1986 4x4 Sierra

Discussion in 'GMC Truck Forum' started by Rageincoming, May 29, 2015.

  1. Rageincoming

    Rageincoming Full Member

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    Ok so I just bought this truck from a guy off of craigslist for $2k + $225 to tow home 50 miles due to no insurance. From what the seller has brought to my attention. On the forsale sign it is a 4x4 1986 GMC sierra with a "new" 380 chevy motor with 200 miles on it while I was told it was a rebuilt engine with 200 miles on it. It has 041 heads, 495 camed lifter kit, edelbrock 600 carb, street dominator intake and a new timing kit double roller. Originally the truck was a diesel but was swapped with the 380. The Body is in excellent shape minus a few small blemishes. I don't have a long enough stretch of road to drive it fast enough to see if overdrive is working but transmission has atleast 136k on it. The truck drives decent and sounds great but, there are a few things that need fixed/adjusted. I am not entirely familiar with this style of truck but it wont take me long to find out. So far what is wrong is dash transmission gauge doesn't move with shifter knob, no ac compressor but has condenser and accumulator (probably toast), heater core not hooked up (also probably toast), loose wires hoses vacuum lines throttle cable here and there hanging around, looks like bottom gas line is kinked, water pump is highly rusted on outside and needs replaced, there is a "low coolant" light lit on the dash despite it being full at the cap, missing lenses from some of the gauges, temp gauge doesn't seem to move a whole lot from 160f, might be running a tad rich because I can smell what seems like "fresh" gas from exhaust while it is running, there are no coolant lines coming from the transmission. All these issues beside, it is smoother driving than my 4.3l 1992 s10 only much louder and slower acceleration.


    Atm I have a working vehicle so I can still go to work to pay for these fixes. Any ideas where I should start will be greatly appreciated. Please let me know if you want/need more pics. I was thinking of getting the engine bay degreased and remove all unused wires/hoses then setting up AC and heat. I am also considering converting it to TBI even though this carb setup looks real nice.


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  2. chevychase

    chevychase Semi-Admin
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    Nice find yes i would convert it to tbi.Running cool does it have a thermostat? Smell fuel carb. maybe loading up needs rebuilt.
    If you really want to convert to tbi..good member here we will get it done...help you with this project.
    It is Friday..slow day..other will chime in. Just stick around we will lead you through this project.
    Can do a search also on much info top of page right corner.
    Welcome to the forum .
     
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  3. MrMarty51

    MrMarty51 Full Member

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    Yeah, welcome to the forum ICR.
    Check that the choke is fully opening, on the carb.
    It sounds to Me like there is a lot of nice stuff on/in this engine.
    If the cam has a lope ground into it, it might take a little to get it to accelerate quickly from off the start, if it has a "stall convertor" it then would not leap until X amount of revs is obtained.
    Also, gearing can be a major factor on acceleration.
    The shift indicator is controlled with a string/wire, from the shift collar of the steering column to the needle. Use a flash light, look around the shift collar, right up close to the dash, You might see the indicators clip hanging there, if so, with the lever in park, pull on the clip/string until the indicator is where You like it then, shove the clip onto the collar.
    If the clip is not available then, it will require partial removal of the dash until you get to where the clip/string is visible then, hook it up.
    First though, check that the clip is not clipped to the shift collar first and, that the string is broken, not allowing the needle to move.
     
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  4. Bad88

    Bad88 Full Member

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    Wow - what a deal! Based on the pictures, the frame looks cherry! The water pump looks like it only has surface rust. As long as it is not leaking or making noise it should be fine. Of course, as time permits you could take it off and clean it up and apply some paint.

    It looks to me like some good old boys did the job themselves - that's fine. I would slowly go through and put the correct size hose clamps on and just put things right.

    I am curious as to the "380" engine! 350 or perhaps a 383?

    Throttle cable looks a little frayed at the carb - should be easy to get. I would replace that right away; you would not want to lose throttle while on the road.

    An 8 lug'ger. I wonder if this was an Army truck in a previous life? Would explain why it was a diesel previously.

    The P/S pump reservoir looks a little hokey sitting on top of the motor. Maybe a local junkyard has a good pump with the right brackets for your truck? While you re there, you can see if they have a fan shrould for the radiator. That shroud will help pull air through the radiator keeping everything cool and at the right temp.

    Please keep us posted on how you are making out!

    Welcome to the forum!!!
     
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  5. MrMarty51

    MrMarty51 Full Member

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    I forgot about the rusty waterpump, Yeah, pull/push the fan blades front to back, watch the pulley, if the pulley and shaft moves then, replace the pump.
    A lot of people install a new or re-manufactured pump without painting them, I know I am guilty of this, they get a real nice rusty patina in a very short while.
    The water pump might be new, just set and seen enough humidity/moisture to rust it up.
     
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  6. Rageincoming

    Rageincoming Full Member

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    #6 Rageincoming, Jun 5, 2015
    Last edited: Jun 5, 2015
    So I did some research and found that this truck comes standard with a TH400 transmission. Since this truck might have originally been a diesel, it also means that if this is the original transmission and it might not be the same as its gas counterpart. How can I identify exactly what transmission this is?
     
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  7. Bad88

    Bad88 Full Member

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    Try the VIN or look for the RPO codes in the glove box. Barring that, there may be a number stamped on the tranny somewhere - maybe up around the bell housing area or on a pad just above the oil pan rail on the side of the tranny.
     
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  8. MrMarty51

    MrMarty51 Full Member

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    pan_id.jpg

    [TABLE]
    [TR]
    [TD="width: 20, bgcolor: #C0C0C0"]1[/TD]
    [TD="width: 160, bgcolor: #C0C0C0"]Aluminum Powerglide[/TD]
    [TD="width: 70, bgcolor: #C0C0C0"]14 bolts[/TD]
    [/TR]
    [TR]
    [TD="width: 20, bgcolor: #C0C0C0"]2[/TD]
    [TD="width: 160, bgcolor: #C0C0C0"]TH200 Metric[/TD]
    [TD="width: 70, bgcolor: #C0C0C0"]11 bolts[/TD]
    [/TR]
    [TR]
    [TD="width: 20, bgcolor: #C0C0C0"]3[/TD]
    [TD="width: 160, bgcolor: #C0C0C0"]TH350[/TD]
    [TD="width: 70, bgcolor: #C0C0C0"]13 bolts[/TD]
    [/TR]
    [TR]
    [TD="width: 20, bgcolor: #C0C0C0"]4[/TD]
    [TD="width: 160, bgcolor: #C0C0C0"]TH400[/TD]
    [TD="width: 70, bgcolor: #C0C0C0"]13 bolts[/TD]
    [/TR]
    [TR]
    [TD="width: 20, bgcolor: #C0C0C0"]5[/TD]
    [TD="width: 160, bgcolor: #C0C0C0"]TH200-4R[/TD]
    [TD="width: 70, bgcolor: #C0C0C0"]16 bolts[/TD]
    [/TR]
    [TR]
    [TD="width: 20, bgcolor: #C0C0C0"]6[/TD]
    [TD="width: 160, bgcolor: #C0C0C0"]TH700-R4, 4L60, 4L60E[/TD]
    [TD="width: 70, bgcolor: #C0C0C0"]16 bolts[/TD]
    [/TR]
    [TR]
    [TD="width: 20, bgcolor: #C0C0C0"]7[/TD]
    [TD="width: 160, bgcolor: #C0C0C0"]4L80E[/TD]
    [TD="width: 70, bgcolor: #C0C0C0"]17 bolts[/TD]
    [/TR]
    [/TABLE]
     
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  9. Bad88

    Bad88 Full Member

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    They also made a HD 400 - some people call them the 475. The 475 has more heavy duty stuff in it. I'm not sure of the compatibility of a tranny bolted to a diesel then being mated to a gasser. I can tell you that some tranny's in the 400 size have a thicker tranny pump impeller drive gear. I was in Germany and had to replace my TH350 tranny pump impeller drive and all I could come up with was one from a Army CUCV. I had to mill that drive gear down because it was too thick and I could not mate the torque converter to the tranny because the converter could not slide in all the way allowing the tranny to be bolted to the motor.

    Still curious about the "380" motor.
     
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  10. Rageincoming

    Rageincoming Full Member

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    Well I have compiled a list of the things that need looked at/fixed and found out some new things today. As for the 380 motor, I think this engine is over-bored but by how much I am not sure of. Any chance you guys know how I can identify what model of 350 I have? I wish I could contact the original owner who sold this truck to the guy I bought it from to ask some questions but he scribbled out the guys number and reused the same "for sale" sign..

    #1. When shifting into reverse there is a very loud clunk much louder than shifting into drive.

    #2. I can push the truck forwards and backwards with the transmission in park while hearing clinking noise when moving.

    #3. Steering column not attached to shifter gauge.

    #4. Carb needs tuned.

    #5. The metal nozzle coming off the mechanical fuel pump has been kinked for some reason, might replace with a 6lb pressure Edelbrock pump.

    #6. Adjusting rail on passenger side of bench seat is free moving and half the seat moves with the vehicle.

    #7. Badly needs an alignment, steering wheel turned upside down just to stay straight.

    #8. Belt slips a little when revving.

    #9. Missing various gauge lenses.

    #10. Missing parts to heater and AC I will replace those with new parts and have AC vacuumed and filled.

    #11. Cabin carpet isn't carpet it's like a rubber bed liner cut into pieces and laid there otherwise interior good.

    #12. No transmission coolant lines in engine bay, I need to check if there is a different cooler under there.

    #13. Low coolant light on dash remains on all the time, where are the coolant sensors?

    So far that is it. While converting it to TBI is a good idea it costs alot so I might keep it carbed for now but tune the heck out of it cuz it needs it.
     
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