery to the truck.
  13. Thermos017

    Thermos017 Member
    Messages: 59

    what thermostat do you have in the truck? going with a cooler thermostat can help the oil pressure slightly. if you're running a 190 or 195 you could try a 180. i wouldn't go much colder than that though, and i doubt you're going to see a huge change in the oil pressure. maybe 5 to 7 psi more, at best, when its hot. your best bet for higher pressure will be the oil weight. try 5w40 or 10w30 and see if that helps. if i recall 10w30 is said to be good until 0F according to the gm owners manuals. if you keep your truck in a garage you could run the thicker oils at lower temperatures, provided you always park inside, and warm your truck up a little before you leave the garage. also, if you're running synthetic (full or blend) you should increase your oil weight. for some reason synthetic oil tends to be a about one weight thinner than its conventional mate.
  14. ConnorExum

    ConnorExum Senior Member
    Messages: 282

  15. Rubicon 327

    Rubicon 327 Senior Member
    Messages: 108

    Either way, If it's not something simple and inexpensive it's going to be rather involved and costly.....lower end rebuild/oil pump....something along those lines.

    I forgot what you said about the gauge, but I would probably pick up an aftermarket mechanical gauge and install it and go from there. If the pressure is still low then it is what it is....oil pump/bearings etc,etc...Like Thermos017 said you'll be throwing good money away though.

    You either,

    1. Pony up the money now and fix whatever it is (oil pump/bearings) what ever it may be,You know you probably won't get lucky and have it be a cheep fix meaning.....a sending unit or gauge etc,etc.but who knows.

    2. Run it till it starts making noise and rebuild it.

    3.Throw a new crate motor in it now and be done with it.

    4.Trade/Sell it and get something else while it is still good.

    You kinda have or will have after today an idea what it may be and you can go from there.

    I kinda get the impression that even your mechanic knows it's not a big deal right now or it's more than he really wants to get into.

    I don't remember or even see if you ever said how many miles this motor has on it?....and was the oil pressure like this when your father bought it?

    Let us know how you make out!
  16. ConnorExum

    ConnorExum Senior Member
    Messages: 282

    Well, I'm pushing myself towards the sell it for as much as possible and purchase a better and more importantly "BIGGER" truck. I agree with you totally about not fixing it, if the problem is something super-serious like a rebuild or ring job. However, I also want to know a rough estimate of how much life this truck has left on it. I'm not exactly sure on the miles probably a 150k or so. Yes, it is getting older, but right now it is the only viable means of plowing our driveway. I really don't want this thing breaking down on me when I'm plowing, then I have a 3500lb GMC Lawn Jockey. I was just really curious if anyone here had a similar issue with 5.7L engine. All of the trucks we've owned with these engines ran in the 30-50psi range from idle to high work load no matter temperature of the engine. This one runs well low-- and that to me is an understatement.

    Thanks for the help.
  17. ConnorExum

    ConnorExum Senior Member
    Messages: 282

    I hate this Chevy...

    I've come to the conclusion that this Chevy my dear old pop's purchased is worthless. Now, the truck will only show a full charge on the meter if I turn off the radio or heater while plowing. I'm guessing the battery has reached its useful life cycle but, I'm still curious if the alternator itself is still too small. I think I will have the battery changed when we take it to the shop now.

    Now the truck overheats too.. It does it more with the plow up but it will do it with the plow down too. We had the radiator changed in the summer. I doubt it break this soon, it is new. I don't see any leaks or signs of fluid loss. I wonder if it is excessive heat from the oil-pressure issue.

    I'm voting for trading this Chevy in for a Classic Oshkosh...
  18. aeronutt

    aeronutt Senior Member
    Messages: 262

    One of the more common upgrades for plow trucks is more battery capacity. You've mentioned upgrading the alternator several times now, but that's actually not as useful as the battery. Get the battery tested first and if it's not checking out A-OK, buy the biggest capacity battery you can get. The reason a battery is more critical than an alternator is because you only need to run the hydraulic pump for a few seconds at a time. During those few seconds you will draw 200-300 amps, which very few alternators can keep up with. A good high capacity battery can dump those amps quickly, then recover from the 75 amp alternator for the next 20-60 seconds until it needs to dump 200 amps for another 2-3 seconds. My F350 nearly died from the voltage drop prior to getting a battery upgrade. I had to plow with lights off and heater on low in order to leave enough electricity for the fuel injectors. Once I upgraded the battery, I don't have any problems running everything and I'm still using the stock 72 amp alternator.

    Snowplows are notorious for causing overheating thanks to blocking air flow to the radiator. A heavy duty fan clutch fixes it.

    I think anybody who plows their driveway with an Oshkosh is seriously compensating for something... :D
    Last edited: Jan 17, 2010
  19. ConnorExum

    ConnorExum Senior Member
    Messages: 282

    My problem is that the truck really only plows one or two drive ways. Ours which includes a small section to house which we rent and one of my cousins up the street. So the amount of recharge time I have is limited most of the time. In fact I drove it around for another 20-30 miles with only the bare minimum of accessories being on and the truck's recovery time on the meter was still slow. I mean 40 minutes of driving with nothing but the wipers and lights on should have had the meter at 14-16 volts most of the time. It took 10 minutes for the meter to register 14volts which is okay but usually it was reading a hair or two more than that. So while I agree the higher capacity battery is a must, I think this alternator needs to be looked at. I should have had a faster recovery time on the meter than 10 minutes. I only plowed with the truck for 30 minutes tops. I just don't think this alternator produces enough amperage to really recharge this battery in the time span we use it. I would prefer a diesel truck myself with mechanical injection because the engine would use almost no power to run (only power for the oil sender, rpm sensor and so on) I think that would be really nice for our application. However, no such luck. Simple can be great. Hence the reason I love the older Oshkosh's with the simple easy to use Cummins power plants.
  20. MeeksCo

    MeeksCo Senior Member
    Messages: 214

    I practically have the same truck.
    Unless you get two batteries that are exactly the same age...the 'dual' battery setup will not work.
    There are also other ways of making two batteries that are not the same age work...you have to run one wire to this one, another to that one, back to the alternator from this one...and so on. Look it up.

    FIRST THINGS FIRST! Check your grounds.
    The ground for your plow probably needs to be grinded, cleaned, tightened, and put some dielectric grease on it.
    Also...it could be your plow motor...when those go bad...they pull too many amps. Get a voltage meter and check everything from the alternator to the plow motor to the battery. If you have a solenoid...maybe consider replacing that.

    As far as the oil pressure....it's an older truck.
    Your oil is thick when its colder and thin when its warmer.
    As long as it's in the 40's when you start the truck...you are good! That's it!
    The oil thins as it warms up and your gauge will distract you...don't let it.
    Does it go back up when you accelerate???? I am sure it does. It's fine.

    My 1/2 pushes snow with balls! I've pushed parking lots with 1' of snow plenty of times. It's all in your finesse. I'd prefer a bigger truck...but the ol lady wont let me. She'd rather have me renovate the kitchen...