I dropped the pan in my 700R4 this weekend to replace the 4th gear pressure switch. Since one of the aux valve body bolts was stripped out (by the trans shop that allegedly rebuilt my trans a couple of years ago), I heli-coiled that while I was in there.

To get the switch out, I had to drop the aux valve body anyway, so it all worked out quite well -- or so I thought.

Now, it bangs into drive and reverse quite hard. To make matters worse, this morning on the way to work, it didn't want to shift into fourth gear. I fiddled with the shifter (downshifting to third, then fourth, then neutral, and back into fourth) and it eventually went on into fourth and was fine all the way into work.

I searched the board and learned that the first problem is likely a missing check ball. It did fall out a couple of times while I was messing with it, but I felt certain that I had it in place when I finally installed the aux valve body (there were no leftover parts, any way ).

This business of not going into fourth bothers me, though. It's too coincidental that this behavior started after my futzing witht the transmission. I conceivably could have lost the check ball, but what else could be wrong. Perhaps a speck of aluminum from drilling out the stripped threads? If so, will it work itself out?

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'87 IROC 5.7l TPI - original owner!

 

Are yuoiu saying that all you did was to drop the Aux VB? There is a ball in there but that would only affect Forward. Are the shifts late now too? IF so do this: To adjust the TV Cable skip the book method and do this: Press the D button on the adjuster and loosen the cable setting. Now, have someone floor the gas pedal while you check to see if the throttle plate is open all the way. Usually they are off a little and will wiggle. Do whatever you have to do to get it open solid. Now, with the pedal still floored, press the D button and pull the cable casing (the black tube) back as hard as you can and release the button. You now have the engine, tranny and gas pedal all in sync at WOT. Mark the cable so if for some reason it gets moved you can know where to put it again. The problem with the 'self adjust method' is that it bends things and puts them permanently out of whack. It is also the full TV setting, which is theoretically what the GM method does.

 

I didn't touch the TV cable. The 1-2 and 2-3 shifts are unaffected. It just didn't want to go into 4th.

I get into 4th four times on the way to work. Twice while in town, and the third is on the way out of town onto the highway. It was on this third "attempt" that it acted funny. Everything was fully warmed up at that point.

All I did was remove the aux VB, R&R the 4th pressure switch, drill, tap, & heli-coil the stripped hole, and reinstall the aux VB.

I was really uncomfortable drilling into the case while lying on my back. I went real slow so as to avoid slinging chips around. They mostly fell straigt down, but some clung to the case around the hole. I tried my best to clean all of the chips off the case, but you never really know...

The trans has over 220K miles on it, but was allegedly (I took it in and paid for the work) rebuilt at around 160K. That's when the bolt got stripped. Based on a later experience with the same tranny shop, I'm not sure I really got a rebuild. I think they like to install seal kits and tell you they rebuilt it. Point is, many of the wear parts could be original...


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'87 IROC 5.7l TPI - original owner!

[This message has been edited by P J Moran (edited July 30, 2001).]

[This message has been edited by P J Moran (edited August 03, 2001).]

 

It did this only once, on the day after performing the work (Monday). The tranny worked fine Monday evening, Tuesday, and Wednesday. But on Thursday, it acted up again just as described, both to and from work. No problem this morning (Friday), though.

This is an intermittent problem, apparently. Does that mean there is some trash in there that hasn't worked it's way out, yet? Can I count on it eventually getting flushed out and captured by the filter? Should I just be patient and let it "heal" or should I take some corrective action?

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'87 IROC 5.7l TPI - original owner!

 

Well, it would appear that I found the problem. I dropped the pan again and removed the aux VB. No check ball!

I found it up in the case. I apparently put it in the wrong socket (there are two side-by-side that look like homes for check *****). Where I put it, it was able to jump out and fall into an adjacent passage. When looking at the case, there is a teardrop shaped opening. I saw the bottom of the ball in the narrow end of that teardrop. I reached up in there with a pick and knocked back over where it fell right out.

I also pulled the TV valve and sleeve and cleaned everything up and reassembled (with the check ball in the correct hole). All of my problems have gone away! No harsh thump into D or R. No upshifting problems. I hope this information helps someone else some day.

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'87 IROC 5.7l TPI - original owner!

 

Thanks for posting the fix on this. One question though, Was it the Aux VB (four bolts) or the 1-2 acuumulator housing (three bolts) that you had the problem with? The reason I ask is that I have seen the ball left out of the Aux VB and it makes for a rougher engagement into Drive and if the ball is put into the other hole it takes forever to get into Drive.

 

It was the aux VB (one long bolt, two medium bolts, one short bolt w/special head). I guess that check ball was wandering around in the case causing intermittent behavior problems. I have been symptom free all week.

I'm about to take the car on a 1200+ mile round trip and was getting really nervous about tranny failure. What a relief this is!

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'87 IROC 5.7l TPI - original owner!