Question about 1991 GMC C1500

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700r4 transmission problems

I have a 91 GMC Sierra 1500. Original 5.7L motor with no problems. I have just went through my 6th transmission, 5 of them being the 700r4 and this last one being a 350 turbo from a 74 Chevrolet pickup. All of the 700r4's do the same thing and go bad within a mile. They will shift all the way through maybe one time and then after downshifting they only have 1st and 2nd and then pops into what seems like neutral, and reverse works. Ive tried new ones, used ones, rebuilt ones, ive put a new computer in it, new radiator with trans cooler, new detent cable and had the dealership dial it in and they couldnt figure out why it wouldnt shift into 3rd..had 2 or 3 local shops look at it and none could give me an answer. I just recently put the 350 turbo longshaft in it with only having to run a vacuum line and move my crossmember a few inches up and it would work perfect until it drives a little bit and gets warm then it shakes when starting off from stop sign or redlight or something, maybe this one is going bad i tried it as a last resort and it worked for a few months. The truck was given to me from my father who was the only owner and took excellent care of it and i wont get rid of it and i wont to get it driving. If anybody has ran into a problem like this or can help with any advice i'd greatly appreciate it. -Ryan

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  • ryant199 Dec 11, 2008

    When the dealership had my truck they ran a $90 full diagnostics on it and said it was just a bad transmission (it was the 4th) then i had AAA Transmission shop rebuild it and it did the same. What would be the best and cost efficient route..Gettin the 350 rebuilt and changing my rear end or replacing the wiring harness and going back with the original 700r4?..

  • ryant199 Dec 11, 2008

    The original radiator had the trans cooler in it so i replaced it when dealing with the 700's. The lines matched right up to the 350 when installing it so i didnt think anything of it..possibly need an external cooler?

  • ryant199 Dec 11, 2008

    Ok. Ive been told the 400's are great. Any idea about other modifications i will have to do for a 400? I appreciate all the help

  • Anonymous Feb 15, 2009

    I have had the same problem with 700R4 transmissions. They are junk -- I had the same one rebuilt three times in 30 days. If the throttle valve adjustment cable isn't just so, it will burn up in a heartbeat. With a TH350 or TH400, you lose the mileage that an overdrive can offer on the highway, and you will lose some torque in 1st gear (the 700R4 is 30% lower ratio) but I firmly believe that the TH350 is a much better transmission longevity wise. The trick is that to swap a TH350, if the truck is 4WD you will need a 4WD version of the transmission (tailshaft housing is different)

  • yadayada
    yadayada May 11, 2010

    U need to consult a professional trans shop, u are getting no where fast, 1st I susspect u have a bad wiring harness on the 700r4 failures, u need special equip to test this, also the high revs without any overdrive on the 350 will wear your engine out, if u run a 350 change the rear end grear ratio to a 3.08 gear set. And yes the shudder is most likely the forward clutch pack, and yes the trans is most likely toast.

  • Walter Morris May 11, 2010

    did you put the right trans cooler for the 350 turbo if you used the cooler for the 700 on the 350 it might not be cooling right

  • Ben Buell Oct 01, 2011

    There may be a bypass valve in the radiator or cooler for the transmission fluid. If its stuck it might be starving the transmission of fluid causing it to burn out

  • Brian Anderson Mar 14, 2014

    im having the same problems in my 93 suburban are there any adjustment i can do or is D an over Drive most likely blown

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Just rebuilt700r4 transmission and it is sliping in reverse what can cause this.

Posted on Apr 11, 2010

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  • taylor74 Apr 11, 2010

    is it possible that the housing can a crack

  • travis coleman Oct 12, 2011

    y want a 700r4 shift

  • travis coleman Oct 12, 2011

    y want a 700r4 shift

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I went thru the same problem years ago. When the 700R trans grinds itself up, all the stuff get into the trans cooler. It is located in the radiator. This needs to be flushed, preferably by a good rad shop. If not the junk in the cooler gets in the rebuilt trans. clogs the filter and burns it up.

Posted on May 08, 2010

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Stay with the 350 sounds like your slip yoke is wore out

Posted on Jun 25, 2009

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  • GMC Master
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Stick with the 350 or a 400, buy a heavy duty unit from SUMMIT RACING PARTS, they are on the internet, they are sometimes cheaper than having yours rebuilt, on the 350 or 400 that is for sure, and far superior, also they can supply the gear set at a fraction of the dealer cost, remember u need a 3.08 gear set. 700R4's have been a problem from day one, I worked for a GM truck dealer, lost count of the number we removed that were still in warranty, GM could not supply the rebuilds fast enough, every one was slated as the new revised design, end result junky design, they finally abonded it and cam out with a new transmission design.

Posted on Dec 11, 2008

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I have a 700r4 and it will not shift out of first I change the valve boby and still doing the same thing maybe it the wiring

Posted on Sep 03, 2012

  • randy_wal119
    randy_wal119 Sep 03, 2012

    I have a 700r4 and it will not shift out of first I change the valve boby and still doing the same thing maybe it the wiring

  • wimberleyz
    wimberleyz Oct 16, 2012

    TV cable to lose

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  • GMC Master
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Www.tvmadeez.com/tvinstadj.php
This is great info, need to pressure check trans to properly set up trans. for long life, check it out
Be cool

Posted on May 03, 2009

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Try using a t5 transmission. I have a sport 1500 chevy that originally had a 305 and later had dropped a 350 bored over .40 and the transmission has not messed up one bit. the t5 is a 5 speed transmission and im sure you know how to drive stick so give that a shot. If it doesnt work just write me and let me know. zach_drummer_1990@yahoo.com thanks

Posted on Apr 15, 2009

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