hard shifting???

[frotosride]

I've had these problems from the moment I got the truck and had noticed them while driving it before it was given to me however, now i think I may have time to do something about it so I'm asking the pros what might be the cause...
(Issue #1)When shifting with foot on brake either into forward or reverse you can feel the shift as if someone just hit your bumper...out of the thousands of miles I have put on this truck there has never been a moment that Drive or reverse didn't seem to slam into gear.

(Issue #2) The first time this hapended and several times after, until I kind of got used to it, I thought some one nudged me while at at redlight or stop sign. BUt when I come to a stop and have to sit for atleast 30sec to a minuet I can feel what seems like the tranny down shifting. My first thoughts are just coming out of lock up but that should happen as soon as i hit the brakes and definately after i drop fourth gear, right? Currently the lock up is still controlled by the ecm/pcm.

350 tbi 700r4, np208 xcase...any starting points that are maybe dummy checks to start with because i am currently out of a working space due to being relocated and having to live in a hotel with four kids until we can move into our new house.

[bake74]

     Does your truck have a tv cable, it might need adjustments done to it.  The slamming, or feeling like you get bumped at a stop sign could be the valve assy in the trans.  As far as the hard shift into gear, you do not have any kind of shift kit in it that you know of ?
     Most of it sounds like it could be from valving in the trans, but I am not an expert on auto trans, so someone will see and respond with more ideas or solutions.

[frotosride]

Bake, yes I have a tv cable as it is a '87 model 700r4 and there are no problems when actualy burning through gears. Whan I need to get on it she kicks down like she was fresh from the factory and shifts up on time as best as I can tell without a tach. It's only when I come to complete stops for extended periodsof time like at red lights that I feel the that kick down nudge.

[zieg85]

Sounds to me the torque converter wants to move the truck kinda like sitting there with a manual and the clutch engaging all by itself??

[bake74]

Sounds to me the torque converter wants to move the truck kinda like sitting there with a manual and the clutch engaging all by itself??

     Hey Zeig, or someone else, how would you check to see if the torque converter is doing this ?  Now I want to know.

[zieg85]

Sounds to me the torque converter wants to move the truck kinda like sitting there with a manual and the clutch engaging all by itself??

     Hey Zeig, or someone else, how would you check to see if the torque converter is doing this ?  Now I want to know.

Wish I knew, I know I have had several GM's do that over the years.  That is part of the reason I don't like AT transmissions... Don't like havin nuttin to do with my left foot...

[bake74]

Sounds to me the torque converter wants to move the truck kinda like sitting there with a manual and the clutch engaging all by itself??

     Hey Zeig, or someone else, how would you check to see if the torque converter is doing this ?  Now I want to know.

Wish I knew, I know I have had several GM's do that over the years.  That is part of the reason I don't like AT transmissions... Don't like havin nuttin to do with my left foot...

     Took the words right out of my mouth, and top of that I have never really tore into a auto trans before.

[zieg85]

     Took the words right out of my mouth, and top of that I have never really tore into a auto trans before.
[/quote]

My third car a 1971 Cutlass S I bought from a friend with a bad transmission.  A friend at the time knew how to rebuild them and had all the special tools it took.  I helped rebuild it and we put a shift kit in it.  I actually still have a kit I bought sitting in the shed, probably all the steel parts are rusted by now.  I guess I was always partial to the standard shift cars/trucks because I can service them no matter what.

[frotosride]

So are you basically saying that my converter is locking the impeller and turbine without actually being in the correct parameters for lock up?

[bd]

Just thinking out loud, here...

(Issue #1) ...out of the thousands of miles I have put on this truck there has never been a moment that Drive or reverse didn't seem to slam into gear.

Idle is a little high, or there is a lot of play in the drivetrain (t/case, u-joints, differential, axle splines, etc).

(Issue #2) ...when I come to a stop and have to sit for at least 30sec to a minuet I can feel what seems like the tranny down shifting.  My first thoughts are just coming out of lock up....

If the TCC was actually locked up it would kill the engine at a stop, unless you were in Park or Neutral.  However, a TCC solenoid that is partially plugged with debris could restrict TCC exhaust and delay release.  But, if you have that kind of debris in the pan, your looking at an O/H. 

Try this:
At road speed, depress the brake pedal slightly, but not enough to apply the brake.  You should "feel" the TCC disengage.  Releasing the brake pedal you should "feel" the TCC engage.  Sometimes it's subtle - helps if you have a tach.  TCC disengagement/engagement should occur within ~1 second of depressing/releasing the brake pedal.  If the TCC seems to be functioning as described, the TCC is not your issue.

Perhaps you have a little spring wrap that is storing energy when you brake, and then releasing after you're stopped(?).  Of course, there are issues in the trans that could cause your symptoms, but would require teardown.

[frotosride]

BD, well I tried your test and the lock up seems to be working fine. I didn't think about the idel thing but I'm almost positive tht isn't it because If it were the idel then it would do it especially hard in winter where the idle is higher than usual until the engine warms up and that was not a noticable issue....I'm begining to think that it's time for that monster-in-a-box. I just thought about this but I do have another symptom but I don't think they are related. I have and have had a stalling issue. It only happens in certian situations like if I were in reverse with the steering wheel turned a considerable amount in either direction or if I just blip the throttle but only while in gear under/load. in park or nutural I can blip the loud pedal and no issues. I almost sure that with the milage I am going to have to recal the IAC but I have no scantools so I'm going to leaveit alone until I do.

[frotosride]

After listening to the truck you may have something with the high idle. I am going to check the egr and Iac for proper function and then go from there. Heres an idea of how hard it hits when I shift out of park...
  When I first got the truck and when i drove it before owening it I noticethat the brakes were far below par. I did the usual and checked the fluid but like an idiot I just looked at the resivor and called it good. But it still bugged me so i poped the top and realized the the front well for the rear brakes was completly dry. Lord knows how long that had been. So i put new fliud in and bled them and test drove, stopped like a brand new truck again until the nest morning I parkedthe truck and saw brake fluid pooling on the driveway out ofthe driversidedrum. wheel cylinder gave up so i replaced both and put new pads and spings on. prior to replacing all of this When I would shift out of park the tranny would slam into gear and the truck would lurch in the appropriate direction if the break pedal wasn't matted.   
High idle is probly the cause of this and now I'm on the hunt for the true symptom.   Thanks! I will post my findings.

[bd]

You're correct that the IAC could be your problem.  Functioning properly the IAC adjusts idle speed seamlessly - it's virtually instantaneous and unnoticable.  But, you mentioned "recal the IAC."  Unless you have software to flash the PROM, there's no such thing.  As long as the IAC is working it's strictly controlled by the ECM.  There's no adjustment.  Although, the ECM closes and "zeros" the IAC whenever driving over ~30 MPH. 

Is the factory steel plug covering the base idle screw still intact?  If the base idle setting has been cranked, it can override IAC idle function.  So can vacuum leaks; the early truck TBI has a propensity for digesting base gaskets.  While you're there, check the throttle body for shaft and plate wear.

Another possible cause for hammering the drivetrain might be a shift kit and/or way oversized boost valve in the valve body and pump, or cocked and jammed accumulator pistons.

[frotosride]

Recalibrate may have been the wrong word but it is possible to restore/reset the base line for the IAC. Its a real simple procedure using the ALDL, unpluging the IAC and setting the idle to 650+/-50rpm the tech book sets it out really easily. However I am going to get me a can of starter fliud and check for vaccum leaks on the shafts and TB. The IDle screw plug has never ben touched. Oh and the tranny is completly stock. This I know for a fact because the truck has been in the family since the day it rolled off the St Louis assembly line. I'm Going to save the tranny for last if it is the culprate because it's due for a rebuild especially once I finish the new motor.

Restoring IAC baseline procedure

Remove the wing nut on top of the air cleaner and lift the air cleaner off the throttle body to access the vacuum lines. These are attached to the bottom of the air cleaner. Twist and pull the vacuum off of the bottom of the air cleaner and lay the air cleaner aside. Plug the vacuum lines with golf tees or other suitable item.
  Remove plug over the idle screw located on the right front of the throttle body by using a hammer to drive a punch into the plug and then using the punch to pry the plug out of the throttle body. Discard the plug. Start the engine and let it run until it warms up.
  Turn off the engine and leave the ignition key in the "Off" position. Unfold a paper clip and bend it into a "U" shape. Push the ends of the paper clip into the "A" and "B" terminals of the ALDL (Assembly Line Diagnostic Link) connector, also called the diagnostic connector. In GM vehicles that use this TBI injection, the connector is a black plastic rectangular connector located under the driver side of the dash. The "A" and "B" terminals are located on the top right of the connector.
  Unplug the IAC valve located on the passenger side, rear of the throttle body. Start the engine. Insert a T-30 size Torx driver into the Idle adjustment screw that is located behind the plug removed earlier. Turn the screw to adjust the idle speed to 650 RPM +/- 50 RPM.
  Turn off the engine and disconnect the negative battery terminal from the battery using a wrench. Reconnect the IAC valve. Reinstall the air cleaner and remove the paper clip from the ALDL connector. Reconnect the battery terminal after 5 minutes and test drive the vehicle.

[bd]

Okay - now I'm on the same page with you.

IAC attempts to maintain about 600 RPM at idle, in gear.  I generally don't want to take idle control away from the IAC, so I use a modified method to set the base idle speed.  I plug the inlet air passage feeding the IAC, so I can properly set base idle whether the IAC is working correctly or not.  If the IAC isn't responding, it should be replaced.  IMO, for a stock engine, setting the base idle to 650 RPM +/- 50 is too high, can result in the IAC closing completely in an attempt to lower the idle, and may result in dieseling at shut down and slamming into gear.  If base idle is set too low, it may stall at idle, surge at idle, or hesitate on acceleration.

Rather, with the IAC air passage completely blocked, set idle speed to ~500 RPM in drive with brakes set.  Then, place the trans in park, shut OFF the ignition, remove the plug from the IAC air passage, and restart the engine.  DO NOT REMOVE THE PLUG from the IAC air passage while the engine is running, or you may launch the vehicle!!!  This is because the IAC may open all the way trying to increase idle RPM.  It's probably best to have an assistant mashing on the brakes during this procedure.  If you want to disconnect the IAC during this procedure, you can; but you will have to disconnect ECM battery power for 20+ seconds to clear the trouble code.

Also, starter fluid is very volatile and may give you false indications.  If you spray starter fluid around a "perfect" engine, you'll probably increase idle speed.  Instead, use Berrymans B-12 or equivalent when checking for vacuum leaks.  And don't forget to inspect the throttle plates for wear along the sides where they pass over the throttle shaft.