Question about 1987 Chevrolet Blazer

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Changed 5.7 350 motor in 87 chevy k5 blazer with same from 90 caprice, motor's only mod. was using throttle body from previous motor. Full tune up but from 35mph to 45mph it lacks power and drinks gas service soon light jumps on for a minute or two then goes off even when ran at normal driving speed . No apparent vacuum leaks, computer threw EGR valve and O2 censer codes, replaced them still same problem oil pressure and gas hand not reading either, all new fuses, reverse lights not working, "HELP!!"

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  • Stephen McCormick Feb 27, 2011

    A well experienced opinion goes further than jumping into a major project somewhat (blindfolded) on tranny internals and their functions. Your responding has saved me quite a bit, THANK YOU!!! That does make a lot more sense not to use compressed air, I have no doubts to your expertise on matters of mechanics, (much appreciated help from afar). If the 1-2 shift solenoid reads (open) does this shut down other internals as well and what should I test and keep an eye out for?



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If you are set on using this engine for its increased power and fuel efficiency, the only way you will realize these benefits is by changing the ECM/PCM from the engine donor vehicle to yours, put the 90 model engine's throttle body back on it, use the engine wire harness from the donor vehicle--in other words, the engine has to think it's still in the Caprice, and the only way to do this is to put the Caprice electronics and fuel management system (throttle body) back on it. If you have to modify the throttle linkage, the kick-down/TV cable, to make it work, then do it. Also, you will have to put an Oxygen sensor from a 90 Caprice into the manifold/collector/crossover pipe of your vehicle, and not one for the 87 truck. If it wont fit, plug the factory hole on your truck's Oxygen sensor location with a threaded plug using high-temp thread sealant, cut/weld in a proper-threaded orifice for the Oxygen sensor from a 90 Caprice. If the Caprice had two Oxygen sensors, you will have to put one on each cyclinder bank's exhaust outputs.
Swaps such as these are great if all the details are attended to, but headaches if you just try to throw and go.
If you do all this, the codes will not come back after you reset them, the engine will run great, you will have better power and greater fuel economy (the Caprice and the Blazer weigh within a couple hundred pounds of each other), and you will have a 1987 K5 Blazer which "thinks" it's a 1990 Caprice.
And remember when buying engine parts in the future to tell the counter guy "It's for my other car--the 1990 Caprice."
You get less **** out them that way.

Posted on Feb 15, 2010

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  • sjohnson137 Feb 16, 2010

    Just so everyone knows, I did not use any profanity. I said "You get less trap-t+c out of them that way." Filter way too sensitive...

  • Stephen McCormick Feb 17, 2011

    sorry its been a while, took your advise and engine is doing great, but, have another draw back. blazer set awhile, started it up let it idle awhile, put it in gear and "thud", 0-15 pulled fine, then engine revs up and it stops pulling. at about 25-30 motor still reved somewhat high, then "thud" kicks into third. afterwards 4rth gear is a struggle to get to. Flushed lines and changed filter and fluid, no debris was on magnet in bottom of pan, replaced TV cable backed with a full tune up, but still same results. where do i look first valve body, 2-4 servo, governor, stumped with this, could really use some advise before i spend unnecessary gobs of needed funds

  • sjohnson137 Feb 18, 2011

    Hey, Lock Ness. Answer 2 additional questions: is this the K5's original tranny? And how long did it sit between uses?
    You're describing one of several possible problems; could be debris lodged in servos, pistons, or oil passages, could be a a stuck check ball, shift solenoid, or shift valve, could be a loose connection even. The lack of metal in the pan is very good news. But it sounds more like a dead 1-2 clutch pack. If this is a second vehicle, quit driving it until you go further into the tranny. If you are very handy with the wrenches, remove the tranny, drain it, remove the valve body intact and lay it aside in a very clean and protected place. Remove the TC, and treat it the same way. Get a 4L60E master rebuild GASKET kit, and a full set of clutches, 1-2, 3-4, Reverse, and OD if it is the Caprice tranny; a TH350 or 700R4 GASKET kit and 1-2-3 and reverse (TH350), or 1-2, 3-4 and reverse (700R4) clutches. Get only Alto Red Eagle red surface clutches and Kolene full-thickness steels. Get a 1-2 shift solenoid, a Sonnax pinless accumulator piston kit, a Sonnax 1-2 shift servo, and (if it is the Caprice box) a high performance 3-4 shift servo, at least the Corvette one.
    The trans will have to be disassembled to replace the clutch packs, and you might as well replace the power band at the same time; use the new thicker, extra-wide one. There is a compression spring in the clutch pack which can be tricky to remove and re-install, but you can do it.
    The servos, solenoids, and accumulator can be replaced without tearing the valve body apart, but do the clutches first: if the 1-2 clutches already in the tranny don't look burned or defaced, then the problem is either electrical- or debris-based. If the clutches look okay, reassemble the clutch pack into the drum in the exact reverse order of disassembly (take pictures along the way in), and replace the band, then re-install the drum into the trans case. You can view or order on-line trans manuals for the work you need to do. If the clutches look okay, take the undisturbed valve body to a transmission shop and tell them you want it rebuilt and thoroughly cleaned. Don't go into the valve body; the Dark Lord Sauron lives there. The rebuild and cleaning will repair any problem with the valve body.
    Once you have it back, re-install it, and change out the other parts with the newer, high-perf parts, pan it, hang it, juice it, crank it and see what happens. There is no need to pay for a full rebuild if you just need clutches in it.
    If you don't feel comfortable going into it, take it to a shop. It's not fluid and filter.

  • sjohnson137 Feb 18, 2011

    meant to say "sounds like a dead 2nd gear clutch pack." 1st gear obviously works.

  • Stephen McCormick Feb 19, 2011

    Thanks for responding, yes it is the original K5 tranny, and due to a fender bender in my 89 firebird this is my only vehicle as of the moment. "Question", is there a way i can shoot low pressure compressed air through the system to check for debris without hurting any components.

  • sjohnson137 Feb 19, 2011

    Do not use compressed air. You've already done the easy stuff. This is a disassemble and locate thing. Use of compressed air may force any debris into an irretrievable location and may damage as yet undamaged components. Compressed air is typically used only on disassembled individual parts, and the air used for that is oiled by an in-line oiler with transmission fluid. If you do the clutch replacement, be sure to soak the clutch plates overnight in Dexron-III transmission fluid in a clean, covered bucket before installation. I really think it's clutches. Metal usually appears in the pan after continuing to drive a car with a partially failed tranny. I know this is not what you wanted to hear, but I have been doing this since the early seventies, and IMO, you need to replace some parts to fix this thing. Feel free to ask more questions as needed.

  • sjohnson137 Feb 19, 2011

    HOLY MACKEREL, BATMAN! Something just occurred to me...Drain the trans, remove the pan, and make sure the 1-2 shift solenoid is connected. The connectors can get pushed off when replacing the filter and gasket. If it is connected, it comes off easily (2 screws). Take it off and check it with an ohmmeter. It should read 0 Ohms. if it reads infinity (open), replace it. $5 new in bag from {slapping myself on forehead}
    If THIS doesn't work, refer to the clutch thing.
    Do this FIRST...

  • Stephen McCormick Feb 27, 2011

    A well experienced opinion goes a lot further than starting a major project somewhat (blindfolded) on tranny internal functions. Thank you (much appreciated help from afar), you've saved me plenty on this project thus far. (QUESTION)... If the 1-2 shift solenoid does read (open), will this effect other internal electrical functions as well, and which other components should I keep the ohmmeter and an eye out for: (first tranny tear down) unfamiliar territory (for now). Safety and knowledge is key for me.

  • sjohnson137 Mar 01, 2011

    A bad shift solenoid just makes the next highest gear unavailable. The vehicle 'skips' the gear, going to the one above it, and this gives you the operator a bad driving experience...noise, rude shifting, uneven acceleration, overall poor performance. This will eventually kill the tranny, so the computer puts the vehicle into 'limp home mode' to help save the vehicle and alert you to the problem. If only the solenoid coil is bad, when you replace the solenoid, everything will be fine once you reset the 'service engine soon' or 'check engine' light.


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Motors are designed differently for these two engines with many different sensors. The computers for these engines are also different. MIX & MATCH does not work this was. I think you will have a headache with this unless you get the correct engine back in your truck

Posted on Feb 02, 2010


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