1. Welcome to PlowSite. Notice a fresh look and new features? Explore this quick video tour of updates and enhancements. It’s now easier to share photos and videos, find popular topics fast, and enjoy expanded user profiles. If you have any questions, click HELP at the top or bottom of any page, or send an email to help@plowsite.com. We welcome your feedback.

    Dismiss Notice

1990 Chevy K3500 Tranny Problem

Discussion in 'Chevy Trucks' started by Chipmunk, Dec 14, 2009.

  1. Chipmunk

    Chipmunk Member
    Messages: 48

    Hey guys, wondering if you can't help me out,

    I have a 1990 Chevy K3500 1 Ton 454ci Dump truck with a tranny problem.
    Its not shifting automatically. Of course, it has an auto tranny.
    What I have to do to get it to shift takes a certain procedure.

    To shift into 2nd from 1st, I have to start out in Drive and shift the lever to 2nd to and back into Drive to shift it into 2nd. Then to shift into 3rd, I have to get up to 50 MPH and shift the lever to 2nd and then back into Drive to shift into 3rd from 2nd. There is no overdrive.

    I changed the tranny fluid, filter and gasket before it starting doing this. It did it once after we put the new dump box on and driving it home. But not after that. Changed the fluid and filter and now it does it everytime.

    So basically, its an auto tranny that has to be shifted manually without the clutch.

    My first thought is that the Valve Body has crud built up into it and needs to be cleaned out. Other than that, I'm really not sure. Maybe a sensor has failed and causes the issue. Possibly a torque converter problem?

    As you can see, I'm kinda up in the air on this one.
    Think you can help me?

    Thanks guys, really appreciate it. :)
     
  2. B&B

    B&B PlowSite Fanatic
    Messages: 12,777

    There's a few things that can cause this but none of them would require trans removal or complete tear down to fix.

    1) Loss of vacuum to the vacuum modulator.
    2) Defective vacuum modulator
    2) Stuck governor.

    Pull the vacuum line from the modulator and attach a vacuum gauge with the engine running. Should see about 16-19 in of vacuum there. If you do, then go ahead and replace then modulator. It's a $13 part and takes 10 minutes to replace. While you have the modulator off reach into the port and stoke the spool valve and spring in there. Should move freely. If it doesn't then its stuck or the spring behind it is broken. Need to free it up or replace the spring.

    If all that checks out fine then the next cause is debris trapped in the governor. But the Turbo 400's virtually never have a governor issue even on a very neglected trans so my money would be on a modulator issue.

    You also mentioned a valvebody issue but I highly doubt it's an internal valve body issue...they just never give any problems.
     
  3. Chipmunk

    Chipmunk Member
    Messages: 48

    Awesome, thanks B&B. Your post is making me feel so much better about the situation.
    When I get back out to Freeport, I'll give those things a try.

    Again, thanks so much. :)
     
  4. rayzor32

    rayzor32 Junior Member
    Messages: 11

    A lot of ford trannies used to get the governors stuck, we would throw them in park going over 50mph and that would rattle them loose, just make sure your going over 50 or else the pawl might catch.
     
  5. Camden

    Camden PlowSite Fanatic
    Messages: 6,599

    We had to wait 349 days for the post of the year to be made but here it is.
     
  6. sno commander

    sno commander PlowSite.com Addict
    from ct
    Messages: 1,063

    :laughing::laughing::laughing:
     
  7. dchr

    dchr Senior Member
    Messages: 159

    Priceless:laughing: Thanks guy's I needed a good laugh today:waving:
     
  8. JD Dave

    JD Dave PlowSite Fanatic
    Messages: 11,029

    You must not own a Ford. I like to be going around 53 mph the tranny works perfect after I put it in park at that speed. :rolleyes:
     
  9. 2COR517

    2COR517 PlowSite Fanatic
    Messages: 7,118

    Oh man is that funny. My wife and kids still don't understand why I sometimes just start laughing when I'm on this site.
     
  10. rayzor32

    rayzor32 Junior Member
    Messages: 11

    laugh all you want it gets the governors unstuck was taught that trick from my instructor in college and he ran a tranny shop for 25+yrs. At that speed the park pawl wont catch and it will just rattle and its right next to the governor and that loosens up any gunk that might be on it.
     
  11. terrapro

    terrapro PlowSite Veteran
    from MI
    Messages: 3,868

    LOL :laughing:

    A buddy of mine and I were hauling some stuff in his Dads dodge and he backups up then before he stops in reverse he jams it into drive and I freak out tellling him he can't do that and he says "well no wonder he has gone through 3 trans already"....he usaully drives manuls so i can't blame him.
     
  12. Chipmunk

    Chipmunk Member
    Messages: 48

    Yeah, I don't think I'm gonna throw my tranny in park at any speed. If that pawl does happen to catch at those speed, it'll bring it right off and mess up all sorts of ****.

    I rather find the issue and fix it properly, lol.

    What we are gonna try is what B&B mentioned and also checked for loose or pinched wires. Last time I was under there, I did notice a harness not plugged into anything, not sure if thats the issue or if it just doesn't plug into anything.

    Dunno, but we'll see. I'll post back when I start working on it if I figure it out.
     
  13. B&B

    B&B PlowSite Fanatic
    Messages: 12,777

    Wise idea, because the Turbo 400's tend to shear the park pawl pin out of the case when you do that. :nod:

    No electronics that control the shifting on a 400 except for the single lead wire down to the kick down solenoid. But it wouldn't cause your issue if it was disconnected or not. Shifting is done all mechanically.

    Keep use posted and good luck.
     
  14. Chipmunk

    Chipmunk Member
    Messages: 48

    Lol, I've accidently put a vehicle in park when it was still moving, not fast, less than 2 MPH. But oh boy, the particular noise it makes is hell on the ears and heart, lol.

    Awesome, I love dealing with mechanical over electrical any day, hehe.

    Will do, suppose to be getting on this Saturday as long as the weather allows, which is looking good.
    Its about time I'm getting my brothers Ram wrapped up, lol.

    And thanks for all your help guys. You have know idea how much its appreciated. :)
     
  15. Chipmunk

    Chipmunk Member
    Messages: 48

    Apologies for the post, but its kinda different enough to suffice a new post.

    Since we are on the topic of my transmission, I have another "issue." I put it in quotes, since its not necessarily an issue, more of an annoyance.

    My shift selector is kinda sloppy, not the causing the issue above though.
    Is there a way to tighten it up? Would it be in the steering column or the linkage down to the tranny to tighten it up?

    More detailed, when in neutral, I can move the lever up and down about an inch or two.
    When in reverse, I can move the lever up and down about an inch and if moved into the right position, its still in reverse but disables the reverse switch for the backup alarm and reverse lights.
    All other gear position are sloppy of about 3/4" or less.

    My guess is that I'll need to get into the steering column for this one.

    These trucks are prone for a sloppy gear selector lever, aren't they?
     
  16. B&B

    B&B PlowSite Fanatic
    Messages: 12,777

    Some of the slack will be in the column and isn't easily resolved but you can tighten the majority of it up by freshening the bushings in the linkage from the column down to the trans. There's one at the base of the column where the shift rod connects that runs down to the trans, and a second plastic one on the bellcrank between the trans and frame rail. At the same location there's also a coil spring that holds tension on the bellcrack and those often rot off on the older trucks, thus the bell crank gets sloppy. Also check the nut on the trans shift shaft itself were it protrudes from the case. They get loose often times.

    Have a helper wiggle the shifter while you watch the various pivot points and you'll see where the wear is rather easily.
     
  17. welded wrenches

    welded wrenches Senior Member
    Messages: 177

    sloppy what shiftfer

    i also agree with the above post;;;;hi.th400 shift linkage common wear issues at the shift linkage that goes from frame rail to trans.yes the one that has spring on the linkage and a small cone shaped platic bushing..most likely worn out on the tranny side of this linkage this is the 1 that has the small hair pin or cotter pin in it.ya cant really see how grooved wornout this actually is untill u take off the cooter pin n slip out that linkage..
     
  18. Chipmunk

    Chipmunk Member
    Messages: 48

    Awesome, thanks guys. If we don't get a pushable snow event this weekend, I'll be able to get under there and fix the issues with the truck.

    Can't wait till its done and I can post back here what it was, lol.
     
  19. Mark Oomkes

    Mark Oomkes PlowSite Fanatic
    Messages: 10,058

    :laughing: :dizzy: :drinkup: :confused:
     
  20. Chipmunk

    Chipmunk Member
    Messages: 48

    Well, got the vacuum modulator replaced and before even touching it, noticed the steel line was rotted away.

    Unfortunately, GM discontinued the steel line apparently, so I ran to Farm & Fleet and picked up a 1/4" PolyArmor steel brake line. Cut off the ends and bent it into position. I didn't run it the same way GM did so if I ever have to replace it again, it'll be easier to remove.

    So with a new vacuum line and a new modulator, took it out for a test run and it works perfectly now.

    Shifts so much smoother now, too.

    Thanks everyone for the help.