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Problem with gaining speed, been to several dealships

Discussion in 'Performance & Fuel' started by dalepre, May 19, 2013.

  1. dalepre

    dalepre New Member

    Hello Everyone,
    I have spent thebetter part of the past 6 months trying to figure out the issue with my truck,I have spent hours searching on several forums but now find myself having toask to keep what little hair I have left..
    Specs:
    1995 Chevy K1500, Extended Cab, 350 with TBI, 4L60E trans,234,000 miles, standard bed,

    I have owned this truck since new, I have always changed theoil every 30,000 and run Mobil One oil, the only thing till now that has beenreplaced under the hood before this issue was:
    1 Water Pump
    1 Raditator
    3 Sets of OEM original plugs
    3 Sets of OEM wires
    3 Dist caps and rotor
    1 starter
    3 Throttle Position Sensors
    That's It!!

    Transmission was replaced app. 70k ago with a new GM crateunit, system was not just flushed, I replaced all lines, coolers, everythingthere was.

    Only other repair was to replace the speed sensor on thetransfer case app. 50k ago.

    Only other service has been brakes, rotors, hardware, etcand no other chassis parts at all.

    The only towing has been my 19 foot Skeeter Bass boat(reasonfor the tranny replacement) glad I don't fish any more..lol

    When this problem raised it's ugly head, it did it in just 2or 3 miles, like a switch was flicked.

    Now, items that I have replaced trying to clean this messup:

    NEW GM Complete Dist Unit
    New Plugs, wires.
    New OEM bolt on GM Cat. converter
    New OEM O2 Sensor
    New right hand exhust manifold (saw a hair line crack whiledoing plugs)
    New MAP Sensor
    New Thermostat(just for the heck of it) have had no issuesat all with engine temps at all
    New Coil
    New AC Delco Vacuum Valve
    New Vapor Canister Purge Solenoid

    All of these items have less than 10 miles on them.
    3 different GM dealerships, 4 other lifelong mechs and a few others along the way.

    The truck starts like it did the first day, just tap theswitch and she roars to life in a instant, no missing on any cyls, no backfire,no sputtering, baby smooth idle always, oil pressure hangs around 50-60 psi atall times, lowest you might see is 45. Water temp just were it should be rathersolid on 210.
    You can start it upand take off, also engine hot or cold has no bearing at all.
    If you pull out on the hwy and apply the gas VERY lightlyand allow the truck to build up its speed very slow you can go down theinterstate with curise on at 80-90 and never know there is a problem.
    Now, if you go WOTwhen you are running 55, in O/D, tach at app 1500 rpm, the tach jumps up to3400-3500 RPM in a instant, like a rocket, no missing, sputtering nothing atall, but the truck speedo stays on 55 and you go no faster, you can stay at WOTfor 5 10 seconds and the tach stays wound out, but no go. Same action if you gofrom a dead stop taking off and go WOT, tach goes to above and speed may be20-30MPH and no increase. Back of the pedal and let her get up to speed slowlyand it will twist the spedo till the limiter cuts her off. I had her on thelast mile or so the the above 10 and she hit 100 and running as smooth as ababys bottom.
    The tranny neverslips, whines, nothing at all to notice. I also change my tranny fluid andfilter every 50,000 like clock work.

    I swaped the TBI unit off of my 1995 Suburban, TBI has same numbers stamped on it , same running gear, 90k on it, no problems at all, put it on my truck, that says the TBI unit as a whole isnot involved, Put the TBI off my truck on the Suburban and it ran justlike it did with its TBI installed, so no problem there..Dang...glad I don'tdrink, but a trip to the American Boys Colledge may be in order soon.
    Thanks in advance forany and all help.

    Beaten,
    Dale
  2. Conlan Rose

    Conlan Rose Active Member 2 Years 1000 Posts

    Not to sound mean or stupid but what exactly is the problem? I didn't fully understand it the way you explained it. Also I think you mean oil change every 3,000, not 30,000.
  3. dalepre

    dalepre New Member

    Problem

    If you pull out on the hwy and apply the gas VERY lightlyand allow the truck to build up its speed very slow you can go down theinterstate with curise on at 80-90 and never know there is a problem.
    Now, if you go WOTwhen you are running 55, in O/D, tach at app 1500 rpm, the tach jumps up to3400-3500 RPM in a instant, like a rocket, no missing, sputtering nothing atall, but the truck speedo stays on 55 and you go no faster, you can stay at WOTfor 5 10 seconds and the tach stays wound out, but no go. Same action if you gofrom a dead stop taking off and go WOT, tach goes to above and speed may be20-30MPH and no increase. Back of the pedal and let her get up to speed slowlyand it will twist the spedo till the limiter cuts her off. I had her on thelast mile or so the the above 10 and she hit 100 and running as smooth as ababys bottom.

    The tranny neverslips, whines, nothing at all to notice. I also change my tranny fluid andfilter every 50,000 like clock work. And yes, I meant 3000..
  4. Ceej

    Ceej New Member

    4x4? The gear may have failed in the transfer case. 2wd? Your trying to beat a ticket. Pay them. 4x4, replace the gear. And pay your ticket. You were hauling ass, and you know it. :happy: CJ
  5. dobey

    dobey Rockstar 3 Years 100 Posts

    Does the CEL come on when this happens? It should come on and show a VSS code or something, as engine speed and vehicle speed would be incorrect. If it doesn't come on, it sounds like the kickdown cable is maybe sticking and forcing the trans to stay in a lower gear perhaps.

    Forget taking it to the dealer. Take it to a tuning shop with a dyno, duplicate the problem on the dyno, and log all the data off the ALDL port, then see what's happening. If you can find a shop near you, that will still tune pre-OBD-II vehicles, anyway.

    You don't happen to have a Hypertech or other aftermarket ECU chip installed do you? If so, replace it with a stock tune chip, then go back to step 1. :)
  6. zippstripp

    zippstripp Member 1 Year

    Just out of curiosity,have you tried changing the fuel filter? I know it sounds weird but I have had that bite me in the butt before.
  7. dalepre

    dalepre New Member

    No engine problems at all, and to the one who thought I had received a ticket..no tickets, none in 23 years.. Looks like the transmission has decided to give problems. Never shows a code nor does the cel light ever come on at all. The trans in the truck had hardly no miles on it and was a GM crate unit, the warranty has expired in time, but not miles, but still looks like another chance to pull it out and feed it another one.
  8. phoebeisis

    phoebeisis Epic Member 5+ Years 1000 Posts

    So the engine is making power- and RPMS
    but the transmission is in effect "slipping"
    Those RPMS aren't making it to the wheels??
    Wish I knew more about ATs and torque converters

    Oh I wouldn't test it-do any WOT- until I had this fixed
    whatever clutch you have in the AT- isn't grabbing-and a slipping clutch will wear itself out.
    Are these ATs so "electronic" that they can "tell" a clutch to "soft engage" and "forget" to tell it to fully engage.
    Kinda stuck in soft mode-springs or whatever engages these clutches-not fully "on"

    You need a forum member who fools with ATs-
    Maybe repost with " 1995 transmission problem-slipping" because problem gaining speed sounds like a power-engine fuel injection fuel pump "stuff" problem-and your problem isn't those things
    Yeah-get the transmission forum members into play.

    Luck
    charlie
  9. zippstripp

    zippstripp Member 1 Year

    It really doesn't sound like a trans. problem to me. Because you don't lose or gain speed when this happens. What I have seen is the fuel filter gets restricted enough to allow just enough flow for normal driving and not the sudden rush it needs at WOT. Take it off and try blowing through it,if your ears pop it's junk. Or if it has even slight resistance replace it, you've already tried everything else. The TBI systems only have a 9-13LB. running system.
  10. dobey

    dobey Rockstar 3 Years 100 Posts

    The problem with this though, is if it was the fuel filter, the engine would sound awful, and run worse, at WOT, rather than consistently run OK at the higher RPMs It should also cause the CEL to come on in such a case, as the engine would be running lean. The ECM would trigger the light due to the lean condition. The OP suggests the engine is running fine, but the car just isn't moving any faster, and the CEL isn't coming on. I would also be hesitant to blame the transmission outright as well, given the lack of a CEL about the VSS indication being wrong.

    In fact, given everything stated, the first things I would look at, would be to make sure the CEL was lighting correctly, and didn't have a burned out bulb. Then check for trouble codes stored in the ECM. And then start looking at possibly the tach and/or speedo just being wrong.

    - - - Updated - - -


    The transmission in the 95 era trucks isn't that complicated. If the clutches in the trans are burning, checking the fluid will tell you (or you'll smell it outside the trans anyway). If the clutches or the convertor are slipping, it should be noticable. If engine speed vs. transmission gear vs. vehicle speed doesn't fit within parameters, a CEL should occur.

    If there is no CEL, and the engine is running fine, and the transmission isn't slipping, then the most likely thing it sounds like to me is that the gauges are just wrong, or the kickdown cable is sticking, and forcing the transmission to remain in a lower gear, rather than upshift, when shoving the pedal to the floor at speed.

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