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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

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    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
    #1
  2. Conlan Rose

    Conlan Rose Super Moderator

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    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.
    #2
  3. dalepre

    dalepre New Member

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    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..
    #3
  4. Ceej

    Ceej New Member

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    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
    #4
  5. dobey

    dobey Member

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    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. :)
    #5
  6. zippstripp

    zippstripp New Member

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    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.
    #6
  7. dalepre

    dalepre New Member

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    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.
    #7
  8. phoebeisis

    phoebeisis New Member

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    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
    #8
  9. zippstripp

    zippstripp New Member

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    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.
    #9
  10. dobey

    dobey Member

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    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.
    #10
  11. phoebeisis

    phoebeisis New Member

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    But if it remained in a lower gear-it should accelerate-
    According to the OP-it jumps up to 3500 RPMs right away
    but the speed REMAINS at 55 mph
    so the RPMs double-speed stays the same
    power RPMs are being made at the crank-but it sure isn't getting to the driveshaft
    Eve if it IMMEDIATELY downshifted 2 gears-it wouldn't explain the no acceleration-since even at 3500 RPMs
    he has 2000 MORE RPMS on tap??
    Why the heck don't the RPMs KEEP going up??

    OP do you FEEL hear a downshift or two??
    Strange it doesn't increase RPMS- why "stuck at 3500 rpms and 55 mph??
    If nothing is slipping what gear gives 55 and 3500- 2nd gear??

    Maybe it is a strange fuel flow problem??
    Enough fuel flow to do 3500 RPMS and 55 mph in second gear or 3000 RPMS and 100 mph in 4th
    Maybe it is fuel flow
    STRANGE??
    If it was slipping-should slip all the way to the rev limiter or to 6000 RPMs if no limiter-guess probably no limiter on a 1995-
    so probably not slipping-maybe fuel flow??
    #11
  12. dobey

    dobey Member

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    A drop from 4th to 2nd with a 3.08 rear, would keep the MPH exactly the same, if the RPM increased from 1500 RPM to 3500 RPM, and it stayed there. If the tach never goes above 3500 when mashing the gas at speed, and it stays at 55, then first place to look would be the kickdown.

    If it stays at 55 and the tach goes above 3500, then I'd look at the tach or the speedo being wrong.

    Take it back to the dealer, or your favorite mechanic, or someone who knows what they're looking for, and tell them to check the kickdown. Have them drive it on the highway, cruising at 55 MPH for a bit, and then mash the gas as if to pass, and see what happens. Have them do that at least 10 times.

    If you never go over 3500 when this happens, I guarantee the problem is the kickdown, or something related, forcing the trans to stay in 2nd gear. Or even if the RPMS do go higher, as the failure to shift could result in slipping clutches or converter, resulting in the engine RPM being higher than it should be, for the speed you're going.

    If you have a stretch of country road near you, go out there and put the truck in 1st, take off, and manually shift to 2nd. Stay there and see if you can go over 55 MPH in 2nd. You should be able to hit 80 MPH in 2nd, but you don't need to go that fast. Getting to 65 MPH is enough, as the RPM should be at about 4000 @ 65 in 2nd. What matters is that you're spinning the engine at more than 3500 RPM, and going faster than 55 MPH, in 2nd gear.

    Or if you can just get a reasonably good video (at least 480p with good sound, that means windows up), of this happening, it would certainly help. But my guess is you should be looking at the kickdown, and the TCC lockup.
    #12
  13. phoebeisis

    phoebeisis New Member

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    Dobey
    So 2nd gear is about 3500 RPMS 55mph and 1500 in 4th is same 55 mph?

    What is this kick down??
    It must be downshifting-kicking down to 2nd gear-but not doing ANYTHING after that?
    Not increasing RPMs or MPH
    AND not upshifting?
    What does the kickdown normally do
    and what do you figure it is doing on the OPs vehicle?
    Thanks
    Charlie
    #13
  14. dobey

    dobey Member

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    Yes, 2nd is about 3500 at 55, and 4th is about 1500 at 55, with the 3.08 final drive gear, and factory diameter tires at proper inflation.

    The kickdown cable is a cable that connects between the throttle body and a valve on the transmission, so that when you mash the pedal to pass someone for example, the cable closes the valve which forces the transmission to shift down to a lower gear, so that you can apply more power to the wheels and gain speed quickly.

    There could be something wrong with the cable, the valve, or the TCC switch, most likely, which is causing the transmission to remain in 2nd (and not shift back up to 3rd and then 4th), and possibly causing the convertor to slip, or burning up the clutches in the transmission, causing them to slip. Though if the engine only ever remains at 3500 and 55, then something else could be wrong, but still I wouldn't suspect fuel, unless there was obvious misfire, or CEL indicating it.

    The engine can only spin as fast as the load being placed on it allows for. If it's spinning faster than that, something is slipping. If anything is slipping though, there should be a CEL come up, and a code may be stored in the ECM.
    #14
  15. phoebeisis

    phoebeisis New Member

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    Thanks
    Tricky problem-really curious what the answer turns out to be
    OP please keep us posted
    Charlie
    #15
  16. dalepre

    dalepre New Member

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    Finally an end to the Nightmare

    Well Guys, after many trips to three dealerships, 3 or 4 other shops with no idea, myself not a bad wrencher (but..mostly my collection of T/As and Mustangs..ie no computers..lol) I myself found the ghost in the machine yesterday. By the way,, there is No kickdown cable on my truck from the TBI to the trans. all electronic. I dug out my original GM tech manual on this truck and dove in with a vengence. I first shot it on the lift again and wnt over every single wire from the trans, sensors, speed sensor, transfer case, etc under the truck and viewed every single inch and found no problems. Stop for a second to scratch head or butt and then let her down and pull the glove box out, verfiy version of ecm, flip to that unit and proceed to get the truck up to normal temp(took it for a 5 mile romp) pulled back in the shop, cut it off. Unplugged the ecm and pulled it out were I coud get a up close and personal look, plugged it it back up, start het back up and check every connection on the ecm with my fluke and a scope also and found most to be right on the money, couple measurements a little off. Turned truck off, unplugged ecm, got it in my lap for close inspection, removed the prom access panel and then when into a fit of cussing that made me blush...Of all things, the lock leveron the left side had became loose and the prom had rose up a wee bit on that end, the right side lock was still firmly enganged. Pressed the prom back down, push the lock VERY well into place and then placed a wire tie around the prom to ensure that wil never happen again. Started the truck back up, jumped into the driver seat, as soon as I hit the pedal rather hard in reverse, I knew then, all was going to be like old times again. Hit the highway, went WOT and be damm, she got up and went like a chevy should do. Shifting was a wee bit of as the ecm was a little stupid at this point. Went back to the shop, mounted the ecm correctly, hit the road for app 50 mile ride and by the time I got back, shifting was compeletly normal, perfect in every way. And NO, the ecm has NEVER been out of the truck, ever. I guess strange things happen. Hard to think 3 dealerships missed that, but so did I after several days of loosing hair. I hope this helps some other poor lost soul someday... Dale
    #16
  17. phoebeisis

    phoebeisis New Member

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    WOW

    GREAT STORY!!
    What is the PROM?? Some electronic bit on/in the ECM?? ROM read only memory??

    What is the PROM?? It is under the ECM cover-so I can't see it right??
    And it had become SLIGHTLY UNPLUGGED-?
    1)there is a locking lever on the left side that holds the PROM in place
    2)it was not fully locked down
    3)so the PROM lifted up a bit on that side-became SLIGHTLY UNPLUGGED
    4) and that made it RUN WEIRD?? not gain RPMS not upshift??



    WOW-GREAT FIND-and FREE- except for cerebral elbow grease -and whatever the shops charged you??
    Cover never removed-so heat vibration bumps caused to lever to unlock??
    Glad it worked out-great job!! REALLY GREAT JOB!!
    Charlie
    #17

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