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Thread: Pulled the trigger on the 383

  1. #11
    Certifiable Vanatic Z-Machine (aka VanZack)'s Avatar
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    I would keep it in third on any uphills. The way it was explained to me by a transmission tech is, the speed of the engine determines the speed of the trans pump that circulates the fluid. In fourth, it doesn't circulate fast enough for adequate cooling. Once you get that trans temp gauge, you'll be able to watch it. Heat is the big killer of auto trannies.
    1969 G10 108, 307 V8, TH350, 3.08 gears
    1966 G10 Panel, 194 I6, three on the tree (I think it's an old Ma Bell van)

  2. #12
    VCVC Member lvjjj's Avatar
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    Quote Originally Posted by Z-Machine (aka VanZack) View Post
    I would keep it in third on any uphills. The way it was explained to me by a transmission tech is, the speed of the engine determines the speed of the trans pump that circulates the fluid. In fourth, it doesn't circulate fast enough for adequate cooling. Once you get that trans temp gauge, you'll be able to watch it. Heat is the big killer of auto trannies.
    I do pull it down to 3rd on "hills." Sometimes hard to tell what is a hill and what isn't. If it starts to lug at all I pull it down. Although its hard to tell if its lugging as the 383 is so torquey. Also use 3rd in town traffic. So its a matter of paying real close attention, which I always do when towing.

    I've discovered a forum called GMT 400 which is for '88 to '98 GM trucks. Most of them have been telling me the 4L60E tranny is a weak link and suggest I replace it with a 4L80E. So far the 60 is working ok even though I drove it 40,000 miles without flushing the fluid, getting it flushed this week.
    LARRY OF THE PACIFIC NW
    1965, 292, TH350
    purchased Nov. 22, 1970

  3. #13
    Certifiable Vanatic Leroy Jackson's Avatar
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    What kind of transmission are we talking about? 200R4, 700R4 or an electronic trans like a 4l80e?

    The 200 and 700 series with the tv cables.. definitely don't run them in overdrive under heavy loads. Wire up the converter lockup to work off a switch too. The overdrive clutch packs are tiny in these transmissions.

    The 4l80e is plenty strong to keep in overdrive. The computer will also control the gear, pressure and lock out depending on throttle position and speed. The only real reason to shift down would be to keep an engine in the meat of its torque curve.

    The 6l85e or 6l80e I would downshift to 3rd as well. They are just an electronic version of the 700r4. Pretty much the same wimpy planetary a d clutch pack.
    The Raped Ape
    1970 G-20 Krylon black
    Swing up cargo doors
    Supercharged 383
    4L80E transmission
    Detroit trutrac rear limited slip

  4. #14
    Certifiable Vanatic Leroy Jackson's Avatar
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    One more item to note, chevy auto 4 speeds transmission are 1:1 in third, direct connection to the crank and they are the strongest in this gear. In over drive, the torque is being put through an additional clutch pack and depending on the model, may only be 1 or two plates thick. Under heavy loads, they can slip.
    The Raped Ape
    1970 G-20 Krylon black
    Swing up cargo doors
    Supercharged 383
    4L80E transmission
    Detroit trutrac rear limited slip

  5. #15
    VCVC Member lvjjj's Avatar
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    holy van Leroy, just noticed your 383 is supercharged, must go fast.

    As my first experience towing a travel trailer was with the early with the 292, I paid very close attention to everything going on as you have to actually drive the vehicle as there is no computer to warn you of a problem (thankfully). Constantly monitored my 9 gages and listened for any weird sounds coming from the engine and tranny.

    I do the same with the Burb. I won't run in 4th if it seems to bog, only use it when it runs easy, usually level and/or tailwind. Last trip we had a strong headwind and I had to drive in 3rd. Whenever in 4th and I see a hill coming up, I pull it down before the hill. If it ever starts to slip, I will notice it. When towing I am super alert.
    LARRY OF THE PACIFIC NW
    1965, 292, TH350
    purchased Nov. 22, 1970

  6. #16
    Certifiable Vanatic Leroy Jackson's Avatar
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    Quote Originally Posted by lvjjj View Post
    holy van Leroy, just noticed your 383 is supercharged, must go fast.

    As my first experience towing a travel trailer was with the early with the 292, I paid very close attention to everything going on as you have to actually drive the vehicle as there is no computer to warn you of a problem (thankfully). Constantly monitored my 9 gages and listened for any weird sounds coming from the engine and tranny.

    I do the same with the Burb. I won't run in 4th if it seems to bog, only use it when it runs easy, usually level and/or tailwind. Last trip we had a strong headwind and I had to drive in 3rd. Whenever in 4th and I see a hill coming up, I pull it down before the hill. If it ever starts to slip, I will notice it. When towing I am super alert.
    She runs like a raped ape 😁. 2700 stall tq converter, 3.73 posi, cam profile builds tq hard after 2500 rpm and the blower is over driven. This thing pulls hard off the line and sings from 2500 - 6000 rpm. I don't spool it up any higher as there is no need. The torque curve is stupid flat and the hp just climbs. The hardest part is not breaking traction. If I punch it, it just lays rubber.
    The Raped Ape
    1970 G-20 Krylon black
    Swing up cargo doors
    Supercharged 383
    4L80E transmission
    Detroit trutrac rear limited slip

  7. #17
    VCVC Member lvjjj's Avatar
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    Breaking the tires loose may be a blessing. With my 292, it doesn't spin the tires (although I've never tried, don't want to hurt anything I can't fix) it just leaps. From a stop, if I stomp on it, it digs in and just leaps ahead without warning. If I don't have the tires straight ahead I could end up in a ditch or flip it. Even towing the trailer it leaps and bangs the hitch and trailer. I'm surprised I haven't ripped the hitch off.

    I can't imagine a blown 383 in a van because I consider the 292 too much engine when running solo. When cruising on the interstate, if I decide to punch it to change lanes to pass somebody I have to be careful not to turn the wheel too quick as it will leap ahead and I could end up swapping ends or in the ditch. Have almost done that.

    After my long rods linkage finally died, I built a pully system that is super smooth. So, since I only drive it once every 3 months or so, I tend to forget how quickly it accelerates. So the first time out I usually snap my neck back without meaning to. This is also why I use my left foot on the brake most of the time, have to be ready to slow it down. Tranny is a TH350 that was built specifically for RV towing, shifts are hard and quick and actually jerk the van and trailer when it shifts under hard acceleration.
    LARRY OF THE PACIFIC NW
    1965, 292, TH350
    purchased Nov. 22, 1970

  8. #18
    VCVC Member lvjjj's Avatar
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    Sort of an update on 383, computer chip

    Since the Service Engine light kept coming on when driving on the freeway, thought I should see about buying a computer chip since the current chip still thinks its controlling a 350. Apparently its running too lean based on the original chip. On GMT 400 forum I found a guy who custom makes chips based on actual computer logs taken while driving. So I had to buy an ALDL cord that connects from the OBD I connector to the computer. Log onto TunerPro RT and hit record, drive 15 minutes, save the log, send to Old EFi in Vancouver WA along with the chip. We've gone back and fourth 4 times now as he fine tunes it. For some reason the new engine has never liked to idle on start up from the beginning. He is improving on that with his chip tweaks. Still has lots of power, maybe more now. The TunerPro RT program shows 8 gauges including vehicle speed, MAP, fuel usage, spark advance, etc. Sure is interesting watching these gauges driving down the road, can only afford a quick glance cause have to stay on the road. Its a good time to be doing this as with this Corona thing we don't go anywhere except groceries, and I go to the post office to mail the chip to Vancouver. RV parks are closing so we can't really travel.

    So if anyone needs a chip made for a GMT 400 truck, let me know. Lot better than buying something from Summit of Jegs that might help.

    The goodest news is, while the Burb is out of service, I'm left with driving the van, oh darn. Starts up everytime, running real good.

    Everyone stay safe, stay healthy.
    LARRY OF THE PACIFIC NW
    1965, 292, TH350
    purchased Nov. 22, 1970

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