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  1. #1
    Newbie
    Join Date
    Jun 2013
    Location
    Cedar City, Utah, United States
    Posts
    2

    Default 91 Suburban 2500 wont move

    recently purchased a 91 Suburban 2500 back in december. Had the transmission serviced in January. Truck ran and drove great...until a few weeks ago. I had been driving the truck to and from work all week no problem whatsoever. Even that day, I had drove the truck to work and home several times with no issues. I parked it, went in to work. Came back out 2 hours later to go home and the the truck would not reverse. So I turned it off, waited a couple minutes hoping maybe I was just imagining things. I turned the truck on. Motor runs fine, but the transmission wont engage. There is no movement whatsoever in the drivetrain. What could it be? Im on a budget so any trans work I would be doing myself. this is just a standard 91 3/4 ton burb from what I can tell. It has the 4l80e I have determined from the 17 bolt pan. Any clues? Is this common? Where do I start? Help Please! This is my dream rig and I hate to see it sitting after only 6 months...

    I havent done any maintenance on this vehicle yet. My parents were driving it until theirs was repaired a couple months ago. I have done some checking since last night. here is what I have observed. And sorry but I am a newbie when it comes to servicing my own vehicles, but I am very mechanically inclined and I do my research as much as possible.

    ANYWAY, upon checking the trans dipstick I discovered it was dry! ugh! not a drop on it. I do not see any apparent leaks although there is fresh fluid on the tip of the breather hose? I believe its a breather hose. black rubber hose coming out of the top of the transmission at the rear where it meets the transfer case. Anyway, I filled with fluid, and when i attempted to shift into gear, no response still. after a min, the vehicle acted like it wanted to go forward, but seemed like it was in a higher gear maybe? seemed sluggish and hesitant to accelerate. No odd noises. Motor is in great shape sounds great. but shifting the column doesnt seem to affect it like normal....doesnt lower rpms or engage at all. So I turned it off for fear of making it worse? and had it towed back to my house. now that its home, i turn it on, and back to no response.

    sorry i should add the whole story i suppose...Had been driving all day no hard shifting, no overheating, no problems at all, drove like i imagine a new one would. 2 hours later when I originally started it after work, it would go forward, but when I attempted to shift into reverse, it still wanted to go forward, no matter which position the column was in. So i turned it off. waited a second. turned back on. no response from any location on the column. checked and discovered dry dipstick. filled with fluid and truck would seem to want to go forward, no reverse, but like it was in 2nd or 3rd maybe... turned it off. towed it home. turned it back on. no response again.

    I should also add that Ill be doing any repairs myself. No matter how technical or involved or tools necessary. I believe in learning everything I can about maintaining and repairing the vehicles i drive. Any helps would be appreciated. Thanks! I can upload any pics or answer any questions in return.

  2. #2

    Default

    Hopefully you haven't done any major damage to the clutch packs or valve body. Once you filled it with fluid, did you cycle through the gears on the shifter and then check the fluid again? Depending on how low the fluid level was, it could take several cycles of filling the transmission, cycling the shifter, and checking again before it reaches a stable level. Once you've done that, if it still doesn't move, you may have done damage and it may need the transmission to be dropped and rebuilt, but let's not get hasty with that diagnosis. Follow the procedure I outline and get back with us. Keep in mind that process needs to be done on level ground and the final level check needs to be done when the transmission is warm.
    Christopher

    1991 Chevy Suburban 1/2 ton 2WD w/ chevy SBC 350-3/4 ton drivetrain upgrade w/4.10 gears 200K miles
    2005 Saturn ION-2 Stock 265K miles
    1982 Bronco, 1993 Bronco (sold), 1971 M35A2 Deuce and a Half



    There are 10 kinds of people, those who understand binary, and those who dont...

    Remember kids, the only difference between screwing around and science is writing it down- Adam Savage

  3. #3

    Default

    bummer..... well first thing you need to find out is how youre loosing fluid!
    especially if it is indeed through the breather tube...
    fill the transmission again. check the fluid level with the truck level, hot, running, and in neutral.
    once the stick shows the correct level and clean fluid (does not smell burnt, or appear foamy on the stick) then carefully get under the vehicle while someone slowly shifts through the gears.
    watch for any leaks and listen to the trans shift. (if you have loud exhaust a stethoscope would help)
    have your friend do some brake stands too in each gear to get the RPMs up with the trans in gear.

    the 91 wasn't meant to have that transmission, so someone could've easily cut corners.... I don't even know if it has vacuum lines or not... but start there, start reading about it, and let us know

    good luck!
    Gas was $1.83 when Obama took office.....

  4. #4

    Default

    Quote Originally Posted by K15 Blazer Guy View Post
    bummer..... well first thing you need to find out is how youre loosing fluid!

    the 91 wasn't meant to have that transmission, so someone could've easily cut corners.... I don't even know if it has vacuum lines or not... but start there, start reading about it, and let us know

    good luck!
    This is my first post in this forum and I do not own one yet, but am looking to buy 89-91 suburban. The 1991 WAS SUPPOSED to have the 4L80E transmission. It is the last year of that body style (the best of them), and it was the FIRST year of the 4L80E trans in the 3/4 ton. This is a great year sub you have. It is the only year you can have a 4 spd tranny in the old style body in a 3/4 ton. As far as ur trucks problem, I wish I could be of more help. I wouldn't just keep adding fluid and testing it as you don't know where the fluid is going. If the tranny is dry, then it is leaking/going somewhere. This stuff doesn't just evaporate. I would tow it to the transmission place that did the service. I am all for DIY if you can, but trans are not the easiest things to diagnose. You HAVE to figure out where the fluid went. Retrace your route before it happened and see if there is a trail of ATF. If it's leaking, you should see some signs of it on the undercarriage unless you were sitting/going pretty slow then it would just leave a trail or a puddle of ATF. Good luck..

  5. #5
    Jr. Apprentice
    Join Date
    Jun 2013
    Location
    Interlachen, Florida
    Posts
    10

    Default

    Check your radiator or overflow tank, if it looks like a foamy yellow milkshake then the transmission cooler in the radiator has leaked and that is were your transmission fluid is going. Also check to see if you have another cooler in front of the radiator and inspect the lines for leaks. If you have the towing package then they put an external transmission cooler in series with the transmission cooler in the radiator.

  6. Thanks 08silverado3500hd thanked for this post

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