Possible Transmission Issues??

[brlarl]

I have a 1985 C10 Silverado 2X2 with a 5.7 engine and tranny Combo out of a 1990 Chevy Suburban.  Vehicle runs great.............well up until a few days ago.  The motor was over hauled about 3 years ago and with the exception of a few small oil leaks it runs good.  The tranny on the other hand has not been over hauled and has probably about close to 300,000 miles on it.  I know the time is getting closer for me to have to overhaul the tranny but the truck still drives and goes into reverse.  Now a few days ago as I'm on the freeway I noticed that it feels like the a/c compressor is kicking off and on (but its not) while driving.  While this happens if feels as if the engine rpms is rising and dropping and the truck feels like it is surging back and forth in a forward motion?  It does the samething with the A/C off just not as noticeable.  Confused?  Sorry it is kind of hard to explain.  It is almost as if the tyranny clutches are releasing off and on.  Can anyone explain what it feels like when a tyranny is slipping?  I have never had the pleasure of driving a vehicle with a failing tyranny.  I'm trying to eliminate the tyranny as the culprit.  The only thing that was done on the day is started driving funny was oil being added. I checked it and it was not over filled with oil either???  What other issues can cause this symptom? Any help?  Thanks in advance.

[zieg85]

If it has the 700R4 the lock up torque converter may be disengaging.

[brlarl]

I was thinking about that.  It does have the 700R4.  Is there a way to find out if it is indeed the torque converter?

[VileZambonie]

unplug the connector on the side of the trans and see what it does

[brlarl]

Cool, thanks.  Now if it is the lock up torque converter, does it mean its the converter or the solenoid or both?  How can I tell?

[VileZambonie]

If you determine that is the cause there are several things you need to check. Let us know if that is the cause and check the TV cable adjustment.

[brlarl]

I will do that and get back to you guys.  THanks

[brlarl]

Will a transmission unit from a 1997 Chevy Tahoe switch over in place of the 1990 700R4 currently in my truck?

[Captkaos]

Not without the ECM to control it.  the 97 uses a 4L60E vs your 4L60 (700R4)

[brlarl]

What years are exchangable from 1990 on?  THanks

[VileZambonie]

1991 and part of 1992

[fitz]

Do you have a tach so you can watch the rpm's as the engine surges?

[joesgarage71]

Vile,
  Didn't they change the 700R4 after 93 and then started to call it 60LE
 Steve

[VileZambonie]

Late 92-93 the 4L60E was being produced. 93 up would be 4L60E and can be easily identified by the connector on the trans. The 4L60 is identical to the 700R4 just renamed presumably due to the bad rap it had gotten in the early days.

[brlarl]

Yeah I have a tach and I noticed on the ride home yesterday that the RPMs were not jumping during the time the truck was surging.  I had my check engine light come on this past Sunday and went off once I shut the truck off and has not been back on.  I checked the system and got code 032 which is "Incorrect EGR Flow" could this possibly be the culprit causing my surging?  I did also notice that while the rpms rise just before shifting to the next gear is when I feel the surging then once it goes into the next gear I don't feel it again until just before it shifts again.  Once it is in OD I can't say that I feel it.  Also if the A/C is on it is A LOT more noticeable.  When the tranny is in OD and the brake pedal it is applied shouldn't the RMPs jump up a little meaning the torque converter is unlocking?  If so I can't say that I notice mine jump up.  In OD I'm running at about 1200 RMPs according to my tach.  Any Thoughts?  Thanks