Register now to get rid of these ads!

transmission help??? stall issue

Discussion in 'The Hokey Ass Message Board' started by DMFB, May 20, 2011.

  1. DMFB
    Joined: May 22, 2009
    Posts: 551

    DMFB
    Member

    Hey fellas,
    I have a th400 that is a factory mate to the 500 ci cadillac in my truck. I completely rebuilt the motor and the recommended stall size was 3000. I did not rebuild the transmission (ran out of money, lol) however, I did put a shift kit in it, new rear seals, trans cooler, new modulator valve and a TCI 3000 stall converter. When I am driving my truck it will not shift until 3500 no matter if I'm on the throttle hard or not. I understand that is where it flashes, but is that normal? My truck doesn't weigh very much, therefor I get up to the speed limit extremely quick and I am running 50 mph in second at 2600 rpm. 35 mph I'm in first running 3000 rpm. Also, at lights it inches forward pretty hard. I have always ran 4 speeds, this is my first stall. People say that it is completely normal to fret about it at first, like the tanny is slipping....but I thought that under normal throttle that it would shift somewhat normally. It doesn't bother me too much, I just do not want to damage my tranny if this potentially bad. Thanks for any info!

    -DMFB
     
  2. DMFB
    Joined: May 22, 2009
    Posts: 551

    DMFB
    Member

    I appreciate the info. I will try adjusting the modulator tomorrow before I head to work in it and see what that does. Hopefully I don't end up buying another stall, but the extremely high rpms isn't helping slow gas visits, lol. Be nice to see something above 6 mpg.
     
  3. Larry T
    Joined: Nov 24, 2004
    Posts: 7,875

    Larry T
    Member

    I don't think the convertor is the problem with the transmission shifting late. I'd check the modulator valve and the governor weights before I did anthing else, but I'm not really a transmission guy.

    I did have a 10"/3200 stall convertor in my 454 powered, 2500 lb. International Pickup. You really couldn't tell it was a high stall convertor until you brought the rpms up against the brakes or really nailed it. Shifted normally.
    Larry T
     
  4. mysteryman
    Joined: Apr 20, 2011
    Posts: 253

    mysteryman
    Member
    from atlanta

    im no transmission man but i would look at the shift kit.the 3000 stall should keep it from inching forward at a normal idle.try what LARRY T did hold the brakes and load up the convertor see where it starts pulling at.could be a bad convertor
     

  5. d2_willys
    Joined: Sep 8, 2007
    Posts: 4,285

    d2_willys
    Member
    from Kansas

    I agree with the shift kit. Modulators will increase throttle valve pressure, but from the numbers you give, I doubt it will adjust out that much. If you could restore the valve body back to original I would try that first. The stall speed sounds reasonable.
     
  6. You might also want to check the adjustment on the kick down linkage
     
  7. From your post this stood out to me. I know you said more but this is what stuck:
    I installed shift kit , now it wont shift.

    I'd look at that kit install real good, see if the direction have different options based on the characteristics you expect. You should be able to get another plate if you drilled it differently than you wanted.

    Hope you fix it easily.
     
  8. d2_willys
    Joined: Sep 8, 2007
    Posts: 4,285

    d2_willys
    Member
    from Kansas

    No kickdown linkage, kickdown is electrically operated.:eek:
     
  9. I suggest you research and understand the diffrence from the flash and the stall of a aftermarket converter. Very typical, and a big misconception that a high stall speed converter will allow you to not feel it pulling on the brakes at a stop light. ESPECIALLY in a light car. My 26 wieghs in at 1700 lbs, and I have a 3500 stall converter, and I somewhat fight the brakes at a light. When drag racing though, I can bring the revs right up to where the torque curve starts to flatten out, and leave /launch like no tommorow. The converter is multiplying torque, the torque of a monster Cad in a very light car in your case. The engine is NOT "stalling", but the converter is simply trying to "hydraulic couple" the engine to the input shaft of the tranny.
     
  10. DMFB
    Joined: May 22, 2009
    Posts: 551

    DMFB
    Member

    Thanks guys, a lot of awesome info. I adjusted the modulator this morning. I noticed no real change, except it seems to shift harder, and I can run at 70 mph at 2200 rpms steady. Don't recall that happening before, so thats good. As for something two of you touched base on. Reving at a light. It does not stall at all, that is one of the big things that confuse me. if I touch the gas, whileholding the brakes, it moves. Also when driving, in any gear if I'm doing 50 mph at 2800 rpm and I let off the gas.....then press the gas again, it just revs until I resume 2800 rpms again (if I have maintained the same speed, if I have slowed down, obviously it resumes at a lower rpm). Is that normal? MAybe it is a shift kit issue. I know I followed the directions spot on, but maybe it was a bad decision to run one. I also have a piece of shit b&m ratchet shifter (man I'm not a fan). It is a pain in the ass to find Drive. At first I thought it might be relevant, but I checked the shift linkage/ gear position points several times. I think I can rule it out as being the problem....just an annoyance. Anyway, I really appreciate all the help.
     
  11. DMFB, warm it up to operating temp, disconnect the shifter from the tranny, put it in drive and then go for a test run. See if you have full automatic and make note of the shift points. Check the fluid level while it is warm by first going through each gear, count to yourself 1 one thousand- 2 one thousand and shift. Go through each gear, pausing foward and backward two times, then check the fluid. Sorry, you should do this before the test drive with the shifter disconnected. TR
     
  12. For the cooler, did you use trans cooler compatable rubber lines? If you didn't stop and go to Napa, they should have the Goodyear oil cooler rubber lines, and yes it will say it right on the side. Is the kickdown electrically operated as stated above? Maybe its not a kickdown but like a 700R4, a TV cable. This cable controls line pressure, and you will surely toast the tranny if its not adjusted properly. I am NOT a electronic trans controller expert by any means, so maybe someone more knowledgeable will help you from here. TR
     
    Last edited: May 21, 2011
  13. justpassinthru
    Joined: Jul 23, 2010
    Posts: 524

    justpassinthru
    Member

    If the transmission worked before you installed the torque converter and shift kit, then I would suspect the most likley cause is the installation of the shift kit. What kit was it?

    Did you install the proper valve body gaskets and in the proper position (top and bottom)? There are different gaskets for late model th400s.

    Another thing that will make the trans not shift or shift late is not tightening up the passing gear solenoid, or not using a gasket on the can type solenoid. Later model solenoids that do not have a can cover do not use a gasket due to a hard rubber type gasket made into them. Also on the can type solenoid there should be a steel disc that is staked into the face of the solenoid that can fall out, about the diameter of a nickel.
    Leaving the solenoid loose has bitten probably every trans builder at least once in their career including me!

    Many early th400s also had a spark control switch screwed into the valve body by the 3rd accumulator piston. They are very prone to internal leaking and will cause a late third gear. If left out it will not shift into 3rd.

    Also you must make sure the vacuum to the modulator is manifold vacuum, not ported vacuum. Ported vacuum will make the trans shift a little later than normal and can cause the transmission to overrun when the vacuum drops off to 0", meaning it will take throttle to get it to catch up and pull again.What happens is lets say its in 3rd gear and you lift off the gas, the vacuum will drop to 0" and many times the trans will go to 2nd gear. Then what happens is the intermediate sprag overruns due to the rpm the input shaft is spinning slower than the output shaft, then you have to raise the engine rpm to catch up.

    With the torque converter, the rated stall speed is just the rough RPM that the torque converter will hydraulicly lock up. Meaning the outer housing is turning at the same RMP the input shaft is turning. One thing to keep in mind is most stock non lockup torque converters are at best 9/10 efficient. Meaning there will always be a certain amount of slippage. As the stall speed goes up, many times the efficiency goes down some. Some converter makers are better than others to control that slippage. The car will still creep in that range of the stall speed. It will not rev up to 3000RPM and hook up. If the car has a numerically low rear end gear like a 273-1 ratio, it will feel like there are marshmellows under the hood. One other issue with th400s is it is quite common for the stator splines to be machined of the pump stator shaft (larger of the two splined shafts) due to wear.
    The symptom of this would be no torque multiplication in the converter. Meaning the converter is stalled at idle. The car would have excessive creep in drive, lug down the idle speed and leave the light like a stone.
    good luck
    Bill
     
  14. Tenacious A
    Joined: Nov 14, 2006
    Posts: 284

    Tenacious A
    Member
    from Willis Tx

    Replace the modulater valve. Classic symptoms
     
  15. DMFB
    Joined: May 22, 2009
    Posts: 551

    DMFB
    Member

    Man, ask and you shall recieve. You guys are awesome! Justpassinthru, I have no idea how the trans was before this. It was a motor/tranny that was laying around for a few years. The whole truck is a new build. I completely rebuilt the motor, but didn't go all the way through the transmission. I installed a TCI 3000 stall, B&M shift kit, new modulator valve, SFI certified flywheel, and new rear seals. The vacuum issue/scenario you mentioned is spot on what mine is doing. Is running vacuum off of the carb to the modulator a possible issue?
     
  16. Engine man
    Joined: Jan 30, 2011
    Posts: 3,480

    Engine man
    Member
    from Wisconsin

    Cadillac used pretty low ratio gears in their cars. What ratio are you running in your truck? The turbo 400 uses the modulator and the governor along with the valve body to control shift points. If your rear end ratio is deeper it can fool the trans into shifting at the wrong time. There are different gears available for the governor.

    If the tranny worked in this vehicle before you changed the convertor and modified the valve body, one of those is likely the problem. Does you engine have good vacuum?
     
  17. Engine man
    Joined: Jan 30, 2011
    Posts: 3,480

    Engine man
    Member
    from Wisconsin

    You need to use intake manifold vacuum! A port on the carb might be connected above the throttle plate so you won't get vacuum until you crack the throttle and it will be much lower than engine vacuum. The transmission modulator senses engine load by engine vacuum.
     
  18. DMFB
    Joined: May 22, 2009
    Posts: 551

    DMFB
    Member

    The truck does have good vacuum, which suprised me due to the cam size. Again, I have no idea what the tranny was like before. The whole truck is a fresh build. I built the motor/trans for this truck. Just trying to see where I may have went wrong. As for the rear end, it has 2.73 gears I believe in a 9 inch ford.
     
  19. DMFB
    Joined: May 22, 2009
    Posts: 551

    DMFB
    Member

    Thank you engine man! I guess there is my problem. I made a block plate to cover the old egr valve. I guess I will try running it from there instead and see what that does.
     
  20. justpassinthru
    Joined: Jul 23, 2010
    Posts: 524

    justpassinthru
    Member

    You can get manifold vacuum off the carb or directly from the manifold. Put a vacuum gauge on the port you are using and at idle and read the gauge. It should read vacuum. Recomended vacuum should be above 15" at idle, it should drop if you speed up the engine quickly and then build back up quickly. The more radical the camshaft, the lower the vacuum reading will be. Trans should still shift with 10" of vacuum but will upshift later than normal and should upshift if you let up off the gas. If you are using a ported vacuum port (incorrect) the vacuum will be 0" at idle and increase steadly as the throttle is opened.
     
  21. Mr4Speed
    Joined: Nov 16, 2008
    Posts: 89

    Mr4Speed
    Member

    Not every vacuum port has manifold vacuum, some are ported vacuum and have non to little vacuum when the throttle blades are at rest or at cruising position.
    So make sure it's connected to manifold vacuum.
     
  22. johnstonad
    Joined: May 28, 2011
    Posts: 3

    johnstonad
    Member

    Me neither. I hope that it will not damage our used transmissions for sale. I don't want to have a damage one. :D
     
    Last edited: May 31, 2011
  23. rudaluda
    Joined: May 28, 2011
    Posts: 2

    rudaluda
    Member

    Very informative thread I encountered a similar problem with the trans some months back but learned more from this thread.
     

Share This Page

Register now to get rid of these ads!

Archive

Copyright © 1995-2021 The Jalopy Journal: Steal our stuff, we'll kick your teeth in. Terms of Service. Privacy Policy.

Atomic Industry
Forum software by XenForo™ ©2010-2014 XenForo Ltd.